The Chemicals of Living Cells ©The Wellcome Trust.
-
Upload
nathanael-stearn -
Category
Documents
-
view
215 -
download
0
Transcript of The Chemicals of Living Cells ©The Wellcome Trust.
![Page 1: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/1.jpg)
The Chemicals of Living Cells
©The Wellcome Trust
![Page 2: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/2.jpg)
The chemicals of life
All living organisms are made up of chemical substances
Reactions between these substances keep the cytoplasm(and the organism) alive. They are living processes.
The chemical substances described in the next seriesof slides are carbohydrates, proteins and lipids, but there are hundreds of others.
2
![Page 3: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/3.jpg)
Carbohydrates
Carbohydrates contain the elements carbon, hydrogen and oxygen
Familiar carbohydrates are sugar and starch
Glucose, fructose, maltose and sucrose are sugars
Glucose and fructose have the same formula, C6H12O6
Sucrose and maltose have the same formula, C12H22O11
Carbohydrates provide the main source of energy forrespiration in living organisms
3
![Page 4: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/4.jpg)
Glucose C6H12O6
C
C
C
C
C
C
HO
HO H
HO H
H OH
H OH
H2OH
A glucose molecule as a straight chain
5 of the carbon atoms maybe arranged in a ring
This molecule is often represented simply as a hexagon
C O
C C
C C
C
4
![Page 5: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/5.jpg)
Other carbohydrates2 molecules of glucose canjoin together to form a molecule of maltose
maltose
sucrose is formed whena molecule of glucose anda molecule of fructose combine
Starch and cellulose are formed from hundreds ofglucose molecules joinedto form a long chain
part of a starch molecule
5
![Page 6: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/6.jpg)
ProteinsProteins are made up of carbon, hydrogen and oxygenmolecules but with the addition of nitrogen
Carbohydrates are made up of glucose units.Proteins are made up of units called amino acids
There are about 20 different amino acids. Examples are glycine (Gly), alanine (Ala), valine (Val) and cysteine (Cyst)
The amino acids, Gly-Val-Val-Cyst-Ala-Gly-Ala-Valjoined together would make a small protein
Proteins make up the structure of cells; cytoplasm, nucleuscell membranes and enzymes
6
![Page 7: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/7.jpg)
Protein structure and shapeThe way the amino acids join up, gives a protein molecule a particular shape, which is different for every protein
Ser-Cyst-Val-Gly-Ser-Cyst Ala Val Val-Cyst-Ser-Ala-Ser-Cyst-Gly
Val- Cyst-Ala-Ala-Ser-Gly
This is a small, imaginary protein molecule showing howit acquires a shape
High temperatures or certain chemicals can cause theprotein molecule to lose its shape and its properties.
7
![Page 8: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/8.jpg)
Lipids
Lipids are fats and oils
They are made up from glycerol and fatty acids
Examples of fatty acids are stearic acid, oleic acid and palmitic acid
stearic acid
oleic acid
palmitic acid
C
C
H
H2
H2 C
O
O
O
glycerol fatty acids
A simple lipid
8
![Page 9: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/9.jpg)
Salts and water
In addition to proteins, carbohydrates and lipids, cytoplasm contains salts and water
Water makes up the bulk of cytoplasm
All the chemical reactions in cytoplasm take place in solution, i.e. in water
Water itself takes part in many of these chemical reactions
Salts of sodium, potassium and calcium and many othersplay an important part in these reactions
9
![Page 10: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/10.jpg)
Enzymes
Enzymes are special proteins
They are present in the cytoplasm of all cells
They help to speed up the chemical reactions in the cell
There are hundreds of different enzymes but each enzymespeeds up only one kind of reaction
For example, glucose and fructose might join up slowly toform sucrose
glucose--fructose
With the right enzyme present, the reaction happens faster
glucose--fructose
10
![Page 11: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/11.jpg)
Enzyme action (1)
Enzymes are large protein molecules
Like all proteins, each enzyme molecule has a particular shape
This shape determines which chemical reaction the enzymecan speed up
In speeding up the reaction, the enzyme combines temporarilywith the substances it is acting on
Any substance an enzyme acts on is called a substrate
11
![Page 12: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/12.jpg)
enzyme
substrate A
substrate B
The substrate molecules fit the shape of the enzyme12
![Page 13: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/13.jpg)
13
![Page 14: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/14.jpg)
substrates combine temporarily with enzyme
enzyme joins substrates together
14
![Page 15: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/15.jpg)
new compound released by enzyme
enzyme unchangedand ready fornext reaction
15
![Page 16: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/16.jpg)
Different types of enzyme reaction
The last 4 slides show how an enzyme is involved in combining substrates to create a larger molecule
For example, the enzyme could be building up a sucrosemolecule from glucose and fructose
The next sequence shows how an enzyme can help to break a large molecule into smaller molecules
For example an enzyme can split a sucrose moleculeinto the smaller glucose and fructose molecules
16
![Page 17: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/17.jpg)
A ‘breaking-down’ reaction
the shape of the substrate molecule fits the enzyme shapethis is called
the active siteof the enzyme
17
![Page 18: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/18.jpg)
Intermediate stage (1)
substrate combinestemporarily with enzyme
enzyme will breakmolecule here
18
![Page 19: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/19.jpg)
Intermediate stage (2)
substrate splits andseparates from enzyme
19
![Page 20: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/20.jpg)
Final break-down products
end-products
enzyme ready for next reaction
20
![Page 21: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/21.jpg)
Properties of enzymes
They always produce the same end products
Although they take part in the reaction, they are not used up
Because enzymes are proteins, they are denatured by heator some chemicals
Enzymes can act on only one type of substrate
Denaturing involves a change of shape in the enzyme molecule so that it cannot combine with the substrate
Individual enzymes work best at a particular temperatureand pH (acidity or alkalinity)
21
![Page 22: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/22.jpg)
Enzymes can act on only one type of substrate
this substrate cannot combine with this enzyme
this substrate cannot combinewith this enzyme
22
![Page 23: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/23.jpg)
Because enzymes are proteins, they are denatured by heat or some chemicals
enzymedenaturedby heat
denatured enzyme cannot combine with substrate
enzyme +substrate
23
![Page 24: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/24.jpg)
1
glucosemolecules
E
1. A glucose molecule combines with the active site on an enzyme
ENZYME ACTION 24
![Page 25: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/25.jpg)
E
2 A region of the active site is still available
25
![Page 26: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/26.jpg)
part of starchmolecule
E
3 One end of a growing starch molecule combines with the glucose molecule at the active site
26
![Page 27: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/27.jpg)
E
4 The growing starch molecule breaks free from the enzyme which is now free to repeat the reaction
27
![Page 28: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/28.jpg)
Enzyme action
E
E
E 2
E 3
E 4
part of starchmolecule
1
glucosemolecules
E1
28
![Page 29: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/29.jpg)
Question 1
The correct formula for glucose is
(a) C12H22O11
(b) C5H10O5
(c) C4H8O4
(d) C6H12O6
29
![Page 30: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/30.jpg)
Question 2
Which is the most accurate description of a carbohydrate?
A carbohydrate contains
(a) carbon and oxygen
(b) carbon, oxygen and nitrogen
(c) carbon, hydrogen and oxygen
(d) carbon and hydrogen
30
![Page 31: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/31.jpg)
Question 3
When two molecules of glucose combine, they form
(a) maltose
(b) sucrose
(c) fructose
(d) ribose
31
![Page 32: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/32.jpg)
Question 4
Which is the most accurate description of a protein
Proteins contain
(a) carbon, hydrogen and oxygen
(b) carbon, hydrogen, oxygen and nitrogen
(c) carbon, hydrogen and nitrogen
(d) carbon, nitrogen and oxygen
32
![Page 33: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/33.jpg)
Question 5
Which statements are correct?
Proteins are present in
(a) cell membranes
(b) cell walls
(c) cytoplasm
(d) nucleus
33
![Page 34: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/34.jpg)
Question 6
High temperatures damage proteins by
(a) decomposing them
(b) changing their chemical composition
(c) changing their shape
(d) making them soluble
34
![Page 35: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/35.jpg)
Question 7
A protein is made up of a series of
(a) glucose units
(b) fatty acids
(c) amino acids
(d) carbohydrates
35
![Page 36: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/36.jpg)
Question 8
Lipids are made up of
(a) glycerol and amino acids
(b) glycerol and fatty acids
(c) protein and fatty acids
(d) starch and fatty acids
36
![Page 37: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/37.jpg)
Question 9
Enzymes are
(a) proteins
(b) lipids
(c) carbohydrates
(d) a combination of these
37
![Page 38: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/38.jpg)
Question 10
An enzyme can
(a) change a reaction
(b) prevent a reaction
(c) slow down a reaction
(d) speed up a reaction
38
![Page 39: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/39.jpg)
Question 11
A substrate is a substance which
(a) an enzyme acts on
(b) is produced by an enzyme reaction
(c) is a particular kind of enzyme
(d) is any chemical substance in a cell
39
![Page 40: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/40.jpg)
Question 12
An enzyme can
(a) combine with different substrates
(b) form different kinds of end-product
(c) function at temperatures above 90oC
(d) speed up a reaction in the cytoplasm
40
![Page 41: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/41.jpg)
Question 13
The part of an enzyme which combines with the substrateis called
(a) the reaction centre
(b) the active site
(c) the action centre
(d) the reaction site
41
![Page 42: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/42.jpg)
Question 14
After being exposed to a high temperature an enzyme cannot function because
(a) it has been broken down
(b) its shape has been changed
(c) its composition has been changed
(d) it cannot separate from its substrate
42
![Page 43: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/43.jpg)
ANSWER
Correct
43
![Page 44: The Chemicals of Living Cells ©The Wellcome Trust.](https://reader035.fdocuments.us/reader035/viewer/2022062511/551ada985503466b6a8b58b4/html5/thumbnails/44.jpg)
ANSWER
Incorrect
44