Biochem Final Bioenergetics

Question 1

autotrophs vs. heterotrophs

Answer 1

autotrophs: produce their own high energy molecules
heterotrophs: require nutrients to produce high energy molecules

Question 2

bioenergetics definition

Answer 2

quantitative study of energy transduction in living cells and of the nature and function of chemical processes underlying transductions
obeying law of thermodynamics

Question 3

∆S positive vs negative

Answer 3

Entropy = S (J/mol x K)
+∆S = entropy increases
-∆S = entropy has decreased
∆S is relative

Question 4

H definition
∆H definitions +/-

Answer 4

enthalpy - heat content of a system
- ∆H (J/mol) = heat release from system (exothermic)
+ ∆H = heat absorbed by system (endothermic)

Question 5

∆G definition

Answer 5

Gibbs free energy - amount of energy capable of doing work during a reaction at a constant temperature and pressure
∆G (J/mol)
Gives direction of reaction and equilibrium position
-∆G = spontaneous reaction going forward, exergonic
+∆G = non-spontaneous moving forward, endergonic
∆G=0 at equilibrium

Question 6

∆G is negative when either

Answer 6

∆S is positive (entropy increases) or ∆H is negative (exergonic)

Question 7

when will ∆G be positive?

Answer 7

when ∆H is positive and and ∆S is negative

Question 8

∆G^o1

Answer 8

standard free energy change at pH 7

Question 9

how can thermodynamically unfavorable reactions be driven forward?

Answer 9

by coupling with a highly exergonic reaction through intermediate
summative ∆G^o1
Keq1 x Keq2

Question 10

exergonic reaction of ATP

Answer 10

ATP to ADP, Pi (inorganic phosphate)
AMP to PPi
4 negative charges on phosphate groups repel each other (high energy)
phosphoanhydride bonds break by hydrolysis
non-ATP forms are more stable by resonance and better solvation

Question 11

direct hydrolysis of ATP as source of energy for endergonic conformational changes

Answer 11

minority of cases
usually group transfer reaction: a transfer of phosphoryl, pyrophosphoryl or adenyl group to a substrate/enzyme to couple energy

Question 12

energy to recreate ATP from ADP

Answer 12

derived from food in heterotrophs
derived from photosynthesis in autotrophs

Question 13

enzymes that add or remove phosphates

Answer 13

kinase - adds phosphate
phosphatase - removes phosphate

Question 14

forming phosphate esters

Answer 14

ATP often the donor of a phosphate to form phosphate ester like glucose-6-phosphate

Question 15

how does specific binding sites facilitate ATP coupling of endergonic reactions?

Answer 15

substrates bind on specific enzyme sites which facilitate phosphorylation of substrate to catalyze endergonic reaction

Question 16

glucokinase

Answer 16

type of hexokinase only present in the liver - phosphorylation enzyme of glucose molecules at the start of glycolysis
regulate the rate at which glucose is utilized in glycolysis (and amount of free glucose in the body)

Question 17

lower energy positioning of electrons on reactants vs products

Answer 17

reactants share their electrons more equally than products which hold them more tightly, creating a lower potential

Question 18

why are fuels chemically good energy sources?

Answer 18

reduced organic compounds from which electrons (and H+) can be stripped such as methane
the more reduced a carbon atom is, the more free energy there is to release upon oxidation (think fatty acid hydrocarbon tails)

Question 19

how does ETC keep the electrons moving down

Answer 19

the electronegative oxygen is strong enough to attract electrons down a series of of electron acceptors
electron acceptors increase potential as electrons are received

Question 20

standard reduction potential

Answer 20

E - measure in volts of electron affinity in flow of electrons
∆E^o’ = E^o’(e acceptor) - E^o’ (e donor)

Question 21

NADH and FADH2 are

Answer 21

electron carriers, ready to shift form back and forth giving and receiving H+ and electrons

Question 22

for ∆G to be negative, ∆E must be

Answer 22

positive

Question 23

do you reverse the sign of ∆E^o’ when reaction direction is reversed?

Answer 23

NO, only with ∆G equations

Question 24

redox reactions never involve

Answer 24

formation of free electrons