Chapter 5

Front 1

activation energy

Back 1

the energy required to start a chemical reaction

Front 2

homolactic acid fermentation

Back 2

a pathway in which pyruvic acid is directly converted to lactic acid using electrons from reduced NAD (NADH)

Front 3

autotrophy

Back 3

"self-feeding" - the use of CO2 as a source of carbon atoms for the synthesis of biomolecules

Front 4

catabolic pathway

Back 4

a chain of chemical reactions that capture energy by breaking down large molecules into simpler components

Front 5

active site

Back 5

area on the surface of an enzyme to which its substrate binds

Front 6

anaerobic respiration

Back 6

respiration in which the final electron acceptor in the electron transport chain is an inorganic molecule other than oxygen, e.g. a sulfate, nitrate, etc.

Front 7

cyclic phosphorylation

Back 7

pathway in which excited electrons from chlorophyll are used to generate ATP without the splitting of water or reduction of NADP

Front 8

fermentation

Back 8

anaerobic metabolism of the pyruvic acid produced in glycolysis

Front 9

electron transport chain

Back 9

(also called respiratory chain) a series of compounds that pass electrons to oxygen (the final electron acceptor)

Front 10

competitive inhibitor

Back 10

a molecule similar in structure to a substrate that competes with that substrate by binding to the active site

Front 11

substrate

Back 11

(1) the substance on which an enzyme acts (2) a surface or food source on which a cell can grow or a spore can germinate

Front 12

oxidative phosphorylation

Back 12

process in which the energy of electrons is captured in high-energy bonds as phosphate groups combine with ADP to form ATP

Front 13

quinone

Back 13

(also called coenzyme Q) a nonprotein, lipid-soluble electron carrier in oxidative phosphorylation

Front 14

chemoheterotroph

Back 14

a heterortroph that obtains energy from breaking down ready-made organic molecules

Front 15

glycolysis

Back 15

an anaerobic metabolic pathway used to break down glucose into pyruvic acid while producing some ATP

Front 16

phototransferase system (PTS)

Back 16

a mechanism that uses enrgy from phosphoenolpyruvate to move sugar molecules into cells by active transport

Front 17

catabolism

Back 17

the chemical breakdown of molecules in which energy is released

Front 18

exoenzyme

Back 18

(also called extracellular enzyme) an enzyme that is synthesized in a cell but crosses the cell membrane to act in the periplasmic space or the cell's immediate environment

Front 19

chemoautotroph

Back 19

an autotroph that obtains energy by oxidizing simple inorganic substances such as sulfides and nitrites

Front 20

photoheterotroph

Back 20

a heterotroph that obtains energy from light

Front 21

enzyme-substrate complex

Back 21

a loose association of an enzyme with its substrate

Front 22

electron acceptor

Back 22

an oxidizing agent in a chemical reaction

Front 23

noncyclic photoreduction

Back 23

the photosynthetic pathway in which excited electrons from chlorophyll are used to generate ATP and reduce NADP with the splitting of water molecules

Front 24

FAD

Back 24

Flavin adenine dinucleotide, a coenzyme that carries hydrogen atoms and electrons

Front 25

allosteric site

Back 25

the site at which a noncompetitive inhibitor binds

Front 26

heterotrophy

Back 26

"other-feeding", the use of carbon atoms from organic compounds for the synthesis of biomolecules

Front 27

noncompetitive inhibitor

Back 27

a molecule that attaches to an enzyme at an allosteric site (a site other than the active site), distorting the shape of the active site so that the enzyme can no longer function

Front 28

flavoprotein

Back 28

an electron carrier in oxidative phosphorylation

Front 29

NAD

Back 29

nicotinamide dinucleotide, a coenzyme that carries hydrogen atoms and electrons

Front 30

coenzyme

Back 30

an organic molecule bound to or loosely associated with an enzyme

Front 31

oxidation

Back 31

the loss of electrons and hydrogen atoms

Front 32

alcoholic fermentation

Back 32

fermentation in which pyruvic acid is reduced to ethyl alcohol by electrons from reduced NAD (NADH)

Front 33

light reactions

Back 33

the part of photosynthesis in which light energy is used to excite electrons from chlorophyll, which are then used to generate ATP and NADPH

Front 34

electron donor

Back 34

a reducing agent in a chemical reaction

Front 35

autotroph

Back 35

an organism that uses carbon dioxide gas to synthesize organic molecules

Front 36

amphibolic pathway

Back 36

a metabolic pathway that can yield either energy or building blocks for synthetic reactions

Front 37

endoenzyme

Back 37

an enzyme that acts within the cell producing it

Front 38

anaerobe

Back 38

an organism that does not use oxygen, including some organisms that are killed by exposure to oxygen

Front 39

photolysis

Back 39

process in which light energy is sued to split water molecules into protons, electrons, and oxygen molecules

Front 40

apoenzyme

Back 40

the protein portion of an enzyme

Front 41

aerobe

Back 41

an organism that uses oxygen including ones that must have oxygen

Front 42

surfactant

Back 42

a substanc that reduces surface tension

Front 43

electron transport

Back 43

process in which pairs of electrons are transferred between cytochromes and other compounds

Front 44

Krebs cycle

Back 44

(also called tricarboxylic acid cycle and the citric acid cycle) a sequence of enzyme-catalyzed chemical reactions that metabolizes 2-carbon units called acetyl groups to CO2 and H20

Front 45

dark reactions

Back 45

(also called carbon fixation) Part of photosynthesis in which carbon dioxide gas is reduced by electrons from reduced NADP (NADPH) to form various carbohydrate molecules, chiefly glucose

Front 46

reduction

Back 46

the gain or electrons and hydrogen atoms

Front 47

aerobic respiration

Back 47

process in which aerobic organisms gain energy from the catabolism of organic molecules via the Krebs cycle and oxidative phophorylation

Front 48

phosphorylation

Back 48

the addition of a phosphate group to a molecule, often from ATP; generally increasing the molecule's energy

Front 49

permease

Back 49

an enzyme complex involved in active transport through the cell membrane

Front 50

metabolic pathway

Back 50

a chain of chemical reactions in which the product of one reaction serves as the substrate for the next

Front 51

porin

Back 51

a protein in the outer membrane of Gram-negative bacteria that nonselectively transports polar molecules into the periplasmic space

Front 52

metabolism

Back 52

the sum of all chemical processes carried out by living organisms

Front 53

beta oxidation

Back 53

a metabolic pathway that breaks down fatty acids into 2-carbon pieces

Front 54

photoautotroph

Back 54

an autotroph that obtains energy from light

Front 55

photosynthesis

Back 55

the capture of energy from light and use of this energy to manufacture carbohydrates from carbon dioxide

Front 56

cofactor

Back 56

an inorganic necessary for the function of an enzyme

Front 57

chemical equilibrium

Back 57

a steady state in which there is no net change in the concentrations of substrates or products

Front 58

holoenzyme

Back 58

a functional enzyme consisting of an apoenzyme and a coenzyme or cofactor

Front 59

feedback inhibition

Back 59

(also called end-product inhibition) regulation of a metabolic pathway by the concentration of one of its intermediates or, typically, its end product, which inhibits an enzyme in the pathway

Front 60

specicifity

Back 60

(1) the property of an enzyme that allows it to accept only certain substrates and catalyze only one particular action (2) the property of a virus that restricts it to certain specific types of host cells (3) the ability of the immune system to mount a unique immune response to each antigen it encounters

Front 61

cytochrome

Back 61

an electron carrier functioning in the electron transport chain; heme protein

Front 62

anabolic pathway

Back 62

a chain of chemical reactions in which energy is used to synthesize biologically important molecules

Front 63

enzyme

Back 63

a protein catalyst that controls the rate of chemical reactions in cells

Front 64

heterotroph

Back 64

an organism that uses compounds to produce biomolecules