Enzymes

Question 1

enzymes are……

Answer 1

• biological catalysts

- They are substrate specific (complementary)

Question 2

enzymes are effective in….

Answer 2

tiny amounts

Question 3

enzymes are______ proteins at the _______ structure

Answer 3

globular, tertiary

Question 4

catalyses reactions both ___________ (in cell) and __________ (outside cell) which determines structure/function

Answer 4

intracellular, extracellular

Question 5

enzymes are catabolic what does that mean?

Answer 5

active site effects bonds in substrate, substrate breaks (hydrolysis)

Question 6

what does anabolic mean?

Answer 6

bring substrate molecules together (building, condensation)

Question 7

How should a typical reaction should occur:

1. ______ collide with enzyme with sufficient ______ energy.
2. alters arrangement of _____
3. energy of ______ must be lower than energy of _______

Answer 7

substrate, kinetic
atoms
products, substrate

Question 8

how do enzymes speed up chem reactions?

Answer 8

lower activation energy (reactions can occur at lower temps)

Question 9

what is the area the substrate fits into on a protein called?

Answer 9

the 3D active site

Question 10

what is the name given when a substrate interacts with an enzyme?

Answer 10

enzyme-substrate complex

Question 11

Describe the induced fit model

Answer 11

1. enzyme is flexible + alters shape in presence of substrate (due to change of environment)
2. enzyme puts strain on substrate
3. causes distortion in substrate bond(s) = lowers activation energy

Question 12

Describe the outdated lock + key model

Answer 12

the shape of the substrate exactly fits into the active site

Question 13

name the 5 factors that affect enzyme action

Answer 13

pH, temp, substrate conc., enzyme conc., conc. of competitive and non-competitive inhibitors

Question 14

how is the rate of an enzyme controlled reaction measured?

Answer 14

• rate of formation of products

- rate of disappearance of substrate

Question 15

Describe an enzyme reaction in 6 steps

Answer 15

1. at first easy for substrate to come into contact with enzyme (lots of empty sites)
2. substrate rapidly broken down = increase in product
3. less and less substrate = harder to come into contact with enzyme
4. takes longer for substrate to be broken down = rate of formation + disappearance decreases
5. reaction slows
6. graph flattens = all substrate used up

Question 16

how to measure rate of change? (graph)

Answer 16

measuring gradient at certain point (may need a tangent)

Question 17

How does a rise in temp affect enzyme activity?

Answer 17

increases kinetic energy, more collisions = more enzyme-substrate complexes

Question 18

what happens when you exceed optimum temp/pH of the enzyme?

Answer 18

denaturation of 3D active site = no enzyme-substrate complexes = decrease in rate

Question 19

how does pH affect how an enzyme works?

Answer 19

• can change amino acids making up active site

- can cause breakage of bonds in enzyme tertiary structure (changes active site)

Question 20

what aids in determining the active site?

Answer 20

the ionic bonding between NH2 (amine) and COOH (carboxyl)

Question 21

enzymes work well at low conc. because…

Answer 21

are not used up in a reaction

Question 22

what happens when enzyme conc. is low?

Answer 22

• excess substrate molecules
• not enough active sites
• rate only half of max for no. of substrate

Question 23

what happens when there’s intermediate enzyme conc.?

Answer 23

• all substrate molecules occupy active sites

- rate at max. as all sites filled

Question 24

what happens when there’s high enzyme conc.?

Answer 24

• already enough enzymes to accommodate substrate

- no increase in rate of reaction

Question 25

if conc. of enzyme is fixed and _________ conc. is slowly increased, ____ increases proportionately to conc. of ________

Answer 25

1. substrate
2. rate
3. substrate

Question 26

what happens when there’s low substrate conc.?

Answer 26

• substrate cannot occupy all sites

- rate only half the max. possible

Question 27

what happens when there’s intermediate substrate conc.?

Answer 27

• all active sites occupied

- rate doubled to max

Question 28

what happens when there’s high substrate conc.?

Answer 28

• has no effect (all sites filled)

- no increase in rate

Question 29

define enzyme inhibition

Answer 29

substances that directly or indirectly interfere with the functioning of the active site = reduces activity

Question 30

T or F: competitive and non-competitive inhibitors are permanent

Answer 30

F: they are temporary (reversible)

Question 31

What are competitive inhibitors?

Answer 31

• inhibitors complementary to enzyme’s AS

- block substrate from forming E-SC

Question 32

Competitive inhibitors:
if substrate conc. increased = effect of inhibitor _______
if conc. of inhibitor increased = rate of reaction _______

Answer 32

1. reduced

2. reduced

Question 33

what are non-competitive inhibitors?

Answer 33

• bind to enzyme BUT NOT the active site
• change the 3D shape of AS
• no E-SC formed

Question 34

T or F: non-competitive inhibitors do not compete with substrates

Answer 34

true

Question 35

define metabolic pathways

Answer 35

series of reactions in which each step is catalysed by an enzyme

Question 36

metabolic pathways are…

Answer 36

highly structured

Question 37

why are enzymes in metabolic pathways attached to membranes of cell organelles in a precise sequence?

Answer 37

• the product of one reaction acts as a substrate for the next reaction (greater chance of substrate in contact with enzyme)
• more efficient at producing end product

Question 38

what is end product inhibition?

Answer 38

• used to keep a stable conc. of a specific chem

- (the same chem often inhibits the enzyme at start of reaction)