Kapitel 3

Question 1

Thermodynamic quantity that measures the degree of disorder in a system.

Answer 1

entropy

Question 2

A small molecule that stores energy or chemical groups in a form that can be donated to many different metabolic reactions. Examples include ATP - acetyl CoA - and NADH.

Answer 2

activated carrier

Question 3

Molecule capable of picking up an electron from a molecule with weak electron affinity and transferring it to a molecule with a higher electron affinity.

Answer 3

electron carrier

Question 4

An enzyme-catalyzed process by which complex molecules are formed from simple substances by living cells; also called anabolism.

Answer 4

biosynthesis

Question 5

Removal of electrons from an atom - as occurs during the addition of oxygen to a carbon atom or when a hydrogen is removed from a carbon atom. The opposite of reduction.

Answer 5

oxidation

Question 6

A molecule on which an enzyme acts.

Answer 6

substrate

Question 7

Activated carrier that donates the carbon atoms in its readily transferable acetyl group to many metabolic reactions - including the citric acid cycle and fatty acid biosynthesis; the acetyl group is linked to coenzyme A (CoA) by a thioester bond that releases a large amount of energy when hydrolyzed.

Answer 7

acetyl CoA (acetyl coenzyme A)

Question 8

Activated carrier closely related to NADH and used as an electron donor in biosynthetic pathways. In the process it is oxidized to NADP+.

Answer 8

NADPH (nicotine adenine dinucleotide phosphate)

Question 9

Substance that accelerates a chemical reaction by lowering its activation energy; enzymes perform this role in cells.

Answer 9

catalyst

Question 10

For a reversible chemical reaction - the ratio of substrate to product when the rates of the forward and reverse reactions are equal.

Answer 10

equilibrium constant (K)

Question 11

Nucleoside diphosphate produced by hydrolysis of the terminal phosphate of ATP.

Answer 11

ADP (adenosine 5′-diphosphate)

Question 12

acetyl CoA (acetyl coenzyme A)

Answer 12

Activated carrier that donates the carbon atoms in its readily transferable acetyl group to many metabolic reactions - including the citric acid cycle and fatty acid biosynthesis; the acetyl group is linked to coenzyme A (CoA) by a thioester bond that releases a large amount of energy when hydrolyzed.

Question 13

G - ΔG - ΔG°—see free energy - free-energy change.

Answer 13

ΔG°

Question 14

Addition of electrons to an atom - as occurs during the addition of hydrogen to a carbon atom or the removal of oxygen from it. The opposite of oxidation.

Answer 14

reduction

Question 15

Molecule that easily gives up an electron - thereby becoming oxidized.

Answer 15

electron donor

Question 16

Process by which molecules and small particles move from one location to another by random - thermally driven motion.

Answer 16

diffusion

Question 17

Activated carrier widely used in the energy-producing breakdown of sugar molecules.

Answer 17

NADH

Question 18

Concentration of substrate at which an enzyme works at half its maximum velocity; serves as a measure of how tightly the substrate is bound.

Answer 18

Michaelis constant (KM)

Question 19

The sum total of the chemical reactions that take place in the cells of a living organism.

Answer 19

metabolism

Question 20

Set of metabolic pathways by which large molecules are made from smaller ones.

Answer 20

anabolism

Question 21

General term for any process in a cell in which the uptake of molecular oxygen (O2) is coupled to the production of CO2.

Answer 21

respiration

Question 22

The maximum rate of an enzymatic reaction - reached when the active sites of the enzyme molecules in a sample are fully occupied by substrate.

Answer 22

Vmax

Question 23

Energy that can be harnessed to do work - such as driving a chemical reaction.

Answer 23

free energy (G)

Question 24

Covalent bond whose hydrolysis releases an unusually large amount of free energy under the conditions existing in a cell. Examples include the phosphodiester bonds in ATP and the thioester linkage in acetyl CoA.

Answer 24

high-energy bond

Question 25

Atom or molecule that readily takes up electrons - thereby becoming reduced.

Answer 25

electron acceptor

Question 26

Chemical group derived from acetic acid.

Answer 26

acetyl group

Question 27

State in which the forward and reverse rates of a chemical reaction are equal so that no net chemical change occurs.

Answer 27

equilibrium

Question 28

The acceleration of a chemical reaction brought about by the action of a catalyst; virtually all reactions in a cell require such assistance to occur under conditions present in living organisms.

Answer 28

catalysis

Question 29

“Delta G”: in a chemical reaction - the difference in free energy between reactant and product molecules. A large negative value of ΔG indicates that the reaction has a strong tendency to occur. The standard free-energy change (ΔG°) is the free-energy change measured at defined concentration - temperature - and pressure.

Answer 29

free-energy change (ΔG)

Question 30

The concentration of substrate at which an enzyme works at half its maximum rate. Large values of KM usually indicate that the enzyme binds to its substrate with relatively low affinity.

Answer 30

KM

Question 31

Small molecule used to carry and transfer acetyl groups needed for a variety of metabolic reactions - such as the synthesis of fatty acids.

Answer 31

coenzyme A

Question 32

A protein that catalyzes a specific chemical reaction.

Answer 32

enzyme

Question 33

Set of enzyme-catalyzed reactions by which complex molecules are degraded to simpler ones with release of energy; intermediates in these reactions are sometimes called catabolites.

Answer 33

catabolism

Question 34

Nucleotide produced by the energetically favorable hydrolysis of the final two phosphate groups from ATP - a reaction that drives the synthesis of DNA and RNA.

Answer 34

AMP (adenosine 5′ monophosphate)

Question 35

Linked pair of chemical reactions in which free energy released by one reaction serves to drive the other reaction.

Answer 35

coupled reaction

Question 36

The number of substrate molecules an enzyme can convert into product per second.

Answer 36

turnover number

Question 37

The energy that must be acquired by a molecule to undergo a chemical reaction.

Answer 37

activation energy