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biology > 2.1.5: plasma membrane > Flashcards

2.1.5: plasma membrane Flashcards

1
Q

what is meant by a partially permeable membrane?

A

allows some molecules to pass through molecules and other not to. for example large molecules can’t get through but small ones can

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2
Q

what is cell signalling?

A

communication between or within cells

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3
Q

what is intracellular signalling?

A

communication between one part of a cell and a different part of the same cell (within the a singular cell)

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4
Q

what is intercellular signalling?

A

communication between two different cells

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5
Q

what are the 3 different types of cell plasma membranes?

A

cell surface membranes, membranes within cells and membranes within organelles

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6
Q

where are cell surface membranes?

A

on the surface of cells

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7
Q

where are membranes within cells?

A

found surrounding and within organelles

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8
Q

what is compartmentalisation?

A

to separate organelles from each so reactions don’t interfere

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9
Q

what are some examples of how membranes within cells controls what enters and leave the cell?

A

mrna leaves the nucleus and ribosomes leave the nucleolus

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10
Q

what are 2 roles of cell surface membranes?

A

act as partially permeable membranes and are involved in cell signalling

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11
Q

what are 3 roles of membranes within cells?

A

separate organelles from the cytoplasm, control what enters and leaves the organelle and can be involved in intracellular cell signalling

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12
Q

what are 2 roles of membranes within organelles?

A

act as a partially permeable barriers between parts of organelles and can be sites of chemical reactions

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13
Q

what is an example of a partially permeable membrane within organelles?

A

mitochondria have 2 membranes

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14
Q

what is a example of membranes being a site of chemical reactions?

A

there are many proteins embedded in the thylakoid membranes and similar enzymes also embedded in mitochondrion

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15
Q

what is the model of a plasma membrane?

A

fluid mosaic model

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16
Q

why is the structure of a plasma membrane called the fluid mosaic model?

A

fluid because it is flexible and can change structure or shape. mosaic because it is studded with proteins in a random patterns

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17
Q

how are cell surface membranes structured?

A

phospholipid bilayer

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18
Q

what are the components that make up plasma membranes?

A

phospholipids, glycolipids, cholesterol, channel proteins, carrier proteins, glycoproteins and various extrinsic proteins

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19
Q

what is the structure of the phospholipid bilayer?

A

two layers of phospholipid molecules with their hydrophilic heads facing outwards and their hydrophobic tails facing inwards

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20
Q

what is the function of the phospholipid bilayer?

A

act as a barrier to separate the inside of the cell from the environment

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21
Q

what is the structure of the glycolipids?

A

a lipid with attached carbohydrate (sugar) chains

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22
Q

what is the function of glycolipids?

A

recognised by the cells of the immune systems as self or non-self and to maintain the stability of the cell membrane and to facilitate cellular respiration

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23
Q

what is the structure of cholesterol?

A

a lipid with a hydrophilic end and a hydrophobic end

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24
Q

what is the function of cholesterol?

A

regulates the fluidity of membranes and adds stability to membranes without making them too rigid

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25
Q

what are the 3 intrinsic proteins in membranes?

A

channel, carrier and glycoproteins

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26
Q

what is an intrinsic protein?

A

proteins that are embedded within the membrane

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27
Q

what is an extrinsic protein?

A

proteins that are loosely bound to the membrane from the outside

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28
Q

what is the shape of a channel protein?

A

tubular shaped

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29
Q

what is the function of a carrier protein?

A

allows the passive movement of polar molecules and ions down a concentration gradient, acting like a pore

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30
Q

what is the structure of a carrier protein?

A

each type has one more specific binding site for its solute

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31
Q

what is the function of a carrier protein?

A

important role in both passive transport and active transport into cells

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32
Q

what is the structure of glycoproteins?

A

a protein with sugar molecules attached

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33
Q

what is the function of glycoproteins?

A

play a role in a cell adhesion and as a receptor for chemical signals

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34
Q

what is the structure of various extrinsic proteins?

A

primary, seconday, tertiary and quaternary protein structure

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35
Q

what are various extrinsic proteins used for?

A

required for transport

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36
Q

what are signalling molecules called?

A

local transmitters

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37
Q

what are the 5 different types of cell siugnalling?

A

endocrine, paracrine, neuronal (synaptic), contact- dependent and autocrine

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38
Q

what type of signals do cells use to communicate?

A

chemical signals

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39
Q

how do cells detect a target cells?

A

they have complementary receptors

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40
Q

what is endocrine cell signalling?

A

when a cell needs to transmit signals over long distances using the circulatory system as a distribution network

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41
Q

what is paracrine cell signalling?

A

when the cells are near one another, they communicate through the release of chemical messengers

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42
Q

what is neuronal (synaptic) cell signalling?

A

a unique example of paracrine signalling. when impulse reaches neurotransmitters, which quickly cross the small gap between nerve cells

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43
Q

what is contact-dependent cell signalling?

A

gap junctions are tiny channels that directly connect with neighbouring cells, which allow small signalling molecules to diffuse between two cells

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44
Q

what is autocrine cell signalling?

A

a cell signals to itself, releasing a ligand that binds to receptors on its own surface

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45
Q

what are 5 ways that molecules can move across a membrane?

A

diffusion, facilitated diffusion, osmosis, active transport and bulk transport

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46
Q

what does selective permeability mean?

A

certain molecules can move across it relatively easily whilst others may need a little help to be able to cross it

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47
Q

how is the method by which a molecule passes a membrane dependant on?

A

size, whether it’s charged or polar and whether it needs to move down or against a concentration gradient

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48
Q

what is passive transport?

A

molecules are moving down a concentration due to their own kinetic energy - no extra energy in the form of atp is needed

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49
Q

what is active transport?

A

extra energy in the form of atp is needed to move molecules against the concentration gradient

50
Q

what is an example of active transport?

A

bulk transport

51
Q

what is diffusion?

A

the net movement of particles from a region of high concentration to a low concentration down a concentration gradient until equilibrium is reached

52
Q

what are the 6 factors that affect the rate of diffusion?

A

properties of diffusing molecules, concentration gradient, temperature, surface area to volume ratio, thickness of membrane and number of channel/carrier proteins

53
Q

how does the properties of diffusing molecules affect the rate of diffusion?

A

non-polar molecules diffuse faster (go through hydrophobic cores) smaller molecules diffuse faster

54
Q

how does concentration gradient affect the rate of diffusion?

A

the bigger difference in concentration the faster the diffusion

55
Q

how does temperature affect the rate of diffusion?

A

higher temperature means higher kinetic energy and therefore faster diffusion

56
Q

how does surface area to volume ratio affect the rate of diffusion?

A

a larger surface area means a faster rate of diffusion. larger organisms have a smaller surface area to volume ratio so the rate of diffusion is lower

57
Q

how does thickness of membranes affect the rate of diffusion?

A

shorter the diffusion distance means the faster rate of diffusion

58
Q

how does the number of channel/carrier proteins?

A

more proteins mean faster diffusion

59
Q

why does diffusion happen?

A

molecules in a fluid move randomly due to their kinetic energy and diffusion occurs due to this random motion

60
Q

what is meant by diffusion reaching dynamic equilibrium?

A

means particles are no longer moving more in one direction than the other. there is no net movement

61
Q

what are the 2 types of diffusion?

A

simple diffusion and facilitated diffusion

62
Q

what are the types of molecule that can diffuse through a plasma membrane via simple diffusion?

A

large and small non-polar molecules can cross the hydrophobic core. small, polar molecules can pass because they are so small

63
Q

what are the types of molecule that can diffuse through a plasma membrane via facilitated diffusion?

A

charged ions and larger, polar molecules are repelled by the hydrophobic core so it cannot diffuse through the phospholipid bilayer

64
Q

how does facilitated diffusion work?

A

a carrier or a channel protein is used to help the movement of molecules

65
Q

how does a carrier protein work?

A

it changes shape when a particular molecule binds to it, which then moves the molecule from one site of the membrane to the other

66
Q

how does a channel protein work?

A

have a hole in the middle creating a hydrophilic passageway, meaning dissolved ions can move through and avoid the hydrophobic core

67
Q

is oxygen polar or non-polar?

A

non-polar

68
Q

what is the charge distribution of oxygen?

A

evenly distributed

69
Q

what size is oxygen?

A

small

70
Q

is oxygen hydrophilic or hydrophobic?

A

hydrophobic

71
Q

what kind of diffusion does oxygen use?

A

simple diffusion

72
Q

what size is glucose?

A

large

73
Q

is glucose polar or non-polar?

A

polar

74
Q

is glucose hydrophobic or hydrophilic?

A

hydrophilic

75
Q

is water polar or non-polar?

A

polar

76
Q

what size is water?

A

small

77
Q

what type of diffusion does water use?

A

simple diffusion

78
Q

are sodium ions charged or uncharged?

A

charged

79
Q

are sodium ions hydrophobic or hydrophilic?

A

hydrophilic

80
Q

is carbon dioxide hydrophilic or hydrophobic?

A

hydrophobic

81
Q

is carbon dioxide polar or non-polar?

A

non-polar

82
Q

what type of diffusion does carbon dioxide uses?

A

simple diffusion

83
Q

are steroid hormones polar or non-polar?

A

non-polar

84
Q

are steroid hormones hydrophilic or hydrophobic?

A

hydrophobic

85
Q

what type of diffusion does steroid hormones use?

A

simple diffusion

86
Q

what type of diffusion does glucose use?

A

facilitated diffusion

87
Q

what type of diffusion do charged ions use?

A

facilitated diffusion

88
Q

what are the 2 types of active transport?

A

primary active transport and secondary active transport

89
Q

what is primary active transport?

A

involves the movement of ions/molecules against their concentration gradient with the direct use of atp to power the process

90
Q

what is an example of when primary active transport is used?

A

the proton pump which pumps hydrogen ions across a membrane against the concentration gradient

91
Q

what is the general process of active transport?

A
  • molecule/ion to be transported binds to receptors in the channel of the carrier protein on the outside of the cell
  • on the inside, atp binds to the carrier protein and is hydrolysed into adp and phosphate
  • binding of the phosphate molecule to the carrier proteins causes the protein to change shape, opening up the inside of the cell
  • the molecule or ion is released to the inside of the cell
  • the phosphate moelcule is released from the carrier proetin and recombines with adp to form atp
  • the carrier protein returns to its original shape
92
Q

what is secondary diffusion?

A

when a concentration gradient established by a transmembrane pump is used to move another molecule into the cell against a concentration gradient

93
Q

what is one example of secondary active transport?

A

in cells lining your small intestine to ensure that all of the glucose from the digested food is reabsorbed

94
Q

what is bulk transport?

A

another form of active transport that transports large molecules (enzymes, hormones etc) that are too large to move through channel and carrier proteins

95
Q

what is endocytosis?

A

bulk transport into cells. the cell surface membrane bends inwards when it comes in contact with the material to be transported. the membrane enfolds the material until a vesicle is formed. this moves into the cytoplasm to transfer the material further processing within the cells

96
Q

what are the 2 types of endocytosis?

A

phagocytosis and pinocytosis

97
Q

what is phagocytosis for?

A

solids

98
Q

what is pinocytosis used for?

A

liquids

99
Q

what is an example endocytosis?

A

vesicles containing bacteria are moved towards lysosomes, where bacteria is digested by enzymes

100
Q

what is exocytosis?

A

the reverse of endocytosis. vesicles, usually formed by the golgi apparatus, move towards and fuse with the cell surface membrane, releasing the contents outside of the cell

101
Q

what is osmois?

A

the movement of water molecules across a partially permeable membrane from a high concentration to a low concentration

102
Q

what is the water potential of pure water at standard temperature and pressure?

A

zero

103
Q

what is water potential?

A

the pressure exported by water molecules on a membrane or a container

104
Q

what is the symbol for water potential?

A

a trident symbol or “psi”

105
Q

what does it mean if a solution has a high water potential?

A

has a low concentration of solute and higher concentration of water

106
Q

what does it mean if a solution has a low water potential?

A

has a high concentration of solute and a lower concentration of water

107
Q

what is water pressure measured in?

A

pascals

108
Q

how many pascals are there in a kilopascal (kpa)?

A

1000 pascals

109
Q

how many pascals are in a megapascal?

A

100,000 pascals

110
Q

how does adding solutes affect water potential?

A

lowers the water potential, so it makes the water potential more negative

111
Q

what water potential values do solutions always have?

A

negative pascals/kilopascals/megapascals

112
Q

what is a hypertonic medium?

A

has a high solute concentration then the cell within it (lower water potential)

113
Q

what is a hypotonic medium?

A

has a low solute concentration then the cell within it (higher water potential)

114
Q

what is an isotonic medium?

A

the same solute concentration and water potential as the cell within it

115
Q

what is hydrostatic pressure?

A

the pressure of a liquid/a fluid

116
Q

why is hydrostatic potentially damaging to cells?

A

if the cell shrivels up, it could burst

117
Q

what is the method for investigating the effect of ethanol concentration on membrane permeability?

A

take 5 test tubes and label each on with a different ethanol concentrations. trim 5 beetroot cylinders to 30 mm, rinsing each one and then patting it dry. label the cuvette tray with the ethanol concentrations. swirl the tubes once and remove the cylinders. pour the remaining liquid into the cuvette for the corresponding concentration and fill an extra cuvette with distilled water. use the colorimeter with a green filter to measure the absorbance of each concentration and plot a graph of ethanol concentration against absorbance

118
Q

what is the independent variable when investigating the effect of ethanol concentration on permeability?

A

the concentration of ethanol

119
Q

what is the dependent variable when investigating the effect of ethanol concentration on permeability?

A

absorbance of the beetroot solution

120
Q

what are the control variables when investigating the effect of ethanol concentration on permeability?

A

the size of the disks, amount of ethanol, thickness of disc (diameter) the amount of time in the test tube and the same filter colour

121
Q

what is the method for determining the water potential by measuring changes in mass?

A

label 6 boiling tubes with different concentrations of salt solution and place 30cm of distilled water in one tube and 30cm of the appropriate salt solution in the others. make 5 potato cylinders that are 50mm long and divide a piece of filter paper into 6 sections for each potato and blot the cylinders dry. record the mass and put them in the test tubes. leave for 45 minutes then take them out and blot them dry again. reweigh the cylinders and calculate the percentage change in mass

122
Q

how do you work out the percentage change in mass?

A

change in mass
———————– x100
original mass

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