Ch 9 Cellular Respiration and Fermentation

Reduction Oxidation Reactions (Redox)

Transfer electrons from one substance to another

Ex. the ionic bond in NaCl: sodium loses electrons (iodized) and chlorine gains electrons (reduced)

Reduction

Substance gains electrons

Oxidation

Substance loses electrons

Cellular Respiration

Cells convert glucose & oxygen into carbon dioxide, water, & ATP

• glucose loses electrons and is oxidized to carbon dioxide

• oxygen gains electrons and is reduced to water

Phosphorylation

Cells add a phosphate to ADP, making ATP

Substrate Level Phosphorylation

Enzyme catalyzed

• substrate with a phosphate & an ADP bind to the active site of an enzyme

• the enzyme catalyzes the removal of the phosphate from the substrate & adds it to the ADP to make ATP

Oxidative Phosphorylation

Generated by the addition of a free/unbound inorganic phosphate to ADP

• powered by the electron transport chain in cellular respiration

Cellular Respiration

• energy is stored in the bonds of organic molecules (food)

• catabolic pathways break these bonds to release energy (exergonic)

Cells covert Food to Energy through:

Cellular Respiration

• in presence of O2

• more efficient

Fermentation

• in absence of O2

• less efficient

Energy and Bonds

• bonds in food (carbs, lipids, proteins) are potential energy waiting to be released

• cells release energy through oxidation

• large molecules can’t be oxidized all at once

  • must be oxidized through a series of reactions

Energy and Electrons

• glucose is oxidized in stages

  • cells transfer the potential energy contained in the bonds of glucose to electron carriers, which store this potential energy in their own bonds

• NAD+ reduced to NADH

  • gains 1 hydrogen & 2 electrons

  • potential energy transferred to NADH

• FAD reduced to FADH2

• will hold electrons until last phase of cellular respiration

Fermentation

• happens after glycolysis

• only makes 2 ATP

• cycle repeats

  • no progression to CAC or oxidative phosphorylation

Alcohol Fermentation

pyruvate is converted to ethanol

Lactic Acid Fermentation

pyruvate is converted to lactate

Other Food Sources

• free glucose is not abundant in most diets

• carbohydrates hydrolyzed to glucose

Proteins

• hydrolyzed to amino acids

• amino acid group removed

• carbon backbone enters glycolysis or CAC

Lipids

hydrolyzed to glycerol or fatty acids

• glycerol enters middle of glycolysis as G3P

• fatty acids are converted to Acetyl-CoA and enter CAC

Cellular Poisons

interupt/block one or more stages of cellular respiration

Rotenone

disrupts complex I to ubiquinone

Cyanide

disrupts cytochrome to C complex

Carbon Monoxide

prevents O2 from being final electron acceptor

Oligomycin

blocks ATP synthase

DNP

allows H⁺ to leak back into matrix