Enzymes

Question 1

What is a co-enzyme

Answer 1

required inorganic ions to fully activate enzyme

Question 2

What is a co-factor

Answer 2

required organic molecules to fully activate enzyme

Question 3

what is a prosthetic group

Answer 3

Its a coenzyme or factor that is tightly associated with the enzyme

Question 4

what are the differences between enzymes and chemical catalysts

Answer 4

enzymes

• have remarkable cataytic power
• require milder conditions
• have a higher degree of specificity
• potential to be regulated

Question 5

Circe effect

Answer 5

allows some enzymes to catalyze reaction faster than predicted by diffusion-control limits

Question 6

what is the relationship between rate of reaction and activation

Answer 6

the relationship is inverse and exponential

Question 7

What are the functions of enzymes

Answer 7

• provides alternate, lower-energy pathways between the substrate and product
• decreases activation energy

Question 8

Major modes of enzymatic catalysis

Answer 8

• substrate binding
• transition-state stabilization
• acid/base catalysis

Question 9

Substrate binding

Answer 9

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

Question 10

Transition-State Stabilization

Answer 10

• increased enzyme-substrate interaction

- enzyme distorts substrate forcing it towards the transition state

Question 11

What is the active site shape in relation to its substrate

Answer 11

similar enough to ensure specificity and different enough to promote change

Question 12

Transition-state analogs

Answer 12

• competitive inhibitors - structures resemble unstable transition states and have
• higher affinity to the enzyme than the natural substrate

Question 13

Which side chains most often participate in mechanisms of catalysis

Answer 13

Polar, ionizable residues

Question 14

Acid-base catalysis

Answer 14

• achieved by catalytic
• transfer of a proton.
  uses the side chain of some amino acid as a proton donor or acceptor.

Question 15

Covalent Catalysis

Answer 15

perfomed sucrose phosphorylase

Question 16

Kinetics

Answer 16

study of the rates at which reactions occur. Product/time

Question 17

ways in which enzyme kinetics is influenced

Answer 17

change in protin structure, temperature, pH, enzyme and substrate concentration

Question 18

What does the Michaelis-Menten equation and graph represent

Answer 18

describes the relationship between substrate concentration and initial velocity
V0 = Vmax{S}/ km+{S}

Question 19

what does Km represent

Answer 19

substrate required to reach half of max velocity of the enzyme

Question 20

What is an enzyme turnover number (kcat)

Answer 20

number of molecules of substrate converted to product/time

Kcat=Vmax/{E}t

Question 21

Lineweaver-Burke plot

Answer 21

describe relationship between velocity and substrate concentration

Question 22

What is an inhibitor

Answer 22

compound that binds to an enzyme to interfere with its activity

Question 23

Competitive inhibition

Answer 23

inhibitor binds to free enzyme. Vmax is the same but Km increases

Question 24

Uncompetitive Inhibition

Answer 24

inhibitor binds to ES. Km decreases, v max decreases

Question 25

Irreversible inhibitors

Answer 25

form stable covalent bonds with the enzyme to inactivate the enzyme

Question 26

Suicidal inactivators

Answer 26

converted to a reactive species that inactivates the enzymes

Question 27

WHat are properties of Serine proteases

Answer 27

• digestive enzymes that cleave peptide bonds in protein substances.
• ## synthesized and stored in the pancreas as inactive zymogens to prevent damage to cellular proteins

Question 28

What are the members of serine protease

Answer 28

Trypsin, Chymotrypsin, and elastase

Question 29

what amino acids does trypsin cleave by

Answer 29

Lys and Arg

Question 30

what amino acids does chymotrypsin cleave by

Answer 30

Phe and Tyr

Question 31

what amino acids does Elastase cleave by

Answer 31

Gly and Ala

Question 32

What roles are performed by the serine protease catalytic triad

Answer 32

• Histidine removes H from Serine’s hydroxyl
• Asp stabilizes the “+” charged His to facilitate serine ionization (acid-base catalysis)
• Serine acts as a nucleaphile attacking the carbonyl group of the polypeptide substrate (covalent catalysis)

Question 33

properties of Allosteric enzymes?

Answer 33

• activities that regulated by interaction with metabolic intermediates
• binds noncovalently to allosteric enzymes
• usually quaternary structures
• often catalyze branch-point reactions
• often catalyze slow
• doesnt obey michaelis- menten kinetics
• obey sigmoidal curves

Question 34

What are the allosteric inhibitors and activators of Phosphofructokinase (allosteric enzymer)

Answer 34

Phosphoenolpyruvate (PEP) inhibits PFK1

ADP activates PFK1

Question 35

WHat is PFK1 involved in

Answer 35

it catalyzes an early step in glycolysis.

The concentrations of PEP and ADP act allosterically through it to regulate ATP production in glycolysis.

Question 36

In phosphorylation, What do kinases and phosphatases do

Answer 36

kinases add a phosphoryl group, while phosphatases remove them

Question 37

How is the production of glycogen from glucose regulated

Answer 37

glycogen synthase catalyzes prod of glycogen from glucose, while glycogen phosphorylase catalyzes the breakdown of glucose into glucose

Question 38

What does phosphorylation do in respect to the enzyme

Answer 38

phosphorylation activated the catabolic (breakdown) enzyme and inactives the anabolic (builds) enzyme