Energy Production

1
Energy Production
2
Oxidation Reduction

• Oxidation removal of electrons from a molecule
  (sometimes along with a hydrogen proton)
  usually releases energy
• Reduction addition of electrons to a molecule
  (sometimes along with a hydrogen proton)
• Both must occur at the same time - when one
  molecule is oxidized, another is reduced

3
Phosphorylation

• Phosphorylation addition of a phosphate group
  to a molecule
• One example addition of phosphate group to ADP
  to make ATP
• ADP P -----------gt ATP
• Energy is required to phosphorylate since a new
  covalent bond is formed

4
Energy to phosphorylate comes from three sources

• Substrate level energy comes from chemical
  reactions (when substrate is converted to
  product)
• oxidative energy is released from the
  oxidation of a molecule
• photo- energy comes from light
  (photosynthetic bacteria)

5
Carbohydrate Catabolism

• Breakdown of carbohydrates into smaller molecules
• energy is released in the oxidation of
  carbohydrates (usually glucose)
• oxidation of glucose involves removal of hydrogen
  electrons
• when electrons removed, covalent bond breaks,
  energy released, some absorbed by electrons

6

• Electrons (with energy) picked up by coenzymes
  NAD or FAD along with hydrogen protons
• two forms of carbohydrate catabolism
  respiration and fermentation
• respiration - aerobic and anaerobic (differ in
  their final electron acceptor
• in fermentation, NADH gives its hydrogen to an
  organic molecule (final elect acceptor)

7
Respiration

• Begins with glycolysis
• products of glycolysis enter the Krebs cycle
  where molecules are oxidized to CO2 and water
• NADH and FADH2 produced in glycolysis and Krebs
  enter the Electron Transport Chain

8
Glycolysis

• A ten step metabolic pathway that starts with 6
  carbon glucose and ends with two molecules of 3
  carbon pyruvic acid
• Along the way
• two oxidations occur 2 NADHs made
• four ATPs made and two used up so net
  gain of two ATPs
• Details

9
Preparatory Stage

• Between glycolysis and Krebs cycle
• Each pyruvic acid is oxidized and one NADH is
  produced per pyruvic acid 2
• Each pyruvic acid looses a carbon as CO2
  (decarboxylation) and becomes acetyl
• Coenzyme A picks up acetyl and carries it into
  the Krebs cycle

10
Krebs Cycle

• An eight step cyclic metabolic pathway
• step 1 - Coenzyme A gives acetyl to oxaloacetic
  acid forming citric acid
• after eight steps, oxaloacetic acid is formed
  again
• two Krebs cycles per glucose since two pyruvic
  acids are formed

11
Krebs Cycle

• Summary of one Krebs cycle
• 2 decarboxylations (CO2 removed)
• 1 ATP formed (substrate level phos)
• 4 oxidations forming 3 NADHs and 1
• FADH2
• Per glucose 4 CO2, 6 NADH,
• 2 FADH2, 2 ATP

12
Electron Transport Chain

• A chain of seven molecules (FMN, Coenzyme Q,
  cytochromes) that can accept electrons (reduced)
  and then give up electrons (oxidized)
• energy released in 3 of the transfers and is used
  to pump hydrogen electrons outside of plasma
  membrane

13

• Electrons can re-enter cell only through ATP
  synthetase enzyme which harnesses flowing
  electron energy to make 3 ATP
• Oxygen atoms pick up 2 electrons and 2 hydrogen
  protons to form water

14
Total ATP Count

• 2 from glycolysis
• 2 from the two Krebs cycles
• 34 are formed by chemiosmosis in the ETC
• Total 38