Enzymes

Question 1

Enzymes

Answer 1

Control and regulate chemical reactions in cells, lower the energy barrier allowing chemical reactions to occur more quickly

Question 2

Digestion

Answer 2

R group of amino acids lining the active site interact with the substrate which weakens the bonds within the substrate and lowers the activation energy required for the reaction

Question 3

Lock and key model

Answer 3

Shape of the active site is complementary to the shape of the substrate molecule

Question 4

Induced fit model

Answer 4

Shape of the active site changes when the substrate binds to it. The presence of the substrate induces a better fit

Question 5

Structure

Answer 5

Pure proteins: folded with an active site (tertiary structure)
Some require other factors to become active:
Cofactors - non-protein (metallic ions)
Coenzymes - an organic cofactors (ie. vitamins)

Question 6

Reaction rates

Answer 6

Substrate concentration: increase in substrate = increase in amount of product but not reaction rate
Enzyme concentration: increase in enzyme = increase in amount of product per unit time

Question 7

Limiting factors

Answer 7

Saturation: all active sites are taken up and the rest of the substrate cannot be broken down until the sites are free

Question 8

Reversible enzyme inhibition

Answer 8

Molecules bind to the enzyme non-covalently and can dissociate from the enzyme

• competitive reversible inhibition
• non-competitive reversible inhibition

Question 9

Competitive reversible inhibition

Answer 9

Inhibitor competes directly with substrate

Question 10

Non-competitive reversible inhibition

Answer 10

Inhibitor binds to enzyme away from the active site. It doesn’t block the substrate, but catalytic activity is inhibited as it won’t take place while the inhibitor is bound. Inhibitor causes a change of shape to the active site which decreases the likelihood of the substrate binding effectively

Question 11

Irreversible enzyme inhibition

Answer 11

Inhibitors bind covalently to the enzymes active site and cause a permanent loss of catalytic activit

Question 12

Protein secretion

Answer 12

• DNA is transcribed into mRNA
• mRNA and tRNA are translated
• mRNA, tRNA and ribosomes produce amino acids
• polypeptide is produced on ribosome
• polypeptide enters ER tubule where it’s modified
• polypeptide is enclosed in transport vesicle
• polypeptide is modified in Golgi complex
• protein is placed in transport vesicle
• protein transport vesicle fuses with plasma membrane
• exocytosis occurs

Question 13

Changing the active site

Answer 13

Above optimum value: intermolecular binds as broken, leads to a loss of function
Below optimum value: reaction slows/does not occur