3 Bioenergetics and Oxidative Phosphorylation

Bioenergetics

The study of the transfer and utilization of energy in biologic systems.

Exergonic

A reaction that has a net loss of energy and a negative ΔG.

Endergonic

A reaction with a positive ΔG.

Negative ΔG

A reaction that is spontaneous.

Equilibrium

If ΔG = 0

Opposite

The ΔG of a forward reaction is equal in magnitude but this in sign to the reverse reaction.

ΔGo

The standard free energy change is denoted as this.

1.987 cal/mol K

The gas constant (R) used in bioenergetics.

Direction

ΔGo cannot predict this of a reaction under physiologic conditions.

Additive

ΔGo values of two consecutive reactions are this.

ATP (adenosine triphosphate)

The universal energy currency of the cell.

-7.3 kcal/mol

The ΔG for hydrolysis of each terminal phosphate of ATP is approximately this.

ATP-ADP cycle

The cycle of ATP breakdown and synthesis is called this.

Adenylate kinase

The enzyme that converts 2 ADP → ATP + AMP.

Allosteric

AMP acts as an this stimulator of metabolic pathways.

2

In ischemic tissues

Uric acid

AMP is eventually degraded into this and excreted in urine.

NAD+ and FAD

Metabolic intermediates donate electrons to these.

NADH and FADH2

The reduced forms of NAD+ and FAD are these.

Oxidative phosphorylation

The process in which electrons flow to oxygen while generating ATP is called this.

Inner mitochondrial membrane

The electron transport chain occurs in this.

Water (H2O)

The final common pathway of electrons in the ETC reduces oxygen to this.

Complex I

The first protein complex inhibited by rotenone is this.

Antimycin A

The inhibitor of Complex III (cytochrome bc1) is this.

Complex IV (cytochrome a + a3)

Cyanide

ATP synthase

The enzyme that directly synthesizes ATP using the proton gradient is this.

3 ATP molecules

One full rotation of the c-ring of ATP synthase produces this many ATP molecules.

Hydrolysis

ATP synthase can also catalyze this of ATP.

Proton (H+) gradient

The driving force for ATP synthesis in oxidative phosphorylation is this.

ATP

An increase in ADP and Pi leads to increased synthesis of this.

UCP1 (thermogenin)

The physiological uncoupling protein in brown adipose tissue is this.

Cold activation of UCP1 expression

Cold activates UCP1 expression through Catecholamines.

Brown fat

Brown fat is associated with energy Expenditure.

White fat

White fat is associated with energy Storage.

2

4-DNP (dinitrophenol)

Energy release from uncoupling by 2

4-DNP

Synthetic uncouplers

Two other examples of synthetic uncouplers are carbonyl cyanide m-chlorophenyl hydrazone and Carbonyl cyanide phenylhydrazone.

Valinomycin

A potassium ionophore that inhibits ATP synthesis.

Aspirin and salicylates at high doses

At high doses

Adenine nucleotide antiporter

The protein that exchanges ATP and ADP across the inner mitochondrial membrane.

Adenine nucleotide antiporter function

The adenine nucleotide antiporter imports ADP into the matrix and exports ATP.

Symporter

The cotransporter that moves Pi and H+ into the mitochondrial matrix.

Inner mitochondrial membrane transporter

The inner mitochondrial membrane lacks a transporter for NADH.

Cytosolic NADH transport

Reducing equivalents from cytosolic NADH are transported by Substrate shuttles.

Glycerol 3-phosphate shuttle ATP yield

The glycerol 3-phosphate shuttle yields 1.5 ATP per NADH.

Glycerol 3-phosphate shuttle usage

The glycerol 3-phosphate shuttle is mainly used in Skeletal muscle.

Malate-aspartate shuttle ATP yield

The malate-aspartate shuttle yields 2.5 ATP per NADH.

Malate-aspartate shuttle usage

The malate-aspartate shuttle is mainly used in Hepatocytes and cardiac myocytes.

Energy capture during exergonic reactions

The energy released during exergonic reactions is captured in the form of ATP.

Endergonic reaction

A reaction that requires energy input is termed Endergonic.

Logarithmic function in ΔG equation

The logarithmic function used in the ΔG equation is Natural logarithm (ln).

Substrates for ATP synthase

The substrates for ATP synthase are ADP and Pi.

Oxidative phosphorylation location

Oxidative phosphorylation occurs only in cells containing Mitochondria.

Proton gradient created by ETC

The proton gradient created by the ETC is also called the Proton motive force.

ΔGo and concentration changes

ΔGo is not affected by changes in substrate or product Concentrations.

Reaction feasibility

The initial and final energy states of reaction components determine whether a reaction is Possible.

Free energy change at 1 mol/L

When reactants and products are at 1 mol/L

Relationship between ΔG and ΔGo

The relationship between ΔG and ΔGo includes the terms concentration of reactants

NADH

The reduced coenzyme that donates electrons to Complex I.

FADH2

The reduced coenzyme that donates electrons to Complex II.

Complex IV function

Complex IV reduces oxygen to Water (H2O).

Uncoupling

The process by which ATP is produced without capturing the H+ gradient is called Uncoupling.

Heat production in brown adipose tissue

Heat production in brown adipose tissue is an example of Non-shivering thermogenesis.

Nonshivering thermogenesis

Heat production in brown adipose tissue.

Ionophore

A compound that facilitates transport of ions across membranes.

Energy

A nonspontaneous process requires input of this.

Fuels

The ETC is the final pathway for electrons derived from various substances.

NAD+

The coenzyme formed from niacin.

FAD

The coenzyme formed from riboflavin.

Negative

The ΔG of a coupled reaction can be made favorable if the sum of ΔGo values is this.

c-ring

The portion of ATP synthase that rotates during proton flow.

Spontaneous

The free energy change determines whether a reaction is this under given conditions.

Inner

The ETC complexes are embedded in this mitochondrial membrane.

Adipose tissue

The organ where brown fat is abundant in newborns.

Heat

Excess uncoupling leads to dissipation of energy as this.

Glycerol 3-phosphate shuttle

One of the two main substrate shuttles for cytosolic NADH.

Malate-aspartate shuttle

The other main substrate shuttle for cytosolic NADH.

Aspirin

High doses of this can lead to metabolic acidosis through uncoupling.

Reactants and products

ΔG depends on concentrations of these.

Reduction

Electrons move through the ETC in a sequence of increasing this potential.

Complex IV

The ETC reduces O2 to water by the action of this complex.

Cytosol and matrix

The mitochondrial membrane transport system ensures exchange of ATP and ADP between these.

ΔG

The name for ΔGo when conditions are not standard is simply this.

IV

The proton gradient is established by complexes I

Coenzyme Q (ubiquinone)

The small lipid-soluble electron carrier in the ETC.

Cytochrome c

The protein that shuttles electrons between Complex III and IV.

Heat production

The main outcome of uncoupling is loss of ATP synthesis and increase in this.

Ferrier

Lippincott Illustrated Reviews: Biochemistry