IntroductionBefore food can be used to perform

work, its energy must be released through the process of respiration.

Two main types of respiration exist in living things. Both begin with glycolysis.Glycolysis: a process by which one

glucose molecule is broken down into two pyruvic acid molecules.

Fermentation (anaerobic respiration): pyruvic acid is broken down without the use of oxygen

Oxidative Respiration (aerobic respiration): pyruvic acid is metabolized using oxygen

GlycolysisGlycolysis occurs in the cytoplasm.It does not require oxygen.Each of its steps is catalyzed by a specific

enzyme.

Glycolysis

GlucoseATP ATP

ADP + P ADP + P

G3P G3P

G3P + P G3P + P

Pyruvic Acid Pyruvic Acid

NADH + H+ NADH + H+

2 ADP + 2 P 2 ADP + 2 P

2 ATP 2 ATP

NAD+ +2 H+ + 2 e-

NAD+ +2 H+ + 2 e-

Fermentation

Fermentation (Anaerobic Respiration)

Fermentation is the breakdown of pyruvic acid without the use of oxygen.

Glycolysis + Fermentation = Anaerobic Respiration

The metabolism of pyruvic acid during fermentation does not produce any ATP.

Instead, the function of fermentation is to break down pyruvic acid and regenerate NAD+ for reuse in glycolysis.

Pyruvic Acid

NADH + H+ NAD+ + 2 H+ + 2 e-

Lactic Acid

Pyruvic Acid

NADH + H+ NAD+ + 2 H+ + 2 e-

EthylAlcohol(Ethanol)CO2

Lactic Acid Fermentation

Alcoholic Fermentation

To Glycolysis

Oxidative Respiration

Aerobic RespirationThe result of glycolysis and aerobic

respiration is shown by the reaction:C6H12O6 + 6 O2 → 6 H2O + 6 CO2 + 36 ATPAerobic respiration occurs in the

mitochondriaouter and inner membranematrix: dense solution enclosed by inner

membranecristae: the folds of the inner membrane that house

the electron transport chain and ATP synthase

Steps:Conversion of Pyruvic AcidKreb’s CycleElectron Transport Chain

Structure of Mitochondrion

Kreb’s CycleThe Krebs Cycle is

the central biochemical pathway of aerobic respiration. It is named after its discoverer, Sir Hans Krebs. Because citric acid is formed in the process, it is also known as the Citric Acid Cycle.

NADH + H+NAD+

CoA

CoA

NAD+

NAD+

NADH + H+

NAD+

NADH + H+

NADH + H+

FAD

FADH2

ATPADP + P

CO2C

PyruvicAcidC C C

Acetyl-CoAC C

Citric AcidC C C C C C

CO2

C

KetoglutaricAcid

C C C C C

SuccinicAcid

C C C CCO2

C

MalicAcid

C C C C

OxaloaceticAcid

C C C C

Electron Transport ChainGlycolysis, the conversion of PA to acetyl-

CoA, and the Krebs Cycle complete the breakdown of glucose.

Up to this point:4 ATP (2 from glycolysis, 2 from Krebs)10 NADH (2 from glycolysis, 2 from the

conversion of PA, 6 from Krebs)2 FADH2 (from Krebs)

Electron Transport ChainNADH + H+ and FADH2 carry electrons to an

electron transport chain, where additional ATP is produced.

8 NADH 24 ATP (WHY????)2 FADH2 4 ATP (WHY????)

2 NADH 4 ATP (WHY????)

Electron Transport Chain

Electron Transport

Hydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

Energy YieldAerobic respiration produces a

maximum of 36 ATP.2 ATP from Glycolysis2 ATP from Krebs32 ATP from ETC

Reasons why ATP yield can be less than 38:Sometimes energy is required to

transport NADH formed by glycolysis from the cytoplasm into the mitochondria.

Some H+ in chemiosmosis may not be recycled and/or wasted

Energy Yield

Energy YieldAerobic Respiration is generally 18

times more efficient than anaerobic respiration.

The ATP produced during aerobic respiration represents about 1/2 of the energy stored in a molecule of glucose.