Extracting the energy

Carbohydrate Fat Protein

Glucose Fatty acids Amino acids

Acetyl CoA

Citric acid cycleOxidative Phosphorylation

ATP

e-

• Large molecules in food are broken down into smaller units (no useful energy generated)

• These smaller molecules are then degraded to a few simple units that play a central role in metabolism (some energy generated)

• The citric acid cycle and oxidative phosphorylation then result in production of ATP (most of the energy generation happens here)

The 3 stages of Energy Metabolism

Extracting the energy

Carbohydrate Fat Protein

Glucose Fatty acids Amino acids

Acetyl CoA

Citric acid cycleOxidative Phosphorylation

ATP

e-

Glycolysis

• The sequence of reactions that converts glucose to pyruvate

C6H12O6 C3H3O3

6 carbon3 carbon

Glycolysis

• 10 steps - 10 enzymes

• First 5 reactions Add 2 phosphate groups and cleave in half to form glyceraldehyde-3-PO4

• Next 5 reactions Generate 2 molecules of ATP from glyceraldehyde-3-PO4 making pyruvate

Citric acid cycle / Krebs cycle

• The final common pathway for the oxidation of fuel molecules

• Pyruvate (C3) Acetyl CoA (C2)

• Acetyl CoA Citric acid cycle

NADH and FADH2 are energy rich molecules with electrons that are used in oxidative phosphorylation

C2

C6C4

C5

C4

NADH

NADH

NADH

FADH2

Oxidative Phosphorylation

• The process in which ATP is formed as electrons are transferred from NADH or FADH2 to O2 by a series of 5 multisubunit complexes located on the inner mitochondrial membrane

Oxidative Phosphorylation

NADH

NAD

FADH2

FAD

Complex 1

Complex 2

Ubiquinone Complex 3 Cyt c Complex 4 Complex 5

ADP

ATP

O2 H2O

Glucose, Fatty acids, Amino acids

Glucose

Pyruvate Acetyl CoA

Fatty acids

NADH / FADH2

ATP

Ketone bodies

GlycolysisBeta oxidation

Citric acid cycle

Oxidative phosphorylationAmino acids Amino acids