Chapter 5

Question 1

Fluid Mosaic Model

Answer 1

the currently accepted model of cell membrane structure, depicting the membrane as a mosaic of diverse protein molecules embedded in a fluid bilayer 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 all together

Question 3

Diffusion

Answer 3

the random movement of particles that result in the net movement of a substance down its concentration gradient from a region where it is more concentrated to where it is less so

Question 4

Concentration Gradient

Answer 4

a region along which the density of a chemical substance increases or decrease. cells often maintain concentration gradients of ions across their membranes. substances move across a gradient from where there is a higher concentration to where there is a lesser concentration

Question 5

Passive Transport

Answer 5

the diffusion of a substance across a biological membrane, with no expenditure of energy

Question 6

Osmosis

Answer 6

the diffusion of free 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

referring to a solution that, when surrounding a cell, causes no net movement into or out of the cell

Question 9

Hypotonic

Answer 9

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

Question 10

Hypertonic

Answer 10

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

Question 11

Osmoregulation

Answer 11

the homeostatic regulation of solute concentrations and water balance by a cell or organism

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 an animal, plant, or microorganism cell 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 an input of enery (often ATP)

Question 15

Exocytosis

Answer 15

the movement of materials out 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 in which a cell engulfs macromolecules, other cells, or particles into its cytoplasm

Question 18

Receptor Mediated Endocytosis

Answer 18

the movement of specific molecules into a cell by the infolding of vesicles containing proteins with receptor sites specific to the molecules being taken in

Question 19

Energy

Answer 19

the capacity to cause change especially to perform work

Question 20

Kinetic Energy

Answer 20

the energy associate with the motion of objects. moving matter does work by imparting motion to other matter

Question 21

Thermal Energy

Answer 21

kinetic energy due to random movement of atoms and molecules; energy in its most random form

Question 22

Heat

Answer 22

thermal energy in transfer from body of matter to another

Question 23

Potential Energy

Answer 23

the energy that matter possesses because of its location or spatial arrangement.

Question 24

Chemical Energy

Answer 24

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

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 or randomness

Question 28

Second Law of Thermodynamics

Answer 28

the principle stating that 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

Cellular Respiration

Answer 29

the aerobic harvesting of energy from food molecules; the energy-releasing chemical breakdown of food molecules (eg 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 chain and Chemiosmosis)

Question 30

Exergonic Reaction

Answer 30

an energy-releasing chemical reaction in which the reactants contain more potential energy than the products

Question 31

Endergonic Reaction

Answer 31

an energy-requiring chemical reaction which yields products with more potential energy than the reactants

Question 32

Metabolism

Answer 32

the totality of an organisms 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

Answer 35

adenosine triphosphate, the main energy source for cells. ATP releases energy when its phosphate bonds are hydrolyzed

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

Activation Energy

Answer 37

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

Question 38

Substrate

Answer 38

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

Question 39

Active Site

Answer 39

the part of an enzyme where a substrate molecule attaches; typically a pocket or groove on the enzymes surface

Question 40

Induced Fit

Answer 40

the change in shape of the active site of an enzyme, caused by entry of the substrate so that it binds the substrate snugly

Question 41

Cofactors

Answer 41

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

Question 42

Coenzyme

Answer 42

an organic molecule serving as a cofactor. most vitamins function as coenzymes in important metabolic reactions

Question 43

Competitive Inhibitor

Answer 43

a substance that reduces the activity of an enzyme by entering the active site in place of the substrate, a competitive inhibitors structure mimics that of the enzymes substrate

Question 44

Noncompetitive Inhibitor

Answer 44

a substance that reduces 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 is no longer effectively catalyzes the conversion of substrate to product

Question 45

Feedback Inhibition

Answer 45

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