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Green > 2.1.5: Biological Membranes > Flashcards

2.1.5: Biological Membranes Flashcards

1
Q

What is the function of glycolipids ?

A

Used for cell signalling as receptors

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2
Q

What are the structure of glycolipids ?

A

Lipids attached to a carbohydrate chain

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3
Q

What are 4 functions of glycoproteins ?

A
  • Used for cell signalling as receptors
  • Act as antigens
  • Receptor for hormones
  • Attach to water molecules to stabilise membrane
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4
Q

What is the structure of glycoproteins ?

A

Proteins attached to a carbohydrate chain

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5
Q

What is the structure of a phospholipid ?

A

Phosphate group hydrophilic head (polar)
2 hydrophobic tails (non-polar)

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6
Q

What type of molecule is a phospholipid ?

A

Lipid

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7
Q

What is the function of a phospholipid ?

A

Forms a bilayer

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8
Q

What are the functions of an extrinsic protein ?

A
  • Mechanical support
  • Make glycoproteins/glycolipids for cell recognition as receptors
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9
Q

What is the function of an intrinsic protein ?

A

Form channel proteins and protein channels
- Channel proteins : Transport of molecules across membranes by binding to ions or larger molecules e.g. changes shape to transport glucose
- Protein channels : form tubes filled with water , water-soluble ions diffuse into channel

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10
Q

What type of molecule is cholesterol ?

A

Lipid

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11
Q

What are the functions of cholesterol

A
  • Controls fluidity of membrane so it can remain stable at body temperature
  • restricts lateral movement of molecules across membrane
  • Binds to phospholipid fatty-acid tails, increasing packing of membrane and reducing fluidity of membrane
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12
Q

How does an increased amount of cholesterol impact a membrane ?

A

Becomes less fluid at high temperatures

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13
Q

How deep is a cell surface membrane ?

A

7nm

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14
Q

Give 3 roles of membranes

A

1) Site of chemical reactions
2) Site of cell communication
3) Partially permeable barrier between cell and its environment (compartmentalisation)

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15
Q

How does cell signalling occur ?

A

Signal by direct contact or by neurotransmitters (chemical messengers)

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16
Q

Why is cell signalling needed ?

A

Molecules can be too large to pass through cell membrane so must bind to membrane bound receptors

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17
Q

Outline an example role of membrane bound receptors

A

Site where hormones and drugs can bind to

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18
Q

What are the 2 ways that drugs can bind to receptors ?

A

Block receptors - blocks normal antagonist messengers binding
Mimic receptors - mimic body’s normal messengers

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19
Q

Define simple diffusion

A

Net movement of particles down a concentration gradient from an area of higher concentration to an area of lower concentration until equilibrium is reached

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20
Q

What are the 2 examples of passive transport ?

A

Simple and facilitated diffusion

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21
Q

Give 2 features of simple diffusion

A
  • Does not require ATP
  • For lipid soluble and small molecules which can diffuse through the bilayer
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22
Q

Give 3 features of facilitated diffusion

A
  • Does not require ATP
  • For lipid larger or non lipid soluble (polar) molecules
  • Require protein channels and carrier proteins to transport molecules across membranes
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23
Q

What can happen at a high concentration of molecules that need to be transported across the membrane ?

A

Carrier molecules become saturated

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24
Q

What are the 5 factors affecting the rate of diffusion ?

A
  • Temperature
  • Concentration difference
  • Surface area
  • Thickness of membrane
  • Size of molecule
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25
Q

How does temperature affect the rate of diffusion ?

A

Higher temperature means a higher rate of diffusion as particles have energy to move at higher speeds

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26
Q

How does concentration difference affect the rate of diffusion ?

A

Larger difference means a higher rate of diffusion as overall movement from high to low concentration is larger

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27
Q

How does surface area affect the rate of diffusion ?

A

The larger the area of the exchange surface the higher the diffusion rate

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28
Q

How does thickness of membrane affect the rate of diffusion ?

A

The thinner the membrane the faster the diffusion rate

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29
Q

How does the size of a molecule affect the rate of diffusion ?

A

A smaller molecule means a faster rate of diffusion

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30
Q

Define active transport

A

Movement of molecules and ions from area of lower concentration to an area of higher concentration against concentration gradient USING ATP

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31
Q

Give 2 features of active transport

A
  • Requires ATP as an immediate energy source and carrier proteins
  • Selective as only certain molecules can bind to receptor site on carrier protein
32
Q

How is the ATP needed for active transport obtained?

A

Binds to protein inside membrane and is hydrolysed into ADP and Pi

33
Q

What are exocytosis and endocytosis examples of ?

A

Active transport and bulk transport

34
Q

Outline the process of endocytosis

A

1) Cell surface membrane bends inwards around molecule to form a vesicle
2) Vesicle pinches off and moves within cytoplasm

35
Q

What are the 2 forms of endocytosis ?

A

Phagocytosis - Solid particle being taken in
Dinocytosis - liquid being taken in

36
Q

Outline the process of exocytosis

A

1) Vesicle moves towards cell surface membrane via cytoskeleton
2) Vesicle fuses with cell surface membrane and releases contents out of cell

37
Q

Why is ATP required in exocytosis ?

A

To move vesicle along cytoskeleton

38
Q

Define osmosis

A

Net movement of water from a region of high water potential to a region of low water potential across partially permeable membrane DOWN A WATER POTENTIAL GRADIENT

39
Q

What happens to concentration of dissolved solutes as water potential decreases ?

A

Increases

40
Q

What is the water potential of pure water ?

A

0 kPa

41
Q

What is a hypertonic solution ?

A

Water potential of solution is more negative than cell ( more concentrated /solute )

42
Q

What happens to an animal cell in a hypertonic solution ?

A

Crenation - volume of cell reduces so cell surface membrane puckers

43
Q

What happens to a plant cell in a hypertonic solution ?

A

Plasmolysis - cytoplasm volume is reduced so cell surface membrane is pulled away from cell wall

44
Q

What is a hypotonic solution ?

A

Where the water potential of a solution is more positive than the cell ( less solute/concentrated)

45
Q

What happens to an animal cell in a hypotonic solution ?

A

Hemolysis - cell swells and bursts due to the increasing hydrostatic pressure

46
Q

What happens to a plant cell in a hypotonic solution ?

A

Turgid - cells hydrostatic pressure increases ,turgor pressure is created as membrane pushes against cells rigid cellulose walls

47
Q

What is an isotonic solution ?

A

Water potential of solution is the same as inside the cell

48
Q

What happens to animal and plant cells in an isotonic solution ?

A

Nothing as constant rate of osmosis in and out of cell

49
Q

What are the 2 factors affecting membrane permeability ?

A

Temperature and solvents

50
Q

How does a high temperature affect membrane permeability ?

A
  • As temperature increases the kinetic energy of phospholipids increases so they move more
  • Increased number of gaps between phospholipids
  • Fluidity of membrane increases, permeability increases
  • Proteins denature
51
Q

How can a temperature that is too high affect membrane permeability ?

A

Denature channel and carrier proteins

52
Q

How can solvents affect membrane permeability ?

A

Organic solvents dissolve in the phospholipids bilayer which damages the membrane and increases its fluidity and therefore permeability

53
Q

Name an organic solvent and it’s polarity

A

Alcohol : non-polar

54
Q

What practical can investigate factors affecting membrane permeability ?

A

Colorimetry

55
Q

Define absolute uncertainty

A

The absolute measure of inaccuracy within a given piece of equipment

56
Q

Explain how cell surface membranes contribute to the process of cell signalling

A
  • Release of signal molecule by exocytosis
  • Glycoproteins act as receptors which are specific to the shape of the signal
  • Cell surface membrane allows entry of some signalling molecules
57
Q

Give 3 roles of cell surface membranes

A

Compartmentalisation
Control what enters and leaves organelle
Creates concentration gradient

58
Q

Name the process by which water is expelled from a cell

A

Exocytosis

59
Q

Which part of the plasma membrane could contain sulfur ?

A

Extrinsic proteins e.g. glycoproteins

60
Q

Name 3 substances that diffuses by simple diffusion and one by facilitated diffusion

A

Simple - oxygen, CO2, water
Facilitated - glucose

61
Q

Why can’t glucose pass through the cell membrane by simple diffusion ?

A

Phospholipids act as a barrier and glucose molecules are too large

62
Q

Give 2 features of the plasma membrane which contribute to its fluidity

A
  • Cholesterol controls membrane fluidity
  • Hydrophobic fatty acid tails and hydrophilic phosphate heads help form bilayer
63
Q

What feature does a substance have to have to diffuse through the plasma membrane ?

A

Be fat soluble/ non-polar

64
Q

How does the fluid mosaic model describe the structure of the plasma membrane ?

A
  • Phospholipid bilayer containing proteins
  • Hydrophilic phosphate heads facing outwards, hydrophobic fatty acid tails facing inwards
  • Proteins free to move in membrane
  • Glycolipids sticking out of bilayer
  • Cholesterol between phosholipids
65
Q

Describe structure of the RER

A
  • Phospholipid molecules form bilayer
  • Cisternae
  • Outside covered in ribosomes
66
Q

Give 4 benefits of carrying out repeats

A
  • Helps identify anomalies
  • Improves repeatability
  • Mean can be calculated
  • Allows statistical tests to be completed
67
Q

What is a limitation of the agar cube practical ?

A

Inconsistency in surface areas of cubes especially the smallest as smaller error in cutting will proportionally have the largest effect

68
Q

How should data for potato experiment be displayed

A

Line graph as continous data with % change in mass on Y as DV and concentration of solution on X as IV

69
Q

How does osmosis help plants ?

A
  • water enters vacuole causing turgor pressure
  • turgid cells support plant
70
Q

Why do we calculate % change in mass in the potato experiment ?

A

different (starting) masses (of plant pieces) allows comparison between plant pieces of different mass

71
Q

How can you use potato data to determine water potential of plant tissue ?

A

No change in mass occurs when water potential of plant tissue = water potential of sucrose solution. Plot graph of
concentration of sucrose solution against (%) change in mass and find which (sucrose) concentration gives no change in mass of potato

72
Q

Define cell signalling

A

Communication between cells to trigger a response inside a cell e.g. the action of a hormone

73
Q

How do cell surface membranes contribute to cell signalling ?

A
  • Signalling molecule released by exocytosis
  • Glycoproteins act as receptors which is specific
  • Shape of receptor and signal are complementary
  • Attachment of signal molecule causes change inside cell
  • Cell surface membrane allows entry of some signalling molecules
74
Q

What routes does water molecules take through the cell surface membrane ?

A

Fits through phospholipid bilayer via aquaporins

75
Q

Describe the process of budding in yeast

A
  • Mitosis
  • Cell bulges
  • Nucleus moves into bulge
  • Pinches off so bud is a separate cell
76
Q

What is the main role of the phospholipid bilayer ?

A

Act as a barrier

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