3.1 Enzymes and metabolism

Question 1

which group of biological molecules do enzymes belong to?

Answer 1

proteins

Question 2

what is metabolism?

Answer 2

complex network of chemical reactions in living organisms

Question 3

what is a anabolic reaction?

Answer 3

build up substrates

Question 4

what is a catabolic reaction?

Answer 4

break down substrates

Question 5

what is the role of enzymes?

Answer 5

speed up chemical reactions

Question 6

what is the structure of enzymes?

Answer 6

tertiary globular structure

Question 7

lock and key mechanism vs. induced fit mechanism

Answer 7

L&K = only a specific substrate can fit into the active site
IF = active site changes shape to fit a substrate

Question 8

evidence for induced fit hypothesis

Answer 8

crystallographic studies

Question 9

effects of low temperatures on enzyme activity

Answer 9

slower rate of reaction due to less kinetic energy thus less successful collisions and ESC

Question 10

effects of optimal temperature on enzyme activity

Answer 10

faster rate of reaction due to more kinetic energy, thus more successful collisions and ESC

Question 11

effects of high temperatures on enzyme activity

Answer 11

enzymes vibrate and hydrogen bonds break. active site changes shape and ESC no longer forms.

Question 12

effects of low or high levels of PH on enzyme activities

Answer 12

H+ and OH- ions can disrupt ionic and hydrogen bonds causing it to denature

Question 13

what does it mean that enzymes are ‘specific’?

Answer 13

One enzyme will only work with one specific substrate

Question 14

how do enzymes affect the activation energy of a reaction?

Answer 14

reduce activation energy

Question 15

stages of lock and key model

Answer 15

• Specificity
• Enzyme-substrate complex
• Enzyme-product complex
• Products released

Question 16

what factors affect the rate of reaction of enzymes

Answer 16

• concentration of substrates
• concentration of enzymes
• temperature
• Ph levels

Question 17

how does substrate concentration affect the rate of reaction

Answer 17

rate of reaction increases as concentration of substrate increases and then it plateaus.

Question 18

why does the rate of reaction of enzymes increase at first with higher concentration of substrates?

Answer 18

more substrate particles so higher frequency of successful collisions.

Question 19

why does the rate of reaction of enzymes plateau at a certain point?

Answer 19

all the active sites are taken up

Question 20

what does activation energy mean?

Answer 20

The minimum energy required for a reaction to take place

Question 21

how does substrate and enzyme concentration affect enzyme activity?

Answer 21

as substrate/enzyme concentration increases, so does the rate of reaction and then it plateaus.

Question 22

why does the rate of reaction plateau at a certain point as concentration of substrate/enzyme keep on increasing?

Answer 22

all enzymes are occupied or there are not enough substrates compared to enzymes.

Question 23

what is the difference between intracellular and extracellular enzyme-catalysed reactions?

Answer 23

intracellular = within cells
extracellular = outside of cells

Question 24

what does a non-competitive inhibitor do?

Answer 24

binds to allosteric site of enzymes changing the active site shape.

Question 25

what does a competitive inhibitor do?

Answer 25

similar shape to substrate binding to active site so substrate cannot.

Question 26

what is the process of end product inhibition?

Answer 26

when end products are in excess it will act as an inhibitor by binding to the allosteric site of the first enzyme in the metabolic pathway to regulate the amount of product produced.

Question 27

what is a linear pathway?

Answer 27

series of steps with a distinct beginning and end.

Question 28

what is a cyclical pathway?

Answer 28

involves the end product starting the next cycle (starting substrate is regenerated)

Question 29

what is an example of a linear pathway?

Answer 29

glycolysis

Question 30

what is an example of a cyclical pathway?

Answer 30

calvin and krebs cycle

Question 31

how does increasing substrate concentration affect rate of reaction when competitive inhibitors are present?

Answer 31

increasing substrate concentration can allow the rate of reaction to reach the maximum like when there is no competitive inhibitor because it increases the chances of the substrates binding to the active sites before the inhibitors do.

Question 32

how does increasing substrate concentration affect rate of reaction when non-competitive inhibitors are present?

Answer 32

the maximum rate of reaction will never be reached again as the shape of the active site has permanently changed.

Question 33

what is mechanism based inhibition?

Answer 33

inhibitor binds permanently to the active site