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BSC 2010 Dennis > The Plasma Membrane > Flashcards

The Plasma Membrane Flashcards

1
Q

The ______ membrane is the boundary that separates the living cell from its surroundings

A

plasma

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2
Q

The plasma membrane exhibits ______ ________ allowing some substances to cross it more easily than others

A

selective permeability

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3
Q

_______ are the most abundant lipid in the plasma membrane

A

phospholipids

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4
Q

Phospholipids are _______ molecules, containing hydrophobic and hydrophilic regions

A

amphipathic

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5
Q

The ____ ______ model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it

A

fluid mosaic

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6
Q

In 1935, Hugh Davson and James Danielli proposed a _______ model in which the phospholipid bilayer lies between two layers of globular proteins

A

sandwich

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7
Q

___________ studies of the plasma membrane supported the fluid mosaic model

A

freeze-fracture

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8
Q

Freeze-fracture is a specialized preparation technique that _____ a membrane along the middle of the phospholipid bilayer

A

splits

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9
Q

Phospholipids in the plasma membrane can move within the ____

A

bilayer

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10
Q

Most of the lipids, and some proteins, drift ______

A

laterally

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11
Q

As temperatures cool, membranes switch from a _____ state to a ____ state

A

fluid to solid

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12
Q

Membranes rich in unsaturated fatty acids are more _____ that those rich in saturated fatty acids

A

fluid

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13
Q

Membranes must be fluid to ____ properly; they are usually about as fluid as salad oil

A

work

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14
Q

At warm temperatures (such as 37°C), cholesterol ______ movement of phospholipids

A

restrains

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15
Q

At cool temperatures, cholesterol ______ fluidity by preventing tight packing

A

maintains

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16
Q

A _______ is a collage of different proteins embedded in the fluid matrix of the lipid bilayer

A

membrane

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17
Q

_______ determine most of the membrane’s specific functions

A

proteins

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18
Q

______ proteins are bound to the surface of the membrane

A

Peripheral

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19
Q

_____ proteins penetrate the hydrophobic core (they are ingrained in the membrane)

A

Integral

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20
Q

Integral proteins that span the membrane are called ______ proteins

A

transmembrane

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21
Q

The hydrophobic regions of an integral protein consist of one or more stretches of nonpolar amino acids, often coiled into _____ _____

A

alpha helices

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22
Q 
Transport
Enzymatic activity
Signal transduction
Cell-cell recognition
Intercellular joining
Attachment to the cytoskeleton and extracellular matrix
A

the 6 major functions of membrane proteins

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23
Q

Cells _______ each other by binding to surface molecules, often carbohydrates, on the plasma membrane

A

recognize

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24
Q

Membrane carbohydrates may be ________ bonded to lipids (forming glycolipids) or more commonly to proteins (forming glycoproteins)

A

covalently

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25
Q

Carbohydrates on the ______ side of the plasma membrane vary among species, individuals, and even cell types in an individual

A

external

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26
Q

The ___________ distribution of proteins, lipids, and associated carbohydrates in the plasma membrane is determined when the membrane is built by the ER and Golgi apparatus

A

asymmetrical

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27
Q

_________ (nonpolar) molecules, such as hydrocarbons, can dissolve in the lipid bilayer and pass through the membrane rapidly

A

Hydrophobic

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28
Q

_____ molecules, such as sugars, do not cross the membrane easily

A

polar

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29
Q

______ proteins allow passage of hydrophilic substances across the membrane

A

transport

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30
Q

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

A

channel

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31
Q

Channel proteins called _________ facilitate the passage of water

A

aquaporins

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32
Q

Other transport proteins, called ____ proteins, bind to molecules and change shape to shuttle them across the membrane

A

carrier

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33
Q

A transport protein is specific for the…

A

substance that it moves

34
Q

Although each molecule moves _______, diffusion of a population of molecules may exhibit a net movement in one direction

A

randomly

35
Q

At ______ _______, as many molecules cross one way as cross in the other direction

A

dynamic equilibrium

36
Q

Substances diffuse _____ their concentration gradient, the difference in concentration of a substance from one area to another

A

down

37
Q

No work must be done to move substances down the _______ _____

A

concentration gradient

38
Q

The diffusion of a substance across a biological membrane is ______ transport because it requires no energy from the cell to make it happen

A

passive

39
Q

______ is the diffusion of water across a selectively permeable membrane

A

Osmosis

40
Q

Water diffuses across a membrane from the region of _____ solute concentration to the region of _____ solute concentration

A

lower;higher

41
Q

______ is the ability of a solution to cause a cell to gain or lose water

A

tonicity

42
Q

________ solution: Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

A

isotonic

43
Q

________ solution: Solute concentration is greater than that inside the cell; cell loses water

A

Hypertonic

44
Q

________ solution: Solute concentration is less than that inside the cell; cell gains water

A

hypotonic

45
Q

___________, the control of water balance, is a necessary adaptation for life in such environments

A

Osmoregulation

46
Q

Cell walls help maintain _____ balance

A

water

47
Q

A plant cell in a ______ solution swells until the wall opposes uptake; the cell is now turgid (firm)

A

hypotonic

48
Q

If a plant cell and its surroundings are _______, there is no net movement of water into the cell; the cell becomes flaccid (limp), and the plant may wilt

A

isotonic

49
Q

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

A

plasmolysis

50
Q

Passive Transport Aided by Proteins

A

Facilitated Diffusion

51
Q

In facilitated diffusion, _______ ________ speed the passive movement of molecules across the plasma membrane

A

transport proteins

52
Q

_______ proteins provide corridors that allow a specific molecule or ion to cross the membrane

A

channel

53
Q

channel proteins for facilitated diffusion of water

A

aquaporins

54
Q

channel proteins like Ion channels that open or close in response to a stimulus are called _____ _______

A

gated channels

55
Q

Carrier proteins undergo a subtle change in shape that translocates the _____-______ _____ across the membrane

A

solute-binding site

56
Q

Some diseases are caused by _________ in specific transport systems, for example the kidney disease cystinuria

A

malfunctions

57
Q

Active Transport - uses energy to move solutes _____ their gradients

A

against

58
Q

Facilitated diffusion is still ______ because the solute moves down its concentration gradient

A

passive

59
Q

Some _______ proteins, however, can move solutes against their concentration gradients

A

transport

60
Q

_____ transport moves substances against their concentration gradient

A

active

61
Q

Active transport requires ______, usually in the form of ATP

A

energy

62
Q

_____ transport is performed by specific proteins embedded in the membranes

A

active

63
Q

Active transport allows cells to __________ concentration gradients that differ from their surroundings

A

maintain

64
Q

Membrane ________ is the voltage difference across a membrane

A

potential

65
Q

The sodium-potassium pump is one type of active ______ system

A

transport

66
Q

______ is created by differences in the distribution of positive and negative ions

A

voltage

67
Q

An _________ pump is a transport protein that generates voltage across a membrane

A

electrogenic

68
Q

The sodium-potassium pump is the major electrogenic pump of _____ cells

A

animal

69
Q

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

A

proton

70
Q

_________ occurs when active transport of a solute indirectly drives transport of another solute

A

Cotransport

71
Q

______ commonly use the gradient of hydrogen ions generated by proton pumps to drive active transport of nutrients into the cell

A

Plants

72
Q

_____ transport across the plasma membrane occurs by exocytosis and endocytosis

A

Bulk

73
Q

Small molecules and water enter or leave the cell through the _____ _____ or by transport proteins

A

lipid bilayer

74
Q

______ molecules, such as polysaccharides and proteins, cross the membrane in bulk via vesicles

A

Large

75
Q

Bulk transport requires ______

A

energy

76
Q

In _________, transport vesicles migrate to the membrane, fuse with it, and release their contents

A

exocytosis

77
Q

Many _______ cells use exocytosis to export their products

A

secretory

78
Q

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

A

endocytosis

79
Q

________ is a reversal of exocytosis, involving different proteins

A

Endocytosis

80
Q

In ________ a cell engulfs a particle in a vacuole

The vacuole fuses with a lysosome to digest the particle

A

phagocytosis

81
Q

In _________, molecules are taken up when extracellular fluid is “gulped” into tiny vesicles

A

pinocytosis

82
Q

In __________________, binding of ligands to receptors triggers vesicle formation

A

receptor-mediated endocytosis

BSC 2010 Dennis (4 decks)

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