Question

What is the reducing agent (or electron donor) in the following reaction? Pyruvate + NADH + H^+ rightarrow Lactate + NAD^+ A. oxygen B. NADH+H^+ C. NAD^+ D. lactate E. pyruvate Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's A. entropy B. heat content. C. activation energy. D. endothermic level. E. free-energy content. What does the chemiosmotic process in mitochondria involve? A. establishment of a proton gradient B. reduction of water to produce ATP energy C. diffusion of electrons through the thylakoid membrane D. oxidation of glucose, releasing carbon dioxide, NADH+H^+ and FADH_2 E. movement of water by osmosis into the intermembrane space from the matrix Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as_______ is to_______ A. exergonic; spontaneous B. exergonic; endergonic C. free energy; entropy D. work; energy E. entropy; enthalpy Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule? A. the citric acid cycle B. the electron transport chain C. glycolysis D. synthesis of acetyl CoA from pyruvate E. reduction of pyruvate to lactate

Answer 1

When sufficient axygen is not present in the muscle cells for further axidation of pyruvate and NADH produced n glycoyss, NAD+ is regenerated from NADH by reduction of pyruvate to lactic acid. Pyruvate is conveted to lactic acid by theenzyme lactate dehydrogenase. 20. Ans: C. Activation energy The activation energy for the forward reaction is the amount of free energy that must be added to go from the energy level of the reactants to the energy level of the transition state. The source of activat ion energy is typically heat, with reactant molecules absorbing thermal energy from ther surroundings. 21. Ans: A. Establishment of a proton gradient In oxidat ive phosphorylation, the hydrogen ion gradient formed by the electron transport chain Key points of chemiosmosis: During chemiosmosis, thefree energy from the series of reactions that make up the electron transport chain is used to pump hydrogen ions across the membrane, establishing an electrochemical gradient. Hydrogen ions in the matr space can only pass through the inner mitochondrial membrane through amembrane protein called ATP synthase. .As protons move through ATP synthase, ADP isturned into ATP The production of ATP using the proces of chemiosmosis in mitochondria is called ox darve phosphorylaion. 22. Ans: E. entropy, enthalpy Living organisms are able to make highly ordered structures by coupling free energy- yielding catabolic processes (increase entropy) with energy-requiring anabolic processes (decrease entropy). 23. Ans: C. Glycolysis Fermentation and cellular respiration are alike in that they both begin with a series of reactions known as gycolysis which breaksglucose molecules into smaller pyruvate molecules. They are also similar in that during both processes, ATP is produced for the cell to use.