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Biological Membrane Flashcards

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1
Q

What do some organelles have and what do these do?

A

Have membranes within them and form barriers too

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2
Q

What does permeability refer to?

A

The ability to let substances pass through

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3
Q

How do very small molecules get through the cell membrane?

A

Diffuse through cell membrane between structural molecules

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4
Q

What do some substances do to get through the membrane?

A

Dissolve in the lipid later and pass through

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5
Q

How do other substances pass through cell membrane?

A

Pass through special protein channels it are carried by carrier proteins

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6
Q

Why are these membranes described as partially permeable?

A

The membranes don’t let all types of molecules to pass through

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7
Q

What determines the cells permeability?

A

The properties if the component molecules of the cell membrane
I.e. Which molecules it allows through

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8
Q

What is the plasma membrane sometimes referred to?

A

Cell surface membrane

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9
Q

What are some roles of membranes at the surface of cells?

A

Separates cell’s components from its external environment
Regulates transport into and out of cell
May contain enzymes involved in specific metabolic pathways
Has antigens
May release chemicals that signal to other cells
Contains receptors for chemical signals
May be site of chemical reactions

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10
Q

How does a membrane separate cells components from external environment in single and multicellular organisms?

A 
Single celled organisms environment is external surrounding 
Multicellular organism (humans) each cell's environment is tissue fluid or cells surrounding it
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11
Q

Why does the cell membrane have antigens?

A

So organisms immune system can recognise organisms immune system can recognise cell as self and not attack it

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12
Q

What does the membranes around organelles present in eukaryotic cells separate what?

A

Organelle contents from cell cytoplasm

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13
Q

Why does it departs the organelles content?

A

Discrete entity

Able to perform its function

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14
Q

Where do metabolic processes happen on some organelles?

A

On membranes

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15
Q

What do mitochondria folded inner membranes gives?

A

Large surface area for some of the reactions of aerobic respiration and localise some of enzymes needed for respiration to occur

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16
Q

What do inner membranes of chloroplasts call themselves?

A

Thylakoid membranes

House chlorophyll

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17
Q

What do you find on these membranes?

A

Some of reactions of photosynthesis occurring

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18
Q

Where are some digestive enzymes?

A

On plasma membrane of epithelial cells that line small intestine
Enzymes catalyse some final stages in breakdown of certain types of sugars

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19
Q

State the year and what singer and nicolson?

A

1972

Proposed model allowed passage of molecules through membrane

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20
Q

What did their structure explain and who are they?

A

Singer and Nicolson explained how cell membranes could be more dynamic and interact more with cell’s environment

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21
Q

What was singer and Nicolsons 1972 model called?

A

Fluid mosaic model

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22
Q

What did fluid mosaic model propose?

A

Fabric of membrane consisted of phospholipid bilayer with proteins floating in it making mosaic pattern
Lipid molecules change places with each other
Some proteins may move giving fluidity

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23
Q

What is the fabric of the membrane?

A

Lipid bilayer made of 2 layers of phospholipid molecules
Hydrophilia heads in contact with watery exterior or cytoplasm
Hydrophobic tail regions in centre of membrane away from water

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24
Q

How thick is the phospholipid bilayer?

A

About 7nm in width

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25
Q

What does a carrier protein have?

A

Water-filled channel inside channel protein lined with hydrophilic amino acids

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26
Q

What makes a glycoprotein?

A

Glycocalyx attached to protein

Carbohydrate chain attracted to protein molecules

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27
Q

What can a protein not spanning the lipid bilayer act as?

A

An enzyme

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28
Q

Phospholipid info

A

Fatty acid tails hydrophobic

Phosphate head has charge and is hydrophobic

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29
Q

Cholesterol does what in the cell membrane? What do

A

Gives mechanical stability and flexibility

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30
Q

What’s glycocalyx?

A

Carbohydrates molecules on outside of membrane very hydrophilic and attract water with dissolved solutes helping cells interact with watery environment and obtain substances

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31
Q

Glycolipid is?

A

Carbohydrate chain attached to lipid

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32
Q

What do some protein membranes have?

A

Pores and act as channels
Some proteins are carriers by changing shape
Other proteins may be attached to carrier proteins

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33
Q

What does Pores and act as channels mean?

A

Some membranes have pores and act as channels to allow ions, have electrical charge surrounded by water molecules to pass through

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34
Q

What does the meaning Some proteins are carriers by changing shape?

A

Some proteins are carriers by changing shape, carry specific molecules across the membrane

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35
Q

What is the meaning of Other proteins may be attached to carrier proteins?

A

Other proteins may be attached to carrier proteins and functions as enzymes, antigens or receptor sites for complementary-shaped signalling chemicals such as hormones

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36
Q

What do eukaryotic cell membrane contain?

A

Cholesterol

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37
Q

What is the importance of this?

A

Helping to regulate fluidity of the membrane

Maintain mechanical stability and resist effects of temperature changes on structure of the membrane

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38
Q

What is the width thickness of a cell membrane?

A

5 to 10 nm

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39
Q

What is outside the membrane?

A

Glycocalyx

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40
Q

Wha cud glycocalyx Formed from?

A

Carbohydrates chain attached to either (glycolipids) or proteins (glycoproteins) in the membrane

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41
Q

What may membranes have a particular and to allow what?

A

Particular distributions of proteins

Enable them to carry out their specific functions

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42
Q

What allows entry and exit of ions?

A

In neurones, protein channels and carriers in plasma membrane covering long axon

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43
Q

What does this bring?

A

Conduction of electrical impulse along their length

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44
Q

Why does the cell membrane need to allow some molecules through, into it out of the cell?

A

Cell membranes form barriers and separate cell content from cell’s exterior environment

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45
Q

Neurones features?

A

Myelin sheath formed by flattened cells wrapped around them several times giving several layers of cell membrane
Membrane forming myelin sheath.

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46
Q

What percentage lipid and protein is a neurone?

A

76% lipid

20% protein

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47
Q

What’s the plasma membrane of a white blood cell like?

A

Contains special protein receptors that ape recognition antigens on foreign cells usually from invading pathogens

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48
Q

When could the white blood cell react?

A

Invading pathogens

Organ transplant

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49
Q

What do root hair cells have?

A

Many carrier proteins

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50
Q

What do these carrier proteins do?

A

Actively transport nitrate ions from soil into cells

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51
Q

What percentage lipid and protein is the mitochondria?

A

76% protein

24% lipid

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52
Q

Why is this so?

A

Inner membrane contains many electron carriers made of protein and hydrogen ions channels associated with ATP synthase enzymes

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53
Q

What do cells need to receive?

A

Raw material or reactants for reactions

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54
Q

What do they respire to make?

A

ATP

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55
Q

What does ATP provide?

A

Cellular energy to drive biochemical reactions

They need oxygen and glucose to do this

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56
Q

What do they also need to do?

A

Remove toxic metabolic waste products e.g. Carbon dioxide

Need to export some molecules that they make like enzymes m, hormones and other signalling molecules

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57
Q

How can some substances cross the cell membrane?

A

Without using ATP

Passive processes as use kinetic energy

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58
Q

What’s simple diffusion?

A

GCSE diffusion

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59
Q

What does simple diffusion rely on?

A

All molecules have kinetic energy that can move freely and randomly within gas or liquid media
Will happen without being shaken/stirred

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60
Q

What causes diffusion?

A

High concentration bump into each other as randomly move
Eventually will spread further from each other
More will move to lower concentration until dispersed

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61
Q

What happens when molecules have to move down their concentration gradient?

A

Still moving randomly
Remain evenly dispersed so net diffusion
Reached equilibrium

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62
Q

How can some molecules like oxygen and carbon dioxide pass through?

A

Simple diffusion because they are small

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63
Q

How can larger fat-soluble molecules get through?

A

Things like steroid hormones can diffuse through cell membranes as dissolve in lipid bilayer
Still move down concentration gradient

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64
Q

Why is water a special case?

A

Polar and insoluble in lipid
Phospholipid layer would seem to be an impermeable barrier
Water in such great concentration significant direct diffusion occurs

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65
Q

What do molecules where high water movement required have?

A

Aquaporins to allow water molecules to cross membrane without challenge of moving lipid environment

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66
Q

What maintains the concentration gradient?

A

Many molecules entering cells pass into organelles used for metabolic reactions

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67
Q

What does it also do?

A

Keeps more molecules entering the cell

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68
Q

What does oxygen do here?

A

Diffuses into cytoplasm of respiring cells

Diffuses into microchrondria used for aerobic respiration

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69
Q

What does carbon dioxide do?

A

Diffuse into palisade mesophyll cells of plant leaf will then diffuse into chloroplasts and be used for photosynthesis

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70
Q

What factors affect simple diffusion?

A 
Temperature
Diffusion distance 
Surface area 
Size of diffusing molecule
Concentration gradient
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71
Q

Temperature affects rate of diffusion how?

A

Hotter temperature more molecule movement rate of diffusion increases
Colder temperature less molecule movement rate of diffusion decreases

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72
Q

How does diffusion distance affect rate of diffusion?

A

Thicker membrane across which molecules have to diffuse the slower the rate of diffusion

73
Q

Size of diffusing molecules affect simple diffusion?

A

Smaller ions or molecules diffuse more rapidly than larger molecules

74
Q

How does concentration gradient affect the rate of diffusion?

A

Steeper gradient (more molecules on one side of membrane compared with other side) the faster diffusion to the side where there are fewer molecules down the gradient

75
Q

Facilitated diffusion depends on?

A

Small molecules have polarity such as ions that have electrical charge are insoluble in lipids because they can’t interact with hydrophobic tails of lipid bilayer

76
Q

What did that mean?

A

Diffuse through water filled protein channels (pores) embedded in membrane
Channels around 0.8 nm in diameter

77
Q

What do the cholesterol do here?

A

Reduce permeability of membrane to water-soluble molecules

78
Q

Can glucose diffuse through?

A

No they are too large through water-filled protein channel in a membrane

79
Q

So how does glucose get in?

A

They can bind to transmembrane carrier proteins which opens allows glucose to pass out on outer side of membrane, there are specific carrier proteins for different types of molecules

80
Q

What do different cell types have?

A

Differing proportions of transmembrane protein channel and transmembrane protein carriers.

81
Q

What does this allow?

A

Cells to control types of molecules that pass in or out

82
Q

What do Neurone plasma membrane have?

A

Many channel specific to either sodium ions/ potassium ions

83
Q

What is the diffusion of ions into and out of the neurone axon crucial for?

A

Diffusion of ions into and out of neurones axon crucial for conduction of nerve impulses.

84
Q

What are at the synapses?

A

Calcium ion channels

Many have chloride ion channels

85
Q

What plays a crucial role in regulating composition of mucus to trap particles and pathogens?

A

Plasma membrane of epithelial cells that line your airways have chloride ions channels

86
Q

What is the liquid in a solution that solute molecule are dissolved in?

A

Solvent.

87
Q

What is the solvent in an aqueous solution?

A

Water

88
Q

What can water do with a phosolipid bilayer?

A

Pass directly through

89
Q

What do some membranes also have?

A

Aquaporins which allow water molecules to cross more rapidly

90
Q

What do water molecules have?

A

Kinetic energy

91
Q

What does this cause them to do?

A

Move randomly thus spreading out

92
Q

Define osmosis

A

Net diffusion from a region of relatively more water molecules to an area of fewer water molecules

93
Q

What happens when solute molecules are added to water?

A

The relative number of water molecules in the solution changes.

94
Q

What happens if solute molecules dissociate into charged ions?

A

They exert more effect on relative number of water molecules than larger non-polar molecules like glucose.

95
Q

Why?

A

Sodium chloride molecules dissociate into sodium ions and chloride ions, number of particles in solution doubles

96
Q

Water potential is?

A

Measure of tendency of water molecules to diffuse from one region to another

97
Q

What has the highest water potential and what is it?

A

Pure water 0

98
Q

What happens when solute molecules are added?

A

Lower water potential of solution. The more solute molecules in solution the lower the water potential

99
Q

What will happen if two aqueous solutions are separated by a partially permeable membrane?

A

Water molecules will move from solution with high water potential to solution with lower water potential

100
Q

What happens if the water potential both sides of the membrane become equal?

A

There will be no net osmosis although water molecules will continue to move randomly.

101
Q

What is water potential measured in?

A

kPa

102
Q

Which is lower the water potential inside the cell or in pure water?

A

The water potential inside the cell

103
Q

Why is this?

A

Solutes in solutions in cytoplasm and inside large vacuole of plant cells

104
Q

What happens when cells are placed in a solution of higher water potential?

A

Water molecules move by osmosis down the water potential gradient across the plasma membrane into the cell.

105
Q

What is cytolysis?

A

In animals cell when lots of water molecules enter the cell causing it to swell and burst as the plasma membrane breaks.

106
Q

What do plant cells have to prevent bursting?

A

A rigid and strong cellulose cell wall

107
Q

What will plant cells do with high water potential?

A

Cell will swell to certain size when contents pushed against cell wall resisting further swelling.

108
Q

What is the swollen cell called?

A

Turgid.

109
Q

What does turgidity do?

A

Helps support plants especially non-woody ones

110
Q

What happens when cells are placed in solution of lower water potential?

A

Water leaves cells by osmosis across partially permeable membrane

111
Q

When is the word crenated used here?

A

Animal cell shrivel

112
Q

What do plant cells do?

A

Cytoplasm of plant cell shrinks. Membrane pulls away from cellulose cell wall. (Plasmolysis).

113
Q

What are plant tissue with plasmolysis cells described as?

A

Flaccid.

114
Q

What do plasmolysed cells suffer from?

A

Degree of dehydration. Metabolism can’t proceed as enzyme-catalyst reactions need to be in solution.

115
Q

What does increasing the temperature do to the kinetic energy?

A

Gives all molecules more energy to move

116
Q

What does an increase in kinetic energy in molecules cause?

A

These molecules to move faster

117
Q

What does decreasing the temperature do to the kinetic energy?

A

Lowers the kinetic energy

118
Q

What does a lower of kinetic energy do to the molecules?

A

Slows them down

119
Q

What don’t cold blooded animals do?

A

Generate heat to maintain their body temperature so their temperate varies with their environment

120
Q

What do saturated fatty acids become when temperature drops?

A

Compressed

121
Q

What do many unsaturated fatty acids making up the cell membrane phosolipid layer do when the temperature drops?

A

Become compressed

But their kinks in their tails push adjacent phosolipid molecules away. Maintaining membrane fluidity

122
Q

What does the proportion of saturated and unsaturated fatty acids within a cell membrane determine?

A

The membrane’s fluidity at cold temperature

123
Q

What does cholesterol in the membrane do when the temperature drops in a cell?

A

Buffer the effect of lowered temperature

124
Q

What is the point of cholesterol buffering in the cell membrane when the temperature drops?

A

Prevent reduction in membranes fluidity

125
Q

How does cholesterol Prevent reduction in membranes fluidity?

A

By preventing the phosolipid molecules from packing too closely by being between groups of phospholipid molecules

126
Q

What can fish and microorganisms change the composition of in their cell membrane?

A

The composition of fatty acids in response to lowered temperatures

127
Q

What else can change its composition of fatty acids?

A

Some plants

128
Q

What happens to the phosolipid as as the temperature increases?

A

They acquire more kinetic energy and move more in a random way increasing membrane fluidity

129
Q

What happens as a result of the membrane fluidity increasing?

A

Permeability increases

130
Q

What does this change also affect?

A

The way membrane embedded proteins are positioned and may function.

131
Q

What happens if some of the enzymes in a membrane drift sideways?

A

It could alter the rate of reactions they catalyse

132
Q

What may an increase in membrane fluidity affect?

A

The unfolding of the plasma membrane during phagocytosis

133
Q

What may an increase in membrane fluidity change?

A

The ability of cells to signal to other cells by releasing chemicals by exocytosis

134
Q

What does the presence of a cholesterol molecule buffer?

A

The effects of increasing heat as it reduces the increase in membrane fluidity

135
Q

What can and can’t be altered by the movement of phosolipids by changing temperature?

A

Movement can be altered but integral molecular structure can’t be.

136
Q

Are proteins as stable as these lipids?

A

No proteins are not as stable as lipids

137
Q

What can high temperature therefore cause the atoms in a large protein molecule do?

A

Causes atoms within large molecule to vibrate which breaks hydrogen bonds and ionic bonds that hold their structure they unfold.

138
Q

What happens to denature proteins?

A

Tertiary structure change and can’t change back again when they cool

139
Q

What are just underneath plasma membrane?

A

Cytoplasm threads

140
Q

What are cytoplasm made of?

A

Protein

141
Q

What happens if the membrane embedded proteins and the cytoskeleton threads become denatured?

A

The plasma membrane will begin to fall apart becoming more permeable as holes appear in it.

142
Q

Will the membrane embedded enzyme continue to work if it’s denatured?

A

No

143
Q

What will happen if the shape of their active sites changes slightly or the enzymes move within the membrane?

A

The rate of reactions that they catalysed will be slowed

144
Q

Give two examples of organic solvents?

A

Acetone and ethanol

145
Q

What will organic solvents do the cell membrane and why?

A

Organic solvents will damage the cell membrane as they dissolve lipids

146
Q

What does active transport mean?

A

Movement of substances against concentration gradient of that substance across a cell membrane using ATP protein carriers

147
Q

What does endocytosis mean?

A

Bulk transport of molecules too large to pass through a cell membrane even via channel or carrier proteins into a cell.

148
Q

What does exocytosis mean?

A

Bulk transport of molecules too large to pass through a cell membrane even via a channel or carrier proteins out of a cell.

149
Q

Sometimes cell to move substances in or out across their plasma membrane (ATP required) gradient

A

Against each substances concentration gradient

150
Q

Why is doing this like swimming against the tide?

A

Requires more energy than kinetic energy of the molecules

151
Q

How is the energy provided?

A

Hydrolysis of ATP

152
Q

How can cells or organelles accumulate a particular ion?

A

Simple diffusion

Facilitated diffusion

153
Q

How can cells or organelles accumulate more of a particular ion?

A

Root hair cells use active transport to absorb ions from soil

154
Q

What do membrane have specific?

A

Regions or sites

155
Q

What do these membrane protein sites do?

A

Combine reversibly with only certain solute molecules or ions

156
Q

What do membrane also have a region for?

A

Binds to

Allows hydrolysis Of molecule of ATP to release energy and act as an enzyme

157
Q

What this energy help carrier proteins to change?

A

It’s conformation (shape) and doing so carries ions from one side of the cell to other.

158
Q

Give an example of carrier protein.

A

Guard cells ATP made by chloroplast provides energy to actively transport potassium ions from surrounding cells into guard cells

159
Q

What does this influx of ions do?

A

Lowers the water potential in guard cells so water enters from surrounding cells by osmosis as guard cells swell their tips bulge opening the stoma between them

160
Q

When is bulk transport used?

A

When cells need to transport large molecules and particles that are too large to pass through plasma membrane in or out

161
Q

What does bulk transport require?

A

ATP energy

162
Q

How are large molecules brought into the cell?

A

Endocytosis

163
Q

What happens in endocytosis?

A

Segment of plasma membrane surrounds and enclosed the particle and bring it into the cell enclosed in a vesicle

164
Q

What is phagocytosis?

A

Type of endocytosis

Refers to intake of solid matter

165
Q

What is pino(endo)cytosis

A

Type of endocytosis

Refers to intake of liquid

166
Q

What is ATP needed for in endocytosis?

A

To provide energy to form vesicles and move them using molecular motor proteins along cytoskeleton threads Ito cell interior

167
Q

Exocytosis is?

A

How large molecules can be exported out of cells

168
Q

How does exocytosis happen?

A

Doesn’t pass through plasma membrane

Vesicle containing them is moved towards and then fuses with plasma membrane

169
Q

Give an example of exocytosis

A

Synapses where chemicals on vesicles are moved by motor proteins moving along cytoskeleton threads to presynaptic membrane. Vesicle membranes and plasma membranes fuse and neurotransmitter chemical are released into synaptic cleft.

170
Q

What is needed in all cases for exocytosis?

A

ATP to fuse membranes together as well as moving the vesicles
Molecule of ATP hydrolysed for every step that a motor protein takes along cytoskeleton thread as it drags the vesicle

171
Q

What is the first stage of exocytosis?

A

Membrane-bound vesicle containing substance secreted moved towards cell surface membrane

172
Q

What is the second stage of exocytosis?

A

Cell surface membrane and membrane of vesicle fuse together

173
Q

What is step 3 of exocytosis?

A

Fused site opens releasing contents of secretory vesicle

174
Q

Isotonic

A

Solution in which solute and solvent equally distributed

175
Q

Hypertonic

A

a solution which contains more solvent than solute

176
Q

Hypotonic

A

a solution which contains more solute than solvent

177
Q

Function of glycoprotein?

A

Plays important role in hormones.

178
Q

Function of glycolipid?

A

A recognition site in the body for cell-cell interactions

Biology A Level (26 decks)

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