Chapter 2- Enzymes

Question 1

zymogen

Answer 1

inactivated form of enzyme

Question 2

Oxidoreductases

Answer 2

catalyze oxidation-reduction reactions (transfer of electrons between biological molecules). typically have cofactor that acts as electron carrier (ex: NAD+ or NADP+) reductant (electron donor), oxidant (electron acceptor)

Question 3

oxidase

Answer 3

catalyze oxidation reduction reactions and typically have oxygen as the final electron acceptor

Question 4

Transferases

Answer 4

catalyze movement of a functional group from one molecule to another. (kinases are included in this group- transfer of phosphate group, generally from ATP to another molecule)

Question 5

Hydrolases

Answer 5

catalyze breaking of a compound into two molecules using the addition of water (ex: phosphatase- cleaves phosphate group from another molecule)

Question 6

Lyases

Answer 6

catalyze cleavage of single molecule into two products. dont require water. typically referred to as synthases. (ex: ATP into AMP and inorganic phosphate)

Question 7

Isomerases

Answer 7

catalyze rearrangement of bonds within a molecule.

Question 8

ligases

Answer 8

catalyze addition or synthesis reactions generally b/w large similar molecules. often require ATP.

Question 9

two enzyme theories (also note which is more supported)

Answer 9

lock and key theory induced fit model (more supported)

Question 10

lock and key theory

Answer 10

enzymes active site (lock) is already in appropriate conformation for the substrate (key) to bind.

Question 11

induced fit model

Answer 11

substrate induces a change in shape of the enzyme. requires energy so its endergonic to change shape, but to release the substrate from the enzyme is exergonic.

Question 12

cofactors/coenzymes

Answer 12

nonprotein molecules that participate in catalysis of reaction. typically carry charge and recruited only when needed.

Question 13

apoenzymes

Answer 13

enzymes without their cofactors

Question 14

holoenzymes

Answer 14

enzymes containing cofactors

Question 15

prosthetic groups with respect to enzymes

Answer 15

tightly bound cofactors or coenzymes that are necessary for enzyme function

Question 16

cofactors

Answer 16

inorganic molecules/ metal ions (often ingested as dietary minerals)

Question 17

coenzymes

Answer 17

small organic groups, vast majority are vitamins or derivatives of vitamins such as NAD+, FAD, and coenzyme A.

Question 18

water-soluble enzymes

Answer 18

Vitamin B and C (ascorbic acid) are important and must be replenished regularly b/c they are easily excreted.

Question 19

fat-soluble vitamins

Answer 19

Vitamin A, D, E, and K are better regulated by partition coefficients (quantify ability of a molecule to dissolve in polar/nonpolar environments.

Question 20

saturation

Answer 20

when all available enzymes are working with substrates. this is where the enzymes are working at a maximal velocity as long as enzyme concentration stays constant.

Question 21

Michaelis-Menten equation (with enzyme concentration constant)…how to find velocity of an enzyme

Answer 21

v = Vmax [S] / Km + [S]

Question 22

when reaction rate is equal to half of Vmax

Answer 22

Km = [S]

Question 23

Km (Michaelis constant)

Answer 23

substrate concentration at which half of the enzymes active sites are full

Question 24

Km and enzymes affinity for substrate

Answer 24

low Km = high affinity high Km = low Km *note: Km cannot be changed, its an intrinsic property

Question 25

Lineweaver-Burk plots

Answer 25

x-intercept: -1/Km y-intercept: 1/Vmax

Question 26

T vs. R state

Answer 26

T (low affinity Tense state) R (high affinity Relaxed state)

Question 27

enzymes and temperature

Answer 27

reaction rate doubles in velocity for every 10degree increase in temperature until optimum temperature is reached. (37 degrees for human body).

Question 28

optimal pH in body

Answer 28

stomach- 2 pancreas- 8.5 rest of body- 7.4

Question 29

feedback regulation

Answer 29

regulation of enzymes by products further down a given metabolic pathway

Question 30

feed-forward regulation

Answer 30

regulation of enzymes by intermediates in the pathway

Question 31

negative feedback

Answer 31

feedback inhibition, which helps to maintain homeostasis

Question 32

4 types of reversible inhibition

Answer 32

1. competitive- inhibition by occupying active site, can be overcome by adding more substrate (larger Km and same Vmax) 2. noncompetitive- bind to allosteric site instead of active site, which induces a change in enzyme conformation, cannot be overcome (same Km and larger Vmax) 3. mixed- inhibitor can bind to enzyme or enzyme-substrate complex, but has different affinity for each, binds at allosteric site 4. uncompetitive- bind only to enzyme-substrate complex and essentially lock substrate in the enzyme, bind at allosteric site

Question 33

glycosylation

Answer 33

covalent attachment of sugar moieties (an enzyme modification that can tag an enzyme for transport within a cell or can modify protein activity/selectivity)

Question 34

how to tell if an enzyme is a zymogen?

Answer 34

it will end in -ogen

Question 35

hydrolysis

Answer 35

breaking a bond by adding water