12.2 Proteins and enzymes

Question 1

Haemoglobin function

Answer 1

Allows oxygen to bind to be transported around the organism

Question 2

Antibody function

Answer 2

binds to specific antigen, used in organisms immune response to pathogen

Question 3

Enzymes fucntion

Answer 3

Reduces activation energy within a metabolic reaction

Question 4

Actin and myosin function

Answer 4

Structural protein involved in muscle contraction

Question 5

Keratin function

Answer 5

Structural protein found in nails, hair and hooves

Question 6

Collagen function

Answer 6

Structural protein found in tendons

Question 7

What are proteins made from?

Answer 7

Amino acids

Question 8

How many types of amino acids are there?

Answer 8

20

Question 9

What is the general structure of an amino acid?

Answer 9

NH2 - C(RH) - COOH

Question 10

What two groups do amino acids have ?

Answer 10

Amino group - NH2
Carboxylic acid group - COOH

Question 11

How do two amino acids join?

Answer 11

By condensation reaction to form a dipeptide joined by peptide bonds

Question 12

What does a peptide chain always have?

Answer 12

An amine group at the N terminal and a carboxyl group at the C terminal

Question 13

What is the protein structure?

Answer 13

Primary, secondary, tertiary, quaternary

Question 14

What is primary structure?

Answer 14

The number and sequence of amino acids in a polypeptide chain

Question 15

What is secondary structure?

Answer 15

Alpha helices or beta pleated sheets
Held together by weak hydrogen bonds

Question 16

What is tertiary structure?

Answer 16

Contains 3 types of bonds -
Weak hydrogen bonds
Ionic bonds
Disulphide bridges
Gives them a specific active site shape

Question 17

What is quaternary structure?

Answer 17

Two or more polypeptide chains joined together

Question 18

What is denaturation?

Answer 18

A permanent change to the specific 3d tertiary structure of a protein

Question 19

What is the structure of proteins?

Answer 19

A polymer of amino acids joined by peptide bonds formed by condensation reaction. Primary structure is order and sequence of amino acids. Secondary structure is folding of polypeptide chains due to weak hydrogen bonds, forming alpha helices and beta pleated sheets. Tertiary structure is the 3d folding due to hydrogen bonding and ionic/disulphide bonds. Quaternary structure is two or more polypeptide chains joined together.

Question 20

How do you test for proteins?

Answer 20

Add equal volume of buret solution
Colour changes from blue to purple if protein is present

Question 21

Activation energy definition

Answer 21

The m minimum energy required for a successful chemical reaction

Question 22

What do enzymes act as?

Answer 22

Biological catalysts
They take part in the reaction but do not get used up

Question 23

What do enzymes do?

Answer 23

Increase the rate off reaction by lowering the activation energy by stressing the bonds in the substrate during forming an enzyme substrate complex

Question 24

Describe the lock and key theory

Answer 24

The active site is rigid and doesn’t change shape
The substrate binds to the enzymes active site
The substrate is complimentary to the active site
Products are formed and no longer fit the active site
The enzyme is free to take part in another reaction

Question 25

Describe the induced fit model

Answer 25

Thye substrate enters the enzymes active site and binds to it forming an enzyme substrate complex This induces a change in the shape of the active site This distorts the bonds, lowering the activation energy When the substrate leaves, the active site returns to its original shape

Question 26

Contrast the way that the lock and key is different to the induced fit model

Answer 26

The active site of the lock and key model does not change shape whereas in the induced fit model the active site does change shape

Question 27

One enzyme will catalyse one reaction, explain why

Answer 27

Enzyme has a specific active site shape Only one substrate fits the active site

Question 28

Suggest why a protein can be a substrate for 2 different enzymes

Answer 28

Different parts of the protein have different amino acid sequences so are a different shape each enzyme active site is a specific shape and complementary to a different part of the protein

Question 29

What factors affect enzyme action

Answer 29

Temperature pH Inhibitors Substrate concentration

Question 30

Optimum temperature definition

Answer 30

The maximum energy that can be supplied to the molecules before the hydrogen and ionic bonds start to break

Question 31

What happens when you increase the temp of a reaction?

Answer 31

The atoms have more kinetic energy and vibrate more. This breaks the hydrogen and ionic bonds between the amino acids, causing a change in the tertiary structure and active site. Active site no longer complimentary so less ESC can be formed. Enzyme denatures

Question 32

effect of pH on enzyme action

Answer 32

Changing the pH changes the charge on the R group and the ionic bonds are broken. The active site changes and then substrate can't bind. Less ESC formed and enzyme is denatured

Question 33

effect of substrate concentration

Answer 33

Low substrate concentration = less frequent successful collisions so fewer ESC. The substrate is a limiting factor. High substrate concentration = more active sites filled, rate of reaction increases, more ESC formed, substrate is a limiting factor. The rate of reaction doesn't increase any further as all active sites are saturated. Enzyme concentration is now the limiting factor.

Question 34

Inhibitors definition

Answer 34

Substances which decrease the rate of reaction

Question 35

How do competitive inhibitors work?

Answer 35

Have similar structure to substrate Inhibitor binds to active site Less substrate binds so less ESC formed Less product is produced

Question 36

How do non-competitive inhibitors work?

Answer 36

Inhibitor is not similar shape to substrate Inhibitor binds away from active site at allosteric site Changes the shape of active site Less substrate binds so less ESC formed Less product formed

Question 37

How do you overcome a competitive inhibitor?

Answer 37

Increase substrate concentration