enzyme regulation and bioenergetics

Question 1

catabolic pathway

Answer 1

enzymes in a pathway can function to breakdown biomolecules and release energy

Question 2

anabolic pathway

Answer 2

enzymes in a pathway can also make complex biomolecules, needed by the cell, from small precursors

Question 3

pathways may contain unfavorable reactions

Answer 3

an unfavorable reaction can be driven forward by a favorable reaction

Question 4

pathways are regulated

Answer 4

substrates or products of one step in the pathway can interact with one of the enzymes to effect its activity and alter the efficiency of the entire pathway

Question 5

cells do not waste energy, or building blocks, …

Answer 5

making biomolecules that are already plentiful enough, or that are not needed under a given environmental condition; down-regulated to decrease production of end-product

Question 6

if a cell needs more energy, or more of a particular biomolecule, under a given set of circumstances…

Answer 6

the cells will produce more; up regulated to increase production of end product

Question 7

what is usually the first enzyme and why?

Answer 7

often the regulatory enzyme; more efficient since other steps do not waste energy unnecessarily

Question 8

what do enzymes in a pathway do that regulatory enzymes do not?

Answer 8

follow Michaelis-Menten kinetics

Question 9

what are the two main types of regulation?

Answer 9

allosteric and reversible covalent modification

Question 10

allosteric regulation

Answer 10

reversibly bind regulatory molecules that alter enzyme activity

Question 11

reversible covalent modification

Answer 11

a group is added to the enzyme to modulate its activity, and this group can be removed to reverse the effect

Question 12

what is true about positive regulators and negative regulators?

Answer 12

binding of positive regulator increases activity and the absence of a negative regulator increases activity

Question 13

what is the substrate concentration that gives 1/2Vmax

Answer 13

K0.5

Question 14

how can an enzyme regulate the activity of a second enzyme in regulation by reversible covalent modification?

Answer 14

by covalently modifying the enzyme

Question 15

bioenergetics

Answer 15

study of energy transductions in living systems

Question 16

what obeys the laws of thermodynamics?

Answer 16

biological energy

Question 17

gibbs free energy, G

Answer 17

measure of the amount of work a system can perform at constant temperature and pressure

Question 18

exergonic reaction

Answer 18

releases free energy, -delta G (favorable)

Question 19

endergonic reaction

Answer 19

gains free energy, +delta G (not favorable)

Question 20

enthalphy, H

Answer 20

reflects the number and kind of bonds in reactants (substrate, S) and product, P

Question 21

exothermic reaction

Answer 21

heat is released, -delta H

Question 22

endothermic reaction

Answer 22

heat is absorbed, +delta H

Question 23

entropy, S

Answer 23

measures randomness or disorder

Question 24

change in gibbs free energy equation

Answer 24

deltaG= deltaH-TdeltaS

Question 25

what do reacting systems tend to move towards?

Answer 25

equilibrium

Question 26

delta G naut

Answer 26

measure of how far a reaction must go to reach equilibrium, when initial concentrations of each component are 1M, with standard state conditions; constant for a given reaction

Question 27

what does actual free energy change for a reaction depend on?

Answer 27

initial concentrations of substrates and products, and on the temperature

Question 28

when deltaG<0, reaction tends to go

Answer 28

forward direction

Question 29

when deltaG>0, reaction tends to go

Answer 29

reverse direction

Question 30

when deltaG=0, reaction tends to go

Answer 30

it is at equilibrium

Question 31

______ DO NOT affect equilibrium, only the reaction rate and rate of approach to equilibrium

Answer 31

enzymes

Question 32

standard free energy changes for sequential reactions are additive therefore

Answer 32

thermodynamicaly unfavorable reaction can be coupled to a thermodynamically favorable reaction to drive the unfavorable reaction forward

Question 33

the deltaGnaut for ATP hydrolysis is

Answer 33

large and negative

Question 34

in metabolism, it is not _________, but ________, that couples the energy of ATP breakdown to endergonic reactions

Answer 34

ATP hydrolysis; group transfer

Question 35

for some mechanoenzymes, energy of ATP hydrolysis drives..

Answer 35

conformational changes to drive reactions

Question 36

what is the “true” cellular substrate?

Answer 36

Mg*ATP^2-

Question 37

in thermodynamics, what really matters?

Answer 37

relative energies of the reactants and the products