ch 6 - Enzymes

Question 1

efficiently and selectively catalzye chemical reactions

Answer 1

enzymes

Question 2

how do enzymes contributes to human health?

Answer 2

• can pathologically impact diseases
• therapeutic causes (target specific enzymes in body)
• indicate diseases (biomarkers)

Question 3

true or false. all enzymes are proteins, and all proteins are enzymes.

Answer 3

false. all enzymes are proteins but not all proteins are enzymes

Question 4

how are enzymes classified?

Answer 4

into 6 groups, based on the type of reaction they catalyze

Question 5

3 characteristics of catalysts

Answer 5

1. lower E needed for rxn to proceed
2. speed up attainment of equilibrium but dont change equilibrium
3. unchanged by the rxn

Question 6

Enzymes ________ increase the rates of reaction.

Enzymes ________ affect the equilibrium of the reaction.

Answer 6

Do

Do not

Question 7

how does substrate binding promote reactions?

Answer 7

• reduces the entropy
• dissolves the substrate to expose reactive enzymes
• aligns functional groups of enzyme with substrate
• distorts substrates
• induced fit of enzyme in response to substrate binding

Question 8

explain transition state binding in enzymes

Answer 8

• enzyme distorts the substrate, forcing it toward transition state
• enzyme must be shape and chemically compatible
• enzyme changes shape without breaking to fit into a binding site

Question 9

name the equation:
Vo = Vmax[S]
Km + [S]

Answer 9

Michaelis-Menton

- measures relationship between velocity and substrate concentration

Question 10

what is Km?

Answer 10

• amount of substrate required for enzyme to be functioning at 1/2 maximal velocity

Question 11

what is a Lineweaver-Burk plot?

Answer 11

• describes relationship b/w [S] and Vo
• double reciprocal of 1/Vo vs 1/[S]
• more precise was to analyze kinetic data
• determines Vmax and Km

Question 12

what is kcat?

Answer 12

• enzyme turnover number
• number of molecules of substrate converted to product per unit time under saturated conditions
• cVmax/[Et]

Question 13

What reversible enzyme inhibitor is being described and name an example.

• usually resembles substrate
• can only bind to free enzymes
• results in a increase in Km, and a decrease in affinity for substrate molecule

Answer 13

• Competitive inhibitor
• example: transition state analogue
• normal crosses y-axis at same point as inhibitor

Question 14

What reversible enzyme inhibitor is being described?

• bind only to enzyme substrate
• vmax and km are both decreased

Answer 14

• Uncompetitive inhibitor

- lines are parallel on graph/plot

Question 15

Name the enzyme inhibitor.

• binds both enzyme and enzyme substrate
• vmax decreases and theres no change in km

Answer 15

• noncompetitive inhibitor

- start at same spot on graph, but the noncompetitve inhibitor crossed the y-axis higher up than the no inhibitor

Question 16

what type of inhibitor is useful for killing organisms? (herbasides, pestasides, chemical warfare)

Answer 16

• irreversible inhibitors
• 1 specific type is suicidal inactivators
  - trojan horse
  - very effective drugs, initially unreactive but convert to a reactive species that inactivates the enzyme

Question 17

what are serine proteases and name examples.

Answer 17

• digestive enzymes that cleave peptide bonds in protein substrates
• mediate turnover of self proteins
• examples: trypsin, chymotrypsin, elastase

Question 18

what are the general characteristics of allosteric enzymes?

Answer 18

• have activities regulated by interactions with metabolic intermediates
• bind non-covalently to at sites distinct from active site
• usually quaternary structure
• often catalzye branch-point reactions
• slow
• dont obey Michaelis-Menten kinetics
• have sigmoidal curves