Chapter 6 Biology Concepts And Connections

Front 1

kilocalories

Back 1

a quantity of heat equal to 1,000 calories. Used to measure the energy content of food

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redox reaction

Back 2

a chemical reaction in which electrons are lost from one substance and added to another. These reaction always occur together

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oxidation

Back 3

the loss of electrons from a substance involved in a redox reaction; always accompanies reduction

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reduction

Back 4

the gain of electrons by a substance involved in a redox reaction; always accompanies oxidation

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dehydrogenase

Back 5

an enzyme that catalyzes a chemical reaction during which one or more hydrogen atoms are removed from the molecule

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NAD

Back 6

nicotinamide adenine dinucleotide; a coenzyme that can accept electrons during the redox reactions of cellular metabolism. The plus sign indicates that the molecule is oxidized and ready to pick up hydrogens

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electron transport chain

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a series of electron carrier molecules that shuttle electrons during the redox reactions that release energy used to make ATP; located in the inner membrane of mitochondria, the thylakoid membranes of chloroplasts, and the plasma membranes of prokaryotes

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glycolysis

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the multistep chemical breakdown of a molecule of glucose into two molecules of pyruvate; the first stage of cellular respiration in all organisms; occurs in the cytoplasmic fluid

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citric acid cycle

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the metabolic cycle fueled by acetyl CoA formed after glycolysis in cellular respiration. Chemical reactions in this cycle complete the metabolic breakdown of glucose molecules to carbon dioxide. The cycle occurs in the matrix of mitochondria and supplies most of the NADH molecules that carry energy to the electron transport chains. The second major stage of cellular respiration

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oxidative phosphorylation

Back 10

the production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration

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chemiosmosis

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energy coupling mechanics that uses the energy of hydrogen ion gradients across membranes to phosphorylate ADP; powers most ATP synthesis in cells

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ATP synthases

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a cluster of several membrane proteins that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentration gradient to make ATP

Front 13

substrate-level phosphorylation

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the formation of ATP by an enzyme directly transferring a phosphate group to ADP from an organic molecule (for example, one of the intermediates in glycolysis or the citric acid cycle)

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intermediates

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one of the compounds that form between the initial reactant and the final product in a metabolic pathway, such as between glucose and pyruvate in glycolysis

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acetyl CoA

Back 15

the entry compound for the citric acid cycle in cellular respiration; formed from a fragment of pyruvate attached to a coenzyme

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lactic acid fermentation

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the conversion of pyruvate to lactate with no release of carbon dioxide

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alcohol fermentation

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the conversion of pyruvate from glycolysis to carbon dioxide and ethyl alcohol

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obligate anaerobes

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an organism that only carries out fermentation; such organisms cannot use oxygen and also may be poisoned by it

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facultative anaerobe

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an organism that makes ATP by aerobic respiration if oxygen is present, but that switches to fermentation when oxygen is absent