3.1.3 Cell and Transport

1.

The drawing shows part of a cell as seen under an electron microscope.

(a)

Identify structures A to D. A ................................................................................ B ................................................................................ C ................................................................................ D ................................................................................(4)

(b)

Describe how a sample of whole chloroplasts could be obtained from leaf tissue. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3) (Total 7 marks)

Seven Kings High School

1

2. B C D (b)

(a)

\A

Cell wall

Cell membrane Ribosomes / rough endoplasmic reticulum Chloroplast 4

Homogenise; in ice cold; isotomic solution; then centrifuge

any three

3[7]

3.

(a) Complete each box in the table, which compares a prokaryotic and a eukaryotic cell, with a tick if the statement is correct or a cross if it is incorrect. Prokaryotic cell Contains ribosomes attached to the endoplasmic reticulum Genetic material consists of linear chromosomes Diameter of the cell is 1 m (b) A student was asked to describe the structure of two organelles which were present on an electron micrograph. From the descriptions below, identify the organelles and, in each case, name the internal structures underlined. (i) This organelle was disc shaped and had an outer envelope of two membranes. Within it was a series of further membranes which crossed the organelle like railway tracks. At intervals the membranes appeared to repeatedly double back on themselves to form stack-like structures. In the spaces between the membranes was a granular material. Organelle............................................................................................................ Internal structures .............................................................................................(2)

Eukaryotic cell

(ii)

This organelle had a round shape and had an outer envelope of two membranes, which was perforated in places. Within it were thin strands which did not appear to have the width or organisation of membranes. One large round structure was visible internally. Organelle............................................................................................................ Internal structures .............................................................................................(2) (Total 6 marks)


2

4.

(a) X X X (All symbols in a column need to be correct for a mark) (b) (ii) (i) chloroplast; grana / thylakoids; 2 nucleus; chromosomes / chromatin / chromatids; 2[6]

2

5.

(a)

(i)

Give two ways in which active transport differs from diffusion.

1.......................................................................................................................... ............................................................................................................................ 2......................................................................................................................... ...........................................................................................................................(2)

(ii)

Sodium ions move from the surrounding solution where they are at a low concentration into the cytoplasm of a cell where they are at a higher concentration. Cyanide ions stop the functioning of the electron carrier system in mitochondria. Use these two pieces of information to explain how the addition of cyanide ions would affect the uptake of sodium ions by a cell. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


3

(b)

Two major routes by which molecules are thought to cross membranes are: 1. 2. by dissolving in the phospholipid layer. by passing through channels in protein molecules.

These routes are illustrated in the diagram. The graphs show the rate of entry of molecules into the cell by these two routes in relation to the external concentration of the molecules. O u ts id e In s id e A R a te of e n tr y in to c e ll

X

E x te rn a l c o n c e n tra tio n M o le c u le s d is s o lv e in p h o s p h o lip id la y e r O u ts id e In s id e B R a te of e n tr y in to c e ll

X

E x te rn a l c o n c e n tra tio n M o le c u le s p a s s th ro u g h p ro te in c h a n n e ls (i) Explain why curves are similar up to point X ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)


4

(ii)

Explain what causes the shapes of the curves to differ after point X. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1) (Total 6 marks)

6. (ii)

(a) (i) ATP used; movement is against a concentration gradient; stops / less movement of ions; movement of ions needs ATP; ATP / production linked to respiration / electron carrier system;

2

max. 2

(b)

(i) greater concentration difference / increased gradient therefore more molecules move in external concentration limiting factor / increased concentration increases rate; (ii) (limit imposed in situation B by) limited number of molecules can move through the pores in unit time / pores are full / number of pores is limiting factor;

1

1[6]

7.

Cell organelles can be separated by centrifuging a cell extract in a sucrose density gradient. The organelles settle at the level in the sucrose solution which has the same density as their own. Some animal cells were broken open and the cell extract centrifuged in a sucrose density gradient. Three distinct fractions were obtained, A, B and C, as shown in the diagram.

In c re a s in g d e n s ity o f su c ro se s o lu tio n

A B C


5

One fraction contained nuclei, one contained ribosomes and a third contained mitochondria. Complete the table by identifying the organelle in each fraction and describing one function of each organelle. Fraction A Organelle Function

B

C(Total 4 marks)

8. A B C Ribosomes Mitochondria Nuclei Making proteins/ assembling amino acid chain/ protein synthesis Respiration/ formation of ATP/ Krebs cycle/ Oxidative phosphorylation; DNA/RNA synthesis/ controls protein production/ cell activity/ carries genetic information; 1 mark 1 mark 1 mark

1 mark[4]


6

9.

The diagram shows an animal cell.

20m (a) The scale bar on the diagram represents a length of 20 pm. Use this to calculate the magnification of this diagram. Show your working.

Magnification........................(2)

(b)

Use a guideline and the appropriate letter to show, on the diagram, a site in this cell where (i) (ii) the enzymes controlling glycolysis are found (A);(1)

molecules of enzymes are synthesised (B).(1)


7

(c)

The number of cristae in the mitochondria of a cell with a high metabolic activity is greater than the number in a cell with lower metabolic activity. Explain why. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 6 marks)

10. (b)

(a) Two marks for correct answer of 3000; One mark if answer obtained by dividing actual length by 20 m; (i) (ii) (c) Letter A indicating cytoplasm; Letter B indicating ribosome;

2 1 1

Cristae are site of ATP synthesis/oxidative phosphorylation; by electron/hydrogen carriers; Metabolism requires energy input/ATP;

max 2[6]

11.

The diagram shows the structure of part of a cell as seen using an electron microscope.

C B

A

E

D

(a)

Name two features shown in the diagram which indicate that this is a eukaryotic, rather than a prokaryotic cell. 1 .................................................................................................................................. 2 ..................................................................................................................................(2)


8

(b)

At which of the lettered sites, A to E, would you expect each of the following to be produced in the greatest amount? (i) (ii) (iii) proteins carbon dioxide mRNA _______________ _______________ _______________(3)

(c)

This cell was supplied with a radioactive isotope which specifically labels thymine. In which part of the cell would this label be most concentrated?(1) (Total 6 marks)

12.

(a) presence of nucleus / nuclear membrane; presence of named organelle (not ribosome) (Features must be named - disallow letters) (b) (ii) (iii) (c) (i) A/nucleus; C/ribosome; 3 D/mitochondnon;

2

A/Nucleus; 1[6]

13.

The diagram shows a mitochondrion. R ib o s o m e s D N A lo o p

X

(a)

(i)

Name the part labelled X.(1)

........................................................................................................................... (ii) A human liver cell contains several hundred mitochondria. A cell from a plant root has only a small number. Suggest an explanation for this difference. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)Seven Kings High School 9

(iii)

Mitochondria contain some DNA and ribosomes. Suggest the function of these. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(b)

Mitochondria may be separated from homogenised sells by differential centrifugation. During this process the cells must be kept in an isotonic solution. Explain why. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(c)

Ribosomes in bacterial cells differ from those in the cytoplasm of eukaryotic cells. When centrifuged at high speed, the eukaryotic cell ribosomes sediment more rapidly than bacterial ribosomes. Explain what this tells you about the difference between bacterial and eukaryotic ribosomes ..................................................................................................................................... .....................................................................................................................................(1) (Total 8 marks)

14. (ii)

(a)

(i)

Crista 1

(Mitochondria) provide energy / ATP; liver cells have high energy requirement for metabolism- reactions specific liver function, eg. glycogen synthesis or deamination (not just: active transport/ growth) Principle - protein synthesis; Function of protein in mitochondria - e.g. synthesis of (respiratory) enzymes / growth / repair / replication. or: DNA has genetic information; ribosomes produce proteins / allows replication of mitochondria.

2

(iii)

2

(b)

Maintain concentrations/water potential same inside & outside (cells / mitochondria) / prevent osmosis; Prevent bursting / shrinkage of mitochondria/organelles (not cells)

2


10

(c)

Eukaryotic ribosomes denser/ heavier (not just larger).

1[8]

15.

The diagram shows a cross-section of a typical red blood cell. Red blood cells can carry both oxygen and carbon dioxide. Each cell has a thinner central area as shown in the diagram.

(a)

Explain one advantage of the shape of red blood cells. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(b)

Red blood cells do not have a nucleus or rough endoplasmic reticulum. Give one function that red blood cells are therefore unable to carry out. .....................................................................................................................................(1)

(c)

In an experiment, the phospholipids were extracted from the surface membrane of a single red blood cell. They were placed on the surface of water and allowed to spread out. (i) Using ### to represent a single phospholipid molecule, draw on the diagram how you would expect ten phospholipid molecules to be arranged on the water surface.

C o n ta in e r

W a te r(2)


11

(ii)

The area of water covered by the phospholipid molecules was calculated. This area was given an arbitrary value of 1. The surface area of an intact red blood cell was measured on the same scale. What would you expect the arbitrary value of the red blood cell surface area to be? Explain your answer. Arbitrary value ............................................. Explanation ...................................................................................................... ..........................................................................................................................(2)

16.

(a) Faster gas exchange / diffusion; Large / big / increased surface area / shorter pathway for gas exchange / Hb not too far from membrane; (NOT more / bigger / greater / easier / more efficient) OR Increases flexibility; To pass through capillaries; (b) (c) Protein synthesis / Cell division / Mitosis; (NOT Meiosis) (i) Monolayer; Tails up / heads in water; (NOT completely submerged or floating in air) (ii) 0.5 / ; Phospholipids are arranged in a bilayer;

2 1

2 2[7]


12

17.

The diagram shows part of an animal cell as seen through an electron microscope.

X

A

B

Y C (a) Name organelles A, B and C. A .................................................................... B .................................................................... C ....................................................................(3)


13

(b)

Describe the function of organelle X. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(c)

The actual diameter of organelle Y is 0.5 pm. m. Calculate the magnification of the diagram. Show your working.

Magnification .....................................(2) (Total 7 marks)

18.

(a)

A mitochondrion;

1

B nucleus; 1 C endoplasmic reticulum rough ER / ER; (reject smooth ER, ribosomes neutral ) (b) ref to proteins / glycoproteins / enzymes / lipids / hormones; ref to fate of proteins / glycoproteins / enzymes / lipids / hormones; (linked to previous mark e.g. vesicles / exocytosis / packaging / synthesis / processing modifying) If neither of these: reference to vesicles / exocytosis / packaging / synthesis processing /modifying gains 1 mark (Max 1 mark if incorrect function given) (c) 30 000 - 34 000 gains 2 marks;; If neither of these: evidence of sensible measured diameter actual (0.0005 mm) gains 1 mark[7]

1

2 2


14

19.

(a) Complete the table to give two ways in which active transport differs from diffusion. Active transport 1 ................................................... ................................................... 2 ................................................... ................................................... Diffusion ................................................... ................................................... ................................................... ...................................................(2)

(b)

The diagram represents a phospholipid. A B C

(i)

Name the parts of the molecule A, B and C. A ................................................................................ B ................................................................................ C ................................................................................(3)

(ii)

Describe the role of phospholipids in controlling the passage of molecules through the cell membrane. ........................................................................................................................... ...........................................................................................................................(1)


15

(c)

(i)

The diagrams show the water potentials ( ) of three cells in contact with one another. Use arrows to show the net direction of water movement between all three cells.

= 230 kPa

= 214 kPa

= 135 kPa(1)

(ii)

If solute were added to a cell, what effect would this have on the water potential within the cell? ...........................................................................................................................(1) (Total 8 marks)

20.

(a)

Max 2 Active transport may move substances against concentration gradient; Requires ATP / energy; Requires membrane proteins / carriers; Diffusion Substances moved down concentration gradient; Does not require ATP / energy; Does not (necessarily) require membrane proteins / carriers;

(b) B C (ii)

(i) Glycerol Fatty acid

A

Phosphoric acid / phosphate 3

Prevent passage of water-soluble molecules / ions / named molecules OR allow passage of lipid-soluble molecules OR retain water-soluble substances (i) All arrows in correct direction 1 More negative

1 1[8]

(c) (ii)

21.

The diagram shows the fluid mosaic model of cell membrane structure.

P ro te in m o le c u le s


16

(a)

Suggest why this model is known as fluid mosaic. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2)

(b)

Give two functions of the protein molecules in the cell membrane. 1. ................................................................................................................................ .................................................................................................................................... 2. ................................................................................................................................ ....................................................................................................................................(2)

(c)

Explain how hydrophobic areas in the membrane are important to its function. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2)

(d)

(i) The diagram shows the water potentials ( ) of three cells in contact with one another. Use arrows to show the net direction of water movement between all three cells.

= 230 kPa

= 214 kPa

= 135 kPa (1)

(ii)

If solute were added to a cell what effect would this have on the water potential within that cell ? ...........................................................................................................................(1) (Total 8 marks)

22.

(a) Molecules within the membrane able to move; mixture of phospholipid and protein / arrangement of protein;

217


(b)

Carriers / reference to transport role; receptors / antigens / reference to recognition; enzyme; max. 2 Selectivity; stops the loss of water soluble / polar molecules from inside the cell; e.g. enzyme; OR converse allows movement of lipid soluble / non polar molecules; e.g. vitamins; (i) (ii) Arrows from high to low water potential; Water potential is lower / more negative ;

(c)

max. 2 1 1[8]

(d)

23.

The roots of two groups of pea plants were placed in solutions containing radioactive potassium ions. For the experimental plants a respiratory inhibitor was added to the solution. The control plants had no respiratory inhibitor added. At regular intervals the solutions surrounding the roots were tested for radioactive potassium ions. The table shows the results of this investigation. Time from placing roots in solution / minutes 0 15 30 60 120 240 (a) Concentration of radioactive potassium ions in the solutions surrounding the roots / arbitrary units Experimental plants 7.5 6.6 6.4 6.3 6.3 6.3 Control plants 7.5 3.3 2.9 2.4 1.2 0.6

(i) The rate of uptake of potassium ions by the experimental plants in the first 15 minutes was 0.06 units per minute. Calculate the rate of uptake of potassium ions by the control plants over the same time period.

Rate of uptake by control plants = ..................................................................(1)


18

(ii)

Suggest an explanation for the difference between the rates of uptake by the experimental and control plants in the first 15 minutes. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iii)

The rate of potassium ion uptake by the control plants in the first hour was faster than in the second hour. Suggest why. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(b)

At the end of the investigation sections were cut across the stems of the pea plants and the amount of radioactivity in each tissue was measured. The diagram shows a section across the stem of a pea plant.

(i)

Give one feature by which this section can be recognised as a stem. ........................................................................................................................... ...........................................................................................................................(1)


19

(ii)

Using a guideline, label and name the tissue in which you would expect to find the greatest amount of radioactivity.(1) (Total 7 marks)

24. (ii)

(a)

(i)

0.28; 1

uptake by active transport; use energy / ATP from respiration; amount absorbed by experimental plants is due to diffusion; concentration falls so rate of diffusion falls; active transport involves carrier/membrane proteins; more potassium ions so more chance of collisions with carriers (i) cylindrical arrangement of vascular bundles/in vascular bundles correct label to xylem;

max 2

(iii)

max 2 1 1[7]

(b) (ii)

25.

Protein molecules in the cell surface membrane are involved in the active transport of glucose molecules into the cell. (a) The graph shows how the uptake of glucose by red blood cells varies with the glucose concentration of the surrounding medium.

R a te o f u p ta k e g lu c o s e

C o n c e n tra tio n o f g lu c o s e in s u rro u n d in g m e d iu m


20

Explain the shape of the curve. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3)

(b)

The table shows the results of an investigation into differences in the rates of uptake of different sugars by red blood cells. Sugar Glucose Galactose Xylose (i) Relative rate of uptake 100 13 7

Give one factor, other than the concentration of sugar in the surrounding medium, which should have been standardised in this investigation. Describe and explain how variation in this factor would affect the rate of uptake.

Factor........................................................................................................................... Explanation.................................................................................................................. ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(ii)

Use your knowledge of protein molecules in cell surface membranes to suggest why the rate of uptake of these sugars differs. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2) (Total 7 marks)

26.

(a) In first part of the curve concentration of glucose in surrounding medium limiting/rate of uptake dependent on glucose; More glucose molecules, more protein carriers occupied; In second part number of proteins/carriers limiting/working at full capacity; All carriers occupied;

max 321


(b)

(i) Temperature; Would increase the rate of movement/kinetic energy of molecules/ gives more chance of colliding with carrier; or Temperature/pH; Denature protein carriers; or Number of red blood cells; More uptake because greater surface area/more carriers; or Oxygen; Linked to ATP/energy/respiration and active transport; (ii) Concept of shape of different molecules/receptor site; Concept of fit determining specificity; More carriers for glucose;

2

max 2[7]

27.

Read the following passage. Most fruits are green when unripe because they contain a number of chlorophyll pigments. Some varieties of apple remain green when fully ripe, some turn yellow and others go red. The yellowing of apples is mainly due to the disappearance of the chlorophyll allowing other pigments called carotenoids to show their colour. These carotenoids are located in the same organelles as the chlorophyll molecules. The red colour, however, is due to the formation of a new pigment called anthocyanin. Unlike carotenoids and chlorophyll which are located in organelles in the cytoplasm, anthocyanin is dissolved in the cell sap inside the vacuole of the cell. It can be extracted by boiling a piece of apple skin. As the water boils, the red colour of the skin starts to disappear because the pigment is being released from the cells into the water in which the skin is boiled. This can be demonstrated by adding a few drops of acid to the water. It will immediately turn red because anthocyanin turns red in the presence of an acid. More information can be obtained by watching the process more closely. If another piece of skin is dropped into boiling water, it will be seen to turn briefly from red to purple before the colour fades away. Since alkalis turn anthocyanin purple, the anthocyanin must have momentarily encountered alkaline cytoplasm during breakdown of the cell. This and similar observations show that different parts of the cell have different characteristics. In a living cell there must be some form of barrier between these different parts. This barrier will allow certain molecules to pass through but not others.


22

(a)

Suggest how you could use chromatography to separate and identify chlorophyll pigments present in the skin of different varieties of apple. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(b)

Using the information in the passage, complete the diagram of the cell from the skin of an apple to show (i) (ii) the location of the chlorophylls, carotenoids and anthocyanins; those parts of the cell that are acidic and those parts that are alkaline.

C e ll w a ll V a c u o le

(2)


23

(c)

Suggest an explanation for each of the following observations. (i) The volume of the vacuole increases if the cell is placed in distilled water. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

(ii)

Enzymes which are normally found in cell sap would be unable to function if they were in the cytoplasm. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3) (Total 12 marks)

28.

(a) Make extract of pigments by grinding; Load onto chromatography paper with reference to position; Small droplets/number of drops to concentrate; Run with paper dipped into solvent; Mark solvent front; Calculate Rf value/use standards; (b) Diagram showing (i) (ii) carotenoids and chlorophyll in cytoplasm and anthocyanin in cell vacuole; Vacuole acid and cytoplasm alkaline;

max 4 1 1


24

(c)

(i) Concentration of vacuole contents/solute greater than surrounding medium; Vacuole has lower/more negative water potential; Vacuole surrounded by partially permeable membrane; Water enters by osmosis; max 3 (ii) Difference in pH; Affects tertiary structure of/denatures enzyme/charges around active site/ shape of active site; Substrate will no longer fit/bind;

3[12]

29.

The diagram shows how an experiment was set up to investigate absorption by active transport and diffusion in the small intestine. A piece of small intestine was turned inside out, so that the surface with the villi was on the outside. The ends of the intestine were tied to form a sac. The sac was placed in an oxygenated, buffered solution at 37C. Substances which were transported through the villi in the normal direction became concentrated within the sac. m u c o s a l s u rfa c e o u tsid e

in te stin a l s a c

(a)

Suggest why, in order to investigate active transport, the solution in which the sac was placed was (i) oxygenated; .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (ii) buffered. .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................(3)


25

(b)

Using this technique, the following data were obtained about the absorption of sugars from small intestine which had been treated with a respiratory inhibitor and from untreated small intestine.

R e la tiv e r a te s o f a b s o r p tio n f r o m s m a ll in te s tin e S ugar tre a te d w ith re s p ira to r y in h ib ito r 30 31 u n tre a te d 100 30

G lu c o s e F ru c to s e

Explain what the table suggests about the ways in which glucose and fructose are absorbed from the small intestine. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4) (Total 7 marks)

30. (ii) (b)

(a) (i) to allow aerobic respiration/respiration in mitochondria; providing ATP; to prevent denaturation of / provide optimum pH for enzymes/ protein carriers 3

Glucose - active transport; absorption much less in poisoned gut; Fructose - diffusion; absorption rates similar in normal and poisoned gut;

4[7]


26

31.

The table shows the relative rate of diffusion of oxygen through three different media. Medium Air Water Muscle tissue (a) Relative rate of diffusion 11.0 3.4 105 1.4 105

The measurements in the table were all made at the same temperature. Explain how an increase in temperature affects the rate of diffusion. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2)

(b)

The lung alveoli have a moist surface. (i) It is sometimes suggested that this moist surface makes gas exchange more efficient. Use the information in the table to explain why this suggestion is incorrect. ............................................................................................................................ ............................................................................................................................(1)

(ii)

Explain how diffusion results in the alveoli having a moist surface. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................(2)


27

(c)

The diagram shows the position of the tracheoles which supply oxygen to the muscles of an insect.

T ra c h e o le s

M u s c le

This insect has more than 1.5 million tracheoles. The distance between the ends of the tracheoles in the muscle is approximately 4 pm. Explain how these features allow efficient oxygen supply. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(3) (Total 8 marks)

32.

(a) Molecules will have more (kinetic) energy; Move faster; Reject references to vibrating in this context (b) (ii) (i) Oxygen diffuses faster/has a higher rate of diffusion in air than in water; Alveolar epithelium/surface is permeable to small molecules; Water is a small molecule; Higher concentration of water in cell/blood than outside; Water diffuses from blood/cells into alveoli;

2 1

max 2


28

(c)

Large number gives large (total) surface area; For diffusion; Short distance between tracheoles gives short pathway; Movement/diffusion through muscle is slow; Reject references to muscle simply being close to tracheoles. Must convey idea of short pathway to gain credit for third point.

3[8]

33.

(a)

Give two differences between active transport and facilitated diffusion.

1 .................................................................................................................................. ..................................................................................................................................... 2 .................................................................................................................................. .....................................................................................................................................(2)

(b)

Describe how ions are transported through a cell surface membrane by active transport. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(c)

The table shows the concentration of three ions inside and outside a cell of an alga that lives in pond water. Ion Chloride Potassium Sodium (i) Concentration of ion in cytoplasm / mmol dm3 58.0 93.0 51.0 Concentration of ion in pond water / mmol dm3 1.3 0.1 1.0

By how many times have the potassium ions been concentrated in the cytoplasm compared with the pond water? ...........................................................................................................................(1)


29

(ii)

The ions enter the cell of the alga by active transport. What does the information in the table suggest about the active transport of these three ions through the cell surface membrane? Explain your answer. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2) (Total 7 marks)

34. (b)

(a) Active transport requires energy / uses ATP; moves substances against concentration gradient. Carrier protein (in membrane); (accept: channel/pore/intrinsic proteins; reject: extrinsic protein, or just protein); ion transported by change of shape / flipping of carrier protein; energy used to attach ion to carrier protein /.change shape.( not just ATP provides energy) (i) (ii) 930 1 Carrier proteins different or specific / ref to potassium (or other) carrier / ions moved independently; more potassium than other ions transported; different degrees of concentration of ions. (not just moved against concentration gradient)

2

max 2

(c)

max 2[7]

35.

Peeled potatoes were cut into two sizes of cubes - 1cm3 (1cm x 1cm x 1cm) and 27cm3 (3cm x 3cm x 3cm). After weighing, twenty-seven of the 1cm3 cubes were placed in one beaker of distilled water, and one 27cm3 cube was placed in another beaker. One hour later the cubes were removed and their surfaces carefully dried. They were then reweighed. The results are shown in the table. Small cubes Volume of cube / cm3 Surface area of cube / cm2 Number of cubes in beaker Surface area : volume ratio of one cube Total mass of cubes at start / g Total mass after 1 hour in water / g Increase in mass / g Percentage increase in mass 52.75 55.31 2.56 52.97 53.55 0.58 1 6 27 Large cube 27 54 1


30

(a)

Complete the table to show (i) (ii) the surface area : volume ratio for each size of cube; the percentage increase in mass after 1 hour in water.(2)

(b)

(i)

Why did the experimenter use twenty-seven small cubes?

........................................................................................................................... ...........................................................................................................................(1)

(ii)

Explain, in terms of water potential, why the potato cubes increased in mass when placed in the distilled water. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iii)

The percentage increase in mass of the smaller cubes was greater than the percentage increase in mass of the large cube. Explain the difference. ........................................................................................................................... ...........................................................................................................................(1) (Total 6 marks)

36. (ii) (b) (ii) (iii)

(a) (i) 6 : 1 and 2 : 1 (Accept 54:27;reject 6 and 2) 4.85 / 4.9 and 1.09 / 1.1 (i) Same volume of potato / only surface area different Potato (cubes) have lower/more negative water potential; so water enters cubes (by osmosis). Larger surface area (: volume ratio) of smaller cubes (for osmosis).

1 1 1 2 1[6]


31

37.

(a)

Describe the fluid-mosaic structure of a cell surface membrane.

.................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(5)

(b)

Explain each of the following processes by which substances pass through a cell surface membrane. (i) diffusion of oxygen ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(5)

(ii)

facilitated diffusion of glucose ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................

(iii)

active transport of sodium ions ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(9) (Total 14 marks)


32

38.

(a) Phospholipids and proteins; Phospholipid bilayer; Arrangement of phospholipid molecules Tails to tails; Floating(protein) molecules / molecules can move in membrane; Intrinsic proteins extend through bilayer; Extrinsic proteins in outer layer only; (Ref. to intrinsic and extrinsic, unqualified, gains 1 mark); Detail of channel proteins / protein shapes / glycoproteins; Presence of cholesterol. (b) (i) Random movement of oxygen molecules; (Net) movement from high to lower concentration; Molecules can pass between phospholipid molecules / through bilayer; Rate dependent on concentration gradient. (ii) Movement from high to lower concentration; Use of carrier / channel / intrinsic protein; Proteins specific (to glucose); Changes shape of protein and passes through channel / membrane; No energy/ATP needed. Movement against concentration gradient; Use of carrier/channel/intrinsic/pump proteins; Protein specific (to ion); Energy / ATP required; Energy used to change shape of proteins / attach ion to protein; Ions moved through membrane as proteins change shape / position.

5

(iii)

max 9[14]

QWC Award 1 or 0 according to criteria

39.

(a)

Give two ways in which osmosis differs from facilitated diffusion.

1 .................................................................................................................................. 2 ..................................................................................................................................(2)

(b)

Jam contains a high concentration of sugar. Explain why bacteria that cause decay do not grow in jam. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3) (Total 5 marks)


33

40.

(a) Osmosis transports water; Proteins / carrier molecules not used / occurs through phospholipid bilayer; (b) Jam has a lower (more ve) water potential than the bacterial cytoplasm; Water leaves the bacteria; Effect (of water loss) on bacteria e.g. killed / chemical reactions cannot occur;

2

3[5]

41.

(a)

Explain the biological importance of water for living organisms.

.................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(5)

(b)

Cylinders of potato were cut using a cork borer. Each cylinder was placed into one of a range of sucrose solutions of different concentrations. The cylinders were left for 6 hours and then removed from the solutions. The mass of each cylinder was recorded before and after immersion. The graph shows the results of this investigation. +10 In c re a se P e rc e n ta g e c h a n g e in m ass D e c re a se 10 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 .0 C o n c e n tra tio n o f su cro se / m o l d m

3


34

(i)

Explain why the change in mass was given as a percentage change. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(ii)

Explain the shape of the curve as the concentration of sucrose decreases from 0.3 mol dm3 to 0.1 mol dm3. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(4)

(iii)

What concentration of sucrose solution is equivalent to the mean water potential of the potato cells? Explain your answer. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(c)

The diagram represents three plant cells and shows the water potential of two of these cells. The arrows show the direction of water movement between these three cells. A 510 kPa B C 550 kPa


35

Suggest the range of possible values for the water potential of cell B. Explain your answer fully. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2) (Total 15 marks)

42.

(a) Chemical reactions occur in solution; Allows transport/secretion/excretion/dispersal of substances; High specific heat capacity (e.w.) so minimises temperature fluctuations; High latent heat of evaporation so cooling effect of sweat/transpiration; Provides internal support e.g. hydrostatic skeleton/amniotic fluid/turgidity; Provides external support e.g. aquatic organisms; High surface tension e.g. pond skaters, cohesion-tension; Transparent e.g. allows light penetration for aquatic organisms; Less dense when frozen so ice floats and insulates; Reactant e.g. hydrolysis/photosynthesis; Lubricant e.g. synovial fluid/pleural fluid/mucus; (b) (ii) (i) Initial mass of cylinders not identiical; To be able to directly compare the results; From 0.3 mol dm3 to 0.1 mol dm3 water moves into potato cells; By osmosis; So mass increases; More water has entered potato cells 0.1 mol dm3 / converse; 0.35; No mass change/no net osmosis/ volume of water in = volume of water out;

5 2

4

(iii)

2

(c)

Range from 511 to 549 kPa; Reason e.g. Water moves from A to B, so must be lower than 510 and Water moves from B to C, so must be higher than 550;

2[15]

43.

(a)

Describe osmosis in terms of water potential.

..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3)


36

(b)

In an experiment, cylinders cut from a potato were placed in sucrose solutions of different concentrations. The cylinders were measured before and after immersion in sucrose solution. The graph shows the effect of the sucrose solutions on the length of the potato cylinders. 1 .3 1 .2 R a tio o f in itia l le n g th to fin a l 1 .1 le n g th o f p o ta to c y lin d e r s 1 .0 0 .9 0 .8 0 .1 0 .2 0 .3 0 .4 C o n c e n tra tio n o f s u c ro s e s o lu tio n / m o l d m 0 .53

(i)

The initial length of the potato cylinder in 0.1 mol dm3 sucrose solution was 5.0 cm. Calculate the final length of this cylinder. Show your working.

Final length ............................. cm(2)

(ii)

On the graph 1 2 mark with a T a point on the curve where the potato cells are turgid; mark with a W a point on the curve where the potato cells have the same water potential as the sucrose solution.(2) (Total 7 marks)

44.

(a)

diffusion / movement of water; 3

through a partially-permeable membrane; (from less negative ) to more negative / (from higher ) to lower ; (b)

(i) 5.55 cm gains 2 marks; (allow 5.5 or 5.6 only if supported by correct working) else evidence of 5.0 0.9 gains 1 mark 2


37

(ii)

T anywhere to left of 0.3 M; W at 0.3 M; 1

1[7]

45.

The diagrams show part of the wall of the small intestine and part of an epithelial cell.

V illu s

E p ith e liu m B lo o d c a p illa r y L a c te a l M ic r o v illu s

C ry p t o f L ie b e rk h n

M ito c h o n d rio n

P a rt o f e p ith e lia l c e ll

M u s c le la y e r (a) Describe one function of the muscle layer in the wall of the small intestine. ..................................................................................................................................... .....................................................................................................................................(1)

(b)

Complete the table about enzyme action in the small intestine. Enzyme Amylase ........................................... Lipase Peptides ........................................... Substrate ........................................... Maltose Dipeptides ........................................... and ....................................(4)

Products


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(c)

Describe the function in the small intestine of: (i) the blood capillaries, ........................................................................................................................... ...........................................................................................................................(1)

(ii)

the lacteals. ........................................................................................................................... ...........................................................................................................................(1)

(d)

Explain how the following features of the epithelial cells increase the rate of absorption of digested foods. (i) Microvilli ........................................................................................................................... ...........................................................................................................................(1)

(ii)

Large numbers of mitochondria ........................................................................................................................... ...........................................................................................................................(1) (Total 9 marks)

46. (b)

(a)

e.g. moves along contents of gut / peristalsis

1

Starch; Exopeptidase; Lipids / fats / triglycerides; Fatty acids and glycerol; (i) (ii) (i) (ii) Absorption of monosaccharides / named or amino acids Increased surface area for absorption Absorption of lipid constituents Provide energy for active uptake

4 1 1 1 1[9]

(c) (d)


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3.1.3 Cell and Transport

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Transcript of 3.1.3 Cell and Transport