Enzymes 1 & 2

Question 1

what is activation energy?

Answer 1

the energy required to go from reactants to products

Question 2

stabilizing transition states makes it more favorable and reduces ___________

Answer 2

delta G

Question 3

definition of an enzyme

Answer 3

increases the rate or velocity of a chemical reaction without changing itself in the process

Question 4

classic enzyme nomenclature

Answer 4

substrate +action+ase

Question 5

systematic enzyme nomenclature

Answer 5

substrate(s) + enzyme type

Question 6

oxidoreductase function

Answer 6

catalyze oxidation-reduction reactions
ex. lactate to pyruvate

Question 7

transferase function

Answer 7

catalyze transfer of C N or P containing groups
ex. serine to glycine

Question 8

hydrolase function

Answer 8

catalyze cleavage of bonds by addition of water
ex. urea

Question 9

Renin

Answer 9

role in regulation of blood pressure

Question 10

pepsin

Answer 10

digestive enzyme

Question 11

how do enzymes accelerate reactions?

Answer 11

-create an alternate reaction pathway in which the transition state has lower free energy
-decreases free energy of activation and lowers the activation barrier of delta G
-increase the concentration of substrate in the transition state and thus increases the rate of the reaction

Question 12

describe the active site of an enzyme

Answer 12

-small 3D cleft or crevice formed by different parts of amino acid sequence
-complementarity of substrate for site
-noncovalent interactions

Question 13

Lyases

Answer 13

catalyzes cleave of C-C, C-S, and C-N bonds
ex. pyruvate to acetylaldehyde

Question 14

Isomerases

Answer 14

catalyze racemization of optical or geometric isomers
ex, methylmalonyl CoA to Succinyl CoA

Question 15

ligases

Answer 15

catalyze formation of bonds between carbon and S, O, N coupled to hydrolysis of high energy phosphates
ex. pyruvate to oxaloacetate

Question 16

what are the noncovalent interactions that hold enzyme and substrate complexes together

Answer 16

-H bonding
-ionic
-van der waals
-hydrophobic

Question 17

what happens at Vmax

Answer 17

all of the enzyme present in the system is saturated

Question 18

what is km

Answer 18

km is the amount of substrate is takes to reach half Vmax
Vmax/2

Question 19

what is kcat

Answer 19

how many substrate molecules are transformed into products per unit time by a single enzyme

Question 20

how to calculate enzyme efficiency

Answer 20

kcat/km

Question 21

at high concentrations of substrate, the velocity of the reaction is ___________________, constant and independent of substrate concentration

Answer 21

zero order

Question 22

at low concentrations of substrate, the velocity of the reaction is ___________, proportional to substrate concentration

Answer 22

first order

Question 23

large Km=

Answer 23

low affinity of enzyme for substrate

Question 24

small Km=

Answer 24

high affinity of enzyme for substrate

Question 25

competitive inhibition

Answer 25

-inhibitor binds to active site -Km increases and Vmax stays the same

Question 26

how can competitive inhibition be overcome?

Answer 26

flooding the reaction with substrate

Question 27

noncompetitive inhibition

Answer 27

-binds to allosteric site -Km stays the same and Vmax decreases graph makes a v shape

Question 28

uncompetitive inhibition

Answer 28

-binds to enzyme-substrate complex -Km decreases and Vmax decreases lines run parallel

Question 29

modifies transpeptidase and prevents bacterial cell wall synthesis

Answer 29

penecillin

Question 30

modifies cyclooxygenase (1&2) & reduces inflammatory signals

Answer 30

Aspirin

Question 31

cooperative binding

Answer 31

binding at one site enhances binding at another

Question 32

Aspartate transcarbamyolase (ATCase)

Answer 32

first committed step of nucleotide biosynthesis -CTP is end product and feeds back to inhibit the enzyme

Question 33

what amino acids can be phosphorylated

Answer 33

serine, threonine, tryosine histidine in bacteria

Question 34

enzymes that add phosphates

Answer 34

kinases

Question 35

regulatory proteins involved in muscle contractility

Answer 35

Troponins T and I

Question 36

released in the plasma in response to cardiac damage -gold standard in diagnosing MI

Answer 36

Cardiac specific isoforms (cTn)

Question 37

cleaves all accessible peptide bonds (serine protease)

Answer 37

subtilisin

Question 38

cleaves after all accessible Lys or Arg (serine protease)

Answer 38

trypsin

Question 39

cleaves only after Arg in a specific sequence

Answer 39

thrombin

Question 40

statins block the 1st committed step in cholesterol synthesis because they are.....

Answer 40

competitive inhibitors in Hydroxymethylglutaryl (HMG) CoA reductase

Question 41

serious side affects of statins

Answer 41

-reduced testosterone -memory loss -transiant global amnesia -muscle pain

Question 42

formulas for delta G

Answer 42

ΔG=ΔH-TΔS ΔG=ΔG0'+1.36log products/reactants

Question 43

formula for standard state ΔG

Answer 43

ΔG0'= -1.36(logKeq)

Question 44

how can unfavorable biosynthetic reactions proceed?

Answer 44

can be accomplished by coupling reaction to a favorable reaction

Question 45

the overall ΔG of a reaction its the sum of....

Answer 45

free energy changes of the individual steps

Question 46

many unfavorable biosynthetic reactions are coupled to ________________

Answer 46

ATP hydrolysis (strong phosphate bonds)

Question 47

hexokinase couples reaction by ......

Answer 47

transferring phosphate directly from ATP to glucose----aided by proximity of both reactants binding to adjacent sites on the enzyme