Chapter 5 ( The Working Cell)

Front 1

What is a fluid mosaic?

Back 1

description of a membrane structure, depicting a cellular membrane as a mosaic of diverse protein molecules embedded ina fluid bilayer of phsopholipid molecules.

Front 2

What is selective permeability?

Back 2

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

Front 3

What is diffusion?

Back 3

spontaneous movement of a substance down its concentration gradient from where it is more concentrated to where it is less concentrated.

Front 4

What is concentration gradient?

Back 4

- region along which the density of a chemical substance increases or decreases.
- cells often maintain one made of ions across their membranes
- when it exists, substacnes tend to move from where they are more concentrated to where they are less concentrated.

Front 5

What is passive transport?

Back 5

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

Front 6

the cell doesn't expend energy to transport substance that are diffusing down their concentration gradient.

Back 6

Why is diffusion across a membrane called passive transport?

Front 7

What is osmosis?

Back 7

diffusion of water across a selectively permeable membrane.

Front 8

What is tonicity?

Back 8

- ability of a solution surrounding a cell to cause that cell to gain or lose water
- mainly depends on its concentration of solutes that can't cross the plasma membrane relative tot he concentration of solutes inside the cell.

Front 9

What is isotonic mean?

Back 9

- referring to a solution that, when surrounding a cell, has no effect on the passage of water in or out of the cell.
- equal solute concentration

Front 10

What does hypotonic mean?

Back 10

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

Front 11

What does hypertonic mean?

Back 11

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

Front 12

What is osmoregulation?

Back 12

homeostatic maintenance of solute concentrations and the balance of water gain and loss

Front 13

What is facilitated diffusion?

Back 13

- passage of a substance through a specific transport protein across a biological membrane down its concentration gradient
- type of passive transport

Front 14

What is aquaporin?

Back 14

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

Front 15

because they are specific for the solutes they transpor, the numbers and kinds of transport proteins affect a membrane's permeability to various solutes.

Back 15

How do transport proteins contribute to a membrane's selective permeability?

Front 16

kidney cells must reabsorb a large a mount of water when producing urine.

Back 16

What are aquaporins important in kidney cells?

Front 17

What is active transport?

Back 17

movement of a substance across a biological membrane against its concentration gradient, aidded by specific transport proteins and requring an input of energy.

Front 18

What is exocytosis?

Back 18

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

Front 19

What is endocytosis?

Back 19

cellular uptakeof molecules or particle via formation of new vesicles from the plasma membrane.

Front 20

What is phagocytosis?

Back 20

- cellular eating
- type of endocytosis in which a cell engulfs macromolecules, other cells, or particles into its cytoplasm

Front 21

What is pinocytosis?

Back 21

- cellular drinking
- type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles.

Front 22

What What is receptor-mediated endocytosis?

Back 22

- movement of specific molecules into a cell by the inward budding of membranous vesicles
=contains proteins with receptor sites specific to the molecules being taken in

Front 23

- exocytosis; when a transport vesicles fuses with the plasma membrane, its contnets are released and the vesicle membrane adds to the plasma membrane

Back 23

As a cell grows, its plasma membrane expands. Does this involove endo/exo cytosis? Explain.

Front 24

What is energy?

Back 24

capacity to cause change, especially to perfrom work.

Front 25

What is kinetic energy?

Back 25

- energy of motion; energy of a mass of matter that is moving
- moving matter does work by imparting motion to other matter

Front 26

What is potential energy?

Back 26

- the energy that matter posesses because of its location or arrangement
- EX: water behind a dam; chemical bonds

Front 27

What are thermodynamics?

Back 27

study of energy transformation that occurs in a collection of matter

Front 28

What is the first law of thermodynamics?

Back 28

- principle conservation of energy
- can be transferred and transformed, but it can't be created or destroyed

Front 29

What is the second law of thermodynamics?

Back 29

- principle stating that every energy conversion reduces the order of the niverse, increasing its entropy
- ordered forms of energy, are at least partly converted to heat

Front 30

What is chemical energy?

Back 30

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

Front 31

What is cellular respiration?

Back 31

- aerobic harvesting of energy from food molecules
- energy-releasing chemical breakdown of food molecules, such as gluecose, and the storage of potential energy in a form that cells can use to perform work
- involves; glycolosis, citric acid cycle, and oxidative phosphorylation (electron transport chain and chemiosmosis)

Front 32

What is entropy?

Back 32

- measure of disorder
EX: heat, which is random molecular motion

Front 33

diffusion across a membrane results in equal concentrations of solutes, which is a more disorded arrangement (higher entropy) than a high concentration on 1 side and a low concentration on the other

Back 33

How does the 2nd law of thermodynamics explain the diffusion of a solute across a membrane?

Front 34

What is an exergonic reaction?

Back 34

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

Front 35

What is an endergonic reaction?

Back 35

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

Front 36

What is metabolism?

Back 36

totality of an organism's chemical reaction

Front 37

What is metabolic pathway?

Back 37

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

Front 38

What is energy coupling?

Back 38

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

Front 39

some of it is stored in ATP molecules; the rest is releasaed as heat.

Back 39

What becomes of the energy extracted from food during cellular respiration?

Front 40

What is ATP?

Back 40

- powers nearly all forms of cellular work
- adenosine triphosphate

Front 41

What is phosporylation?

Back 41

- transfer of phosphate group, usuall from ATP, to a molecule
- nearly all cellular work depends on ATP energizing other molecules by phosphorylation.

Front 42

What are the 3 types of cellular work?

Back 42

- chemical
- mechanical
- transport

Front 43

Describe chemical cellular work.

Back 43

- phosphorylation of reactants provides energy to drive the endergonic synthesis of products.

Front 44

Describe mechanical cellular work.

Back 44

- transfer of phosphate groups to special motor proteins in muscle cells cause the proteins to change shape and pull on protein filaments, in turn causing the cells to contract

Front 45

Describe transport cellular work.

Back 45

- ATP drives the active transport of solutes across a membrane against their concentration gradient by phosphorylating transport proteins

Front 46

ATP is a renewable resource

Back 46

Why can work be sustained?

Front 47

exergonic processes phosphorylate ADP to form ATP, ATP transfers energy to energonic processes by phosphorylating other molecules

Back 47

How does ATP transfer energy from exergonic to endergonic processes in the cell?

Front 48

What is activation energy?

Back 48

- amount of energy that reactants must absorb before a chemical reaction will start
- protects the highly ordered molecules of your cells from spontaneously breaking down

Front 49

What are enzymes?

Back 49

- macromolecule, usually a protein, that serves as a biological catalyst, change the rate of a chemical reaction without being consumed by the reaction
- speeds up reaction by lowering the activation energy needed for the reaction to begin

Front 50

What are substrates?

Back 50

- specific substance on which an enzyme acts. Each enzyme recgonizes only the specific substrate or substrates of the reaction it catalyzes
- surface in or on which an organism lives

Front 51

What is an active site?

Back 51

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

Front 52

What is the catalytic cycle?

Back 52

1. enzyme starts with empty active site
2. sucrose eneters the active site, attaching by weak bonds
- active site changes shape slightly
3. substate is converted to products; glucose and fructose
4. products are released

Front 53

What are induced fits?

Back 53

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

Front 54

What are cofactors?

Back 54

- nonprotein molecule or ion that is required for the proper function of an enzyme

Front 55

Whaat is a coenzyme?

Back 55

- organic cofactor
- most vitamins function as these in important metabolic reaction

Front 56

- enzyme lowers the activation energy needed for a reaction when its specific substrate eneters its activation site
- with an induced fit, enzyme strains bonds that need to break or positions substates in an orientation that aids the conversion of reactants to products

Back 56

How do enzymes speed up a specific reaction?

Front 57

What is a competitive inhibitor?

Back 57

- substance that reduces the activity of an enzyme by binding to the enzyme's active site in place of the substrate
- structure mimics that of the enzyme substrate

Front 58

What is a noncompetitive inhibitor?

Back 58

- substance that decreases the activity of an enzyme without entering an active site
- by binding elsewhere on the enzyme it changes the shape of an enzyme so that the active site no longer effectively catalyzes the conversion of substrate to a product

Front 59

What is a feedback inhibition?

Back 59

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

Front 60

- prevents the cell from wasting valuable resources by synthesizing more of a particular product than is needed

Back 60

What is advantage of feedback inhibition to a cell?

Front 61

- if the inhibitor binds to the enzyme with covalent bonds, the inhibition is usually irreversible.
- when weak chemical interaction bind inhibitor and enzyme, the inhibition is reversible.

Back 61

What determines whether enzyme inhibition is reversible or irreversible?