Chapter 5 Terms

Question 1

Fluid Mosaic

Answer 1

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

Question 2

Selective Permeability

Answer 2

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

Question 3

Diffusion

Answer 3

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

Question 4

Concentration Gradient

Answer 4

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 5

Passive Transport

Answer 5

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

Question 6

Osmosis

Answer 6

The diffusion of water across a selectively permeable membrane

Question 7

Tonicity

Answer 7

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

Question 8

Isotonic

Answer 8

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 9

Hypotonic

Answer 9

In comparing two solutions, the one with the lower concentration of solutes; cells in such a solution will take up water from their surroundings

Question 10

Hypertonic

Answer 10

In comparing two solutions, the one with the greater concentration of solutes; cells in such a solution will lose water to their surroundings

Question 11

Osmoregulation

Answer 11

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

Question 12

Facilitated Diffusion

Answer 12

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

Question 13

Aquaporin

Answer 13

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

Question 14

Active Transport

Answer 14

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 15

Exocytosis

Answer 15

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

Question 16

Endocytosis

Answer 16

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

Question 17

Phagocytosis

Answer 17

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

Question 18

Pinocytosis

Answer 18

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

Question 19

Receptor-Mediated Endocytosis

Answer 19

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 20

Energy

Answer 20

The capacity to perform work, or to rearrange matter

Question 21

Kinetic Energy

Answer 21

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 22

Potential Energy

Answer 22

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

Question 23

Chemical Energy

Answer 23

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

Question 24

Heat

Answer 24

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 25

Thermodynamics

Answer 25

The study of energy transformation that occurs in a collection of matter.

Question 26

First Law of Thermodynamics

Answer 26

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

Question 27

Entropy

Answer 27

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

Question 28

Second Law of Thermodynamics

Answer 28

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

Question 29

Exergonic Reaction

Answer 29

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 30

Cellular Respiration

Answer 30

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 31

Endergonic Reaction

Answer 31

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

Question 32

Metabolism

Answer 32

The totality of an organism’s chemical reactions

Question 33

Metabolic Pathway

Answer 33

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

Question 34

Energy Coupling

Answer 34

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

Question 35

ATP Synthase

Answer 35

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 36

Phosphorylation

Answer 36

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 37

Energy of Activation

Answer 37

The amount of energy that reactants must absorb before a chemical reaction will start

Question 38

Enzyme

Answer 38

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 39

Substrate

Answer 39

(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 40

Active Site

Answer 40

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 41

Induced Fit

Answer 41

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 42

Cofactor

Answer 42

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

Question 43

Coenzyme

Answer 43

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

Question 44

Competitive Inhibitor

Answer 44

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

Question 45

Noncompetitive Inhibitor

Answer 45

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 46

Feedback Inhibition

Answer 46

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