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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 the function of glycoproteins ?

A

Used for cell signalling as receptors

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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 and restricts lateral movement of other molecules across 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 the 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 examples 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
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

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

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

28
Q

How does thickness of membrane affect the rate of diffusion ?

A

The thinner the membrane the faster the diffusion rate

29
Q

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

A

A smaller molecule means a faster rate of diffusion

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

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

How do the protein channels required in active transport work ?

A

Protein changes shape and opens towards inside of membrane and releases molecule contents

34
Q

What are exocytosis and endocytosis examples of ?

A

Active transport and bulk transport

35
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

36
Q

What are the 2 forms of endocytosis ?

A

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

37
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

38
Q

Why is ATP required in exocytosis ?

A

To move vesicle along cytoskeleton

39
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

40
Q

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

A

Increases

41
Q

What is the water potential of pure water ?

A

0 kPa

42
Q

What is a hypertonic solution ?

A

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

43
Q

What happens to an animal cell in a hypertonic solution ?

A

Crenation - volume of cell reduces so cell surface membrane puckers

44
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

45
Q

What is a hypotonic solution ?

A

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

46
Q

What happens to an animal cell in a hypotonic solution ?

A

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

47
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

48
Q

What is an isotonic solution ?

A

Water potential of solution is the same as inside the cell

49
Q

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

A

Nothing as constant rate of osmosis in and out of cell

50
Q

What are the 2 factors affecting membrane permeability ?

A

Temperature and solvents

51
Q

How does a high temperature affect membrane permeability ?

A
  • As temperature increases the kinetic energy of phospholipids increases so they move more
  • Fluidity of membrane increases
  • Structure starts to break which makes it easier for particles to cross the membrane
52
Q

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

A

Denature channel and carrier proteins

53
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

54
Q

Name an organic solvent and it’s polarity

A

Alcohol : non-polar

55
Q

What practical can investigate factors affecting membrane permeability ?

A

Colorimetry

56
Q

Define absolute uncertainty

A

The absolute measure of inaccuracy within a given piece of equipment

57
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
58
Q

Give 3 roles of cell surface membranes

A

Compartmentalisation
Control what enters and leaves organelle
Creates concentration gradient

59
Q

Name the process by which water is expelled from a cell

A

Exocytosis

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