UNIT 2: Enzymes

Question 1

enzymes

Answer 1

folded, globular shaped protein catalysts that speed up reactions without being used up.

Question 2

examples of catabolic enzymes

Answer 2

pepsin - digests proteins into peptides
amylase - digests starch into maltose
lipase- digests fats into fatty acids and glycerol

Question 3

examples of anabolic enzymes

Answer 3

potato phosphorylase - makes starch from glucose

DNA polymerase - makes DNA from its building blocks (nucleotides)

Question 4

active site theory of enzyme action

Answer 4

all enzymes have an active site when the enzyme combines with its specific substrate.
involves two models of enzyme action; 1. lock and key model, 2. induced fit model

Question 5

active site

Answer 5

area of the enzyme where substrate enters and is changes into products

Question 6

specificity

Answer 6

refers to the enzymes ability to react with only one substrate

Question 7

substrate

Answer 7

substance upon which the enzyme acts

Question 8

product

Answer 8

substance that results from the action of the enzyme

Question 9

lock and key model

Answer 9

1. enzyme has a rigid shape.
2. the substrate enters the active site of the enzyme and fits snugly, much like a key fits in a lock,
3. an enzyme-substrate complex is formed.
4. substrate is changed into product(s)
5. products exit the active site.

Question 10

induced fit model

Answer 10

1. substrate enters active site.
2. the enzyme changes its shape slightly to accept substrate.
3. an enzyme substrate complex is formed.
4. substrate is changed into products
5. products exit the active site upon which point the enzyme returns to its original shape

Question 11

optimum activity of an enzyme

Answer 11

refers to the conditions under which an enzyme works best.
generally most human enzymes work best at 37˚C at a pH 7. An exception is pepsin, which acts on proteins in the stomach at a pH of 1-2.
Plant enzymes work bets between the temperatures of 10-30˚C depending on their natural habitat.

Question 12

denaturation

Answer 12

involves a permanent change in the shape of an enzyme so that it does not act on its substrate.
Human enzymes will begin to denature at around 40˚C. During infections the temperature of the human body can reach 42˚C.

Question 13

bioprocessing

Answer 13

the use of enzyme-controlled reactions to produce a product

e. g.
- production of beer using yeast
- production of insulin using genetically-modified E coli bacteria.
- production of cheese using the enzyme rennin
- production of fructose from glucose using glucose isomerase

Question 14

bioreactor

Answer 14

a vessel or container in which living cells or their products are used to make a product

Question 15

immobilized enzymes

Answer 15

enzymes that are attached to or trapped in an inert insoluble material.

1. carrier-blinding method;
   - physical adsorption
   - ionic binding
   - covalent binding
2. cross-linking method
3. entrapment method

Question 16

uses of immobilized enzymes

Answer 16

• immobilized lactase breaks down lactose in milk for lactose-intolerant people
• immobilized rennin is used in the cheese-making process
• immobilized glucose isomerase is used in sweet manufacture as fructose is sweeter than glucose

Question 17

advantages of immobilized enzymes

Answer 17

• immobilized enzymes are more stable
• efficiency of the enzyme is unaffected
• easy recovery of product and enzyme at end of reaction
• immobilized enzymes can be reused many times reducing costs to manufacturers

Question 18

Batch culture

Answer 18

1. a fixed amount of substrate is placed into bioreactor
2. reaction is allowed to proceed.
3. product is collected at end of reaction
4. bioreactor is then cleaned out for next batch

Question 19

continuous flow culture

Answer 19

1. substrate is continually infused into the bioreactor
2. reaction proceeds and conditions within are strictly controlled using sensors
3. product is continually collected

Question 20

Cellular energy

Answer 20

The energy stored in the bonds of biomolecules

Question 21

Catalyst

Answer 21

A substance that speeds up a reaction, without itself being used up in the reaction