Enzymes

Question 1

Prosthetic group

Answer 1

Type of cofactor that is tightly and permanently bound to an enzyme

Question 2

Cofactor

Answer 2

Non-protein component that help transfer atoms or groups between reactions or form part of an active site

Question 3

Where are cofactors obtained from?

Answer 3

Obtained from our diet as minerals (iron, calcium, chloride, zinc ions etc)

Question 4

Coenzymes

Answer 4

Organic cofactors

Question 5

Where are coenzymes obtained from?

Answer 5

Obtained from our diet as vitamins (vitamin B3 etc)

Question 6

Precursor activation via cofactors

Answer 6

Some enzymes are inactive and need a change in their tertiary structure through a cofactor.

apoenzyme + cofactor activator/coeznyme –> holoenzyme

Question 7

Precursor activation via enzymes

Answer 7

Enzymes can change the tertiary shape of other enzymes to activate them.

zymogen / proenzyme + enzyme –> holoenzyme

Question 8

give an example of an intacellular and an extracellular enzyme

Answer 8

intracellular - catalase

extracellular - amylase

Question 9

what do you call enzymes that are activated by either another enzyme or a change in condition?

Answer 9

zymogens or proenzymes

Question 10

why might precursor enzymes be inactive?

Answer 10

• avoid causing damage to cells or tissues that release or transport them
• enzymes may only be needed under certain conditions

Question 11

name an intracellular and an extracellular enzyme and what do they break down?

Answer 11

intracellular: catalase breaks down H2O2

extracellular: amylase breaks down starch into maltose

Question 12

where is amylase secreted?

Answer 12

• salivary glands
• pancreas

Question 13

can cold temperatures denature enzymes?

Answer 13

no, they can inactivate enzymes but not denature them

Question 14

Q10

Answer 14

temperature coefficient - measures the change in rate of reaction over a 10°C temperature change

Question 15

when does Q10 not apply?

Answer 15

once the temperature exceeds its optimum

Question 16

what is the usual Q10 for enzyme controlled reactions?

Answer 16

2 (rate doubles)

Question 17

which extremophilic enzymes are more sensitive/less stable to change and why?

Answer 17

• enzymes in psychrophilic organisms (adapted to cold temperatures)
• more flexible enzyme structures specifically at the active site (small changes will denature them)

Question 18

how do H+ affect enzymes?

Answer 18

• H+ form ionic bonds and H bonds between R groups in enzyme’s tertiary structure
• this also affects the R groups’ interactions with each other

Question 19

which factors permanently (irreversible) or temporarily (reversible) denature enzymes?

Answer 19

temporarily: pH within limits and low temp

permanently: pH beyond limits and high temp

Question 20

renaturation

Answer 20

change in conditions returns a reversibly denatured enzyme back to its original, specific shape

Question 21

how does an acidic pH (beyond optimum) affect enzymes?

Answer 21

• high [H+]
• form ionic and H bonds with R groups
• less R groups can interact with each other
• bonds are broken
• tertiary structure is altered

and vice versa for alkaline conditions (beyond optimum)

Question 22

Q10 formula

Answer 22

Q10=R2/R1

Question 23

how does temperature affect membrane permeability?

Answer 23

• increase temp, increases KE
• phospholipids move more freely
• membrane more fluid therefore more permeable
• AND proteins may denature, leaving gaps in membrane

Question 24

how do solvents affect membrane permeability?

Answer 24

• solvents like ethanol (non-polar alkyl chain and polar OH group) interact with the phospholipids
• solvents dissolves/surrounds phospholipids
• more bigger gaps in membrane increases permeability