Ch. 7 Cellular Repiration

Cellular respiration is the process by which cells convert glucose and oxygen into energy, carbon dioxide, and water.

Key Terms

• Acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a two-carbon fragment of pyruvate attached to a coenzyme

  

• Aerobic Respiration; A catabolic pathway for organic molecules, using oxygen as the final electron acceptor in an electron transport chain and ultimately producing ATP. This is the most efficient catabolic pathway and is carried out in most eukaryotic cells and many prokaryotic organisms.

• Alcohol Fermentation; a metabolic process by which sugars are converted into cellular energy, producing ethanol and carbon dioxide as byproducts, typically carried out by yeast and some bacteria. Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide.

• ATP Synthase; A complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP.

  

• Beta Oxidation; A metabolic sequence that breaks down fatty acids into acetyl-CoA units, which can then enter the citric acid cycle for further energy production. This process occurs in the mitochondria and is crucial for the metabolism of fats.

• Cellular respiration; The catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules and use an electron transport chain for the production of ATP

  

• Chemiosmosis; An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Under aerobic conditions, most ATP synthesis in cells occurs by chemiosmosis.

• Citric Acid Cycle; A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide

  

• Cytochrome; An iron-containing protein that is a component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic cells

  

• Electron Transport Chain; A sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP

  

• Facultative anaerobe; An organism that makes ATP by aerobic respiration if oxygen is present but that switched to anaerobic respiration or fermentation if oxygen is not present.

• Fermentation; A catabolic process that makes a limited amount of ATP from glucose (or other organic molecules) without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.

• Glycolysis; A series of reactions that ultimately splits glucose into pyruvate. Glycolysis occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration.

  

• Lactic Acid Fermentation; Glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD+ with no release of carbon dioxide.

  

• NAD+; The oxidized form of nicotinamide adenine dinucleotide, a coenzyme that can accept electrons becoming NADH. NADH temporarily stores electrons during cellular respiration.

• NADH; The reduced form of nicotinamide adenine dinucleotide, which temporarily stores electrons during cellular respiration. NADH acts as an electron

• Obligate Anaerobe; An organism that only carries out fermentation or anaerobic respiration. Such organisms cannot use oxygen and in fact may be poisoned by it.

• Oxidation; The complete or partial loss of electrons from a substance involved in a redox reaction

  

• Oxidative Phosphorylation; The production of using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration

  

• Oxidizing Agent; The electron acceptor in a redox reaction

• Proton-Motive Force; The potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions (H+) across a biological membrane during chemiosmosis.

  

• Redox Reaction; A chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another; short for reduction-oxidation reaction.

  

• Reducing Agent; The electron donor in a redox reaction

• Substrate-level phosphorylation; The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.