Harvesting Chemical Energy

Respiration is the process of extracting stored energy from glucose to make ATP.

C
6
H
12
O
6
+ 6 O
2
6 CO
2
+ 6 H
2
O and energy
As a result of respiration, energy is released from the chemical bonds found in complex organic molecules
(food).

Aerobic Respiration
• Aerobic Respiration is respiration which takes place in the presence of oxygen

Respiration is controlled by Enzymes
…rate is controlled by enzymes

1. Glycolysis
2. Krebs Cycle
3. Oxidative Phosphorylation

Glycolysis
• Glyco- glucose, -lysis: to split
• Universal step in all forms of respiration
• Likely used to supply energy for the ancient cells.

Glycolysis
• Function - To split glucose and produce NADH, ATP and
Pyruvate (pyruvic acid).
• Location - Cytoplasm.
• Occurs in 9 steps…. 6 of the steps use magnesium Mg as cofactors.

+
• Nicotinamide Adenine Dinucleotide
NAD + + 2 e NADH
NAD + = oxidized form
NADH = reduced form

• Glucose
• 2 ATP…. As activation energy
• 4 ADP
• 2 NAD +
• Enzymes

• 2 Pyruvic Acids (a 3C acid)
• 4 ATP
• 2 NADH

Net Energy Result
• 2 ATP per glucose
• 2 NADH
• In summary, glycolysis takes one glucose and turns it into 2 pyruvate, 2 NADH and a net of
2 ATP.

Also called: Citric Acid Cycle or Tricarboxylic Acid Cycle
• Function: Oxidize pyruvic acid to CO
2
• Produce: 3NADH, 1FADH
2 and 1ATP
• Location: Mitochondria matrix

Formation of Acetyl CoA:
Acetyl CoA is formed when the pyruvate , from glycolysis, combines with Coenzyme A… tis takes place in the matrix.

• Pyruvic acid (3C acid)
• Coenzyme A
• 3 NAD +
• 1 ADP
• 1 FAD
• Double this list for each glucose.

• 3 CO
2
• Acetyl CoA
• 3 NADH
• 1 ATP
• 1 FADH
2
• Double this list for each glucose.

Krebs Cycle
• Produces most of the cell's energy in the form of NADH and FADH
2
… not ATP
• Does NOT require O
2
• The CO
2 produced by the Krebs cycle is the CO
2 animal exhale when they breathe.

Oxidative Phosphorylation
• Process of extracting to energy from NADH and FADH
2 form ATP.
to
• Function: Convert NADH and FADH
2
• Location: Mitochondria cristae.
into ATP.

Oxidative Phosphorylation
• NADH or FADH
2
• ADP
• O
2

Oxidative Phosphorylation
• Requires the Electron Transport
Chain… the Electron Transport
Chain is a collection of proteins, embedded in the inner membrane, used to transport the electrons from
NADH and FADH
2

Cytochrome c
• Cytochrome c: is one of the proteins of the electron transport chain… often used by geneticists to determine relatedness… exists in all living organisms.
• The Cytochromes alternate between RED and OX forms and pass electrons down to O
2

ATP Yield
• Each NADH energizes 3 ATP
• Each FADH
2 energizes 2 ATP

Chemiosmotic Hypothesis
• ETC energy is used to move H + (protons) across the cristae membrane.
• ATP is generated as the H + diffuse back into the matrix through ATP Synthase

ATP Synthase
• Uses the flow of H + to make ATP.
• Works like an ion pump in reverse, or like a waterwheel under the flow of H + “water”.

Alcoholic Fermentation
• Carried out by yeast, a kind of fungus.

Alcoholic Fermentation
• Uses only Glycolysis.
• An incomplete oxidation - energy is still left in the products (alcohol).
• Does NOT require O
2
• Produces ATP when O
2 is not available.

Lactic Acid Fermentation
• Uses only Glycolysis.
• An incomplete oxidation - energy is still left in the products (lactic acid).
• Does NOT require O
2
• Produces ATP when O
2 is not available.

Lactic Acid Fermentation
• Done by human muscle cells under oxygen debt.
• Lactic Acid is a toxin and causes soreness and stiffness in muscles.

Fermentation - Summary
• Way of using up NADH so Glycolysis can still run.
• Provides ATP to a cell even when O
2 is absent.

Aerobic vs Anaerobic
• Aerobic - Respiration with O
2
• Anaerobic - Respiration without O
2
• Aerobic - All three Respiration steps.
• Anaerobic - Glycolysis only.

• Strict - can only carry out Respiration one way… aerobic or anaerobic.
• Facultative - can switch respiration types depending on O
2 availability. Ex - yeast

• Anaerobic - Glycolysis only
Gets 2 ATPs per glucose.
• Aerobic - Glycolysis, Krebs, and Oxidative Phosphorylation
(electron transport chain)
Generates many more ATPs per glucose.

Aerobic ATP yield
• Glycolysis - 2 ATPS, 2 NADHs
• Krebs - 2 ATPS, 8 NADHs,
FADH
2
• Each NADH = 3 ATP
• Each FADH
2
= 2 ATP
2

ATP Sum
• 10 NADH x 3 = 30 ATPs
• 2 FADH
2 x 2 = 4 ATPs
• 2 ATPs (Gly) = 2 ATPs
• 2 ATPs (Krebs) = 2 ATPs
• Max = 38 ATPs per glucose

However...
• Some energy is used in shuttling the NADH from Glycolysis into the mitochondria.
• Actual ATP yield ~ 36/glucose

Yeast
• Would rather do aerobic Respiration; it has 18x more energy per glucose.
• But, anaerobic will keep you alive if oxygen is not present.

Importance of fermentation
• Alcohol Industry - almost every society has a fermented beverage.
• Baking Industry - many breads use yeast to provide bubbles to raise the dough.

Summary
• Know the 3 main reactions of Respiration and the 4 required items for each.