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chapter 7 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

The plasma membrane is the boundary that

A

separates the living cell from its surroundings

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2
Q

The plasma membrane exhibits

A

selective permeability, allowing some substances to cross it more easily than others

  • it chooses. its picky.
  • not just anything gets in the cell. they decide what gets in cell. its like a bouncer at a club that decides who gets to go in or who doesnt.
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3
Q

Phospholipids are the most abundant

A

lipid in the plasma membrane

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4
Q

Phospholipids are

A

amphipathic molecules, containing hydrophobic and hydrophilic regions

-half like water, half doesnt like water

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5
Q

The fluid mosaic model states that

A

a membrane is a fluid structure with a “mosaic” of various proteins embedded in it

-fluid- dynamic, moving
-mosaic- a bunch of little pieces together
made of lots of different molecules/elements

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6
Q

Membranes have been chemically analyzed and found to be made of

A

proteins and lipids

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7
Q

Scientists studying the plasma membrane reasoned that it must be a

A

phospholipid bilayer

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8
Q

two main components of membranes

A

proteins and lipids (phospholipids)

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9
Q

In 1935, Hugh Davson and James Danielli proposed a sandwich model in which the phospholipid bilayer lies between two layers of globular proteins
Later studies found problems with this model, particularly the placement of membrane proteins, which have hydrophilic and hydrophobic regions
In 1972, S. J. Singer and G. Nicolson proposed that the membrane is a mosaic of proteins dispersed within the bilayer, with only the hydrophilic regions exposed to water

A

proteins are embedded across membrane

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10
Q

Freeze-fracture studies of the plasma membrane supported the fluid mosaic model.

A

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

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11
Q

Phospholipids in the plasma membrane can move within the bilayer. (constantly moving)

A

Most of the lipids, and some proteins, drift laterally.(move left to right)
Rarely does a molecule flip-flop transversely across the membrane.

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12
Q

As temperatures cool, membranes

A

switch from a fluid state to a solid state

-this is bad. dont want a membrane to freeze up.

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13
Q

The temperature at which a membrane solidifies depends on the types of lipids

A

Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids

(unsaturated fatty acids- double bonds with kinks)
(saturated fatty acids- will stack much better)

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14
Q

Membranes must be fluid to

A

work properly

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15
Q

The steroid cholesterol has different effects on membrane fluidity at different temperatures
(does different jobs at different times)

A
  • At warm temperatures (such as 37°C), cholesterol restrains movement of phospholipids
  • At cool temperatures, it maintains fluidity by preventing tight packing. and keeps things moving so it doesnt pack or go too slow.

normal body temperature- keep things moving but it restrains it so it doesnt go too fast

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16
Q

Some proteins in the plasma membrane can

A

drift within the bilayer

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17
Q

Proteins are much larger than lipids and

A

move more slowly

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18
Q

Variations in lipid composition of cell membranes of many species appear to be adaptations to specific environmental conditions.

A

Ability to change the lipid compositions in response to temperature changes has evolved in organisms that live where temperatures vary.

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19
Q

A membrane is a

A

collage of different proteins, often grouped together, embedded in the fluid matrix of the lipid bilayer

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20
Q

Proteins determine

A

most of the membrane’s specific functions

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21
Q

The two sides of a membrane have

A

different protein and lipid compositions

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22
Q

phospholipids

A

most common lipid in a membrane

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23
Q

Peripheral proteins

A

are bound to the surface of the membrane

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24
Q

Integral proteins penetrate the hydrophobic core (across the membrane).

A
  • Integral proteins that span the membrane are called transmembrane proteins
  • The hydrophobic regions of an integral protein consist of one or more stretches of nonpolar amino acids, often coiled into alpha helices
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25
Q

Six major functions of membrane proteins

A
  1. Transport
  2. Enzymatic activity (speed up reactions)
  3. Signal transduction
  4. Cell-cell recognition
  5. Intercellular joining
  6. Attachment to the cytoskeleton and extracellular matrix (ECM)

-Membranes are structural and functional mosaics

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26
Q

Cells recognize each other by

A

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

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27
Q

Membrane carbohydrates may be covalently bonded to

A

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

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28
Q

Carbohydrates on the external side of the plasma membrane vary among

A

species, individuals, and even cell types in an individual

Example – Blood types

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29
Q

Membranes have

A

distinct inside and outside faces

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30
Q

The asymmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membrane is determined when

A

the membrane is built by the ER and Golgi apparatus

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31
Q

Molecules that start out on the inside face of the ER end up

A

on the outside face of the plasma membrane

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32
Q

A cell must exchange materials with its surroundings, a process controlled by the

A

plasma membrane

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33
Q

Plasma membranes are selectively permeable, regulating the cell’s molecular traffic.
Three things that influence whether something will get in the membrane or not:

A
  • Size of molecule
  • Polarity of molecule (hydrophobic or hydrophilic)
  • Presence/absence of transport proteins in the membrane
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34
Q

Hydrophobic (nonpolar) molecules, such as hydrocarbons, can

A

dissolve in the lipid bilayer and pass through the membrane rapidly
-Hydrocarbons, CO2 and O2

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35
Q

Polar molecules, such as sugars, do not

A

cross the membrane easily (hydrophilic molecules)

-C6H12O6, or charged molecules

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36
Q

its easy to get in the membrane if it is

A

hydrophobic

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37
Q

Transport proteins allow

A

passage of hydrophilic substances across the membrane

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38
Q

Some transport proteins, called channel proteins, have a

A

hydrophilic channel that certain molecules or ions can use as a tunnel

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39
Q

Channel proteins called aquaporins facilitate

A

the passage of water

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40
Q

Other transport proteins, called carrier proteins, bind to

A

molecules and change shape to shuttle them across the membrane

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41
Q

A transport protein is

A

specific for the substance it moves

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42
Q

Diffusion is

A

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

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43
Q

Although each molecule moves randomly, diffusion of a

A

population of molecules may be directional

44
Q

At dynamic equilibrium,

A

as many molecules cross the membrane in one direction as in the other

45
Q

Types of passive transport

A

diffusion
osmosis
facilitated diffusion

46
Q

Substances diffuse down their

A

concentration gradient, the region along which the density of a chemical substance increases or decreases.

No work must be done to move substances down the concentration gradient
-Oxygen gets into cells this way for cellular respiration

47
Q

The diffusion of a substance across a biological membrane is

A

passive transport because no energy is expended by the cell to make it happen

48
Q

in diffusion, the concentration of one molecule has

A

no effect on the movement of other molecules

49
Q

passive transport-

A

requires no energy to do anything to make it happen. it just happens

50
Q

diffusion

A

movement of molecules from an area of [high mol (high concentration)] to—> [low mol (low concentration)]
“down” the concentration gradient

51
Q

osmosis

A

movement of water across a selectively permeable membrane

water will move from an area of [low solute] to —> an area of [high solute]

52
Q

Osmosis is the

A

diffusion of water across a selectively permeable membrane.

Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration until the solute concentration is equal on both sides

-water moves from where there is less stuff to more stuff.

53
Q

Tonicity is the

A

ability of a surrounding solution to cause a cell to gain or lose water
(its always a comparison)
(how cells gain or lose water)

54
Q

Isotonic solution:

A

Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane
its the exact same thing
water vs. water
x vs. x

55
Q

Hypertonic solution:

A

Solute concentration is greater than that inside the cell; cell loses water
have more solute than what it is being compared to

56
Q

Hypotonic solution:

A

Solute concentration is less than that inside the cell; cell gains water
have less solute than what comparing it to

57
Q

Hypertonic or hypotonic environments create

A

osmotic problems for organisms

58
Q

Osmoregulation,

A

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

(Adapt H2O concentrations)

59
Q

The protist Paramecium,

A

which is hypertonic to its pond water environment, has a contractile vacuole that acts as a pump

60
Q

in a hypotonic solution in animal cells

A

it fills with water until it lyses (explodes)

61
Q

in a isotonic solution in animal cells

A

its normal
an equal amount of water goes in and out
we want cells in isotonic enviornemnt

62
Q

in a hypertonic solution in animal cells

A

it becomes crenate/shriveled

63
Q

in a hypotonic solution in a plant cell

A

it is turgid, normal.

plant cells love to be turgid in hypotonic solution

64
Q

in a isotonic solution in a plant cell

A

it is flaccid, water goes in and out

65
Q

in a hypertonic solution in a plant cell

A

it is plasmolyzed, the plasma membrane rips off edges of plasma membrane, this is bad

66
Q

Cell walls help

A

maintain water balance

67
Q

plant cells like to be in

A

hypotonic solutions

68
Q

animal cells like to be in

A

isotonic solutions

69
Q

A plant cell in a hypotonic solution

A

swells until the wall opposes uptake; the cell is now turgid (firm)

70
Q

If a plant cell and its surroundings are

A

isotonic, there is no net movement of water into the cell; the cell becomes flaccid (limp), and the plant may wilt

71
Q

In a hypertonic environment, plant cells

A

lose water; eventually, the membrane pulls away from the wall, a usually lethal effect called plasmolysis

-cant be fixed. bad.

72
Q

In facilitated diffusion,

A

transport proteins speed the passive movement of molecules across the plasma membrane

  • Most transport proteins are very specific
  • 2 types of transport proteins:
  • -Channel proteins and carrier proteins
73
Q

Channel proteins provide

A

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

74
Q

Channel proteins include

A
  • Aquaporins for facilitated diffusion of water (help move water)
  • Ion channels that open or close in response to a stimulus (gated channels)
75
Q

Carrier proteins undergo a

A

subtle change in shape that translocates the solute-binding site across the membrane

(move things down concentration gradient)

76
Q

Some diseases are caused by

A

malfunctions in specific transport systems, for example the kidney disease cystinuria

77
Q

Facilitated diffusion is still passive

A

because the solute moves down its concentration gradient, and the transport requires no energy
-Channel proteins and carrier proteins

78
Q

Some transport proteins, however, can move

A

solutes against their concentration gradients

-this requires energy

79
Q

Active transport

A

moves substances against their concentration gradients

80
Q

Active transport requires

A

energy, usually in the form of ATP

81
Q

Active transport is performed by

A

specific proteins embedded in the membranes

82
Q

Active transport allows

A

cells to maintain concentration gradients that differ from their surroundings

83
Q

The sodium-potassium pump

A

is one type of active transport system

84
Q

Membrane potential is the

A

voltage difference across a membrane

85
Q

Voltage is created by

A

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

86
Q

Cells have a

A

net negative internal charge

87
Q

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

A
  • A chemical force (the ion’s concentration gradient)

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

88
Q

An electrogenic pump is a

A

transport protein that generates voltage across a membrane

ex. sodium potassium pump

89
Q

The sodium-potassium pump is the major electrogenic pump of animals

A

3 Na+ out, 2K+ in = overall 1 positive charge to the extracellular fluid

90
Q

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

A

proton pump

91
Q

Electrogenic pumps help

A

store energy that can be used for cellular work

92
Q

Cotransport occurs when

A

active transport of a solute indirectly drives transport of other solutes

93
Q

Plants commonly use

A

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

94
Q

Small molecules and water enter or leave the cell through the lipid bilayer or via transport proteins

A

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

95
Q

Bulk transport requires energy

A
  • exocytosis

- endocytosis

96
Q

In exocytosis,

A

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

97
Q

Many secretory cells use exocytosis to export their products

A
  • Pancreatic beta cells releasing insulin
  • Neurons releasing neurotransmitters
  • Plants making cell walls
98
Q

exocytosis

A

taking things out of the cell

99
Q

In endocytosis,

A

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

100
Q

Endocytosis is a

A

reversal of exocytosis, involving different proteins

101
Q

There are three types of endocytosis

A

Phagocytosis (“cellular eating”)
Pinocytosis (“cellular drinking”)
Receptor-mediated endocytosis (“picky eater”)

102
Q

endocytosis

A

bring things into the cell

103
Q

In phagocytosis a cell engulfs a particle in a vacuole

A

The vacuole fuses with a lysosome to digest the particle

104
Q

In pinocytosis,

A

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

105
Q

In receptor-mediated endocytosis,

A

binding of ligands to receptors triggers vesicle formation

106
Q

A ligand is

A

any molecule that binds specifically to a receptor site of another molecule

Biology 1406 (53 decks)

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