Chapter 4

Question 1

What is an enzyme

Answer 1

An enzyme is a biological catalyst that speeds up a reaction without being used up itself

Question 2

What type of reactions do enzymes catalyse

Answer 2

Enzymes catalyse metabolic reactions at cellular level e.g. respiration and for the organism as a whole EG digestion

Question 3

What are the two types of enzyme

Answer 3

Intracellular enzymes and extracellular enzymes

Question 4

Give one example of an intracellular enzyme

Answer 4

catalase is an intracellular enzyme that works inside cells to catalyses the breakdown of hydrogen peroxide into oxygen and water

Question 5

Give two examples of extracellular enzymes

Answer 5

amylase is an extracellular enzyme found in the mouth and secreted by the salivary glands it catalyzes the hydrolysis of starch breaking it down into maltose
trypsin is an extracellular enzyme produced in the pancreas and secreted into the small intestine that catalyses the hydrolysis of peptide bonds which makes a polypeptides smaller

Question 6

What type of proteins are enzymes and how does this affect their structure and function

Answer 6

enzymes are globular proteins that have an active site which has a specific shape that only one substrate can bind and be catalyzed the shape of the active site depends on the enzymes tertiary structure

Question 7

How do enzymes catalyse reactions

Answer 7

enzymes provide an alternative reaction pathway with lower activation energy so more particles have sufficient energy increasing the rate of reaction

Question 8

What is the lock and key hypothesis

Answer 8

The substrate binds to the active site forming a enzyme-substrate complex groups within the active site with the substrate and form temporary phones these has a strain on the ones within the substrate lowering the activation energy the substrate react forming an enzyme product complex and the products are released

Question 9

What is the induced fit hypothesis

Answer 9

induced fit hypothesis is a modified lock and key explanation for enzyme action the active site is modified in shape by binding to the substratethe initial weak interactions between enzyme and substrate induced changes in the enzymes tertiary structure it puts strain on the substrate molecule weakening the bonds and lowering the activation energy

Question 10

How does temperature affect enzyme activity

Answer 10

increasing temperature increases kinetic energy of the particles they move faster and collide frequently increasing rate of reaction

Question 11

What happens when the temperature gets too high

Answer 11

rise in temperature caused the enzyme molecules to vibrate more which continues until they break this changes the tertiary structure of the enzymes the substrate no longer fits it is denatured

Question 12

What is the temperature coefficient

Answer 12

The temperature coefficient for Q10 measures how much rate of reaction change as per 10 degree rise in temperature
Q10= R2 (rate at higher temperature)/ R1 (rate at lower temperature)

Question 13

How does pH affect enzyme activity

Answer 13

enzymes must be kept around the optimum pH to function as the structure of the enzyme and active site relies on ionic and hydrogen bonds which are determined by polarity and h+ and oh minus concentration

Question 14

What happens when pH gets outside of the optimum range

Answer 14

significantly changing pH changes concentration of oh - and h+ ions which can break the ionic and hydrogen bonds holding its tertiary structure in place causing the active site to change shape denaturing it

Question 15

How does enzyme concentration affect enzyme activity

Answer 15

the more enzyme molecules the more likely a substrate molecule is applied and forman enzyme-substrate complex so the rate of reaction increases however if the amount of substrate is limited there comes a point when no molecules to be reacted with this adding more enzyme has no effect

Question 16

How does substrate concentration affect enzyme activity

Answer 16

The more substrate molecules the more likely an enzyme has to collide and from an enzyme substratecomplex fraction increases the amount of enzymes is limited that comes appointment is no more molecules to be reacted with the adding more substrate has no effect

Question 17

How can you practically investigate the effect of temperature on enzyme activity?

Answer 17

1) set up 4 boiling tubes of same volume and concentration of hydrogen peroxide and add a buffer solution to each one
2) add a delivery tube and a bing to each which feed into a submerged upside down measuring cylinder to measure gas produced
3) put each tube in a water bath at 10, 20, 30 and 40 degrees for five minutes
4) add the same volume and concentration of catalase go each and record how much oxygen is produced in 60s
5) repeat three times to determine mean rate at each temperature

Question 18

How can you modify an enzyme investigation for PH

Answer 18

To modify the enzyme investigation for PH in step 1 add different pH buffer solutions to each and keep the temperature constant

Question 19

How can you modify an enzyme investigation for substrate concentration

Answer 19

You can change substrate concentration by preparing for boiling tubes of different concentrations of hydrogen peroxide using a serial dilution and 10 cm cubed of hydrogen peroxide to the first and 5 cm cube of distilled water to the others draw 5 cm from the first add to the second and mix repeat from the 2nd to the 3rd and the 3rd to the 4th

Question 20

How can you modify an enzyme investigation to enzyme concentration

Answer 20

In step 4 add different concentrations of catalase using a serial dilution

Question 21

What are competitive inhibitors

Answer 21

A competitive inhibitor has a similar shape to the substrate that fits into the active site which blocks the substrate from entering and reduces the rate of reaction however it does not change the maximum rate

Question 22

Draw a graph comparing an enzyme with competitive inhibitor to one without

Answer 22

Competitive inhibitor is a last line then without but they both end at the same place

Question 23

What is a non competitive inhibitor

Answer 23

a non competitive inhibitor binds to the enzymes allostatic site which causes a tertiary structure of the enzyme to change and the substrate can no longer bind reducing rate of reaction

Question 24

Draw a graph comparing an enzyme with non competitive inhibitor to without

Answer 24

With non competitive inhibitor is much less sleep and ends much below without

Question 25

What determines whether an inhibitor is reversible or non reversible

Answer 25

it depends on the bonds that makes with an enzyme for example strong covalent bonds are formed by a reversible inhibitors where is weak hydrogen or ionic bonds are formed by reversible inhibitors

Question 26

Give some uses of inhibitors

Answer 26

Inhibitors can be used as drugs such as antiviral drugs that inhibit enzymes which catalyse the replication of viral DNA or antibiotics which inhibit the enzymes which catalyse the formation of bacterial cell walls
inhibitors can also be used as metabolic poisons such a cyanide malonate and arsenic which inhibit an enzyme which catalyses respiration reactions

Question 27

What is a cofactor

Answer 27

A cofactor is a non protein component necessary for the effective functioning of an enzyme

Question 28

Give an example of a cofactor

Answer 28

Chloride ions are cofactors for amylase

Question 29

What is a coenzyme

Answer 29

A coenzyme is a cofactor which is an organic molecule and a changed by a reaction but constantly recycled

Question 30

Give an example of a source of coenzyme

Answer 30

Vitamins are sources of coenzymes

Question 31

What is a prosthetic group

Answer 31

If a cofactor is tightly bound to the enzyme it’s known as the prosthetic group

Question 32

Give an example of a prosthetic group

Answer 32

Zinc ions are prophetic groups for carbonic anhydrase

Question 33

What is an inactive precursor

Answer 33

Many enzymes are produced in an inactive precursor form which need to undergo a change in tertiary structure using a cofactor

Question 34

What is end product inhibition

Answer 34

and product inhibition is where the product of reaction inhibit the enzyme required for the reaction which service of form of negative feedback