Bioenergetics

Question 1

Bioenergetics

Answer 1

• Study of how biological systems operate while obeying the laws of thermodynamics - Uses the change in Gibbs free energy (delta G) to determine energy changes at constant pressure and temperature - Delta G reflects the amount of work a reaction either can perform or requires - Delta G can be estimated for coupled electron loss (oxidation) and gain (reduction) reactions

Question 2

Delta G formula

Answer 2

Delta G = Delta H - T(Delta)S - For any reaction in which A B at constant pressure and temperature

Question 3

Units of Delta G

Answer 3

Kcal/mol or Kjoule/mol

Question 4

Delta H

Answer 4

• The change in enthalpy (aka change in heat content) - Reflects changes in the number and types of chemical bonds and noncovalent interactions broken and formed during the reaction

Question 5

Delta S

Answer 5

• Change in entropy; reflects changes in the system’s randomness - An increase in entropy = increase in disorder = decrease in Delta G - Creating order from disorder takes energy and increases Delta G - Units of Delta S are Kjoules/mol*Kalvin or Kcal/mol*Kalvin

Question 6

If Delta G = 0

Answer 6

The reaction is at equilibrium; there is no net flow in either direction

Question 7

Any reaction with a non-zero Delta G

Answer 7

Proceeds spontaneously to a lower free energy state

Question 8

If Delta G is negative

Answer 8

• The reaction will proceed spontaneously in the direction written
• The reaction releases energy and is said to be exergonic

Question 9

Exergonic Reactions

Answer 9

• Release energy
• Have a negative Delta G

Question 10

If Delta G is positive

Answer 10

• The reaction will proceed spontaneously in the reverse direction
• The reactions required energy to proceed in the direction written and is endergonic

Question 11

Endergonic Reactions

Answer 11

• Require energy to proceed in the direction written
• Have a positive Delta G

Question 12

Delta G for any reaction depends on what variables?

Answer 12

• The nature of the reactants and products
• Concentration of reactants and products
• Temperature
• Pressure
• pH

Question 13

Standard Free Energy Change (Delta G°)

Answer 13

The change in free energy at 25 degrees celcius with all reactants and products initially in their standard states

Question 14

Biochemical Standard Free Energy Change (Delta G°’)

Answer 14

Indentical to Delta G° except pH is specified at being at 7.0

Question 15

Free energy change for non-standard-state concentrations

Answer 15

Question 16

At equilibrium when Delta G = 0, and [C][D]/[A][B] = Keq, and Delta G°’ = - RTLnKeq

Answer 16

Delta G°’ can established by determining Keq

Question 17

Reaction rate is proprtional to what?

Answer 17

Delta G Double Dagger = Free activation energy

This is how enzymes work to speed up reactions, by lowing the free activation energy requried to reach the transitional state

Question 18

Common uses of ATP, GTP, CTP, and UTP

Answer 18

• Adenosine triphosphate hydrolysis provides energy for cellular reactions
• GTP provides energy for protein synthesis and intracellular signalling
• CTP for phospholipid synthesis
• UTP for complex carbohydrate synthesis

Question 19

Delta E°’ equation

Answer 19

Delta E°’ = E°’ (e- acceptor) - E°’ (e- donor)

Delta G°’ = -nF(Delta)E°’

n = number of electrons

F = faraday’s constant

Question 20

What happens to ATP production if oxygen is not available?

Answer 20

• Most ATP production will cease since the energy from oxidation of fuels (electrons carried by NADH and FAD(2H)) cannot be transferred to oxygen
• Oxygen consumption is coupled to total body energy expenditure

Question 21

Oxygen consumption in the body

Answer 21

• 90-95% of O2 consumption in the resting state is used as an electron receptor in the mitochondrial electron transport/respiratory chain
• 5-10% is required for non-mitochondrial oxidases and oxygenases and is not related to ATP sythesis