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Biology > 1.3 cell membranes and transport > Flashcards

1.3 cell membranes and transport Flashcards

1
Q

functions of the plasma
membrane
4

A

-taking in nutrients and other required substances for the cell
- receptor sites for hormone attachment
- secreting chemicals
- cell- cell recognition

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2
Q

what’s lateral movement

A

sideways

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3
Q

3 main types of proteins in the plasma membrane

A

structural
transport
enzymes

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4
Q

what does the polarity of protein molecules affect

A

their position in the membrane

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5
Q

what is glycosylation

A

the process of adding carbohydrates onto either a protein (glycoprotein)
or lipid (glycolipid)

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6
Q

what is glycocalix

A

is the carbohydrate layer on the outer surface of the plasma membrane

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7
Q

what is the cell membrane

A

semi-permeable

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8
Q

what is the cell membrane made up of mainly

A

-phospholipids
-proteins
-some polysaccharides and cholesterol

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9
Q

what are the phospholipid molecules arranged in

A

in a bilayer

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10
Q

explain the arrangement of the phospholipid bilayer

A

hydrophilic heads are polar they are on the outside as they are water loving. and the hydrophobic tails are non polar, they are on the inside because they are water hating

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11
Q

who proposed the fluid mosaic model

A

singer and Nicholson

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12
Q

what does the fluid mosaic model describe

A

the arrangement of phospholipids and proteins in cell membranes

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13
Q

what do the proteins form
(to do with the model)

A

form a mosaic pattern within the phospholipid bilayer

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14
Q

description/function of phospholipid bilayer

A

forms the basis of the cell membrane/ allows transport of small non-polar molecules in and out of the cell by simple diffusion

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15
Q

description of extrinsic proteins

A

proteins found at the edges of the phospholipid bilayer, they do not span the membrane
found above/below the membrane
polar(hydrophilic head)

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16
Q

function of extrinsic proteins

A

-receptor sites
-they bind with proteins such as hormones or neurotransmitters

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17
Q

description of intrinsic proteins

A

proteins found within the bilayer, soon the membrane polar and non polar (hydrophobic/hydrophillic)

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18
Q

function of intrinsic proteins

A

transport
channels/carries take part in facilitated diffusion
pumps take part in active transport/ form ion channels

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19
Q

description/function of the models movement

A

is capable of movement
which is why its called the fluid mosaic model

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20
Q

where is cholesterol found

A

animal cells between the phospholipid molecules

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21
Q

what does cholesterol do

A

increases the rigidity and stability of the membrane

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22
Q

what are glycolipids

A

lipids which have combined with polysaccharides

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23
Q

where are glycolipids found

A

in the outer layer of the membrane

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24
Q

what are glycolipids involved in

A

cell to cell recognition

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25
Q

what are glycoproteins

A

proteins which have combined with polysaccharides

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26
Q

where are glycoproteins found

A

sticking out of some membranes

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27
Q

name the factors affecting the permeability of the plasma membrane

A

increasing temperature
increasing ethanol concentration
increasing sodium chloride concentration
icreasing detergent concentration
pH

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28
Q

explain how increasing the temperature would affect the permeability of the plasma membrane

A

as the temperature increases cell membrane and tonoplast permeability increases due to increased disruption of the membrane. at temps above 40 the cell membrane and tonoplast become increasingly unstable. more heat energy= more kinetic energy so the phospholipids will vibrate more and move further apart

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29
Q

explain how increasing the ethanol concentration would affect the permeability of the plasma membrane

A

ethanol dissolves phospholipids (organic solvent)
the greater the concentration of ethanol the more permeable the membrane becomes

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30
Q

how does increasing sodium chloride concentration affects the permeability of the plasma membrane

A

as concentration increases, the permeability will decrease
sodium ions attach to the oxygen atoms on the hydrophilic heads of the bilayer. reduces the mobility of the phospholipid molecules so less betaken is released

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31
Q

how does increasing detergent concentration affect the permeability of the membrane

A

as the concentration increased the permeability increases because it reduces the surface tension of phospholipids and sippers the membrane.

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32
Q

how does the pH affect the permeability of the membrane

A

denaturation of enzyme

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33
Q

what does directly proportional mean

A

decrease/increase
at the same time.
if the line is straight and goes through the origin

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34
Q

what is diffusion

A

the passive movement of a small non-polar (lipid-soluble) molecule from an area of high concentration to an area of low concentration
until they are equally distributed

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35
Q

what is equilibrium

A

the concentration of molecules is equal either side of the membrane.

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36
Q

what happens at equilibrium

A

molecules/particles still continue to cross the membrane in both directions, but there is no net movement in a particular direction

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37
Q

what are the factors that affect the rate of diffusion
(6)

A

-concentration gradient
- distance of travel
-the surface area of the membrane
-the thickness of the membrane
-an increase in temperature
-particle size

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38
Q

why does the concentration gradient affect the rate of diffusion

A

the steeper the triangle the faster diffusion would occur.

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39
Q

why does the distance of travel affect the rate of diffusion

A

the shorter the distance of travel the greater the rate of diffusion

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40
Q

how does the surface area of the membrane affect the rate of diffusion

A

the larger the surface area the greater the rate of diffusion

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41
Q

why does the thickness of the membrane affect the rate of diffusion

A

the thinner the membrane the greater the rate of diffusion

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42
Q

why does an increase in temperature affect the rate of diffusion

A

an increase in temperature the greatest the rate of diffusion the diffusion path is short

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43
Q

why dies the particle size affect the rate of diffusion

A

small particles diffuse faster than larger molecules

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44
Q

what is co transport

A

is a type of facilitated diffusion that brings molecules and ions into cells together on the same carrier protein

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45
Q

what is osmosis

A

the passive net movement of water molecules from an area of high water potential to an area of low water potential through a semi permeable membrane

46
Q

factors that effect osmosis

A

-temperature
-surface area
-thickness of membrane
-water potential

47
Q

how does water pass through membranes

A

through channel proteins called aquaporins

48
Q

what do aquaporins do

A

increase the rate water molecules can go in and out of the cell through charged (polar) channels (due to the particular hydrophillic R group of the amino acid)
while preventing the passage of ions and other solutes

49
Q

what is water potential

A

the tendency of water to move from one place to another

50
Q

is there a tendency for water to move into pure water

A

no, this means pure water has a water potential of 0KPa

51
Q

what does KPa stand for and what does it describe

A

kilopascal
it describes the pressure exerted on a surface

52
Q

what does a low concentration of water mean

A

a low water potential

53
Q

what does the addition of a solute to pure water do

A

bring water molecules in
lowers the water potential and gives it a negative value

54
Q

how is water potential related to the concentration of the solution

A

the more concentrated a solution gets the more negative its water potential

55
Q

what does the solute potential show

A

the reduction in water potential due to the presence of solute molecules

56
Q

what does solute potential measure

A

how easily water molecules move out of a solution

57
Q

what does the concentration of dissolved substances inside the cell vacuole equal

A

solute potential

58
Q

what makes the tendency of water to move out lower

A

the more solute present

59
Q

is the solute potential +/-

A

always a negative value and lowers the water potential of the cell
a higher concentration solution has a lower, more negative solute potential

60
Q

what is pressure potential

A

the hydrostatic pressure exerted by the contents on the cell wall.
it is equal and opposite to the pressure exerted by the cell wall on the cell contents

61
Q

turgid…..

A

a plant cell that holds as much water as possible. further entry of water is reverted a the cell wall cannot expand any further

62
Q

what does water entering the cell via osmosis do

A

expands the vacuole and pushes the cytoplasm against the cell wall. the cell wall can only expand a little and so pressure (potential) outwards builds up, resisting the entry of more water making it turgid

63
Q

solute potential for pure water

A

0
or negative

64
Q

solute potential in a cell at incipient or full plasmolysis

A

0
or positive

65
Q

water potential equation

A

water potential=solute potential + pressure potential

66
Q

what are the 2 forces plant cells are under the influence of

A

the solute potential
the pressure potential

67
Q

why are plant cells under pressure from the solute potential

A

due to the solutes in the vacuole and cytoplasm pulling water in. the higher the concentration the less likely the water to move out

68
Q

why are plant cells under pressure from the pressure potential

A

a force which increases the tendency of water to move out

69
Q

do animal cells have a pressure potential

A

no because they have no cell wall

70
Q

what is tonicity

A

the ability of an extracellular solution to make water move into or out of a cell by osmosis is known as its tonicity

71
Q

what is hypertonic solution

A

water leaving the cell
the extracellular solution has low H20 and high solute concentration

72
Q

isotonic solution

A

equilibrium
equal amount of water leaving and entering the cell

73
Q

hypotonic solution

A

more water entering the cell
extracellular solution has high H20 and low solute concentration

74
Q

what is haemolytic

A

the destruction of red blood cells by rupture of the cell and release of the contained haemoglobin

75
Q

crenated meaning?

A

a red blood cell in highly concentrated solution

76
Q

what will happen if the cell is crenated

A

water leave the cell and it will shrink

77
Q

examples of active transport

A

reabsorption in kidneys
uptake of inorganic ions in plants
nerve transmissions

78
Q

example of uptake of inorganic ions in plants

A

magnesium in through root hair cells

79
Q

what is the sodium potassium pump in charge of

A

generating a gradient of ions

80
Q

what does the sodium potassium pump do

A

continually pumps sodium ions out of the cell and potassium ions into the cell, powered by ATP
each ATP that is broken down it moves 3 sodium ions out and 2 potassium in

81
Q

what happens to the cell because it is depleted of sodium

A

an electrical gradient is created and a concentration gradient

82
Q

what is the effect of cyanide

A

strong poison. it works as a respiratory inhibitor. the enzyme cytochrome oxidase catalyses the reaction

83
Q

what happens in cytochrome oxidase is inhibited

A

ATP is not produced and the organism quickly dies

84
Q

what are channel proteins

A

with pores lined with polar groups (hydrophilic) allowing charged ions to pass through (Na+)
they open and close depending on needs of the cell, they are specific for one type of ion.

85
Q

what are carrier proteins

A

allow the facilitated diffusion of larger polar molecules e.g sugars, amino acids.
molecule will attach to its binding site, it changes shape and releases the molecule the other side of the membrane

86
Q

what is facilitated diffusion

A

allows the movement of molecules or ions across a membrane down a concentration gradient. it occurs on the cell membrane where there are transport molecules

87
Q

explain the sodium potassium pump

A

1- pump binda 3 sodium and a molecule of ATP
2- splitting ATP provides energy to change the shape of the channel, the sodium ions are driven through the channel
3- the sodium ions go outside the membrane the new shape of the channel allows to K ions to bind
4- the phosphate releases which allows the channels to go back to its orginal form, releasing the potassium ions from the inside of the ions.

88
Q

what do carrier and channel proteins do to the rate of diffusion?

A

increase the rate of facilitated diffusion along the concentration gradient without the need for energy in the form of ATP from respiration

89
Q

why does the line flatten out on a facilitated diffusion graph

A

because carrier proteins are full, the uptake is constant

90
Q

why is facilitated diffusion not affected by a respiratory inhibitor

A

as ATP is not required

91
Q

what does respiratory inhibitors do

A

stop ATP production

92
Q

what is the sodium-glucose co-transport significant in

A

absorbing glucose and sodium ions across cell membranes and into the blood in the ileum and kidney nephron

93
Q

what does active transport allow even when present in a low concentration

A

the uptake of important solutes

94
Q

what is pumping

A

an active process, only transport that can transport substances up/against their concentration gradient
only works in one direction

95
Q

explain how the pump works

A

the molecule/ion that needs to be transported combines with a specific intrinsic protein (pump)
ATP transfers a phosphate group to the pump on the inside of the membrane. the pump will then change shape and transport the ion. this is then released into the cell

96
Q

what does cyanide do

A

stops active transport as it stops the production of ATP

97
Q

why does the rate of active transport level off at higher concentration differences

A

due to the pumps being full, this limits the rate of active transport

98
Q

what is lysis

A

animal cells may burst as they have no cell wall to prevent this happening when too much water moves into the cell

99
Q

what’s plasmolysis

A

when water leaves a plant cell by osmosis the cytoplasm and vacuole shrink and the cell membrane pulls away from the cell wall

100
Q

what is the effect on animal cells when in a hypotonic external medium

A

cells swell and may lyse (burst)
red blood cells in a hypotonic medium burst. this is called haemolytic

101
Q

what is the effect on plant cells when in a hypotonic external medium

A

the cytoplasm and vacuole will swell and push against the cell wall; the cells become turgid. turgid plant cells support the plant tissues and structures
(optimum for plant cells )

102
Q

what is the effect on animal cells when in a hypertonic external medium

A

the cell shrinks

103
Q

what is the effect on plant cells when in a hypertonic external medium

A

the cytoplasm and vacuole shrink causing the cell membrane to pull away from the cell wall. this is called plasmolysis ad cells in this condition are referred to as plasmolyse

104
Q

what is the effect on animal cells when in an isotonic external medium

A

this is animal cell optimum
the water potential of the cell is equal to the water potential of the external medium at this point

105
Q

what is the effect on plant cells when in an isotonic external medium

A

cells become flaccid
point of incipient plasmolysis

106
Q

how do large particles enter the cell

A

by endocytosis

107
Q

what does endocytosis mean

A

the cell membrane engulfs particles or liquid forming vesicle which enters the cytoplasm

108
Q

2 types of endocytosis

A

phagocytosis
pinocytosis

109
Q

what is phagocytosis

A

cell eating

110
Q

what is pinocytosis

A

involves the entry of liquid into a cell

111
Q

what can phagocyles do

A

engulf microbes by phagocytosis

112
Q

briefly explain exocytosis

A

substances leave the cell after being transported through the cytoplasm in transport vesicles (from the rough ER) to the golgi body and then to the cell membrane via secretory vesicles. secretory vesicles fuse with the cell membrane and the contents are secreted outside the cell

Biology (12 decks)

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