Chapter 6: How Cells Harvest Chemical Energy

Question 1

acetyl CoA

Answer 1

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

Question 2

alcohol fermentation

Answer 2

The conversion of pyruvate from glycolysis to carbon dioxide and ethyl alcohol.

Question 3

ATP synthase

Answer 3

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.

Question 4

cellular respiration

Answer 4

The aerobic harvesting of energy from food molecules; the energy-releasing chemical breakdown of food molecules, such as glucose, and the storage of potential energy in a form that cells can use to perform work; involves glycolysis, the citric acid cycle, and oxidative phosphorylation (the electron transport chain and chemiosmosis).

Question 5

chemiosmosis

Answer 5

Energy-coupling mechanics that uses the energy of hydrogen ion (H1) gradients across membranes to phosphorylate ADP; powers most ATP synthesis in cells.

Question 6

citric acid cycle

Answer 6

The metabolic cycle fueled by acetyl CoA formed after glycolysis in cellular respiration. Chemical reactions in the citric acid 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.

Question 7

electron transport chain

Answer 7

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.

Question 8

glycolysis

Answer 8

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.

Question 9

intermediates

Answer 9

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

Question 10

kilocalorie (kcal)

Answer 10

A quantity of heat equal to 1,000 calories. Used to measure the energy content of food, it is usually called a “Calorie.”

Question 11

lactic acid fermentation

Answer 11

The conversion of pyruvate to lactate with no release of carbon dioxide.

Question 12

oxidation

Answer 12

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

Question 13

oxidative phosphorylation

Answer 13

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

Question 14

redox reaction

Answer 14

Short for oxidation-reduction; a chemical reaction in which electrons are lost from one substance (oxidation) and added to another (reduction). Oxidation and reduction always occur together.

Question 15

reduction

Answer 15

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

Question 16

substrate-level phosphorylation

Answer 16

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).