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Flashcards in Biological Membrane Deck (178):
1

What do some organelles have and what do these do?

Have membranes within them and form barriers too

2

What does permeability refer to?

The ability to let substances pass through

3

How do very small molecules get through the cell membrane?

Diffuse through cell membrane between structural molecules

4

What do some substances do to get through the membrane?

Dissolve in the lipid later and pass through

5

How do other substances pass through cell membrane?

Pass through special protein channels it are carried by carrier proteins

6

Why are these membranes described as partially permeable?

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

7

What determines the cells permeability?

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

8

What is the plasma membrane sometimes referred to?

Cell surface membrane

9

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

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

10

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

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

11

Why does the cell membrane have antigens?

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

12

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

Organelle contents from cell cytoplasm

13

Why does it departs the organelles content?

Discrete entity
Able to perform its function

14

Where do metabolic processes happen on some organelles?

On membranes

15

What do mitochondria folded inner membranes gives?

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

16

What do inner membranes of chloroplasts call themselves?

Thylakoid membranes
House chlorophyll

17

What do you find on these membranes?

Some of reactions of photosynthesis occurring

18

Where are some digestive enzymes?

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

19

State the year and what singer and nicolson?

1972
Proposed model allowed passage of molecules through membrane

20

What did their structure explain and who are they?

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

21

What was singer and Nicolsons 1972 model called?

Fluid mosaic model

22

What did fluid mosaic model propose?

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

23

What is the fabric of the membrane?

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

24

How thick is the phospholipid bilayer?

About 7nm in width

25

What does a carrier protein have?

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

26

What makes a glycoprotein?

Glycocalyx attached to protein
Carbohydrate chain attracted to protein molecules

27

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

An enzyme

28

Phospholipid info

Fatty acid tails hydrophobic
Phosphate head has charge and is hydrophobic

29

Cholesterol does what in the cell membrane? What do

Gives mechanical stability and flexibility

30

What's glycocalyx?

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

31

Glycolipid is?

Carbohydrate chain attached to lipid

32

What do some protein membranes have?

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

33

What does Pores and act as channels mean?

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

34

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

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

35

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

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

36

What do eukaryotic cell membrane contain?

Cholesterol

37

What is the importance of this?

Helping to regulate fluidity of the membrane
Maintain mechanical stability and resist effects of temperature changes on structure of the membrane

38

What is the width thickness of a cell membrane?

5 to 10 nm

39

What is outside the membrane?

Glycocalyx

40

Wha cud glycocalyx Formed from?

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

41

What may membranes have a particular and to allow what?

Particular distributions of proteins
Enable them to carry out their specific functions

42

What allows entry and exit of ions?

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

43

What does this bring?

Conduction of electrical impulse along their length

44

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

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

45

Neurones features?

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

46

What percentage lipid and protein is a neurone?

76% lipid
20% protein

47

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

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

48

When could the white blood cell react?

Invading pathogens
Organ transplant

49

What do root hair cells have?

Many carrier proteins

50

What do these carrier proteins do?

Actively transport nitrate ions from soil into cells

51

What percentage lipid and protein is the mitochondria?

76% protein
24% lipid

52

Why is this so?

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

53

What do cells need to receive?

Raw material or reactants for reactions

54

What do they respire to make?

ATP

55

What does ATP provide?

Cellular energy to drive biochemical reactions
They need oxygen and glucose to do this

56

What do they also need to do?

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

57

How can some substances cross the cell membrane?

Without using ATP
Passive processes as use kinetic energy

58

What's simple diffusion?

GCSE diffusion

59

What does simple diffusion rely on?

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

60

What causes diffusion?

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

61

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

Still moving randomly
Remain evenly dispersed so net diffusion
Reached equilibrium

62

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

Simple diffusion because they are small

63

How can larger fat-soluble molecules get through?

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

64

Why is water a special case?

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

65

What do molecules where high water movement required have?

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

66

What maintains the concentration gradient?

Many molecules entering cells pass into organelles used for metabolic reactions

67

What does it also do?

Keeps more molecules entering the cell

68

What does oxygen do here?

Diffuses into cytoplasm of respiring cells
Diffuses into microchrondria used for aerobic respiration

69

What does carbon dioxide do?

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

70

What factors affect simple diffusion?

Temperature
Diffusion distance
Surface area
Size of diffusing molecule
Concentration gradient

71

Temperature affects rate of diffusion how?

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

72

How does diffusion distance affect rate of diffusion?

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

73

Size of diffusing molecules affect simple diffusion?

Smaller ions or molecules diffuse more rapidly than larger molecules

74

How does concentration gradient affect the rate of diffusion?

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

Facilitated diffusion depends on?

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

What did that mean?

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

77

What do the cholesterol do here?

Reduce permeability of membrane to water-soluble molecules

78

Can glucose diffuse through?

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

79

So how does glucose get in?

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

What do different cell types have?

Differing proportions of transmembrane protein channel and transmembrane protein carriers.

81

What does this allow?

Cells to control types of molecules that pass in or out

82

What do Neurone plasma membrane have?

Many channel specific to either sodium ions/ potassium ions

83

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

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

84

What are at the synapses?

Calcium ion channels
Many have chloride ion channels

85

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

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

86

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

Solvent.

87

What is the solvent in an aqueous solution?

Water

88

What can water do with a phosolipid bilayer?

Pass directly through

89

What do some membranes also have?

Aquaporins which allow water molecules to cross more rapidly

90

What do water molecules have?

Kinetic energy

91

What does this cause them to do?

Move randomly thus spreading out

92

Define osmosis

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

93

What happens when solute molecules are added to water?

The relative number of water molecules in the solution changes.

94

What happens if solute molecules dissociate into charged ions?

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

95

Why?

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

96

Water potential is?

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

97

What has the highest water potential and what is it?

Pure water 0

98

What happens when solute molecules are added?

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

99

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

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

100

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

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

101

What is water potential measured in?

kPa

102

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

The water potential inside the cell

103

Why is this?

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

104

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

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

105

What is cytolysis?

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

106

What do plant cells have to prevent bursting?

A rigid and strong cellulose cell wall

107

What will plant cells do with high water potential?

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

108

What is the swollen cell called?

Turgid.

109

What does turgidity do?

Helps support plants especially non-woody ones

110

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

Water leaves cells by osmosis across partially permeable membrane

111

When is the word crenated used here?

Animal cell shrivel

112

What do plant cells do?

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

113

What are plant tissue with plasmolysis cells described as?

Flaccid.

114

What do plasmolysed cells suffer from?

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

115

What does increasing the temperature do to the kinetic energy?

Gives all molecules more energy to move

116

What does an increase in kinetic energy in molecules cause?

These molecules to move faster

117

What does decreasing the temperature do to the kinetic energy?

Lowers the kinetic energy

118

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

Slows them down

119

What don't cold blooded animals do?

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

120

What do saturated fatty acids become when temperature drops?

Compressed

121

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

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

122

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

The membrane's fluidity at cold temperature

123

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

Buffer the effect of lowered temperature

124

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

Prevent reduction in membranes fluidity

125

How does cholesterol Prevent reduction in membranes fluidity?

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

126

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

The composition of fatty acids in response to lowered temperatures

127

What else can change its composition of fatty acids?

Some plants

128

What happens to the phosolipid as as the temperature increases?

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

129

What happens as a result of the membrane fluidity increasing?

Permeability increases

130

What does this change also affect?

The way membrane embedded proteins are positioned and may function.

131

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

It could alter the rate of reactions they catalyse

132

What may an increase in membrane fluidity affect?

The unfolding of the plasma membrane during phagocytosis

133

What may an increase in membrane fluidity change?

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

134

What does the presence of a cholesterol molecule buffer?

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

135

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

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

136

Are proteins as stable as these lipids?

No proteins are not as stable as lipids

137

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

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

138

What happens to denature proteins?

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

139

What are just underneath plasma membrane?

Cytoplasm threads

140

What are cytoplasm made of?

Protein

141

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

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

142

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

No

143

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

The rate of reactions that they catalysed will be slowed

144

Give two examples of organic solvents?

Acetone and ethanol

145

What will organic solvents do the cell membrane and why?

Organic solvents will damage the cell membrane as they dissolve lipids

146

What does active transport mean?

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

147

What does endocytosis mean?

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

148

What does exocytosis mean?

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

149

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

Against each substances concentration gradient

150

Why is doing this like swimming against the tide?

Requires more energy than kinetic energy of the molecules

151

How is the energy provided?

Hydrolysis of ATP

152

How can cells or organelles accumulate a particular ion?

Simple diffusion
Facilitated diffusion

153

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

Root hair cells use active transport to absorb ions from soil

154

What do membrane have specific?

Regions or sites

155

What do these membrane protein sites do?

Combine reversibly with only certain solute molecules or ions

156

What do membrane also have a region for?

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

157

What this energy help carrier proteins to change?

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

158

Give an example of carrier protein.

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

159

What does this influx of ions do?

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

When is bulk transport used?

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

161

What does bulk transport require?

ATP energy

162

How are large molecules brought into the cell?

Endocytosis

163

What happens in endocytosis?

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

164

What is phagocytosis?

Type of endocytosis
Refers to intake of solid matter

165

What is pino(endo)cytosis

Type of endocytosis
Refers to intake of liquid

166

What is ATP needed for in endocytosis?

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

167

Exocytosis is?

How large molecules can be exported out of cells

168

How does exocytosis happen?

Doesn't pass through plasma membrane
Vesicle containing them is moved towards and then fuses with plasma membrane

169

Give an example of exocytosis

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

What is needed in all cases for exocytosis?

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

What is the first stage of exocytosis?

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

172

What is the second stage of exocytosis?

Cell surface membrane and membrane of vesicle fuse together

173

What is step 3 of exocytosis?

Fused site opens releasing contents of secretory vesicle

174

Isotonic

Solution in which solute and solvent equally distributed

175

Hypertonic

a solution which contains more solvent than solute

176

Hypotonic

a solution which contains more solute than solvent

177

Function of glycoprotein?

Plays important role in hormones.

178

Function of glycolipid?

A recognition site in the body for cell-cell interactions