Enzymes

Question 1

How do enzymes work?

Answer 1

Lower activation energy needed to start a chemical reaction.

Question 2

Describe the catalytic cycle of an enzyme.

Answer 2

Substrate enters active site, substrates held in active site by weak interactions (hydrogen and ionic bonds usually,) substrates . are converted to products, products are released from the enzymes active site, active site is now avaliable for new substrates

Question 3

Describe reaction rates.

Answer 3

Vary depending on concentration of enzyme and substrate, rate increases until all enzyme is occupied by substrate (saturtation). Increase by a factor of 10^3-10^8 with enzyme presence

Question 4

What are the mechanisms of catalysis?

Answer 4

Providing an alternative reaction pathway by means of the active site. can be geometrically complimentary (stabilizes TS). Electronic complementarity: aa side chains donate or accept protons, stable covalent ES complex, metal ion catalysis.

Question 5

How are enzymes classified?

Answer 5

By recommended name (substrate name +ase) or by systematic name (oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases)

Question 6

How are enzymes classified?

Answer 6

By recommended name (substrate name +ase) or by systematic name (oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases)

Question 7

What are the functions of coenzymes/cofactors? Give examples.

Answer 7

Metal ions (Mg, Zn, Fe) or organic molecules such as vitamins that are required by enzymes for their activity. may be chemically changed by reaciton and must be regenerated (eg NAD, NADP, FMN, FAD)

Question 8

What are the effects of temperature and pH on enzyme activity?

Answer 8

Optimum exists for enzyme activity, increasing temp increases velocity until enzyme denatures, pH can affect aa side chains in active site and lead to denaturing

Question 9

Describe basic enzyme kinetics and the effect of enzyme inhibitors.

Answer 9

[S] increases until Vmax is reached. inhibition can be reversible or irreversible, competitive or non-competitive. Competitive inhibition only requires higher [S] to reach Vmax, increases Km. noncompetitive inhibition decreases Vmax but Km stays the same

Question 10

Describe basic enzyme kinetics and the effect of enzyme inhibitors.

Answer 10

[S] increases until Vmax is reached. inhibition can be reversible or irreversible, competitive or non-competitive. Competitive inhibition only requires higher [S] to reach Vmax, increases Km. noncompetitive inhibition decreases Vmax but Km stays the same

Question 11

Discuss enzyme regulation.

Answer 11

Phosphorylation and dephosphorylation, induction and repression of enzyme synthesis, allosteric regulation (eg feedback inhibition)

Question 12

Discuss enzyme regulation.

Answer 12

Phosphorylation and dephosphorylation, induction and repression of enzyme synthesis, allosteric regulation (eg feedback inhibition)