Ch 9: Cellular Respiration and Fermentation

Fermentation

a catabolic process where the partial degradation of sugars occurs without oxygen

Aerobic Respiration

the most prevalent and efficient catabolic pathway in which oxygen is consumed as a reactant along with organic fuel

Cellular Respiration

• includes aerobic and anaerobic processes

• performs work by adding a phosphate to ADP

Redox Reaction

the transfer of electrons from one reactant to another in a chemical reaction

Oxidation

loss of electrons from a substance during a redox reaction

Reduction

the addition of electrons to a substance in a redox reaction

Reducing Agent

the electron donor in a redox reaction

Oxidation Agent

the electron acceptor in a redox reaction

NAD⁺

• a good electron carrier

• easily cycles between oxidized and reduced forms

• functions as an oxidizing agent in cellular respiration

Electron Transport Chain

• consists of a number of molecules (mainly proteins) built into the inner membrane of the mitochondria (eukaryotes) or the plasma membrane (prokaryotes)

• electrons from glucose are shuttled by NADH to the top end of the chain

• at the bottom end, O₂ captures the electrons and forms H₂O

Glycolysis

• occurs in the cytoplasm

• breaks glucose into two molecules of pyruvate

• produces two net ATP

• occurs regardless of O₂ presence

Krebs Cycle/Citric Acid Cycle

• acetyl CoA enters and goes through eight steps

• produces 3 NADH, 1 FADH₂ and 1 ATP

• releases CO₂

• oxaloacetate is a product and reactant, making this a cycle

Oxidative Phosphorylation

• where ATP is produced via the ETC

• accounts for most of ATP synthesis in cellular respiration

Substrate Level Phosphorylation

where an enzyme adds an organic phosphate group to ADP from a substrate

Acetyl CoA

• a product of pyruvate oxidation

• a reactant of the Krebs cycle

Cytochromes

a type of protein in the ETC with a heme group that acts as an electron acceptor and donor

ATP Synthase

• an enzyme that makes ATP from ADP and inorganic phosphates

• uses the energy from the ion concentration gradient to power ATP synthesis

• the flow of H⁺ acts as water pushing a waterwheel, causing ATP synthesis

Chemiosmosis

• the use of the energy in a H⁺ gradient to drive cellular work

• the mechanisms that couples the electron transport and energy release to ATP synthesis

Proton-motive force

a name for the H⁺gradient that emphasizes its capacity to do work

Alcohol Fermentation

• occurs in anaerobic conditions

• pyruvate is converted to ethanol in two steps

  1. CO₂ is released from pyruvate, which is converted to aocetaldehyde

  2. acetaldehyde is reduced by NADH to ethanol

Lactic Acid Fermentation

• pyruvate is reduced by NADH to lactate

• occurs during strenuous exercise, or other anaerobic conditions

Obligate Anaerobes

• organisms which carry out only fermentation

• cannot survive aerobic conditions

Faculative Anaerobes

• organisms which can carry out either fermentation or cellular respiration

• pyruvate is a fork in the metabolic road, leading to two catabolic pathways

• must consume sugar much faster in fermentation

Beta Oxidation

a metabolic sequence which breaks down fatty acids to yield acetyl CoA