Chapter 5

Question 1

diffusion

Answer 1

The spontanepus tendency of a substance to move down its concentration gradient from where it is more concentrated to where it is less concentrated.

Question 2

kinetic energy

Answer 2

The energy of motion; the energy of a mass of matter that is moving. Moving matter does work by imparting motion to other matter.

Question 3

competitive inhibitor

Answer 3

A substance that reduces the activity of an enzyme by binding to the enzyme’s active site in a place of the substrate. A competitive inhibitor’s structure mimics that of the enzyme’s substrate.

Question 4

hypertonic

Answer 4

Referring to a solution that, when surrounding a cell, will cause the cell to lose water

Question 5

noncompetitive inhibitor

Answer 5

A substance that impedes the activity of an enzyme without entering an active site. By binding elsewhere on the enzyme, a noncompetitive inhibitor changes the shape of the enzyme so that the active site no longer functions.

Question 6

coenzyme

Answer 6

An organic molecule serving as a cofactor. Most vitamins function as coenzymes in important metabolic reactions.

Question 7

substrate

Answer 7

1) A specific substance (reactant) on which an enzyme acts. Each enzyme recognizes only the specific substrate or substrates of the reaction it catalyzes. 2) A surface in or on which an organism lives.

Question 8

metabolism

Answer 8

the totality of an organism’s chemical reactions.

Question 9

chemical energy

Answer 9

Energy available in molecules for release in a chemical reaction; a form of potential energy.

Question 10

entropy

Answer 10

A measure of disorder. One form of disorder is heat, which is random molecular motion.

Question 11

heat

Answer 11

Thermal energy; the amount of energy associated with the movement of the atoms and molecules in a body of matter. Heat is energy in its most random form.

Question 12

selective permeability

Answer 12

A property of biological membranes that allows some substances to cross more easily that others and blocks the passage of other substances altogether.

Question 13

tonicity

Answer 13

The ability of a solution surrounding a cell to cause that cell to gain or lose water.

Question 14

isotonic solution

Answer 14

a solution having the same solute concentration as another solution, thus having no effect on passage of water in or out of the cell.

Question 15

first law of thermodynamics

Answer 15

The principle of conversation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.

Question 16

feedback inhibition

Answer 16

A method of metabolic control in which a product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

Question 17

second law of thermodynamics

Answer 17

The principle whereby every energy conversion reduces the order of the universe, increasing its entropy. Ordered forms if energy are at least partly converted to heat.

Question 18

potential energy

Answer 18

The energy that matter possesses because of its location or arrangement. Water behind a dam and chemical bonds possess potential energy.

Question 19

pinocytosis

Answer 19

Cellular “drinking”; a type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles.

Question 20

cellular respiration

Answer 20

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 21

enzyme

Answer 21

A protein (or RNA molecule) that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed into a different molecule in the process.

Question 22

hypotonic

Answer 22

Referring to a solution that , when surrounding a cell, will cause the cell to take up water.

Question 23

phagocytosis

Answer 23

Cellular “eating”; a type of endocytosis whereby a cell engulfs macromolecules, other cells, or particles into its cytoplasm.

Question 24

energy coupling

Answer 24

In cellular metabolism, the use of energy released from an exergonic reaction to drive an enderonic reaction.

Question 25

andenosine triphosphate (ATP)

Answer 25

Main energy source for cells.

Question 26

active transport

Answer 26

The movement of a substance across a biological membrane against its concentration gradient, aided by specific transport proteins and requiring input of energy (often as ATP)

Question 27

facilitated diffusion

Answer 27

The passage of a substance through a specific transport protein across a biological membrane down its concentration gradient.

Question 28

energy

Answer 28

The capacity to perform work, or to rearrange matter.

Question 29

exocytosis

Answer 29

The movement of materials out of the cytoplasm of a cell by the fusion of vesicles with the plasma membrane.

Question 30

thermodynamics

Answer 30

The study of energy transformation that occurs in a collection of matter. See first law of thermodynamics; second law of thermodynamics.

Question 31

passive transport

Answer 31

The diffusion of a substance across a biological membrane, without any input of energy.

Question 32

receptor-mediated endocytosis

Answer 32

the movement of specific molecules into a cell by the inward budding of membranous vesicles. The vesicles contain proteins with receptor sites specific to the molecules being taken in.

Question 33

active site

Answer 33

The part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically, a pocket or groove on the enzyme’s surface.

Question 34

osmosis

Answer 34

The diffusion of water across a selectively permeable membrane.

Question 35

concentration gradient

Answer 35

An increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, substances tend to move from where they are more concentrated to where they are less concentrated.

Question 36

metabolic pathway

Answer 36

A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.

Question 37

endergonic reaction

Answer 37

An energy-requiring chemical reaction which yields products with more potential energy than the reactants. The amount of energy store in the product equals the difference between the potential energy in the reactants and the in the products.

Question 38

osmoregulation

Answer 38

Method by which organisms regulate solute concentrations and balance the gain and loss of water.

Question 39

phosphorylation

Answer 39

The transfer of a phosphate group, usually from ATP, to a molecule. Nearly all cellular work depends on ATP energizing other molecules by phosphorylation.

Question 40

aquaporin

Answer 40

A transport protein in the plasma membrane of some plant or animal cells that facilitates the diffusion of water across the membrane (osmosis).

Question 41

exergonic reaction

Answer 41

An energy-releasing chemical reaction in which the reactants contain more potential energy than the products. The reaction releases an amount of energy equal to the difference in potential energy between the reactants and the products.

Question 42

fluid mosaic

Answer 42

A description of membrane structure, deicing a cellular membrane as a mosaic of diverse protein molecules embedded in a fluid bilayer made of phospholipid molecules.

Question 43

endocytosis

Answer 43

Cellular uptake of molecules or particles via formation of new vesicles from the plasma membrane.

Question 44

induced fit

Answer 44

the change in shape of the active site of an enzyme, induced by entry of the substrate so that it binds more snugly to the substrate.

Question 45

cofactor

Answer 45

A nonprotein molecule or ion that is required for the proper functioning of an enzyme.