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M2: Biological Membranes Flashcards

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1
Q

2.1.5 Biological Membranes:

What are the 5 Functions of Membranes?

A

1) Keep all cellular components inside cell
2) Allow entry & exit of selective molecules in a cell
3) Isolate organelles from rest of cytoplasm
4) Site of biochemical reactions
5) Allows cell to change shape

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2
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What’s the structure of the Fluid Mosaic Model?

A
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3
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What’s the Fluid Mosaic Model?

A

When phospholipid molecles form a continuous double layer (bilayer)

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4
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What’s the Phospholipic Bilayer?

Tails facing inwads

A

2 layers of a glycerol + 2 fatty acid tails + phosphate group

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5
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

Why’s the Fluid Mosaic Model described as Fluid?

A

Phospholipids are constantly moving

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6
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

Why’s the Fluid Mosaic Model described as a Mosaic?

A

Protein molecules are scattared through the bilayer like tiles in a mosaic

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7
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

How do Phospholipids form a Barrier to Dissolved Substances?

A
  • head = hydrophillic
  • tails = hydrophobic

Centre of bilayer is hydrophobic : membrane doesn’t allow water soluble substances (ions) through it but fat slubl substances (fat soluble vitamins) can dissolve in bilayer & pass directly through membrane

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8
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What’s the function of Cholesterol?

A

Provides membrane stability

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9
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

How does Cholesterol perform its function?

A

Cholesterol mol fit between phospholipids
↳ bind to hydrophobic tails → pack more closely together making the membrane less fluid & more rigid

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10
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What’s the affect of Cholesterol at Lower Temps?

A

Prevents phospholipids from packing too close together : increases membrane fluidity

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11
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What are Channel Proteins?

A

Proteins that allows small or charged molecules through membrane

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12
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What are Carrier Proteins?

A

Proteins that transport molecules & ions across membrabe through active transport or facilitated diffusion

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13
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

How do Proteins act as receptors in Cell Signalling?

A

When a mol binds to a protein, a chemical reaction is triggered inside the cel

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14
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What are Glycolipids?

A

Carbonhydrate chains attached to lipids

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15
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What are Glycoproteins?

A

Carbonhydrate chains attached to proteins

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16
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What’s the main function for Glycolipids & Glycoproteins?

A

Stabilise the membrane by forming H bonds with sorrounding water mol

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17
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

What are the 3 other Functions for Glycolipids & Glycoproteins?

A
  • Site where drugs, hormones & antibodies bind
  • Act as receptors for cell signalling
  • Could be antigens
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18
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

Extrinsic Proteins

A

Intracts w hydrophillic parts of membrane

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19
Q

2.1.5 Biological Membranes: Fluid Mosaic Model

Intrinsic Protein

A

Interacts w hydrophobic parts of membrabe

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20
Q

2.1.5 Biological Membranes: Cell Signalling

What do cells use to Communicate w each other?

A

Messenger mol

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21
Q

2.1.5 Biological Membranes: Cell Signalling

What are the 3 Steps for Cell Signalling?

A
  1. A cell releases a messenger mol (e.g hormone)
  2. This mol travels to another cell (e.g in blood)
  3. Messenger mol is detected by cell
    ↳ binds to receptor on its cell membrane
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22
Q

2.1.5 Biological Membranes: Cell Signalling

What are Membrane bound organelles?

A

Proteins in the cell membrane that act as receptors for messenger mol

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23
Q

2.1.5 Biological Membranes: Cell Signalling

What do the Membrane bound organelles bind to?

A

Complementary messenger mols

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24
Q

2.1.5 Biological Membranes: Cell Signalling

Why do Membrane bound organelles only bind to complementary messenger mol?

A

Difference cells have different types of receptors
↳ they respond to diff messenger mol

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25
Q

2.1.5 Biological Membranes: Cell Signalling

What’s a Target Cell?

A

A cell that responds to a particular messenger mol

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26
Q

2.1.5 Biological Membranes: Cell Signalling

How’s Glucagon an Example of this?

A
  • Glucagon: hormone released when there isn’t enough glucose in blood

It binds to receptors on liver cells
↳ causing liver cell to break down stores of glycogen into glucose

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27
Q

2.1.5 Biological Membranes: Drugs use in Cell Signalling

How do many drugs work?

A

By binding to receptors in cell membranes
↳ either trigger a response or block the receptor & prevent it from working

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28
Q

2.1.5 Biological Membranes: Drugs use in Cell Signalling

How are Antihistamines an Example of this?

A

Cell damage causes release of histamines
↳ binds to receptors on the surface of other cells causes inflammation

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29
Q

2.1.5 Biological Membranes: Drugs use in Cell Signalling

How do Antihistamines work?

A

By blocking histamines receptors on cell surfaces
↳ prevents histamines from binding to the cells & stops inflammation

30
Q

2.1.5 Biological Membranes: Factors Affecting Fluidity

How do Temps below 0°C affect membrane fluidity?

A
  • Phospholipids don’t have much energy : don’t move much
    ↳ they’re packed closely together & membrane is rigid
  • Channel & carrier proteins in membrane deform
    ↳ increasing membrane permeability
  • Ice crystals may form & pierce the membrane
    ↳ highly permeable when it thaws
31
Q

2.1.5 Biological Membranes: Factors Affecting Fluidity

How do Temps between 0°C & 45°C affect membrane fluidity?

A
  • Phospholipids can move around but aren’t packed as tightly together
  • Membrane = partially permeable
    ↳ as temp increases, phospholipids move around more, they have more Ke & permeability increases
32
Q

2.1.5 Biological Membranes: Factors Affecting Fluidity

How do Temps above 45°C affect membrane fluidity?

A
  • Phospholipid bilayer starts melting & membrane become permeable
    ↳ water inside cell expands → putting pressure on membrane
    ↳ channel & carrier proteins deform → can’t control what enters & leaves cell
    ↳ increases permeability
33
Q

2.1.5 Biological Membranes: Factors Affefcting Fluidity

What’s the affect of Solvents on membrane fluidity?

(detergents/alcohol)

A

Sorrounding cells in a solvent increases permeability

34
Q

2.1.5 Biological Membranes: Factors Affecting Fluidity

How do Solvents affect membrane permeability?

A

Solvents diffuse lipids in cell membranes : membrane loses its structure
* some solvents increase permeability more than others (higher conc = increased permeability)

35
Q

2.1.5 Biological Membranes: Transport across Membranes

What’s Diffusion?

A

Passive process where particles move down the conc gradient through a selectively permeable membrane

36
Q

2.1.5 Biological Membranes: Transport across Membranes

What’s Osmosis?

A

Movement of water molecules from a dilute concentration to a more concentrated one through a selectively permeable membrane

37
Q

2.1.5 Biological Membranes: Transport across Membranes

What’s meant by Selectively Permeable Membrane?

A

Membrane that has small holes in it & allows small molecules through

38
Q

2.1.5 Biological Membranes: Transport across Membranes

What’s meant by Net Movement?

A

Overall movement of particles

39
Q

2.1.5 Biological Membranes: Transport across Membranes

What’s meant by Equilibrium?

A

When the rate is the same at either side

40
Q

2.1.5 Biological Membranes: Factors affecting Diffusion

How does Conc gradient affect the rate of Diffusion?

A

Higher conc gradient = faster rate

41
Q

2.1.5 Biological Membranes: Factors affecting Diffusion

How does Thickness of Exchange Surface affect the rate of Diffusion?

A

Thinner exchange surface (shorter distances) = faster rate

42
Q

2.1.5 Biological Membranes: Factors affecting Diffusion

How does SA affected the rate of Diffusion?

A

Larger SA = faster rate

43
Q

2.1.5 Biological Membranes: Factors affecting Diffusion

How does Temp affect the rate of Diffusion?

A

Warmer = more Ke : faster rate

44
Q

2.1.5 Biological Membranes: Diffusion

What’s meant by Simple Diffusion?

A

Diffusion of small non-polar molecules

45
Q

2.1.5 Biological Membranes: Diffusion

What’s meant by Facilitated Diffusion?

A

Diffusion of larger polar molecules

46
Q

2.1.5 Biological Membranes: Diffusion

What’s the role of Carrier Proteins in Facilitated Diffusion?

A

Move large mol into or out of cell

  1. Large mol attaches to carrier protein in membrane
  2. Protein changes shape
    ↳ releases mol onto opposite side of membrane
47
Q

2.1.5 Biological Membranes: Diffusion

What’s the role of Channel Proteins in Facilitated Diffusion?

A

Form pores in membrane for polar mol to diffuse through

48
Q

2.1.5 Biological Membranes: Active Transport

What’s Active Transport?

A

Movement of molecules from an area of low to high conc using ATP & carrier proteins

49
Q

2.1.5 Biological Membranes: Active Transport

What are the steps that occur in Active Transport?

A
  1. Mol attaches to carrier protein
    ↳ protein changes shape releasing mol across membrane
  2. Energy is used to move solute against conc gradient
50
Q

2.1.5 Biological Membranes: Active Transport

When is Bulk Transport used?

A

When extremely large substances need to be moved across a plasma membrane

51
Q

2.1.5 Biological Membranes Active Transport

What’s Endocytosis?

A

Bulk transport of large material into the cell via carrier & channel proteins

52
Q

2.1.5 Biological Membranes: Active Transport

Why does Endocytosis require ATP?

A

To form the vesicles & move them around

53
Q

2.1.5 Biological Membranes: Active Transport

What are Examples of Endocytosis?

A
  • Phagocytosis: engulfing cells
  • Pinoendocytosis: if cells ingest liquids
54
Q

2.1.5 Biological Membranes: Active Transport

What’s the Mechanism of Endocytosis?

A

Segment of the plasma membrane sorrounds & closes particle & brings into the cell enclosed in a vesicle

55
Q

2.1.5 Biological Membranes: Active Transport

What’s Exocytosis

A

Bulk transport of large material out of the cell via carrier & channel proteins

56
Q

2.1.5 Biological Membranes: Active Transport

Why does Exocytosis require ATP?

A
  • Vesicle pinches off sacs of Golgi Apparatus & moves towards plasma membrane
  • Vesicle fuses w plasma membrane & release their contents outside cell
57
Q

2.1.5 Biological Membranes: Active Transport

What’s the Mechanism of Exocytosis?

A

Vesicle containing substance is moved towards & fuses w plasma membrane

58
Q

2.1.5 Biological Membranes: Active Transport

What’s an Example of Exocytosis?

A

Synapses:
* Chemicals in vesicles are moved by motor proteins along cytoskeleton threads to presynaptic membrane
* Vesicle membranes & plasma membrane fuse releasing neurotransmitted chemicals

59
Q

2.1.5 Biological Membranes: Osmosis

What’s meant by the term Turgid?

(hard)

A

Cell is filled w water

60
Q

2.1.5 Biological Membranes: Osmosis

What’s meant by the term Flaccid?

(soft)

A

Cell lacks water

61
Q

2.1.5 Biological Membranes: Osmosis

What’s meant by the term Plasmolysed?

A

Process where water is loss

62
Q

2.1.5 Biological Membranes: Osmosis

What’s Osmosis in terms of WP?

A

Movement of water mol from an area of high WP to an area of lower WP

63
Q

2.1.5 Biological Membranes: Osmosis

What’s Water Potential?

(measured in kPa)

A

Tendency of water molecules in a system to move into or out of a solution

64
Q

2.1.5 Biological Membranes: Water Potential

What’s the WP of Pure water?

A

Has the highest potential ( value of 0 kPa)

65
Q

2.1.5 Biological Membranes: Water Potential

What’s the WP of Solutions?

A

Have a lower WP than pure water ( negative WP)

66
Q

2.1.5 Biological Membranes: Water Potential

What’s meant when a solution is described to be Higher in solutes?

A

Its less water concentrated

67
Q

2.1.5 Biological Membranes: Solute Potential

What’s meant by Solute Potential?

Affected by the amount of solute it contains

A

The greater the amount of solute, the lower the solute potential
↳ water molecules bind to solute molecules
↳ reducing number of water molecules that are free to diffuse

68
Q

2.1.5 Biological Membranes: Pressure Potential

What’s meant by Pressure Potential?

Affected by the pressure applied to it

A

The greater the pressure, the higher the pressure potential

69
Q

2.1.5 Biological Membranes: Osmotic Concentration

What’s meant by the term Osmotic Concentration?

A

Relates to the amount of dissolved solutes in a solution

70
Q

2.1.5 Biological Membranes: Osmotic Concentration

What’s an Isotonic Solution?

A

Solutions that have the same OC as the cytoplasm of the cell

71
Q

2.1.5 Biological Membranes: Osmotic Concentration

What’s a Hypertonic Solution?

A

Solutions that have a higher OC than the cytoplasm of the cell

72
Q

2.1.5 Biological Membranes: Osmotic Concentration

What’s a Hypotonic Solution?

A

Solutions have a lower OC than the cytoplasm of the cell

Biology (14 decks)

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