Chapter 5 Biology Concepts And Connections

Front 1

fluid mosaic

Back 1

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

Front 2

selective permeability

Back 2

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

Front 3

concentration gradient

Back 3

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

Front 4

passive transport

Back 4

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

Front 5

diffusion

Back 5

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

Front 6

osmosis

Back 6

the diffusion of water across a selectively permeable membrane

Front 7

tonicity

Back 7

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

Front 8

isotonic

Back 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

Front 9

hypotonic

Back 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

Front 10

hypertonic

Back 10

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

Front 11

osmoregulation

Back 11

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

Front 12

facilitated diffusion

Back 12

the passage of a subtance through a specific transport protein across a biological membrane down its concentration gradient

Front 13

aquaporins

Back 13

a transport protein in the plasma membrane of some plant or animal cells that facilitates the diffusion of water across the membrane

Front 14

active transport

Back 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)

Front 15

exocytosis

Back 15

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

Front 16

endocytosis

Back 16

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

Front 17

phagocytosis

Back 17

cellular "eating"; a type of endocytosis whereby a cell engulfs macromolecules, other cells, or particles into its cytoplasm

Front 18

pinocytosis

Back 18

cellular "drinking"; a type of endocytosis in which the cell takes fluid and dissolves solutes into small membranous vesicles

Front 19

receptor-mediated endocytosis

Back 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

Front 20

energy

Back 20

the capacity to perform work, or to rearrange matter

Front 21

kinetic energy

Back 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

Front 22

heat

Back 22

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

Front 23

potential energy

Back 23

the energy that matter possess because of its location or arrangement.

Front 24

chemical energy

Back 24

energy available in molecules for release in a chemical reaction

Front 25

thermodynamics

Back 25

the study of energy transformation that occurs in a collection of matter

Front 26

first law of thermodynamics

Back 26

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

Front 27

entropy

Back 27

a measure of disorder

Front 28

second law of thermodynamics

Back 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

Front 29

exergonic reaction

Back 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

Front 30

cellular respiration

Back 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; involved glycolysis, the citric acid cycle, and oxidative phosphorylation (the electron transport chain and chemiosmosis)

Front 31

endergonic reactions

Back 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

Front 32

metabolism

Back 32

the totality of an organism's chemical reactions

Front 33

metabolic pathway

Back 33

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

Front 34

energy coupling

Back 34

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

Front 35

ATP

Back 35

a cluster of several membrane proteins that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentrations gradient

Front 36

phosphorylation

Back 36

the transfer of a phosphate group, usually from ATP, to a molecule. Nearly all cellular work depends on ATP energizing other molecules using this process

Front 37

energy of activation

Back 37

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

Front 38

enzymes

Back 38

a protein that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed into a different molecule in the process

Front 39

substrate

Back 39

a specific substance on which an enzyme acts. Each enzymes recognizes only the specific one of the reaction it catalyzes.

Front 40

active site

Back 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

Front 41

induced fit

Back 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

Front 42

cofactors

Back 42

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

Front 43

coenzyme

Back 43

an organic molecule serving as cofactor

Front 44

competitive inhibitor

Back 44

a substance that reduces the activity of an enzyme by binding to the enzyme's active site in place of the substrate. It mimics that of the enzyme's substrate.

Front 45

noncompetitive inhibitor

Back 45

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

Front 46

feedback inhibition

Back 46

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