C4 Enzymes

Question 1

What are the different stages of the process of Enzyme action

Answer 1

Enzyme substrate bind together at the active site
An enzyme substrate complex is formed
The substrate is broken down to produce products

Question 2

Enzymes, lock and key model

Answer 2

Active site has a specific shape
Substrate also has a specific shape
Thee 2 are therefore complementary

Question 3

Enzymes examples

Answer 3

Catalyse (intercellular)
Protease- pepsin, trypsin 
Carbohydrase - amalyse, maltase 
Lipase 
(Last three are all extracellular)

Question 4

What are enzymes made out off?

Answer 4

Globular portions
Highly specific (R groups) 3D shape
Specialised region with a highly specialised specific active site
Generally soluble (hydrophilic r groups on the outside, with hydrophobic generally on inside).

Question 5

Introduced fit model (Confirmational change)

Answer 5

Puts the bonds in the substrate under strain

This can weaken a particular bond(s) in the substrate and therefore lower the activation energy required

Question 6

What is meant by biological catalysts

Answer 6

Speeds up metabolic reactions
Anabolic (building up)
Catabolic (breaking down)
Enzymes lower activation energy

Question 7

Q10 Temperature coefficient

Answer 7

It is a measure of temperature consistency of an enzyme reaction. It indicates how much the rate of reaction increases with a change of 10°C.

Question 8

What’s optimum temperature

Answer 8

Temperature at which enzyme has highest rate of activity

Question 9

How does temperature affect enzyme activity

Answer 9

As temperature increases kinetic energy of the particles increase, therefore they move faster and collide more frequently. There is an increase in frequent successful collisions between substrate and enzyme.Therefore the rate of reaction increases.

Question 10

How can temperature cause enzymes to denature

Answer 10

An increase in temperature increases the vibrations in the bonds holding the particles together, until bonds strain, then break, resulting in a change in the precise tertiary structure. As a result the active site changes shape.

Question 11

How does pH affect enzyme activity

(Potential hydrogen)

Answer 11

The active site can only be in the right shape at a certain hydrogen concentration (optimum pH). The more hydrogen ions present the less the R groups are able to interact with each other. The hydrogen ions bind to the O2- atoms. The reverse is true when fewer hydrogen ions are present (enzymes can only function at narrow pH range).

Question 12

What’s renaturation

Answer 12

If the pH returns back to normal/ optimum then the protein will resume its normal shape and catalyse the reaction again

Question 13

What is V max

Answer 13

The rate of reaction increases until its maximum (Vmax) where the substrate or enzyme no longer becomes a limiting factor (can’t increase the rate).

Question 14

How does substrate and enzyme concentration affect enzyme activity

Answer 14

As they increase the concentration and increase the number of substrate molecules atoms or ions in a particular area this results in a higher collision rate with the active site of enzymes as a result this increases the rate and amount of formation of enzyme substrate complexes and therefore increases the rate.

Increasing the number of enzymes will increase the number of available active sites and therefore result with a faster rate of binding.

Question 15

What’s a cofactors, and how do they function?

Answer 15

A helper molecule. A non protein ‘helper’ component that is essential for some enzymes to carry out their function as biological catalysts
They may transfer atoms or groups from one reaction to another in a multi-step pathway or actual form part of the active site of the enzyme.

Question 16

If a cofactor is an organic molecule what is it called

Answer 16

Coenzyme

Question 17

Where are inorganic cofactors obtained from?

Give an example

Answer 17

Via the diet as minerals including iron, calcium, chloride and zinc ions.
E.g the enzyme amylase contains a chloride ion that is necessary for the formation of the correctly shaped active site.

Question 18

What are coenzymes derived from?

E.g

Answer 18

From vitamins (a class of organic molecules found in the diet).
E.g Vitamin B3 is used to synthesis NAD (nicotinamide adenine dinucleotide), a coenzyme responsible for the transfer of hydrogen atoms between molecules involved in respiration.
Vitamin B5 is another example

Question 19

Cofactors: prosthetic group, function

E.g

Answer 19

They are required by certain enzymes to carry out their catalytic function . While some cofactors are loosely or temporarily bound the to the enzyme protein (to activate them), prosthetic groups form a permanent feature of the protein.

E.g zinc ions form an important part of the structure of carbonic anhydrase (an enzyme necessary for the metabolism of CO2).

Question 20

What is meant by competitive inhibition?

Answer 20

A molecule or part of a molecule that has a similar shape to one substrate of an enzyme can fit into an active site of the enzyme, blocking substrate answering active site and therefore preventing enzyme from catalysing reaction. The enzyme cannot carry out its function, set to be inhibited.

Question 21

What do competitive inhibitors and substrates compete for?

And how does this effect the rate of reaction

Answer 21

They both compete to bind to the active site of enzyme catalysing one reaction.
This will reduce one number of substrate molecules attaching in a given time, and hence reduce the rate of reaction.

Question 22

How does competitive inhibitors effect the rate of reaction?

Answer 22

Reduces one rate of reaction for a given conc of substrate, but doesn’t change the Vmax of the enzyme it inhibits. If the substrate conc increases enough there will be more substrate than inhibitors that the original Vmax cab still be reached.

Question 23

Competitive inhibitors examples:

Answer 23

Statins, competitive inhibitors of enzyme used in the synthesis of cholesterol (used to reduced high blood cholesterol conc).

Aspirin irreversibly inhibits one active site of cox enzymes, preventing the synthesis of prostogladins and thrombaxane (chemicals responsible for producing pain and fever).

Question 24

Non-Competitive Inhibition (3):

Answer 24

The inhibitor binds to the enzyme at an allosteric site.
Binding causes tertiary structure enzyme to change, causing active site to change shape too.
Results active site no longer having complementary shape to substrate, unable to bind (enzyme can’t carry out function, ‘inhibited’).

Question 25

Non- competitive inhibitors effect on rates of reaction

Answer 25

Increase in concentration of enzyme or substrate will not overcome affect of a non-competitive inhibitor. Increasing concentration of inhibitor however would decrease the rate of reaction further as more active sites become unavailable.

Question 26

Non-competitive inhibitor examples

Answer 26

The binding of an inhibitor may be reversible or non-reversible.
Proton pump inhibitors (PPI’s) are used to treat long term indigestion. They irreversibly block an enzyme system responsible for secreting Hydrogen ions into the stomach.They are effective in reducing one’s production of excess acid, which if left untreated can lead to formation of stomach ulcers.

Question 27

What is end-product inhibition and example of?

Answer 27

Non-competitive reversible inhibition

Question 28

End-product inhibition

Answer 28

Term used for enzyme inhibition occurs when the product of the reaction act as an inhibitor to the enzyme that produces it (serves as a negative feedback control mechanism for the reaction). Excess products are not made and resources are not wasted.

Question 29

End-product inhibition examples

Answer 29

Respiration is the metabolic pathway resulting in production of ATP. Glucose is broken down in a number of steps. First involves one addition of two phosphate groups, glucose molecules, which results in one initiate breakdown of one glucose molecule, is catalysed by the enzyme phosphorustotindce (PIK).This enzyme is competitively inhibited by ATP. ATP therefore regulators own production. When the levels of ATO are high more ATP binds to allosteric site of PIK, preventing the addiction of the second phosphate group to glucose. Glucose is not broken down and ATP is not produced at one same rate.. As ATP is used up, less bind to PIK and the enzyme is able to catalyse the addition of the second phosphate group to glucose. respiration resumes, leading to one production of more ATP.