Cell Respiration

Question 1

fermentation

Answer 1

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.

Question 2

aerobic respiration

Answer 2

A catabolic pathway for organic molecules, using oxygen (O2) 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.

Question 3

cellular respiration

Answer 3

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

Question 4

redox reaction

Answer 4

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

Question 5

oxidation

Answer 5

The complete or partial loss of electrons from a substance involved in a redox reaction.

Question 6

reduction

Answer 6

The complete or partial addition of electrons to a substance involved in a redox reaction.

Question 7

reducing agent

Answer 7

The electron donor in a redox reaction.

Question 8

oxidizing agent

Answer 8

The electron acceptor in a redox reaction

Question 9

NAD+

Answer 9

Nicotinamide adenine dinucleotide, a coenzyme that cycles easily between oxidized (NAD+) and reduced (NADH) states, thus acting as an electron carrier.

Question 10

electron transport chain

Answer 10

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

Question 11

glycolysis

Answer 11

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.

Question 12

citric acid cycle

Answer 12

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; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; together with pyruvate oxidation, the second major stage in cellular respiration.

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

substrate-level phosphorylation

Answer 14

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

Question 15

acetyl CoA

Answer 15

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

Question 16

cytochrome

Answer 16

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.

Question 17

ATP synthase

Answer 17

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. ATP synthases are found in the inner mitochondrial membranes of eukaryotic cells and in the plasma membranes of prokaryotes.

Question 18

chemiosmosis

Answer 18

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.

Question 19

proton-motive force

Answer 19

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.

Question 20

alcohol fermentation

Answer 20

Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide.

Question 21

lactic acid fermentation

Answer 21

Glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD+ with no release of carbon dioxide.

Question 22

obligate anaerobe

Answer 22

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

Question 23

facultative anaerobe

Answer 23

An organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present.

Question 24

beta oxidation

Answer 24

A metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA.