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A level Biology > Unit 1.3 - Cell Membranes And Transport > Flashcards

Unit 1.3 - Cell Membranes And Transport Flashcards

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1
Q

List the 6 functions of the cell membrane

A

-The boundary that separates the living cell from its non-living surroundings
-Cell recognition
-Controls which substances pass into and out of the cell
-Controls the uptake of nutrients
-Allows waste products to pass out of the cell
-Is responsible for secreting substances such as enzymes and glycoproteins

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2
Q

How does cell recognition work?

A

It’s to do with the surface pattern of the cell - The immune system recognises a parasite by scanning its surface pattern and immune system cells attack and destroy it for being a foreign cell

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3
Q

What is the cell membrane made up of?

A

Almost entirely phospholipids and proteins embedded

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4
Q

What can the phospholipids within the cell membrane do?

A

Form bilayers, with one sheet of phospholipid forming over another

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5
Q

What can the phospholipid bilayer be described as?

A

The basis of membrane structure

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6
Q

What is the basis of membrane structure?

A

The phospholipid bilayer

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7
Q

What type of molecules does the phospholipid bilayer allow to enter and leave the cell through the cell membrane?

A

Lipid soluble (non-polar) molecules (e.g - 02, C02)

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8
Q

Examples of lipid soluble (non-polar) molecules that the phospholipid bilayer allows to enter and leave the cell

A

02, C02

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9
Q

Describe the phosphate head of a phospholipid molecule

A

Hydrophillic (polar) - has an electrical charge
Is attracted to other polar molecules (e.g - water)

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10
Q

Describe the fatty acid tails of a phospholipid molecule

A

Hydrophobic (non-polar) = repels water

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11
Q

How do we know about the existence of the phospholipid bilayer?

A

By looking under an electron microscope (T.E.M. - transition electron microscope, that looks at a thin slice of cell) and adding a water soluble stain, we would see the hydrophilic parts accepting the stain and appearing as a stained dark layer, whereas each side of a hydrophobic layer would reject the stain and appear as an unstained white layer

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12
Q

What’s the name of the space between cells?

A

Intercellular space

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13
Q

Under what type of microscope would be see the staining of the hydrophobic and Hydrophilic parts of the phospholipid bilayer?

A

T.E.M - transition electron microscope

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14
Q

What does a T.E.M. (Transition electron microscope) look at?

A

A thin slice of cell

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15
Q

What is the diameter of the cell membrane and which type of microscope revealed this?

A

7-8nm
T.E.M (transition electron microscope)

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16
Q

What was one of the original structure theories of the cell membrane? How accurate was this?

A

A phospholipid bilayer with proteins on the outside -this theory is incorrect

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17
Q

What type of microscope and process allowed us to advance from the original theory of the proteins on top of the phospholipids structure?

A

S.E.M. (scanning electron microscope)
Freeze-fracture

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18
Q

S.E.M

A

Scanning electron microscope
A type of electron microscope that scans the surface with a focused beam of electrons to create a high resolution image

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19
Q

T.E.M meaning

A

Transition electron microscope

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20
Q

What has the S.E.M and freeze fracture allowed us to see?

A

That on the surface of the cell, protein molecules are embedded in the surface, not on it, as we’ve seen little bumps in the freeze-fracture image

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21
Q

Freeze fracture

A

To rapidly freeze the specimen and then crack it on a plane through the tissue
-Fractures occur on weak parts of the tissue such as membranes or organelle surfaces

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22
Q

On which parts of the tissue do fractures occur during freeze fracture?

A

Weak portions of the tissue such as membranes or organelle surfaces

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23
Q

Which model did the S.E.M and freeze fracture imaging lead to in terms of the structure of the cell membrane?

A

The fluid Mosaic model

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24
Q

Which scientists discovered the fluid mosaic model?

A

Singer and Nicholson

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25
Q

Draw and label the fluid mosaic model

A

(Check notes)

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26
Q

What forms the glycocalyx?

A

Glycolipids and glycoproteins

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27
Q

What do glycolipids and glycoproteins form?

A

they glycocalyx

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28
Q

What are all the parts to label on the fluid mosaic model?

A

-Intrinsic proteins (+channel)
-Extrinsic proteins (+surface proteins)
-Cholestrol
-Glycoprotein
-Glycolipid
-Glycocalyx
-Phospholipid bilayer

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29
Q

Glycolipid

A

A branched polysaccharide attached to a phospholipid

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30
Q

Glycoprotein

A

A branched polysaccharide attached to an extrinsic protein

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31
Q

What function do both the glycolipids and glycoproteins have?

A

Form external patterns to help in cell recognition

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32
Q

Glycocalyx

A

A Glycolipid and glycoprotein covering that surround the cell membrane of cells

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33
Q

What’s the name for the glycolipid and glycoprotein covering that surrounds the cell membrane of cells?

A

Glycocalyx

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34
Q

The branched polysaccharide attached to a phospholipid

A

Glycolipid

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35
Q

The branched polysaccharide attached to an extrinsic protein

A

Glycoprotein

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36
Q

What type of protein is a glycoprotein attached to?

A

Extrinsic protein

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37
Q

Extrinsic protein

A

Sits in one half of the membrane or on its surface (surface proteins are an example)

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38
Q

What type of proteins are surface proteins?

A

Extrinsic proteins

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39
Q

Intrinsic proteins

A

Stretch from one end of the membrane to the other, completely spanning it
-Has to have Hydrophillic parts on the outside - exposed to liquid
-Has the have non-polar centre - no rejection from the non-polar, fatty acid tails

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40
Q

What features does the intrinsic protein have to have and why?

A

-Hydrophillic parts on the outside - exposed to liquid
-Non-polar centre - avoid rejection from the non-polar, fatty acid tails

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41
Q

Cholestrol

A

Helps stabilise some regions of the membrane that are less fluid

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42
Q

Channel

A

Allows charged polar molecules to pass through the membrane (e.g - glucose)

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43
Q

Give an example of a charged particle that the channel of an intrinsic protein would allow through

A

Important charged polar molecules, such as glucose, which is necessary to the cell

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44
Q

Where are the channels within the fluid mosaic model?

A

In the intrinsic proteins

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45
Q

What makes the channels in the cell membrane selectively permeable?

A

If a protein is too big, it won’t be allowed through - the channel doesn’t allow all polar molecules across

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46
Q

What does the fact that the channel within the cell membrane doesn’t allow all charged polar molecules, for example if they’re too big, make it?

A

Selectively permeable

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47
Q

Why ‘fluid’ mosaic model?

A

All parts of the membrane move relative to each other consistently (very dynamic + proteins can change position)

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48
Q

How do the proteins within the membrane move?

A

Relative to each other, consistently + can change position

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49
Q

Why fluid ‘mosaic’ model?

A

Proteins dotted around the membrane like mosaic tiles

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50
Q

What are the 5 different ways of movement across the membrane for molecules and particles?

A

-Simple diffusion
-Facilitated diffusion
-Active transport
-Osmosis
-Exocytosis/Endocytosis
-Cotransport

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51
Q

What are two types of passive transport across the membrane for proteins and molecules?

A

Simple and facilitated diffusion

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52
Q

What type of molecules does simple diffusion allow to freely pass through the membrane?

A

Small, uncharged molecules such as 02 and C02

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53
Q

Which type of movement across the membrane allows small, uncharged particles such as 02 or C02 to freely pass through?

A

Simple diffusion

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54
Q

Examples of small, uncharged particles

A

02, C02
(Move through the membrane through simple diffusion)

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55
Q

Diffusion

A

The movement of molecules or ions from a region where they’re in high concentration to a region of lower concentration until they’re evenly distributed

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56
Q

Until which point do molecules and ions move from a region where they’re in high concentration to a region of lower concentration during diffusion?

A

Until they’re equally distributed

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57
Q

What do molecules move down during diffusion?

A

A concentration gradient

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58
Q

What type of process is simple diffusion?

A

Passive (doesn’t require ATP from the cell)

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59
Q

Passive processes

A

Don’t require ATP from the cell

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60
Q

What will eventually occur during simple diffusion?

A

Unless the molecule is used up by the cell, equilibrium will be reached

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61
Q

When would equililbirum not be reached during simple diffusion?

A

If the molecule is used up by the cell

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62
Q

What does it mean if equilibrium has been reached during simple diffusion?

A

Concentration of molecules is equal on either side of the membrane in both directions, but there’s no net movement in any particular direction

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63
Q

What does the rate of diffusion depend on?

A

How steep the concentration gradient is
(Steeper = faster)

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64
Q

What’s affects the rate of diffusion?

A

How steep the concentration gradient is (steeper = faster rate of diffusion)

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65
Q

Facilitated diffusion

A

Diffusion in or out of cells helped by an intrinsic protein

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66
Q

What does facilitated diffusion still rely on and why?

A

The concentration gradient (requires no ATP) as it’s a type of diffusion

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67
Q

What type of process is facilitated diffusion?

A

Passive - doesn’t require ATP from the cell

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68
Q

What type of particles and molecules does facilitated diffusion help?

A

Charged particles/ions and large molecules such as glucose and protons

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69
Q

What is glucose an example of and which method does it use for movement across the membrane?

A

A large molecule
Facilitated diffusion

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70
Q

What are 02 and C02 examples of and which method do they use for movement across the membrane?

A

Small, uncharged molecules
Simple diffusion

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71
Q

Which protein has two types? What are they?

A

2 types of facilitating proteins
-Channel proteins
-Carrier proteins

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72
Q

What are the 2 facilitating proteins and which process do the help in?

A

Channel and carrier proteins
Facilitated diffusion

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73
Q

How do channel proteins work?

A

-Consist of pores lined with polar groups (Hydrophillic)
-Allows charged particles (such as Na+) to pass through - each one is specific to 1 type of ion
-Can open and close depending on the needs of the cell (gated channels)

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74
Q

What do channel proteins consist of and why?

A

Pores lined with polar groups (Hydrophillic) to allow charged particles to pass through

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75
Q

What can channel proteins do depending on the needs of the cell? What are these called?

A

Can open + close
Gated channels

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76
Q

Do all channel proteins open and close (gated channels)?

A

No, it depends on the needs of the cell

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77
Q

Example of a charged particles that channel proteins allow to pass through

A

Na+

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78
Q

What type of molecules do carrier proteins allow the facilitated diffusion of?

A

Larger polar molecules (e.g - sugars and amino acids)

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79
Q

What type of molecules are sugar and amino acids an example of and what type of proteins help transport them across the membrane?

A

Larger polar molecules
Carrier proteins allow their facilitated diffusion

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80
Q

Can channel proteins carry multiple different ions across the membrane?

A

No, they’re specific to one type

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81
Q

Can carrier proteins carry multiple different types of molecules across the cell membrane?

A

No, they’re specific to a particular molecule

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82
Q

How do carrier proteins work?

A

A particular molecule attaches to a carrier protein at its binding site and causes the carrier protein to change shape or rotate within the membrane to release the molecule on the other side of the membrane (not an open channel)

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83
Q

Why do carrier proteins have to change shape or rotate to transport the molecule across the membrane?

A

They’re not open channels

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84
Q

Where does the molecule attach to a carrier protein?

A

At its binding site

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85
Q

What type of molecules is active transport used to transport?

A

Relatively small molecules

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86
Q

Does active transport require ATP? What does this make it?

A

Yes, so it’s not a passive process

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87
Q

Does active transport use the concentration gradient? Why?

A

No - its not a type of diffusion
Molecules and ions are moved across membranes against a concentration gradient

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88
Q

In which direction to the concentration gradient are molecules and ions moved during active transport?

A

Against it

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89
Q

In which direction in relation to diffusion can molecules and ions move during active transport?

A

The opposite direction

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90
Q

What carries out active transport?

A

A specific intrinsic protein - a pump

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91
Q

What is the pump?

A

A specific intrinsic protein that carries out active transport

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92
Q

How does active transport work?

A

-Molecule or ion that needs to be transported combines with a specific intrinsic protein - a pump
-ATP transfers a phosphate group to the pump on the inside of the membrane, causing the pump to change shape and transport the ion across the membrane and release it into the cell

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93
Q

What does ATP transfer to the pump during active transport and what does this do?

A

A phosphate group - causes it to change shape to transport the ion across the membrane

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94
Q

Examples of processes that use active transport

A

-Protein synthesis
-Muscle contraction
-Nerve impulse transmission
-Absorbance of minerals (e.g - nitrates by plant root hair cells)

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95
Q

Which minerals do plant root hair cells absorb and which process does this require?

A

Nitrates through active transport

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96
Q

What type of transport occurs through exocytosis and endocytosis?

A

Bulk transport

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97
Q

What is bulk transport done through?

A

Endocytosis and exocytosis

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98
Q

How does endocytosis work?

A

-Large particles or liquid enter the cell
-Plasma membrane folds inwards
-Plasma membrane engulfs the material
-Plasma membrane fuses to enclose the material, forming a membrane bound vesicle in the cytoplasm

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99
Q

What type of materials undergo endocytosis?

A

Particles and liquids

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100
Q

What does endocytosis form and where within the cell?

A

A membrane bound vesicle in the cytoplasm after the plasma membrane fuses

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101
Q

What can lysosomes do to the vesicles produced during endocytosis?

A

Fuse with it and digest the small digestive molecules, whilst the vesicle becomes part of the membrane again - reusing!

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102
Q

What are the 2 types of endocytosis?

A

Phagocytosis
Pinocytosis

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103
Q

What are phagocytosis and pinocytosis the 2 types of?

A

Endocytosis

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104
Q

Phagocytosis

A

‘Cell eating’ - the movement of solids

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105
Q

The movement of which type of particles does phagocytosis involve?

A

Solids

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106
Q

2 examples of phagocytosis

A

-White blood cell (phagocytes) swallowing a bacterial cell
-Amoeba engulfing a paramecium

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107
Q

Pinocytsosis

A

Involves entry of liquid into the cell

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108
Q

Example of exocytosis

A

Within the Golgi Body, when vesicles fuse with the membrane to release its contents outside of the cell

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109
Q

Exocytosis

A

The opposite of endocytosis - particles such as hormones and enzymes secreted from cells when the vesicle containing particles migrate to the cell membrane and fuse with it, releasing particles outside the cell

110
Q

What type of particles undergo exocytosis?

A

Hormones and enzymes

111
Q

As the concentration gradient increases, what happens to the rate of transport in simple diffusion?

A

Continues increasing

112
Q

As the concentration gradient increases, what happens to the rate of transport of facilitated diffusion?

A

Increases up to a point - the number of protein channels limit the rate

113
Q

What limits the rate of transport for facilitated diffusion?

A

The number of protein channels

114
Q

What is it that increases the rate of transport for active transport?

A

Concentration difference across the membrane (higher = higher rate of transport)

115
Q

What’s the affect of adding cyanide during active transport? Why?

A

The rate of transport drops to zero - cyanide is a respiratory inhibitor, and active transport requires ATP

116
Q

Give an example of a respiratory inhibitor

A

Cyanide

117
Q

What is cyanide?

A

A respiratory inhibitor

118
Q

What type of transport is osmosis?

A

Passive (type of diffusion)

119
Q

Osmosis

A

When water molecules diffuse through the cells selectively permeable membrane from a solution of high concentration of water molecules to a solution of lower concentration of water molecules

120
Q

What does amoeba engulf during phagocytosis?

A

Paramecium

121
Q

What’s the name for white blood cells? What do they digest?

A

Phagocytes
Bacterial cells

122
Q

Phagocytes + their role

A

White blood cells, which digest bacterial cells

123
Q

How do we figure out the surface area of a membrane if given the surface area of a phospholipid monolayer?

A

Halve it, as phospholipids form bilayers in membranes, not monolayers

124
Q

What type of molecules can diffuse through the bilayer through simple diffusion? Give three examples

A

Non-polar molecules
02
C02
Fat-soluble vitamins (A, D, E and K)

125
Q

Name four fat-soluble vitamins and state how they’re transported through the membrane

A

Vitamins A, D, E and K
Simple diffusion

126
Q

What happens to the membrane if there’s too much Cholestrol? Why?

A

It becomes too rigid
Cholesterol is responsible for stabilising the regions of the membrane that are less fluid

127
Q

Where did the evidence for the ‘mosaic’ part of the fluid mosaic model come from?

A

Freeze-fracture electron microscopy

128
Q

Where did the evidence for the ‘fluid’ part of the fluid mosaic model come from?

A

From experiments (e.g - hybridisation of cells)

129
Q

Example of an experiment that proved the ‘fluid’ part of the fluid mosaic model

A

Hybridisation of cells (fuse two cells together)

130
Q

Hybridisation of cells

A

Fuse two together

131
Q

Give examples of large particles that would enter a cell through endocytosis

A

-Whole cells
-Large protein molecules

132
Q

Does bulk transport via endocytosis or exocytosis require energy?

A

Yes

133
Q

With increased concentration differences, how does this affect the protein channels and how does this affect facilitated diffusion?

A

Channels are simultaneously (saturated with molecules)
= limits facilitated diffusion

134
Q

What are channels if they’re simultaneously busy?

A

Saturated with molecules

135
Q

What are protein channels if they’re saturated with molecules?

A

Simultaneously busy

136
Q

Is cotransport a passive or non-passive process and why?

A

Passive as it depends on a concentration gradient

137
Q

Where does glucose-sodium cotransport occur?

A

In the kidney tubules and small intestine
(In the digestive system - absorb glucose from our food into our blood)

138
Q

What’s the cotransport example that we end to remember?

A

Glucose-sodium

139
Q

What’s the purpose of glucose-sodium cotransport in our digestive system?

A

To absorb glucose from our food into our blood

140
Q

What do the sodium ions and glucose attach to in the first stage of cotransport?

A

A carrier protein - a cotransporter

141
Q

What’s the name for the carrier protein that sodium ions and glucose attach to in the first step of cotransport?

A

A cotransporter

142
Q

What’s a cotransporter?

A

A carrier protein that allows the transport of two different species across the membrane simultaneously

143
Q

What happens to the sodium ions and glucose once they’ve attached to a carrier protein in the cell membrane during the first step of cotransport?

A

Carrier protein changes shape and deposits the sodium ion and glucose molecule into the cell
Sodium ion and glucose molecule diffuse separately across the cell to the opposite membrane

144
Q

How do the sodium ion and glucose molecule diffuse across the cell during cotransport?

A

Separately across the cell to the opposite membrane

145
Q

What type of cells do sodium ions and glucose molecules enter during cotransport?

A

Epithelial cells

146
Q

How do the sodium ions exit the epithelial cells?

A

Pumped out by active transport

147
Q

What happens inside the epithelial cell once sodium ions are pumped out by active transport?

A

Lowers the sodium ion concentration inside the cell, maintaining the concentration gradient needed for the diffusion of sodium ions from the gut lumen into the cell

148
Q

What’s the sodium ion concentration gradient inside the epithelial cell required for?

A

The diffusion of sodium ions from the gut lumen into the cell

149
Q

What carries out the active transport for the sodium ions to exit the epithelial cells during cotransport and what does it use?

A

Na+/K+ pump uses ATP

150
Q

What does the Na+/K+ pump do during cotransport?

A

Turns ATP into ADP whilst pumping out the sodium ions out of the epithelial cells by active transport

151
Q

How does glucose leave the epithelial cells during cotransport?

A

By facilitated diffusion

152
Q

Where does glucose enter after leaving the epithelial cells through facilitated diffusion?

A

The blood in the capillaries

153
Q

What need to be ensured in order for glucose to be able to enter the blood? Why?

A

That the glucose concentration in the blood is low
To create a concentration gradient between the cell and the blood

154
Q

Which uses active transport and which uses facilitated diffusion during cotransport?
Na+ ions
Glucose molecules

A

Na+ ions - Active transport
Glucose molecules - Facilitated diffusion

155
Q

What are most cell membranes permeable to?

A

Water and certain solutes only

156
Q

What is the name of the weird fork Greek letter for water potential?

A

psi

157
Q

Water potential

A

The tendency of water molecules to move from a high to a low concentration of water

158
Q

What’s the unit of water potential?

A

kPa

159
Q

What is water potential actually a measure of?

A

The pressure exerted by water molecules on the membrane (hence it being measured in kPa, units of pressure)

160
Q

Osmosis

A

The movement of water from a region of higher water potential to a region of lower water potential through a selectively permeable membrane

161
Q

Which phrase do we use to define osmosis instead of ‘concentration’ and why?

A

Potential, as water is a solvent

162
Q

What’s the water potential of pure water?

A

0kPa

163
Q

What does a higher concentration of water molecules mean in terms of energy?

A

Higher concentrations of water molecules = greater potential energy

164
Q

What can water molecules do if they have greater potential energy?

A

They’re completely free to move around

165
Q

Give an example of a solute that could be dissolved in water

A

Sugar

166
Q

What’s a solute’s concentrations relationship with water potential?

A

Higher concentration of a solute = lower water potential

167
Q

If a solution has a high concentration of water, how is its water potential?

A

High

168
Q

If a solution has a low concentration of water, how is its water potential?

A

Low

169
Q

If a solute, such as sugar, is dissolved in water, how does this affect the water potential of the solution and why?

A

Water potential of the solution is lowered (becomes more negative)
Proportionally fewer water molecules to move about

170
Q

What actually happens to the water potential figure if the water potential is lowered?

A

Becomes more negative

171
Q

Describe the values of all water potentials and what is the exception for this?

A

All water potentials have negative water potential values, except pure water

172
Q

What does a ‘more concentrated’ solution actually mean?

A

More solutes dissolved in it

173
Q

What does dissolving more solutes in a solution make it?

A

More concentrated

174
Q

How does the concentration affect the water potential of a solution?

A

The more concentrated a solution (the more solutes dissolved in it), the more negative the water potential

175
Q

How does a lower water potential affect the number of free water molecules there are?

A

lower water potential = fewer free water molecules

176
Q

What happens when a solution has a high water potential?

A

Greater tendency of water to leave the system by osmosis

177
Q

Where does water diffuse to and from during osmosis in terms of water potential?

A

Diffuses from a region of higher (less negative) to lower (more negative) water potential

178
Q

Symbol for pressure potential

A

ψp

179
Q

Symbol for solute potential

A

ψs

180
Q

What’s ψp the symbol for?

A

Pressure potential

181
Q

What’s ψs the symbol for?

A

Solute potential

182
Q

Pressure potential

A

As the outward pressure builds up, the cell wall in plant cells develops an opposing force - pressure potential.
(The resistance the cell has to expanding)

183
Q

Is pressure potential a positive or a negative number?

A

Usually a positive number

184
Q

What does pressure potential do?

A

Pushes against the cells tendency to swell

185
Q

Solute potential

A

The concentration of dissolved substances inside the cell vacuole - the water potential of what’s inside the cell

186
Q

Is solute potential a positive or a negative number?

A

Always a negative value

187
Q

Describe the properties of a plant cell wall and explain why it’s like this

A

Inflexible and Inelastic - won’t allow the cell to expand and stretch
Made of cellulose (strong microfibrils)

188
Q

What type of pressure pushes outwards on the cell wall when water enters a plant cell vacuole by osmosis?

A

A hydrostatic pressure

189
Q

Describe the process of a plant cell becoming turgid

A

-Water enters the plant cell vacuole by osmosis
-Hydrostatic pressure is set up and pushes outwards on the cell wall
-The cell swells
-Inflexible cell wall resists the cell from expanding too much
-Cell becomes turgid

190
Q

What is a plant cell’s healthy, natural state?

A

When it’s turgid

191
Q

In what state is a plant cel when it’s turgid?

A

In its healthy, natural state

192
Q

What helps a plant stay upright?

A

Turgidity from a hypotonic external medium

193
Q

What does turgidity help a plant do?

A

Stay upright

194
Q

Symbol for water potential of a cell

A

ψcell

195
Q

ψcell meaning

A

Water potential of a cell

196
Q

Water potential equation

A

ψcell = ψs + ψp

Water potential of a cell = solute potential + pressure potential

197
Q

What are thee types of external medium a cell can be within?

A

Hypotonic
Hypertonic
Isotonic

198
Q

Hypotonic external medium

A

Water potential of external medium is higher than the solution inside the cell

199
Q

Hypertonic external medium

A

Water potential of external solution is lower than the solution inside the cell

200
Q

Isotonic external medium

A

External solution has the same water potential as the cell’s contents

201
Q

What happens in terms of osmosis when a cell is in a hypotonic external medium?

A

Water moves into the cell by osmosis

202
Q

What happens in terms of osmosis when a cell is in a hypertonic external medium?

A

Water moves out of the cell by osmosis

203
Q

What happens in terms of osmosis when a cell is in an isotonic external medium?

A

No net movement of water by osmosis

204
Q

What happens to an animal cell in a hypotonic external medium?

A

The cell swells and may lyse (bust) as they don’t have a cell wall to protect them from bursting

205
Q

What’s the phrase for an animal cell bursting in a hypotonic external medium?

A

Lysis

206
Q

Why is there a risk of animal cells undergoing lysis (bursting) when in a hypotonic external medium?

A

They don’t have a cell wall to protect them from bursting

207
Q

What’s the phase for red blood cells bursting in a hypotonic external medium?

A

Haemolysis

208
Q

Haemolysis

A

Red blood cells bursting when in a hypotonic external medium

209
Q

What could lead to Haemolysis?

A

Kidney problems leading to too much water in the plasma

210
Q

What happens to a plant cell in a hypotonic external medium?

A

The cytoplasm and vacuole swell and push against the cell wall - cell wall becomes turgid
Turgid plant cells support plant tissues and structures (optimal for plant cells)

211
Q

What’s optimal for plant cells?

A

Turgidity

212
Q

What do turgid plant cells do?

A

Support the plant tissues and structures

213
Q

What happens to an animal cell in a hypertonic external medium?

A

The cell shrinks

214
Q

What happens to a plant cell in a hypertonic external medium?

A

The cytoplasm and vacuole shrink, causing the cell membrane to pull away from the cell wall
= plasmolysed and flaccid (floppy) cells (plasmolysis)

215
Q

What shrinks in a hypertonic external medium and what swells in a hypotonic external medium in plant cells?

A

Cytoplasm and vacuole

216
Q

Flaccid

A

Floppy cell
(Plant cell in a hypertonic external medium)

217
Q

Plasmolysis

A

The cytoplasm and vacuole shrinking, causing the cell membrane to pull away from the cell wall when a plant cell is in a hypertonic external medium

218
Q

What will happen to a plant when it undergoes plasmolysis?

A

Usually fatal to them - the whole plant will wilt

219
Q

What’s the phrase for the cytoplasm and vacuole to shrink, causing the cell membrane to pull away from the cell walls when a plant cell is in a hypertonic external medium?

A

Plasmolysis

220
Q

What maintains the situation of an animal cell remaining in an isotonic external medium and what does this ensure?

A

Homeostasis
Ensures there’s no water loss or gain

221
Q

Animal cell in an isotonic external medium

A

Naturally - their bathing medium

222
Q

What’s the natural external medium of a plant cell?

A

Hypotonic

223
Q

What’s the natural external medium of an animal cell?

A

Isotonic

224
Q

What happens to a plant cell in an isotonic external medium?

A

Cells become flaccid (floppy)
The point of incipient (beginning to happen) plasmolysis

225
Q

Describe the potential of the water, solute and pressure in a plant cell when in an isotonic external medium

A

ψp = 0kPa
ψcell= ψs

226
Q

Crenation

A

The formation of abnormal notchings around the edges of a cell after expose to a hypertonic solution

227
Q

In what type of solution does cremation occur to a cell?

A

Hypertonic

228
Q

What’s the phrase for the formation of abnormal notchings around the edges of a cell after exposure to a hypertonic solution?

A

Crenation

229
Q

Describe a solution in an isotonic external medium

A

Equilibrium, with no net movement

230
Q

What’s the net movement in an isotonic external medium?

A

There is none

231
Q

How does the size of a molecule affect how lipid-soluble it is and its rate of diffusion?

A

Smaller =
More lipid soluble
Faster rate of diffusion

232
Q

Overall movement

A

Net movement

233
Q

Net movement

A

Overall movement

234
Q

How do you remove the cell debris after a pigment has been released into the surrounding solution following Haemolysis?

A

By centrifugation

235
Q

How can you measure the depth of colour of pigment released following Haemolysis?

A

-Remove cell debris by centrifugation
-Measure with a colourimeter

236
Q

What do we use to measure depth of colour?

A

A colorimeter

237
Q

Where is the overall water potential of blood cells taken?

A

Where 50% of the cells have burst

238
Q

What does each cell have within a tissue?

A

Its own water potential

239
Q

What does the fact that each cell has its own water potential mean?

A

The cells plasmolyse at different sucrose concentrations

240
Q

At different what do cells plasmolyse?

A

Different sucrose concentrations

241
Q

Incipient plasmolysis

A

The point where the water potential of solution and tissue are equal
(When 50% of the cells are plasmolysed)

242
Q

At which point do we know that the water potential of solution and tissue are equal in a plant cell?

A

When 50% of the cells are plasmolysed (incipient plasmolysis)

243
Q

What has happened when 50% of the cells have plasmolysed?

A

The water potential of solution and tissue are equal
= incipient plasmolysis

244
Q

What’s the name of the state where 50% of cells are plasmolysed - the point where the water potential of solution and tissue are equal?

A

Incipient plasmolysis

245
Q

Which factors is the rate of diffusion dependant on?

A

-Surface area of the membrane
-Length of diffusion pathway
-Steepness of concentration gradient
-Temperature
-Membrane permeablity

246
Q

What causes an increase in the surface area of a membrane?

A

Folds in the cell membrane

247
Q

How does the surface area of the membrane affect the rate of diffusion?

A

A higher surface area gives more places over which diffusion can happen, therefore it increases the rate of diffusion

248
Q

How does the length of a diffusion pathway affect the rate of diffusion?

A

The shorter it is, the faster the rate of diffusion
Flattened cells, thinner membranes and less layers of cells all decrease diffusion pathways

249
Q

Which factors decrease a diffusion pathway?

A

Flattened cells, thinner membranes and less layers of cells

250
Q

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

A

Larger difference between high and low concentrations = faster diffusion
Increased by circulation and ventilation

251
Q

What increases the steepness of a concentration gradient?

A

Circulation and ventilation

252
Q

How does the temperature affect the rate of diffusion?

A

Higher temperatures = more kinetic energy = faster particles = faster rate of diffusion

253
Q

Which factors affect membrane permeability?

A

Salt concentration
Presence of detergents
Organic solvents

254
Q

What do salt concentrations, presence of detergents and organic solvents all affect?

A

Membrane permeability

255
Q

How do we describe the direction of water molecules between cells?

A

From ____ to ____
Not “out of”

256
Q

How is the pressure potential inside a cell built up?

A

Water passes into the cell via osmosis
Cytoplasm expands
Cell becomes turgid as cytoplasm and contents push against the cell wall
Inelastic cell wall resists further expansion

257
Q

When a cell wall expands, which pressure is built up?

A

Pressure potential

258
Q

What do all cells have different?

A

Water potentials

259
Q

What is the rate of active transport affected by?

A

-Respiration rate
-Temperature

260
Q

Why is the pressure potential of a cell in incipient plasmolysis zero?

A

The cell membrane is pulled away from the cell wall

261
Q

When the cell membrane is pulled away from the cell wall during incipient plasmolysis, what does this cause?

A

The pressure potential to be zero

262
Q

What do we NOT mention when a question asks about PASSIVE transport?

A

Carrier proteins or active transport

263
Q

What is diffusion proportional to?

A

Surface area x concentration gradient
——————————————————
Diffusion distance

264
Q

What is surface area x concentration gradient proportional to?
—————————————————
Diffusion distance

A

Diffusion

265
Q

What forms the largest vesicles- phagocytosis or pinocytosis?

A

phagocytosis

266
Q

What do both endocytosis and exocytosis require?

A

Energy in the form of ATP

267
Q

Draw a turgid cell vs a plasmolysed cell

A

(See notes)

268
Q

How do we increase our confidence in data?

A

Repeat and calculate a mean
Exclude anomalies

269
Q

Describe extrinsic proteins in the fluid mosaic model of the plasma membrane

A

Embedded in the lipid layer

270
Q

Where is there already a high Na+ concentration when thinking of cotransport and why?

A

In the lumen, from dietary sources

271
Q

Why should we use thermostatically controlled water baths as opposed to carrying out experiments at room temperature?

A

Room temperature varies, and this reduces reproducibility

A level Biology (26 decks)

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