Bioenergetics 2

Front 1

True or False

ATP is known as the ‘energy currency’ of the cell and needs to be relatively reactive for this role. However, it can remain in a bottle on the shelf (usually in a refrigerator) for many months unchanged. This is because ATP has a relatively high free energy of hydrolysis.

Back 1

False

Front 2

FAD transfers electrons by..

Back 2

accepting one electron and one hydrogen atom in its structure

Front 3

The free energy of ATP hydrolysis essentially comes from..

Back 3

forming ADP and phosphate

Front 4

The Free Energy contained in one mol of glucose (C6H12O6), assuming -220kJ/mol for each reduced bond, is:

Back 4

5 C-C bonds = 5 x -220 kJ/mol = -1100 kJ/mol7

C-H bonds = 7 x -220 kJ/mol = -1540 kJ/mol

Total estimated energy generated from one mole of glucose = -2640kJ/mol

Front 5

The Gibbs free energy change for ATP hydrolysis is large and negative in part because:*

A. the products are relatively less stable

B. the products (phosphate and ADP) are less soluble in water than ATP

C. there is less electrostatic repulsion among four negative charges of phosphate after hydrolysis

D. the terminal anhydride bonds in ATP are ‘weaker’ compared with the bonds in the products.

Back 5

C and D

Front 6

Exergonic reactions can be used to ‘drive’ endergonic reactions. This process requires:*

A. a mechanism for the transfer of energy from the endothermic reaction to the exothermic reactions

B. a mechanism for the transfer of energy from the exergonic reaction to the endergonic reaction

C. a common intermediate shared by the reactions that are coupled

D. a transport protein that couples the two reactons

Back 6

B and C

Front 7

Calculate (with 2 significant figures) the standard Gibbs Free Energy available for the reaction:

Pyruvate + NADH + H+ ——> lactate + NAD+

Given the following information:

Pyruvate + 2H+ + 2e- ——> lactate E’o = -0.19V

NAD+ + H+ + 2e- ——> NADH E’o = -0.32V

Faradays constant (F) = 96485 J V-1 mol-1

Back 7

ΔG’o = -nFΔE’o

-25 kJ/mol

Front 8

Reduction potentials can be used to:*

A. estimate the Free Energy of an oxidation-reduction reaction

B. estimate the enthalpy of ATP hydrolysis

C. track the number of electrons stored or transferred

D. estimate the amount of volts in hydrogen atoms

Back 8

A and C

Front 9

Ubiquinone transfers electrons by...

Back 9

accepting two electrons and two hydrogen ions in its structure

Front 10

Fructose 6-phosphate + ATP -> fructose 1,6-bisphosphate + ADP

Calculate the overall free energy of this reaction given the information below

R = 8.315 J/mol.K

T = 25°C

ATP —> ADP + Pi ΔG’o = -30.5kJ/mol

Fructose 1,6-bisphosphate -> fructose 6-phosphate + Pi ΔG’o = -16.0kJ/mol

Back 10

-14.5

Front 11

True or False:

If the standard Gibbs Free Energy for the hydrolysis of ATP is -30.5kJ/mol, then it would take +30 kJ/mol to synthesise ATP from the concentrations of ADP and Pi that exist in the cell

Back 11

False

Front 12

A carbon is oxidised if...

Back 12

The number of hydrogen atoms bonded to a carbon decreases

and

The number of bonds to more electronegative atoms (e.g. O, N, F, Cl, I or S) increases

Front 13

A carbon is reduced if...

Back 13

The number of bonds to more electronegative atoms (e.g. O, N, F, Cl, I or S) decreases

and

The number of hydrogen atoms bonded to a carbon increases

Front 14

True or False

The tendency of a metabolic reaction to proceed is due to the free energy of both the reactants and products as well as the change in randomness of that reaction

Back 14

True

Front 15

Sucrose + Pi ---> glucose 1-phosphate + fructose Calculate the standard free energy for the reaction above given the following:

sucrose + H2O ---> glucose + fructose ΔG'o =-29

glucose 1-phosphate + H2O ---> glucose + Pi ΔG'o = -21 kJ/mol

Back 15

-29 + 21 = -8kJ/mol

Front 16

Which of the following half-reactions has the greatest reduction potential (i.e. can act as the better reducing agent) compared with all the others in the list.

A. E’o =0.421V

B. E’o = 0.031V

C. E’o = 0.295VD. NA

D. E’o = -0.320V

Back 16

D

Front 17

Electrons are transferred from [A] reactions in the cell to specific [B]. The [C] then transfer the electrons to other [D] reactions and [E] in the inner mitochondrial membrane. The flow of electrons through these carriers and reactions in the inner mitochondrial membrane eventually contributes to the production of [F] molecule.

Back 17

A- oxidation-reduction

B- election carriers

C- election carriers

D- oxidation-reduction

E- election carriers

F- ATP

Front 18

overall charge of NAD+

Back 18

negative

Front 19

True or False

ATP is known as the ‘energy currency’ of the cell because like money it is the intermediate in the transaction of ‘value’ between different ‘entities’.

Back 19

True

Front 20

The free energy for ATP hydrolysis in vivo is actually greater than the standard free energy change of -30 kJ mol-1 because:

A. it can participate in phosphoryl group transfers.

B. it can easily be formed from other nucleotide triphosphates.

C. of the actual concentrations of ATP and its hydrolysis products in cells.

D. it has stronger electrostatic repulsion.

E. All of the above

Back 20

C

Front 21

In which direction to electrons flow?

High to low E values

Low to high E values

Back 21

Low to high

Front 22

True or false

In a coupled reaction we can add the ΔG'o values for each reaction to get the ‘overall’ ΔG'o values for the combined reaction.

Back 22

True

Front 23

‘Reduced bonds’ are a concept that allows us to:

A. estimate the reduction potential of a molecule

B. estimate the enthalpy of a molecule

C. estimate the free energy of a molecule

D. estimate the entropy of a molecule

Back 23

B

Front 24

The Gibbs Free energy change for ATP hydrolysis is large and negative in part because:

A. the products (ADP and phosphate) are relatively more stable

B. the products (ADP and phosphate) are more soluble in water than ATP

C. there is increased electrostatic repulsion among four negative charges of phosphate after hydrolysis

D. the terminal anhydride bonds in ATP are ‘stronger’ compared with the bonds in the products.

Back 24

A and B

Front 25

NAD+ transfers electrons by:

A. accepting two electrons and two hydrogen atoms in its structure

B. accepting one electron at a time in its structure

C. accepting a hydroxyl group in its structure

D. accepting a hydride ion in its structure

Back 25

d