lecture 4

Question 1

negative delta G

Answer 1

spontaneous rxn

Question 2

how can unfavourable rxns occur?

Answer 2

if they are coupled to a favourable one

Question 3

for sequential rxns, standard free energy changes are

Answer 3

additive

Question 4

the free energy is directly related to

Answer 4

the ratio of concentration of product and reactants

Question 5

activation energy (Ea)

Answer 5

energy must be acquired by a molecule to undergo a chem rxn

Question 6

what does delta G not tell us?

Answer 6

the speed of rxn

Question 7

catalyst

Answer 7

lowers Ea of a rxn

Question 8

Enzyme

Answer 8

biological catalyst. speeds up rxn rate by lowering Ea

Question 9

Enzymes are

Answer 9

-not consumed in the process
-highly specific in terms of substate and rxn
-allow rxns to occur quickly

Question 10

does delta G change w time?

Answer 10

yes, bc the concentration of products and reactants is changing

Question 11

steady state equilibrium

Answer 11

relatively stable equilibrium. concentration of products and reactants vary slightly

Question 12

are cells ever at a thermodynamic equilibrium?

Answer 12

no! unless dead

Question 13

living cells are constantly exchanging

Answer 13

material with their environment

Question 14

equilibrium constant

Answer 14

the ratio of substrates and product when the rates of the forward and reverse rxns are equal

Question 15

equilibrium constant (K=?)

Answer 15

[products]/[reactants]

assume delta G is zero if not given

Question 16

A + B –><– AB
if A and B bind non-covalently, is the free energy change positive or negative?

Answer 16

Negative bc rxn is favourable

-if A and B bind strongly, you need less of A and B to make product

Question 17

chemical siphons

Answer 17

drives energetically unfavourable rxns

Question 18

thermal motion

Answer 18

-molecules diffuse
-larger molecules diffuse slower than small ones
-random encounters between substrate and enzyme can lead to formation of an enzyme-substrate complex stabilized by noncovalent interactions

Question 19

enzyme kinetics: velocity

Answer 19

rate of rxn

Question 20

Vmax

Answer 20

the max velocity of a rxn for an enzyme. how quickly it can catalyze a rxn when fully saturated w substrate

Question 21

Michaelis constant (Km)

Answer 21

concentration of substrate at which enzyme is at half Vmax

Question 22

entropy

Answer 22

measure of a system’s disorder

Question 23

do competitive enzymes bind reversibly or irreversibly to the substrate?

Answer 23

reversibly

Question 24

turnover number for an enzyme definition

Answer 24

the maximum number of molecules of substrate that can be converted to product by one enzyme molecule per unit time

Question 25

sugar cube dissolved in a cup of coffee. what happens to entropy of the sugar?

Answer 25

it increases.

sugar cube dissolves, more freedom of movement/random movement; increased entropy (more disordered)

Question 26

what is the first law of thermodynamics?

Answer 26

energy can not be created or destroyed (law of conservation of energy)

states that energy can be transduced from one form to another

Question 27

ATP carries stored potential energy and transfers it through the formation of

Answer 27

phosphate bonds

Question 28

Reactions that have positive standard free energy changes (ΔG’°>0) can be made to occur in cells by:

Answer 28

both coupling them with exergonic reactions via a common intermediate and manipulating the concentrations of products and reactants such that ΔG’<0

Question 29

To predict the direction in which a particular reaction will proceed at a given moment within a particular cellular compartment, one must know all of the following (4)

Answer 29

standard conditions.
the concentrations of reactants and products.
the ratio of [ADP] / [ATP].
the temperature at which the cell is found.

Question 30

For a reaction with a standard free energy change, ΔG’° = +0.7 kcal/mole, how can we make the rxn occur?

Answer 30

The reaction could be made to occur by altering the concentrations of reactants and products