Lecture 1: Bioenergetics

Question 1

Benjamin Murray (life- long alcoholic) developed symptoms of:

Answer 1

dermatitis, diarrhea, dementia

Question 2

Deficiency in the B-Vitamin niacin, present at low levels in alcoholics presents the classical symptoms of _____

Answer 2

pellagra

ethanol inhibits intestinal absorption of niacin

Question 3

Deficiency in niacin affects many ________enzymes

Answer 3

dehydrogenase

Question 4

The Free Energy Change (ΔG) for a reaction is:

Answer 4

ΔG_reaction = G_products – G_reactants

Question 5

When ΔG is negative (<0), reaction occurs _________ it is ______ and the reaction proceeds to the _____

Answer 5

spontaneously, exergonic, right

Question 6

When ΔG is positive, the reaction requires _____ to proceed; it is ______ and the reaction does not occur _______

Answer 6

energy, endergonic, spontaneously

Question 7

At equilibrium ΔG =

Answer 7

0

Question 8

in ΔG is related to the _______ of a reaction

Answer 8

directionality

Question 9

Standard free energy change =

Answer 9

ΔG^0’

Question 10

Change in ΔG is related to the directionality of a reaction but not___

Answer 10

to its rate or path it follows.

Question 11

G = ΔG^0’ under which conditions?

Answer 11

25°C

1 atm pressure

1M Initial concentration of reactants and products

Except [H+], which is 1 x 10-7 M (so pH is 7.0)

Question 12

The Laws of Thermodynamics

Answer 12

1st: Energy can be neither created nor destroyed. The total energy of the universe is constant
2nd: Systems tend toward disorder. Entropy increase in the universe

Question 13

Entropy Equation

Answer 13

ΔG = ΔH - TΔS

Where:

ΔH is the change in enthalpy or heat content of system

ΔH = Hproducts - Hreactants

T is absolute temperature in Kelvin

ΔS is the change in entropy

Question 14

For ΔG to be neg:

Answer 14

Either ΔH is neg.

Or TΔS is pos

Or both

Question 15

The chemical energy of a compound is affected by:

Answer 15

Bond strain

Resonance forms

Steric effects

Solvation

Question 16

When products have less chemical energy (are more stable) than reactants, the excess ____ is liberated as ____ and ΔH is ____.

Answer 16

energy, heat, negative

Question 17

Relationship between ΔG^0’ and the Equilibrium Constant, Keq

ΔG^0’ =

Answer 17

-RT x 2.303 log Keq

R is ideal gas constant (1.987 x 10-3 kcal/mol-K)

T is temperature in Kelvin

Question 18

Typically, if ΔG^0’ is between +3 and -3 kcal/mol, reactions are driven by

Answer 18

“mass action” effects

Question 19

CP levels kept around ____ in muscle; used as phosphoryl donor to rapidly synthesize ATP when [ATP] low in muscle

Answer 19

30 mM

Question 20

During sudden exercise, _________, and CP transfers a phosphoryl group to ADP

Answer 20

ATP is depleted

Question 21

______ is a high energy compound

Answer 21

ATP

Has two phosphoanhydride bonds that, when hydrolyzed, yield a lot of free energy. It has a large negative ΔG⁰’ (hydrolysis)

Question 22

5 examples of high energy compounds are:

Answer 22

Phosphate anhydrides (ATP), enol phosphates (PEP), acyl phosphates (1,3-BPG), guanidinium phosphates (CP) and thiol esters (acyl-CoAs)

Question 23

The transphosphorylation of ATP to ADP requires what cofactor?

Answer 23

Mg²⁺

Question 24

Reasons for large negative Delta G^0’ of hydrolysis of ATP

Answer 24

• Resonance stabilization of the product inorganic phosphate
• Less electrostatic repulsion (bond strain) in product (ADP) compared to reactant (ATP)
• Greater degree of solvation (hydration) of products compared to reactants

Question 25

Method used to make an unfavorable reaction or process favorable

Answer 25

Coupling

Question 26

Ways of Regulating Metabolic Processes (Pathways)

Answer 26

• Amounts of enzymes
• Catalytic activity of enzymes
  
  • Allosteric control (feedback inhibition)
  • Irreversible steps
  • Post-translational modification
  • Hormonally
  • Often responsive to energy charge
• Compartmentalization

Question 27

ATP-generating (catabolic) pathways are [inhibited/stimulated] by high energy charge

Answer 27

inhibited

the reverse is true for ATP-utilizing (anabolic) pathways

Question 28

Energy charge range in cells

Answer 28

0.85-0.95

very narrow and high range

Question 29

______ is a sensitive indicator fo cellular energetic state

Answer 29

AMP

Question 30

When ATP drops 10%, AMP can increase as much as ______.

Answer 30

600%

Question 31

AMPK phosphorylates particular target proteins and thereby acts to shift metabolism: Toward _______ and away from ______

Answer 31

energy-yielding processes; away from energy-consuming ones

Question 32

Activated carriers of electrons for fuel oxidation

Answer 32

• NAD+ (located mainly in matrix)
• FAD

Question 33

Activated carriers of electrons for reductive biosynthesis

Answer 33

• NADPH

Located mainly in cytosol

Question 34

Activated carrier of 2-carbon (and larger acyl) units

Answer 34

Coenzyme-A

Question 35

NADH and NADPH Vitamin precursor

Answer 35

Nicotinate (niacin)

Question 36

FADH₂ and FMNH₂ Vitamin precursor

Answer 36

Riboflavin (vitamin B₂)

Question 37

Coenzyme A vitamin precursor

Answer 37

Pantothenate

Question 38

Thiamine pyrophosphate vitamin precursor

Answer 38

Thiamine (vitamin B₁)

group carried - aldehyde

Question 39

Tetrahydrofolate vitamin precursor

Answer 39

folate

group carried - one-carbon units