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IB Biology > 1.4 Membrane Transport > Flashcards

1.4 Membrane Transport Flashcards

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1
Q

What are the two key qualities of cellular membranes?

A

They are semi permeable and selective

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2
Q

What is semi permeable?

A

Only certain materials may freely cross

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3
Q

What is selective?

A

Membrane proteins may regulate the passage of materials that cannot freely cross

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4
Q

What are the two different categories of transport across a membrane?

A

Passive and active

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5
Q

What is passive transport?

A

The movement of material along a concentration gradient
(high conc to low conc)

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6
Q

Why does passive transport not require the expenditure of energy?

A

Because materials are moving down a conc gradient

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7
Q

Does passive transport need the expenditure of energy?

A

No

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8
Q

What are the three types of passive transport?

A

Simple diffusion
Osmosis
Facilitated diffusion

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9
Q

What is active transport?

A

The movement of materials against a conc gradient using energy
(low conc to high conc)

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10
Q

Why does active transport need the expenditure of energy?

A

Because materials are moving against the gradient

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11
Q

Does active transport need the expenditure of energy?

A

Yes

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12
Q

What are the two main types of active transport?

A

Primary direct active transport
Secondary indirect active transport

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13
Q

What is diffusion?

A

The net movement of molecules from a region of high conc to a region of low conc

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14
Q

What type of transport is diffusion?

A

Passive

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15
Q

When will diffusion continue up until?

A

Until molecules become evenly dispersed

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16
Q

What will be able to freely diffuse across cell membranes?

A

Small and non polar molecules

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17
Q

What are the free factors that can affect the rate of diffusion?

A

Temperature
Molecular size
Steepness of gradient

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18
Q

How does temperature affect the rate of diffusion?

A

Affects kinetic energy of particles in solution

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19
Q

How does molecular size affect rate of diffusion?

A

Larger particles are subjected to greater resistance within a fluid medium

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20
Q

How does the steepness of gradient affect the rate of diffusion?

A

The rate of diffusion will be greater with a higher conc gradient

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21
Q

What is osmosis?

A

The net movement of water molecules across a semi permeable membrane from an area of low solute conce to an area of high solute conc until equilibrium is reached

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22
Q

What is water considered to be?

A

The universal solute

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23
Q

Why is water considered to be the universal solute?

A

It will associate with and dissolve polar or charged molecules

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24
Q

Why must water move to equalise the two solutions?

A

Because solutes cannot cross a cell membrane unaided

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25
Q

When is there less free water molecules in solution?

A

At a higher solute concentration

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26
Q

Why is there less free water molecules in solution at a higher solute conc?

A

As water is associated with the solute

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27
Q

What is osmolarity?

A

A measure of solute concentration

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28
Q

What is the measurement of osmolarity?

A

osmol/L

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29
Q

What are the three categories of solution in accordance to their relative osmolarity?

A

Hypertonic
Hypotonic
Isotonic

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30
Q

What is a hypertonic solution?

A

Solutions with a relatively higher osmolarity

Gains water

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31
Q

What is a hypotonic solution?

A

Solutions with a relatively lower osmolarity

Loses water

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32
Q

What is an isotonic solution?

A

Solutions that have the same osmolarity

No net water flow

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33
Q

How can the osmolarity of a tissue be interpolated?

A

By bathing the sample in solutions with known osmolarities

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34
Q

How can you determine water loss or gain of a sample?

A

Weighing it before and after bathing in a solution

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35
Q

Why must tissues or organs used in medical procedures be kept in solution?

A

To prevent cellular dessication

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36
Q

For organs/tissues used in medical procedures why must the solution be the same osmolarity?

A

To prevent osmosis from happening

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37
Q

What happens to animal cells if left in hypertonic solutions?

A

Water will leave the cell causing it to shrivel

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38
Q

What happens to the animal cell left in a hypotonic solution?

A

Water will enter the cell causing it to swell and burst (lysis)

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39
Q

What moderates the effects of uncontrolled osmosis?

A

An inflexible cell wall

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40
Q

What happens to plant cells in hypertonic solutions?

A

Plasmolysis (shrink) in cytoplasm but cell wall will maintain a structured shape

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41
Q

What will happen to plant cells in a hypotonic solution?

A

The cytoplasm will expand but within the constraints of the cell wall

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42
Q

What are the three effects of solutions on animal cells?

A

Shriveled
Normal
Lysed

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43
Q

What are the three effects of solutions on plant cells?

A

Plasmolysed
Flaccid
Turgid

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44
Q

What is facilitated diffusion?

A

The passive movement of molecules across the cell membrane via the aid of a membrane protein

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45
Q

What molecules utilise facilitated diffusion?

A

Molecules that are unable to freely cross the phospholipid bilayer

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46
Q

What are the two types of proteins in facilitated diffusion?

A

Channel proteins and carrier proteins

47
Q

What are carrier proteins?

A

Integral glycoproteins which bind to a solute and undergo a conformational change to translocate a solute across a membrane

48
Q

What do carrier proteins bind to?

A

Only a specific molecule

49
Q

How do carrier proteins attach to their molecules?

A

Via an attachment similar to an enzyme substrate interaction

50
Q

What may carrier proteins do in the presence of ATP?

A

Move molecules against concentration gradients

51
Q

Out of carrier and channel proteins which one has a faster rate of transport?

A

Channel proteins

52
Q

What are channel proteins?

A

Integral lipoproteins that have a pore which ions may cross from one side of the membrane to the other

53
Q

What are channel proteins selective about?

A

Ions

54
Q

Why may channel proteins be gated?

A

To regulate the passage of ions in response to certain stimuli

55
Q

Can you use channel proteins in active transport?

A

No only passive transport

56
Q

Can you use carrier proteins in active transport?

A

Yes

57
Q

How do axons of nerve cells transmit electrical impulses?

A

By translocating ions to create a voltage difference across the membrane

58
Q

What does the sodium potassium pump do when the neuron is at rest?

A

Expels sodium ions from the nerve cell whilst potassium ions are accumulated within

59
Q

What happens to the ions when the neuron fires?

A

They swap locations via facilitated diffusion via sodium and potassium channels

60
Q

What are potassium channels?

A

Integral proteins with a hydrophilic inner pore via which potassium ions can be transported

61
Q

What is the potassium channel comprised of?

A

Four transmembrane subunits

62
Q

What does the inner pore of the potassium channels contain and what does it do?

A

A selectivity filter at its narrowest region which restricts passage of alternative ions

63
Q

What are potassium channels typically?

A

Voltage gated

64
Q

What do potassium channels do depending on the the transmembrane voltage?

A

Cycle between an opened and closed conformation

65
Q

How may the energy used in active transport be generated?

A

The direct hydrolysis of ATP
Indirectly coupling transport with another molecule that is moving along its gradient

66
Q

Apart from energy what does active transport involve?

A

The use of carrier proteins aka protein pumps

67
Q

In active transport what does a specific solute bind to?

A

The protein pump on one side of the membrane

68
Q

What causes a conformational change in the carrier protein?

A

The hydrolysis of ATP

69
Q

What is the final step of active transport?

A

The solute molecule is translocated across the membrane and is released

70
Q

What is the sodium potassium pump?

A

An integral protein that exchanges 3 sodium ions with two potassium ions

71
Q

In the sodium potassium pump, Where do the three sodium ions move to?

A

Out of the cell

72
Q

In the sodium potassium pump, Where do the two potassium ions move to?

A

Inside the cell

73
Q

In the sodium potassium pump, What is the process of potassium and sodium ion exchange dependent on?

A

Energy

74
Q

In the sodium potassium pump, Where do the sodium ions bind to?

A

The intracellular sites on the sodium potassium pump

75
Q

In the sodium potassium pump, What is transferred to the pump?

A

A phosphate group

76
Q

In the sodium potassium pump, How is a phosphate group transferred to the pump?

A

Via the hydrolysis of ATP

77
Q

In the sodium potassium pump, How is the sodium translocated across the membrane?

A

The pump undergoes a conformational change

78
Q

In the sodium potassium pump, What does the conformational change of the pump expose?

A

Two potassium binding sites on the extracellular surface of the pump

79
Q

In the sodium potassium pump, What happens when the phosphate group is released?

A

The pump returns to its original conformation

80
Q

In the sodium potassium pump, what happens when the pump returns to its original conformation?

A

The potassium is translocated across the membrane completing ion exchange

81
Q

What are vesicles?

A

Membranous containers which materials destined for secretion are transported around the cell in

82
Q

What is the endoplasmic reticulum?

A

A membranous network responsible for synthesising secretory materials

83
Q

What does the Rough ER do?

A

Synthesises proteins destined for extracellular use

84
Q

What is the rough ER embedded with?

A

Ribosomes

85
Q

What is the smooth ER involved with?

A

Lipid synthesis and carbohydrate metabolism

86
Q

When are materials transported from the ER?

A

When the membrane bulges

87
Q

What happens after the membrane bulges?

A

It buds to create a vesicle surrounding the material

88
Q

Where does the vesicle go after the ER?

A

The golgi apparatus

89
Q

Where does the vesicle fuse onto the golgi apparatus?

A

The internal cis face of the complex

90
Q

Where do materials move from and to in the golgi apparatus?

A

From the internal cis face of the golgi to the externally oriented trans face

91
Q

What moves materials in the golgi apparatus?

A

Vesicles

92
Q

What can happen to materials whilst within the golgi apparatus?

A

They may be structurally modified

93
Q

What happens to the material that has been sorted within the golgi apparatus?

A

Either secreted externally or transported to the lysosome

94
Q

Where will vesicles containing materials destined for extracellular use be transported to?

A

The plasma membrane

95
Q

Where will the vesicle fuse after being expelled by the golgi apparatus?

A

To the cell membrane

96
Q

What will happen to the materials within the vesicles after the golgi apparatus?

A

Expelled into the extracellular fluid

97
Q

What is constitutive secretion?

A

Released immediately into the extracellular fluid

98
Q

What is regulatory secretion?

A

Stored within an intracellular vesicle for a delayed release in response to a cellular signal

99
Q

What principally holds the membrane together?

A

Weak hydrophobic associations between the fatty acid tails of phospholipids

100
Q

What allows for larger materials to enter or leave the cell without having to cross the membrane?

A

The spontaneous breaking and reforming of the bilayer

101
Q

What type of process is the spontaneous breaking and reforming of the bilayer?

A

An active process which needs ATP hydrolysis

102
Q

What is endocytosis?

A

The process by which large substances enter the cell without crossing the membrane

103
Q

What envelopes the extracellular material in endocytosis?

A

An invagination of the membrane which forms a flask like depression

104
Q

What happens once the extracellular material is enveloped in endocytosis?

A

The invagination is sealed off to form an intracellular vesicle

105
Q

What are the two types of endocytosis?

A

Phagocytosis and Pinocytosis

106
Q

What is phagocytosis?

A

The process by which solid substances are ingested

107
Q

Where are the products of phagocytosis usually transported to ?

A

The lysosome

108
Q

What is pinocytosis?

A

The process by which liquids/dissolved substances are ingested

109
Q

Why is pinocytosis better than protein channels?

A

It allows faster entry

110
Q

What is exocytosis?

A

The process by which large substances exit the cell without crossing the membrane

111
Q

What does the process of exocytosis add to the cell membrane?

A

Vesicular phospholipids

112
Q

Why are vesicular phospholipids added to the membrane in exocytosis?

A

To replace those lost when vesicles were formed during endocytosis

113
Q

What is the main way of exocytosis?

A

Vesicles that fuse with the cell membrane to expel contents into the extracellular environment

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