Chapter 7

Front 1

____ separating the living cell from its nonliving surrounding

Back 1

Boundary

Front 2

_____, allowing some substances to cross it more easily than others

Back 2

Selectively permeable

Front 3

_____ are the most abundant lipid in the plasma membrane

Back 3

Phospholipids

Front 4

Phospholipids are _____

Back 4

amphipathic molecules, containing hydrophobic and hrydrophilic regions

Front 5

The _____ states that a membrane is fluid structure with a "mosaic" of various proteins embedded in it

Back 5

Fluid mosaic model

Front 6

Fluidity of membranes:

Back 6

-phospholipids in the plasma membrane can move within the bilayer

-most lipids and some proteins drift laterally

-rarely does a molecule flip-flop transversely across the membrane

Front 7

Some proteins in the plasma membrane can drift within the bilayer but are much larger than lipids and move more ____

Back 7

slowly

Front 8

temperature at which a membrane solidifies depends

Back 8

on the types of lipids

Front 9

Membranes must me ___ to work properly

Back 9

fluid

Front 10

The _____ has different effects on membrane fluidity at different temperature

Back 10

steroid cholesterol (acts as temperature buffer)

Front 11

At warm temperatures, cholesterol

Back 11

restrains movements of phospholipids

Front 12

At temperatures, cholesterol

Back 12

maintains fluidity by preventing right packaging

Front 13

Two major populations of membrane proteins:

Back 13

-peripheral

-integral

Front 14

Integral proteins

Back 14

penetrate the hydrophobic core

Front 15

integral proteins that span the membrane are called

Back 15

transmembrane proteins

Front 16

The hydrophobic regions of an integral protein consist of

Back 16

one or more stretches of ninpolar amino acids, often coiled into alpha helices

Front 17

Six major function of membrane proteins:

Back 17

-transport

-enzymatic activity

-signal transduction

-cell-cell recognition

-intercellular joining

-attachment to the cytoskeleton and extracellular matrix

Front 18

Cell recognize each other by

Back 18

binding to surface molecules, often containing carbohydrates, on the extracellular surface of the plasma membrane

Front 19

Membrane carbohydrates may be covalently bonded to

Back 19

lipids (forming glycolipids) or more commonly to proteins (forming glycoproteins)

Front 20

Plasma membranes are

Back 20

selectively permeable, regulating the cell's molecular traffic

Front 21

______ can dissolve in the lipid bilayer and pass through the membrane rapidly

Back 21

Hydrophobic (nonpolar) molecules, suc as hydrocarbons

Front 22

_____ don not cross the membrane easily

Back 22

Hydrophilic molecules including ions and polar molecules

Front 23

____ allow passage of hydrophilic substances across the membrane

Back 23

Transport proteins

Front 24

Some transport proteins, called ____, have a hydrophilic channel that certain molecules or ions can use as a tunnel

Back 24

channel proteins

Front 25

Channel proteins called ____ facilitate the passage of water

Back 25

aquaporins

Front 26

____ bind to molecules and change shape to shuttle them across the membrane

Back 26

carrier proteins

Front 27

Tranport proteins are

Back 27

specific for the substance it moves e.g. glucose transporter

Front 28

Two modes of membrane transport

Back 28

-Passive transport

-Active tranport

Front 29

____ is the tendency for molecules to spread out evenly into the available space

Back 29

Diffusion

Front 30

Substances diffuse down their _______

Back 30

concentration gradient, the region along which the density of chemical substances increase or decreases

Front 31

The diffusion of a substance across a biological membrane is ____ because no energy is expended by the cell to make it happen

Back 31

passive transport

Front 32

____ is the diffusion of water across a selectively permeable membrane

Back 32

Osmosis

Front 33

____ is the ability of a surounding solution to cause a cell to gain or lose water, depends on centration of nonpenetrating solutes

Back 33

Tonicity

Front 34

______: solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

Back 34

Isotonic solution

Front 35

_____: Solute concentration is greater than that inside the cell; cell losses water

Back 35

Hypertonic solution

Front 36

____: solute concentration is less than that inside the cell; cell gains water

Back 36

Hypotonic solution

Front 37

the control of solute concentration and water balance, is a necessary adaption for life in such environments

Back 37

Osmoregulation

Front 38

A plant cell in a hypotonic solution swells until the wall opposes uptake; the cell is now ____

Back 38

turgid(firm)

Front 39

If plant cell and its surroundinds are isotonic, there is no net movement of water into the cell; the cell becomes ___, and the plant may wilt

Back 39

Flaccid(limp)

Front 40

In a hypertonic environment, plant cells lose water; eventually, the membrane pulls away from the wall, a usually lethal effect called

Back 40

Plamolysis

Front 41

_____, transport proteins speed the passive movement of molecules across the plasma membrane; two types of transport proteins- channel proteins and carrier proteins

Back 41

facilitated diffusion

Front 42

Channel proteins include:

Back 42

-Aquaporins, for facilitated diffusion of water

-Ion channels that open or close in response to stimulus (gated channels)

Front 43

Facilitated diffusion is still ____ because the solute moves down its concentration gradient, and the transport requires no energy

Back 43

Passive

Front 44

_____ moves substances against their concentration gradients

Back 44

Active transport

Front 45

Active transport requires

Back 45

energy usually in the form of ATP

Front 46

Active transport is performed by specific proteins embedded in the membranes and are all

Back 46

carrier proteins

Front 47

Sodium Potassium pump is one type of

Back 47

transport system

Front 48

____ is the voltage difference across a membrane and ranges from -50 to -200 mV

Back 48

Membrane potential

Front 49

Voltage is created by

Back 49

differences in the distribution of positive and negative ions across a membrane

Front 50

Two combined forces, collectively called the Electrochemical gradient, drive the diffusion of ions across a membrane:

Back 50

-chemical force (the ion's concentraion gradient)

-An electrical force (the effect of the membrane potential on the ion's movement)

Front 51

_____ is a transport protein that generates voltage across a membrane

Back 51

electrogenic pump

Front 52

The _____ is the major electrogenic pump of animal cells

Back 52

sodium-potassium pump

Front 53

The _____ is the main electrogenic pump of plants, fungi, and bacteria

Back 53

proton pump

Front 54

____ occurs when active transport of solute indirectly drives transport of other solutes

Back 54

Cotransport

Front 55

_____ transports vesicles migrate to the membrane, fuse with it, and release their contents

Back 55

exocytosis

Front 56

____, the cell takes in macromolecules by forming vesicles from the plasma membrane

Back 56

Endocytosis

Front 57

There are three type of endocytosis:

Back 57

-Phagocytosis (cellular eating)

-Pinocytosis (cellular drinking)

-Receptor-mediated endocytosis

Front 58

In phagocytosis a cell ___

Back 58

engulfs a particle in a vacuole

Front 59

Vacuole fuses with a

Back 59

lysosome to digest the particle

Front 60

In pinocytosis, molecules are

Back 60

taken up when extracellular fluid is gulped into tiny vesicles

Front 61

____ binding of ligands to receptors triggers vesicle formation

Back 61

receptor-mediated endocytosis

Front 62

____ is any molecule that binds specifically to a receptor sire of another molecule

Back 62

ligand