3.6 Enzymes

Question 1

What is an enzyme?

Answer 1

An ENZYME is a protein that acts as a catalyst in a living things

Question 2

How does an enzyme work?

Answer 2

An enzyme works by LOWERING the ACTIVATION ENERGY of a chemical reaction

Question 3

How do you name an enzyme?

Answer 3

replace ending at end of substrate with ase

Question 4

What are the 3 characteristics of exergonic reactions?

Answer 4

Downhill
Occur Spontaneously
Produce Energy

Question 5

What are the 3 characteristics of endergonic reactions?

Answer 5

Uphill
Non spontaneous
Needs energy

Question 6

What happens to enzymatic speed with substrate concentration and why?

Answer 6

Enzyme activity increases as substrate concentration increases because there are more collisions between substrate molecules and the enzyme.

Question 7

What happens to enzymatic speed with temperature and why?

Answer 7

As the temperature rises, enzyme activity increases because more collisions occur between enzyme and substrate.
If the temperature is too high, enzyme activity levels out and then declines rapidly because the enzyme is denatured.

Question 8

What happens to enzymatic speed with pH and why?

Answer 8

Each enzyme has an optimal pH at which the rate of reaction is highest.

Question 9

What is inhibition?

Answer 9

active enzyme is prevented from combining with substrate.

Question 10

What is competitive inhibition?

Answer 10

Blocks substrates from entering the active site

Question 11

What is noncompetitive inhibition?

Answer 11

Change formation of enzyme by binding to another site

Question 12

What is feedback inhibition?

Answer 12

The end product of a reaction blocks its own production

Question 13

How does penicillin work?

Answer 13

Block an enzyme that makes the cell wall in bacteria

Question 14

How does aspirin work?

Answer 14

Blocks the enzyme cyclooxygenase

Question 15

How does prozac work?

Answer 15

Inhibits the reuptake of seratonin

Question 16

How does viagra work?

Answer 16

binds to the receptors of the enzyme guanylate cyclase-leads to increased blood flow.

Question 17

What are the 4 characteristics of the enzyme-substrate?

Answer 17

Active site and substrate complement each other in terms of both shape and chemical properties (e.g. opposite charges)

Binding to the active site brings the substrate into close physical proximity, creating an enzyme-substrate complex

The enzyme catalyses the conversion of the substrate into a product (or products), creating an enzyme-product complex

As the enzyme is not consumed in the reaction, it can continue to work once the product dissociates (hence only low concentrations are needed)

Question 18

What is denaturation?

Answer 18

Denaturation is a structural change in a protein that results in the loss (usually permanent) of its biological properties

Question 19

How can lactose free milk be made?

Answer 19

Lactose-free milk can be produced by purifying lactase (e.g. from yeast or bacteria) and binding it to an inert substance (such as alginate beads)

Question 20

What are the 4 uses of lactose free milk?

Answer 20

As a source of milk for lactose-intolerant individuals
As a means to increase the sweetness of milk (glucose and galactose are sweeter in flavour), thus negating the need for artificial sweeteners
As a way of reducing the crystallisation of ice-creams (glucose and galactose are more soluble than lactose)
As a means of shortening the production time for yogurts or cheese (bacteria ferment glucose and galactose more readily than lactose)