2.4 - Enzymes

Question 1

Why are enzymes so remarkable?

Answer 1

• Low temperatures
• Normal pH and pressure
• More specific

Question 2

How many amino acids is the active site made from?

Answer 2

About 6 to 10.

Question 3

What happens in catabolic reactions?

Answer 3

Metabolites are broken down.

Question 4

What happens in anabolic reactions?

Answer 4

Synthesis of larger molecules.

Question 5

Where is catalase found in eukaryotic cells?

Answer 5

Small vesicles called peroxisomes.

Question 6

In our digestive system, where are enzymes secreted from?

Answer 6

Cells lining the alimentary canal, into the gut lumen.

Question 7

Which enzyme contains a zinc ion as a prosthetic group?

Answer 7

Carbonic anhydrase

Question 8

What does carbonic anhydrase do?

Answer 8

Catalysed the inter conversion of carbon dioxide and carbonic acid which then breaks down to protons and hydrogencarbonate ions.

Question 9

Which ion must be present from amylase to make maltose?

Answer 9

Chloride.

Question 10

What are coenzymes?

Answer 10

Small, organic non-protein molecules that bind temporarily to the active site of the enzyme.

Question 11

Where are many coenzymes derived from?

Answer 11

Water soluble vitamins.

Question 12

Define enzyme substrate complex

Answer 12

enzyme model with substrate molecule in active site, joined temporarily by non-covalent forces

Question 13

what is Q10?

Answer 13

temperature coefficient, calculated by dividing rate of reaction at (T+10) by the rate of reaction at T

Question 14

How does pH affect enzymes?

Answer 14

Excess H+ ions interfere with hydrogen bonds and ionic forces, changing shape

Question 15

Benefits of enzyme degradation

Answer 15

elimination of abnormal proteins

eliminating superfluous enzymes

Question 16

What regulates an enzyme controlled reaction

Answer 16

End product inhibition

Question 17

How do many toxins work?

Answer 17

By inhibiting or inactivating enzymes

Question 18

What are two poisons/toxins that inhibit enzyme action?

Answer 18

• cyanide
• snake venom
• malonate (respiration)
• arsenic (respiration)

Question 19

What does cyanide inhibit?

Answer 19

catalase

stop final stage of aerobic respiration

Question 20

Which medicinal drugs act as enzymes inhibitors and how?

Answer 20

• some antiviral drugs (eg reverse transcriptase inhibit reverse transcriptase which catalyses the replication of viral DNA)
• some antibiotics (penicillin inhibits transpeptidase which catalyses the formation of proteins in bacterial cell walls. this weakens the cell wall and the bacterium cant regulate osmotic pressure and bursts)

Question 21

What type of reactions do enzymes catalyse?

Answer 21

Cellular (eg respiration) and whole body (digestion)

Structural ( eg production of collagen) and function (eg respiration)

Question 22

What enzyme catalyses intracellular reactions?

Answer 22

catalase

Question 23

What enzyme catalyses extracellular reactions?

Answer 23

trypsin

Question 24

Describe the role of catalase

Answer 24

Hydrogen peroxide to oxygen and water

Question 25

Describe the role of trypsin

Answer 25

Catalyses the hydrolysis of peptide bonds | made in pancreas and secreted into small intestine

Question 26

Describe the role of amylase

Answer 26

found in saliva | hydrolysis of starch to maltose

Question 27

What about enzymes is responsible for lowering activation energy?

Answer 27

The formation of the enzyme-substrate complex

Question 28

Why does the enzyme substrate complex lower the activation energy?

Answer 28

- if they need to be joined, they are held close together | - if they need to be separated, the active site puts strain on the bonds in the substrate

Question 29

What does Q10 show?

Answer 29

How much the rat of a reaction changes when the temperature is raised by 10 degrees

Question 30

What does a Q10 value of 2 demonstrate?

Answer 30

Rate doubles when temp is raised by 10 degrees

Question 31

What are the factors affecting the rate on enzyme controlled reaction?

Answer 31

- temperature - pH - enzyme concentration - substrate concentration

Question 32

Describe two ways of measuring the rate of an enzyme controlled reaction

Answer 32

1) How fast the product appears, eg for catalase you could collect volume of oxygen 2) you could measure the disappearance of a substrate and compare with different conditions

Question 33

Describe an experiment that investigates the effect of temperature of catalase activity

Answer 33

- boiling tubes with hydrogen peroxide - add equal volumes of buffer solution for constant pH - put each boiling tube in different water bath temp - add catalase - calculate volume of oxygen produced and repeat

Question 34

Whats the difference between cofactors and coenzymes?

Answer 34

Coenzymes are cofactors that are organic molecules - cofactors don't get used up - coenzymes are changed by reactions and recycled

Question 35

Whats a source of coenzyme?

Answer 35

Vitamins

Question 36

What an enzymes prosthetic group?

Answer 36

When a cofactor is tightly bound to the enzyme, | permanent part of active site

Question 37

Cofactor of amylase

Answer 37

Cl-

Question 38

Prosthetic group of carbonic anhydrase

Answer 38

Zn2+

Question 39

Describe competitive inhibition

Answer 39

- similar shape to substrate | - compete for active site

Question 40

Describe non-competitive inhibition

Answer 40

-binds at allosteric site which causes the active site to change shape

Question 41

What happens when you increase the substrate concentration in competitive and non-competitive inhibition?

Answer 41

competitive - increase rate of reaction | non-competitive - wont make any difference an enzyme activity will still be inhibited

Question 42

When is inhibition irreversible?

Answer 42

when there are strong, covalent bonds and the inhibitor cannot be removed

Question 43

When is enzyme inhibition non-reversible?

Answer 43

when there are weaker hydrogen bonds or weak ionic bonds and the inhibitor can be removed

Question 44

Why are enzymes sometimes synthesised as inactive precursors in metabolic pathways?

Answer 44

to prevent them causing damage to cells

Question 45

Example of an enzyme acting as a inactive precursor

Answer 45

some proteases (which break down proteins) are inactive precursors so they don't damage proteins in the cell that they are made

Question 46

How do inactive precursor molecules work?

Answer 46

part of the precursor molecule inhibits its action as an enzyme and this part can be removed when the enzyme needs to be active

Question 47

Why do we need small amounts of cofactors in our bodies?

Answer 47

- they can be reused - enzyme mass is small - some enzymes don't need cofactors

Question 48

What are models used for?

Answer 48

simple representations of processes

Question 49

Define enzyme/biological catalyst.

Answer 49

proteins used in metabolism that alter the rate of chemical reaction lower activation energy not used up in the process