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Bio 181 > Membranes > Flashcards

Membranes Flashcards

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1
Q

The internal and external environments of a cell are separated by a structure known as the plasma ____

A

membrane

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2
Q

What are the three molecular components of cellular membranes?

A

phospholipids

proteins

carbohydrates

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3
Q

The plasma membrane consists of a(n) ___

bilayer.

A

lipid

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4
Q

The two leaflets of a lipid bilayer are formed because

A

the polar head groups of phospholipids can interact with the polar interior and exterior of the cell.

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5
Q

Phospholipids have both hydrophobic and hydrophilic components. As such, they are said to be _____

A

amphipathic

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6
Q

What separates the internal contents of a cell from the extracellular environment?

A

The plasma membrane

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7
Q

The cell membrane is referred to as a mosaic because it is a mixture of what types of molecules?

A

proteins

carbohydrates

lipids

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8
Q

The three main types of macromolecules that comprise the plasma membrane are

A

lipids, proteins, and carbohydrates

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9
Q

Which of the following statements are consistent with the fluid-mosaic model?

  • Phospholipids can move within the plane of the membrane.
  • While lipids can move within the membrane, all proteins remain anchored in one location within the phospholipid bilayer.
  • Membranes are mainly composed of proteins and phospholipids.
  • Many membrane proteins move within the plane of the membrane.
A

Phospholipids can move within the plane of the membrane.

Membranes are mainly composed of proteins and phospholipids.

Many membrane proteins move within the plane of the membrane.

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10
Q

What is the basic structure of the plasma membrane?

A

a phospholipid bilayer

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11
Q

Cellular membranes are described as fluid because

A

their lipids and proteins can move relative to each other.

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12
Q

Which of the following statements explain why the phospholipid bilayer is composed of two leaflets?

  • Membranes must interact with two polar environments, a hydrophilic cytoplasm and a hydrophilic extracellular environment.
  • Two leaflets result when membrane components secreted from inside the cell match up with membrane components gathered from the environment.
  • Hydrophobic nonpolar tails can be isolated into a hydrophobic environment between the two leaflets.
  • Phospholipids are amphipathic and must interact with polar and nonpolar environments.
A

Membranes must interact with two polar environments, a hydrophilic cytoplasm and a hydrophilic extracellular environment.

Hydrophobic nonpolar tails can be isolated into a hydrophobic environment between the two leaflets.

Phospholipids are amphipathic and must interact with polar and nonpolar environments.

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13
Q

One layer, or half of a phospholipid bilayer, is termed a(n) ___

A

leaflet

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14
Q

A phospholipid molecule consists of:

A

a polar head and two nonpolar tails

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15
Q

Because the plasma membrane contains lipids, proteins, and carbohydrates, it is often described as a(n) ___

A

mosaic

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16
Q

According to the ______ model, membrane proteins and lipids are able to move relative to one another within the plasma membrane.

A

fluid-mosaic

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17
Q

Some molecules are known to move laterally in the plane of the membrane. As such, we can say the membrane is

A

fluid

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18
Q

A membrane protein that has a portion integrated into the hydrophobic region of the membrane is called a(n) ______ membrane protein.

A

intergral

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19
Q

A lipid bilayer is composed of ______ leaflet(s).

A

2

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20
Q

Phospholipids have both hydrophobic and hydrophilic components. As such, they are said to be
.

A

amphipathic

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21
Q

Which of the following statements is correct about a biological membrane that is fluid?

  • The composition of the membrane changes over short periods of time.
  • The structure of the membrane is solid and rigid but dissolves readily.
  • Individual molecules can move within the membrane.
  • Individual molecules remain in static locations.
A

Individual molecules can move within the membrane.

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22
Q

hich of the following statements are consistent with the fluid-mosaic model?

  • While lipids can move within the membrane, all proteins remain anchored in one location within the phospholipid bilayer.
  • Membranes are mainly composed of proteins and phospholipids.
  • Phospholipids can move within the plane of the membrane.
  • Many membrane proteins move within the plane of the membrane.
A

Membranes are mainly composed of proteins and phospholipids.

Phospholipids can move within the plane of the membrane.

Many membrane proteins move within the plane of the membrane.

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23
Q

Most phospholipids move freely within a semifluid membrane

A

laterally along the plane of the membrane in two dimensions

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24
Q

Which of the following proteins are integral membrane proteins?

  • lipid-anchored proteins
  • peripheral membrane proteins
  • transmembrane proteins
  • noncovalent helix proteins
A

lipid-anchored proteins

transmembrane proteins

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25
Q

What property of biological membranes describes the ability of individual molecules to move within the membrane?

A

Fluidity

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26
Q

Which of the following movements of a phospholipid are energetically favorable within the bilayer?

  • lateral movements
  • “flip-flop” transfer between leaflets
  • rotational movements
  • inversions
A

lateral movements

rotational movements

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27
Q

The fluidity of the plasma membrane can be increased by incorporating fatty acids with ______ tails or by incorporating ______ lipids.

A

shorter ; unsaturated

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28
Q

Why is it more appropriate to describe membranes as semifluid?

  • Phospholipids spontaneously migrate between leaflets.
  • Molecules move laterally within the membrane leaflet.
  • Membrane proteins and lipids move freely in three dimensions.
  • Phospholipids usually move in two dimensions.
A

Molecules move laterally within the membrane leaflet.

Phospholipids usually move in two dimensions.

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29
Q

Shorter nonpolar tails make the membrane ______ fluid.

A

more

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30
Q

A membrane protein that has a portion integrated into the hydrophobic region of the membrane is called a(n) ______ membrane protein.

A

integral

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31
Q

At a high temperature, cholesterol makes a membrane ______ fluid.

A

less

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32
Q

The plasma membrane of a cell is considered to be

A

selectively permeable.

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33
Q

Movements that keep the phospholipid nonpolar tail within the ___ region of the bilayer are energetically favorable.

A

hydrophobic

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34
Q

Which of the following changes in lipid composition would be expected to increase the fluidity of a phospholipid bilayer?

  • Increasing the length of the fatty acid tails
  • Incorporating more cholesterol at low temperatures
  • Incorporating more cholesterol at high temperatures
  • Incorporating more unsaturated fatty acids
A

Incorporating more cholesterol at low temperatures

Incorporating more unsaturated fatty acids

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35
Q

What are functions of the selectively permeable plasma membrane?

  • provide a barrier that prevents the movement of any molecule into and out of the cell
  • maintain a proper supply of essential molecules such as glucose and amino acids
  • maintain a proper balance of ions within the cell
  • remove waste products from within the cell
A

maintain a proper supply of essential molecules such as glucose and amino acids

maintain a proper balance of ions within the cell

remove waste products from within the cell

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36
Q

Membrane fluidity is increased when membrane lipids

A

have shorter nonpolar tails.

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37
Q

elect the true statements comparing simple and facilitated diffusion.

  • Facilitated diffusion, but not simple diffusion, requires a transport protein.
  • Both simple and facilitated diffusion require concentration gradients.
  • Only simple diffusion requires a concentration gradient.
  • Facilitated diffusion, but not simple diffusion, requires ATP.
A

Facilitated diffusion, but not simple diffusion, requires a transport protein.

Both simple and facilitated diffusion require concentration gradients.

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38
Q

How does cholesterol affect the plasma membrane at low temperatures?

A

It makes the membrane more fluid and prevents freezing.

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39
Q

What types of transport require a transport protein?

A

Active transport

Facilitated diffusion

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40
Q

All cells are surrounded by a ___ permeable plasma membrane, meaning that the membrane allows the passage of some molecules and ions but not others.

A

semi

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41
Q

The transport of a substance that requires an input of energy is called ___ transport.

A

active

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42
Q

Which of the following movements of a phospholipid are energetically favorable within the bilayer?

  • inversions
  • rotational movements
  • lateral movements
  • “flip-flop” transfer between leaflets
A

rotational movements

lateral movements

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43
Q

To move a substance through a membrane against a concentration gradient, which of the following are necessary?

  • A transport protein
  • A membrane vesicle
  • A vacuole
  • A source of energy
A

A transport protein

A source of energy

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44
Q

The selective ___ of the plasma membrane allows the cell to maintain a favorable internal environment.

A

permeability

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45
Q

A key similarity between simple and facilitated diffusion is that both require

A

concentration gradients.

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46
Q

Description of Diffusion

A

Movement of a substance from a region where its concentration is high to a region where its concentration is low

47
Q

Description of Facilitated Diffusion

A

Movement of a substance from a region where its concentration is high to a region where its concentration is low through a passageway provided by a transport protein

48
Q

Description of Active Transport

A

Movement of a substance from a region where its concentration is low to a region where its concentration is high with the aid of a transport protein and a source of energy

49
Q

ATP can be used to power which of the following processes? Simple diffusion, facilitated diffusion, or active transport?

A

Active transport

50
Q

The difference between passive transport and active transport is that active transport requires

A

an input of energy.

51
Q

Phospholipid bilayers are an effective barrier to many charged or polar solutes because of their ___ interior region.

A

nonpolar

52
Q

Which type of transport requires a source of energy and a transport protein?

A

active transport

53
Q

Small, uncharged molecules pass through the membrane via

A

passive diffusion.

54
Q

What are functions of the selectively permeable plasma membrane?

A

remove waste products from within the cell

maintain a proper balance of ions within the cell

maintain a proper supply of essential molecules such as glucose and amino acids

55
Q

Select the true statements comparing simple and facilitated diffusion.

  • Facilitated diffusion, but not simple diffusion, requires a transport protein.
  • Facilitated diffusion, but not simple diffusion, requires ATP.
  • Both simple and facilitated diffusion require concentration gradients.
  • Only simple diffusion requires a concentration gradient.
A

Facilitated diffusion, but not simple diffusion, requires a transport protein.

Both simple and facilitated diffusion require concentration gradients.

56
Q

A term that describes a situation in which the concentration of a solute is higher on one side of a membrane than the other is

A

transmembrane gradient.

57
Q

Which of the following could provide energy to fuel active transport?

  • a concentration gradient
  • carbohydrate
  • flippase
  • ATP
A

ATP

58
Q

A solution in which the solute concentration on both sides of the membrane is equal is classified as

A

isotonic.

59
Q

Why is the phospholipid bilayer an effective barrier to hydrophilic or polar molecules?

A

Because of the hydrophobic interior of the bilayer

60
Q

What is the solute concentration of a solution relative to the solute concentration inside a cell for the following condition: Isotonic Solution

A

The solute concentration outside a cell is equal to the solute concentration inside the cell.

61
Q

What is the solute concentration of a solution relative to the solute concentration inside a cell for the following condition: Hypertonic Solution

A

The solute concentration outside a cell is higher than the solute concentration inside the cell.

62
Q

What is the solute concentration of a solution relative to the solute concentration inside a cell for the following condition: Hypotonic Solution

A

The solute concentration outside the cell is lower than the solute concentration inside the cell.

63
Q

Which of the following can readily diffuse across the cell membrane?

  • Charged molecules
  • Gases
  • Large molecules
  • Ions
  • Small, uncharged molecules
A

Gases

Small, uncharged molecules

64
Q

The selective ___ of the plasma membrane allows the cell to maintain a favorable internal environment.

A

permeability

65
Q

A solution whose solute concentration is higher than the concentration of solutes inside a cell is

A

hypertonic.

66
Q

When the concentration of a solute is higher on one side of membrane than the other, a(n) transmembrane ___ is established.

A

gradient

67
Q

When the concentrations of dissolved particles (solutes) on both sides of the plasma membrane are equal, the two solutions are said to be
.

A

isotonic

68
Q

When the concentration of solutes outside the cell is lower than that intra-cellularly, the solution is said to be ___ relative to the inside of the cell.

A

hypotonic

69
Q

Water diffuses through a membrane from a solution that is ___ (lower concentration of dissolved particles) into a solution that is ___ (higher concentration of dissolved particles). Solutions with identical concentrations are said to be ___.
.

A

hypotonic, hypertonic, isotonic.

70
Q

Osmosis is the flow of ___ across a membrane.

A

water

71
Q

Small, uncharged molecules pass through the membrane via

A

passive diffusion.

72
Q

Osmosis describes the movement of water from areas where the solute concentration is __ to areas in which the solute concentration is __.

A

hypotonic, hypertonic

73
Q

When the concentration of solutes outside the cell is higher than that intra-cellularly, the solution is said to be ___ relative to the inside of the cell.

A

hypertonic

74
Q

A sample of cells is placed in a salt solution. The cells subsequently shrink and the membrane deforms. Relative to the cells, the salt solution is:

A

hypertonic

75
Q

A term that describes a situation in which the concentration of a solute is higher on one side of a membrane than the other is

A

transmembrane gradient.

76
Q

In ___ solutions, animal cells will take up water. In extreme cases, the cells can rupture in a process called osmotic lysis.

A

hypotonic

77
Q

When the solute concentration is higher inside the cell relative to outside the cell, the outside solution is said to be:

A

hypotonic

78
Q

What is osmosis?

A

Diffusion of water from an area of low solute concentration to an area of high solute concentration

79
Q

In osmosis, water moves from areas of

A

low solute concentration to areas of high solute concentration.

80
Q

What categories of proteins assist in the movement of molecules and ions across membranes?

A

transporters

channels

81
Q

An animal cell is placed in a hypertonic medium. Predict which way water will move.

A

Water will move from the inside of the cell to the outside.

82
Q

An animal cell is placed in pure water (which contains no solutes). In what direction will water move?

A

Water will move into the cell from the outside.

83
Q

When the concentration of solutes outside the cell is lower than that intra-cellularly, the solution is said to be ___ relative to the inside of the cell.

A

hypertonic

84
Q

Transmembrane proteins called ___ proteins allow ions and hydrophilic molecules to cross the phospholipid bilayer.

A

transport

85
Q

Osmosis is the flow of ___ across a membrane.

A

water

86
Q

How do transporters differ from channel proteins?

A

Transporters must change conformation to allow solutes to cross the membrane. Channel proteins typically DO NOT change conformation to allow solutes to cross the membrane.

87
Q

Proteins that assist in the movement of substances across membranes can be classified into two types based on how they move solutes across a membrane:

A

transporters and channels

88
Q

What is the significance of being able to gate a channel protein?

A

Gating a channel protein allows the cell to regulate the movement of solutes.

89
Q

A sample of cells is placed in a salt solution. The cells subsequently shrink and the membrane deforms. Relative to the cells, the salt solution is:

A

hypertonic

90
Q

What is an aquaporin?

A

A channel protein for water

91
Q

In ___ solutions, animal cells will take up water. In extreme cases, the cells can rupture in a process called osmotic lysis.

A

hypotonic

92
Q

Transporter proteins transport solutes across the membrane via:

A

a conformational change triggered by solute binding

93
Q

What is one way that solutes that cannot diffuse across the membrane can still gain access to the interior of the cell?

A

transport proteins

94
Q

Unlike transporters, ___ proteins provide an open passageway all the way across the plasma membrane.

A

channel

95
Q

Match the transport dynamics to the type of transporter: A single solute moves in one direction

A

Uniporter

96
Q

Match the transport dynamics to the type of transporter: Two solutes moves in one direction

A

symporter

97
Q

Match the transport dynamics to the type of transporter: Two solutes moves in opposite directions

A

antiporter

98
Q

When channel proteins are ___, it means they can open and close to regulate the movement of ions and molecules across the cell membrane.

A

gated

99
Q

A(n) ______ is a special channel protein that allows the facilitated diffusion of water.

A

aquaporin

100
Q

Transporter proteins bind their solutes in a hydrophilic pocket and then undergo a(n) ___ change that switches the exposure of the pocket from one side of the membrane to the other.

A

conformational

101
Q

Active transport is the movement of a solute across the membrane ___ its concentration gradient.

A

against

102
Q

Transmembrane proteins called ___ proteins allow ions and hydrophilic molecules to cross the phospholipid bilayer.

A

transport

103
Q

The transportation of a solute against its chemical or electrochemical gradient requires a source of

A

ATP

104
Q

Which of the following move solutes in only one direction?

  • Antiporters
  • Symporters
  • Uniporters
A

Symporters

Uniporters

105
Q

Which of the following types of transport involves pumping ions against a gradient using ATP as a source of energy?

  • transmembrane protein channels
  • secondary active transport
  • primary active transport
  • ligand-gated channels
A

primary active transport

106
Q

What is the significance of being able to gate a channel protein?

A

Gating a channel protein allows the cell to regulate the movement of solutes.

107
Q

In an H+/sucrose symporter, H+ moves down its electrochemical gradient, which drives the active transport of sucrose. This is an example of what type of transport?

A

Secondary active transport

108
Q

What is an aquaporin?

A

A channel protein for water

109
Q

___ active transport involves the use of a pre-existing gradient to drive the active transport of another solute.

A

secondary

110
Q

Which of the following best describes the process of active transport?

  • Particles moving across a membrane without energy expenditure.
  • Particles moving across a membrane against a concentration gradient.
  • Particles moving freely down a concentration gradient, facilitated by a transmembrane protein.
  • Particles moving freely down a concentration gradient.
A

Particles moving across a membrane against a concentration gradient.

111
Q

Moving a solute from areas of low concentration to high concentration requires:

A

an input of energy

112
Q

___ active transport involves a pump that uses energy from ATP to transport solutes against a gradient.

A

primary

113
Q

The H+/sucrose symporter is used to bring both H+ and sucrose into the cell. How are each of the two solutes transported into the cell?

A

H+ moves down its electrochemical gradient, while sucrose is actively transported.

114
Q

What type of transport uses a pre-existing gradient to drive the transport of another molecule?

A

Secondary active transport

Bio 181 (18 decks)

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