UNIT ONE CELL BIOLOGY

NATIONAL 5 BIOLOGY

Key Area 1

Cell structure

Starter Activity:

Answer the following question in your jotter.

1. Name three types of cells in your body.

2. Approximately how many cells are there in the human body?

3. How many cells are there in an Amoeba?

Answers

1. Blood, nerve, muscle, bone, brain, liver, skin etc

2. 100 trillion (100 million million)

3. One

Plant Cell structure

Learning Intention: • Investigate the structure of plant cells.

Success Criteria: • Identify the main structures found in a typical

plant cell • State the functions of these structures • Carry out calculations concerning cell size and • cell growth

What is a cell?

• The following video clips will introduce you to the basic features of cells.

What is a cell? (BBC) Plant and animal cell structures (BBC) What is a cell? (Glow)

Examining Onion Cells Aim: To observe and draw onion cells using a

microscope.

Equipment:

• Glass slide

• Cover slip

• Onion skin

• Iodine stain

• Microscope

• Lamp

• Collect a thin piece of onion skin.

• Spread the skin on a slide. The skin must not overlap.

• Stain the cells by adding 2 drops of iodine stain.

• Place a cover slip over the skin. Use a pencil or mounted needle to lower the cover slip gently so the air is pushed out.

• Examine the cells under low then medium power. You should be able to see lots of cells arranged like bricks in a wall.

• Adjust the microscope to a higher power.

• Draw exactly what you see through the “field of view” using a pencil.

• Label as many structures as you can see.

Method:

Onion cells in iodine

cytoplasm

cell wall

nucleus

Examining Pondweed Cells Aim: To observe and draw pondweed cells using a

microscope.

Equipment:

• Glass slide

• Cover slip

• Small leaf from Elodea or Cabomba

• Microscope

• Lamp

• Collect a small leaf of pondweed.

• Place it in a drop of water on a slide.

• Use a pencil or mounted needle to lower the cover slip gently so the air is pushed out.

• Examine the cells under low then medium power. You should be able to see lots of cells arranged like bricks in a wall. Look for green chloroplasts inside the cells.

• Adjust the microscope to a higher power.

• Draw exactly what you see through the “field of view” using a pencil.

• Label as many structures as you can see.

• Return the slide and pack your microscope away carefully.

Method:

Pondweed cells

• These cells are from a pondweed called Elodea.

• These cells are from a pondweed called Cabomba.

What two plant cell structures can you see in the pictures?

Other plant cells • These cells are from a

beetroot. The red dye makes it hard to see the nucleus but if you look closely you will see them.

•These are the cells in the stem of a plant. Some of these cells carry water upwards to the leaves, while others carry sugars from the leaves to other parts of the plant.

Starter Activity:

Starter Activity:

C

Animal Cell structure

Learning Intention: • Re-cap the structures of animal and plant

cells.

Success Criteria: • Identify the main structures found in a typical

animal cell and plant cell • State the functions of these structures • Carry out calculations concerning cell size and • cell growth

Examining Cheek Cells Aim:

To make a slide of cheek cells and draw them.

Equipment:

• Glass slide

• Cover slip

• Cotton bud

• Methylene blue stain

• Microscope and lamp

• Paper towel

• Rub the cotton bud over the inside of your cheek to remove some of the cells.

• Wipe the cotton bud over the surface of a glass slide.

• Place the cotton bud in disinfectant.

• Stain the cells with 2 drops of methylene blue stain.

• Remove some of the stain using paper towel.

• Use a mounted needle to lower the cover slip so the air is pushed out.

• Draw the cells and label the structures.

• Once you have finished, place the slide and cover slip in disinfectant.

• Pack away your microscope carefully.

Method:

Cheek cells in methylene blue

cytoplasm

cell membrane

nucleus

A Typical Plant Cell

cytoplasm green chloroplast

cell wall

nucleus vacuole cell membrane

Cell size calculation

• The field of view in this picture is 0.5mm wide.

• Calculate the width of one cell (clue: count the number of cells from one side to the other across the line shown).

• Now estimate the cell length.

Typical Animal Cell

nucleus

cell membrane cytoplasm

Cheek cell size calculation

• The field of view in this picture is 200 µm. (1mm=1000 µm)

• Estimate the size of these cheek cells. (Clue : how many would fit across the line?)

200 µm

Comparison of Cell Types Copy the table and put a tick or a cross in each

box. (Answers on next slide)

Structure Plant Cell Animal Cell

cell wall

cell membrane

nucleus

cytoplasm

chloroplasts

vacuole

Comparison of Cell Types

Structure Plant Cell Animal Cell

cell wall yes no

cell membrane yes yes

nucleus yes yes

cytoplasm yes yes

chloroplasts yes no

vacuole yes no

Functions of cell structures

• Each cell structure has a different job within the cell. This is called its function.

• Copy the table on the next slide which summarises the functions of the main structures in plant and animal cells.

Magnified cell structures (BBC)

Structure Description Function

Nucleus Large round structure containing

genetic material Controls cell activities

Cell Membrane Very thin layer surrounds the

cytoplasm

Controls the passage of

substances into and out of the

cell

Cytoplasm Fluid, jelly-like material Site of biochemical reactions

Cell Wall Outer layer made of mesh of

cellulose fibres

Provides plant cells with

support

Vacuole Fluid-filled sac in the cytoplasm

Stores water and minerals and

provides extra support for

plant

Chloroplasts Disk-like structures containing

green chlorophyll

Trap light energy for making

food by photosynthesis

Test Your Knowledge

Animal and plant cells

Learning Intention: To review cell structure Success Criteria: •Be able to name the structures common to animal and plant cells which are visible under a light microscope. •Be able to name the structures found only in plant cells which are visible under a light microscope. •Be able to label these on a diagram and state their functions. •Be able to calculate cell size from a picture.

Starter Activity:

Starter Activity:

E

C

Cell ultrastructure

Learning Intention: • To investigate more detailed structures in plant

and animal cells Success Criteria: • Identify cell structures that can be seen at a

higher magnification using an electron microscope

• Be able to label these on a diagram and state their functions

The History of Microscopes

The history of microscopes (Glow)

Electron microscopes

• Light microscopes like the ones in the lab can magnify up to 400 times. Some light microscopes can magnify up to 1000 times.

• Electron microscopes use a beam of electrons instead of light. Some can magnify up to 2 million times.

• This allows us to see other smaller structures inside cells.

Light microscope v electron microscope

• Image of pollen grains under the light microscope

• Image of pollen grains under the electron microscope

High magnification images of pollen using electron microscope

• Many new structures can be seen in the cytoplasm that are not seen using a light microscope.

Animal cell under electron microscope

Plant cells under electron microscope

What is a cell? (Glow)

Cell ultrastructure

• In the cytoplasm of plant and animal cells there are structures called mitochondria.

• They are the site of aerobic respiration.

Mitochondria

Nucleus • The nucleus is made up of many chromosomes. • These are not normally seen very clearly as they

wound up around each other like a ball of string. • They are made of DNA and are the genetic

material of the cell. • How many chromosomes are in each human cell?

Ribosomes

• Even smaller structures can be seen in the cytoplasm called ribosomes.

• They are the site of protein synthesis in plant, animal and bacterial cells.

Ribosomes • Ribosomes

can be found free floating, or attached to membranes in the cell.

(free floating)

(attached to a membrane)

Cell membrane

• The cell membrane can be seen in more detail when using the electron microscope.

Plant cell walls

When viewed with an electron microscope, the cell wall of plant cells can be seen to be made up of fibres of a material called cellulose. Small molecules can easily pass through the spaces between the fibres.

Cellulose fibres

Cell ultrastructure Label the handout

diagram using

these words :

• nucleus

• cytoplasm

• ribosomes

• mitochondria

• Cell membrane

• Cell wall

• Vacuole

• Chloroplasts

Functions of cell structures

• Match up the cell structures with their function.

• Draw a table, with headings, to display this information. Use a ruler!

ribosomes

chromosomes

mitochondria

Made of DNA. Contain genetic material of the cell.

Site of aerobic respiration

Site of protein synthesis

Cell ultrastructure

Learning Intention: To investigate more detailed structures in plant and animal cells Success Criteria: Be able to state that cell structures can be seen clearer and at higher magnification using an electron microscope Be able to name some structures in animal and plant cells which are visible under an electron microscope Be able to label these on a diagram and state their functions

Starter Activity: Answer the following question in your jotter. 1. a) What cell structures are made of DNA? b) How many of these are there in a normal

human body cell? 2. What is the function of ribosomes? 3. Where in the cell are mitochondria found? 4. Which are the smallest – chromosomes,

ribosomes or mitochondria? 5. What kind of microscope is needed to see these

clearly?

Answers

1. a) Chromosomes b) 46

2. Protein synthesis

3. In the cytoplasm

4. Ribosomes

5. Electron microscope

Fungal and bacterial cells

Learning Intention: To investigate the structure of fungal and bacterial cells Success Criteria: • Name the structures found in fungal cells which

are visible under a microscope and label these on a diagram

• Name the method of reproduction in yeast • Name the main structures found in bacterial

cells • State the function of plasmids

Fungal cells

• Fungi are a group of organisms that includes mushrooms, moulds, yeast and toadstools.

• Yeast is a unicellular fungus – made of single cells.

• It has no chloroplasts and cannot photosynthesise.

• It reproduces by ‘budding’. • Yeast cells can reproduce rapidly

if they have a source of food (sugar)and a suitable temperature.

Looking at yeast

Collect the following: • Microscope, slide, yeast suspension, dropper,

cover slip. Method • Place one drop of yeast suspension in the middle

of a microscope slide, and lower on a cover slip. • View the yeast cells at low and high power. Look

for cells that are budding.

Yeast cell

Small bud forming

Yeast cells under the microscope

Typical fungal cell

Yeast budding ( a method of reproduction)

• Copy the diagram.

yeast cell

Uses of Yeast

Brewing Industries

Alternative Fuel Industries

Bread-making

Industries

Bacterial cells

• Bacterial cells are very tiny compared to other plant and animal cells. Viruses are even smaller!

Looking at bacterial cells

• Your teacher will give you prepared slides of bacterial cells to view under the microscope.

• They have been stained to show them up more clearly.

• You will need to use the highest power of lens to see them clearly.

• Start by focusing at low power, then increase to medium power then high power.

Structure of a typical bacterial cell

• Here you can see that bacterial cells have some of the structures we have already seen in plant and animal cells.

• These details can only be seen under electron microscope.

Structure of a typical bacteria

• The DNA in bacteria is not in a proper nucleus. • Instead it consists of a main ring or coil of DNA. • In addition to this, there are other smaller rings of

DNA called plasmids. • Plasmids are involved in bacterial reproduction.

Copy the diagram, labels and notes below.

cell wall plasmid (additional DNA)

cytoplasm

main DNA ring (single chromosome)

flagellum for movement (not always present)

cell membrane

Cell Wall Structure

• The cell walls that surround plant cells are made of cellulose fibres.

• The cell walls that surround bacterial cells and fungal cells are not made of cellulose!

Reproduction in yeast and bacterial cells

• Single celled organisms like yeast and bacteria reproduce by dividing into two cells.

• If the conditions are right, yeast and bacterial cells can divide to make two cells once every 30 minutes. This means that the number of cells can double every 30 minutes!

• What do you think would be the ideal conditions for this to happen?

Answer : Source of food, suitable temperature, oxygen

available

30 mins 1 hour

1 hour 30 mins

2 hours

2 hours 30 mins

REPRODUCTION IN YEAST AND BACTERIAL CELLS

Yeast dividing calculation

• One yeast cell is placed in a sugar solution. It divides to form 2 cells in 30 minutes. How many yeast cells will there be after 12 hours?

• How to work it out

12 hours = 24 divisions

• Number doubles each division

The answer is on the next slide!

1. 2 2. 4 3. 8 4. 16 5. 32 6. 64 7. 128 8. 256 9. 512 10. 1024 11. 2048 12. 4096 13. 8192 14. 16384 15. 32768 16. 65536 17. 131072 18. 262144 19. 524288 20. 1048576 21. 2097152 22. 4194304 23. 8388608 24. 16777216

Answer = 16,777,216 yeast cells

Cell variety • We have looked at the structure of typical animal, plant, fungal

and bacterial cells. However, not all animal cells look the same. • The same is true of plant, fungal and bacterial cells. • The structure of each type of cell is related to its function.

Bioviewer activity • Examine the biosets provided on cell variety. •Read the notes that go with each slide. Types of cells (Glow)

Cell variety challenge

• Your challenge is to use your biological knowledge to identify plant, animal, fungal and bacterial cells.

• Examine each of the microscope slides under the microscope. Do not uncover the label.

• Look at the structures that are visible at low and high power.

• Decide whether the cells are animal, plant, fungal or bacterial.

• Write down the evidence that led you to your decision.

• Reveal the label to find out what each type of tissue is.

Cell variety challenge Copy the table

Slide Plant/animal/ fungal/bacterial

Evidence Name of tissue

A

B

C

D

E

Cell variety challenge Answers

Slide Cell Type Evidence Name of tissue

A animal cell membrane present, no cell wall

muscle tissue

B plant uniform shaped cells, thick cell walls

stem of water plant/leaf tissue

C fungal highest magnification needed, uniform oval shape

Saccaromyces/Mucor zygospores

D animal irregularly shaped cells lung/kidney tissue

E bacterial highest magnification needed, cell structures not visible

rhizobium/E.coli bacteria

Cell variety challenge Answers

Slide A – muscle tissue

Slide B – cross section of a water plant

Slide B – cross section of a leaf

Cell variety challenge Answers

Slide C – Saccaromyces (type of yeast cell)

Slide C – Mucor zygospores (type of mould)

Slide D – lung tissue

Slide D – kidney tissue

Cell variety challenge Answers

Slide E – Rhizobium bacteria Slide E – E. coli bacteria

C

Fungal and bacterial cells

Learning Intention: To investigate the structure of fungal and bacterial cells Success Criteria: Be able to name the structures found in fungal cells which are visible under a microscope Be able to label these on a diagram Be able to name the method of reproduction in yeast Be able to name the main structures found in bacterial cells Be able to state the function of plasmids Be able to do calculations of cell growth

Cell Variety Challenge Your task is to produce an A5 information booklet about

cell structure and function. You must include… Labelled diagrams of the four main cell types: - Plant – Animal – Bacterial - Fungal Describe the functions (jobs) of each labelled part. You should include… Examples of specialised cells from each of the four cell

types. Draw labelled diagrams of your examples and add

information about how their special features make them well suited to their special functions.

You could include… A set of ten questions at the back of your booklet about

the information inside.