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OCR BIOLOGY (MODULE 2) > BIOLOGICAL MEMBRANES > Flashcards

BIOLOGICAL MEMBRANES Flashcards

1
Q

What are the roles of cell membrane

A
  • separates cell contents from environment
  • selectively permeable, allows certain molecules through
  • cell to cell attachment- forms tissue
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2
Q

What are the roles of membranes inside cells

A

Isolated enzymes (might damage cell eg. Lysosomes)
Isolated DNA in eukaryotes
Internal transport system provided
COMPARTMENTALISATION (isolate organelles)

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3
Q

What is the function of phospholipids?

A

Gives membrane fluidity
Barrier to large water soluble molecules and ions
Unsaturated fatty acids=kinks in tail=prevention of close packaging=movement

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4
Q

What is the structure of proteins?

A

Alpha helix proteins (coils)
Intrinsic (all way through membrane)
Extrinsic (one side of membrane)

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5
Q

What is the function of proteins?

A

Structural support

Transport- channel proteins, carrier proteins

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6
Q

What is the function of cholesterol?

A

Fits between fatty acid tails, making the barrier complete (without would be too permeable)

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7
Q

What’s a glycolipid?

A

Carbohydrate chains attached to phospholipids

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8
Q

What is a glycoproteins?

A

Carbohydrate chains attached to proteins

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9
Q

Function of glycocalyx?

A

Helps cells adhere to one another, forming tissues

Forms hydrogen bonds with water to stabilise the membrane

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10
Q

Max magnification of light and electron microscope

A

X2000 nm

X200,000 nm

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11
Q

Max resolution of light and electron microscope

A

200nm
TEM 0.2nm
SEM 2nm

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12
Q

How does temperature change the membrane?

A

Increase in temp=increase in KE
Increase in movement=increase in permeability, as membrane has more fluidity

Phospholipids vibrate causing them to move further apart=larger gaps allowing larger molecules to pass through=increases permeability

Very high temps=phospholipid completely moves apart causing membrane to break down

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13
Q

What are the effects of organic solvents on membrane permeability?

A

Organic solvent are less polar than water and can dissolve lipids
Ethanol dissolves lipids in the cell membrane=membrane loses structure
-very strong alcohol solution, will destroy cells
Increase the conc. of the solvent will increase permeability of membrane

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14
Q

Definition of diffusion (passive process)

A

NET movement of molecules or ions from a region of high concentrations to a region of lower concentration-down a concentration gradient

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15
Q

What are factors affecting the rate of diffusion?

A

Temperature-increase temp=increase in KE-molecules move faster
Surface area-when increased, more molecules or ions move across the membrane so diffusion is faster
Type of molecule-larger=slower as energy needed to break it down first. Non polar molecules diffuse quicker over phospholipid bilayer

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16
Q

What is simple diffusion?

A 
Movement directly to the phospholipid bilayer between phospholipids
Examples:
Small molecules:
-CO2
-H2O
-O2
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17
Q

What is the definition of facilitated diffusion?

A

Passive movement of molecules or ions through a channel or carrier protein from high to low concentration

18
Q

Description of channel proteins and examples

A 
Specific to certain ions, certain shape and size (polar molecules)
Examples:
-sodium ion channels
-calcium ion channels
Channel proteins have hydrophilic lining
Sometimes gated=open or closed
19
Q

Description of carrier proteins and examples

A

For specific large polar molecules (eg: glucose)
Examples:
-glucose
-amino acids
When the specific molecules bind to the protein, it changes shape and allows it to cross the membrane

20
Q

Definition of osmosis (passive process)

A

Special form of diffusion involving water
NET movement of water molecules from high to low water potential (down a water potential gradient) across a partially permeable membrane

21
Q

What is a solute?

A

Substance that dissolves in a liquid to form a solution

22
Q

What is a solvent?

A

Liquid in which a solute dissolves

23
Q

What is a solution?

A

The ,mixture formed when a solute has dissolved in a solvent

24
Q

What is the water potential of pure water?

A

0

25
Q

What is water potential measured in?

A

kPa

26
Q

In animal cells, what’s the effect on the cell with a low water potential?
(concentrated sugar solution)

A
  • reduction in cell volume
  • cytoplasm becomes concentrated
  • cell dies if too much water lost
27
Q

In animal cells, what’s the effect on the cell with a high water potential?
(pure water)

A
  • pressure inside cell will increase

- no cell wall to prevent lysis (cell bursting)

28
Q

In plant cells, what’s the effect on the cell if there’s a low water potential (concentrated sugar solution)?

A

Full plasmolysis=cytoplasm tears away from cell wall, cell dies if membrane rips
Volume of cells will decrease

29
Q

In plant cells, what’s the effect on the cell if there’s high water potential (pure water)?

A
  • turgid (important in photosynthesis as if leaves wilt, surface area is lost)
  • cell wall stops cell bursting
30
Q

Definition of active transport

A

Movement of molecules or ions through carrier proteins across ,membranes against their concentration gradient, using energy from ATP

31
Q

What are examples of active transport?

A

Roots-magnesium ions taken in for chlorophyll
Intestine (villi)-removal of glucose from gut into blood
Kidney-useful molecules reabsorbed (eg: glucose)

32
Q

How is active transport different to facilitated diffusion?

A
  • moves against concentration gradient
  • uses energy (ATP)
  • specific molecules are passed one way
33
Q

What is active transport affected by?

A
  • temperature (more KE)
  • oxygen concentration (needed for aerobic respiration=ATP)
  • poison (stops/kills cells=no respiration)
  • lots of mitochondria (aerobic respiration)
34
Q

What are examples of bulk transport?

A

Hormones-pancreatic cells make insulin. Processed and packaged into vesicles in Golgi-vesicles fuse with outer membrane to release insulin into blood
Plant cells-materials required to build the cell wall are carried outside in vesicles
Phagocytes-engulf invading microorganisms forming vesicles around them. Vesicles fuse with lysosomes, contain hydrolytic enzymes that can break down and digest microorganisms

35
Q

What is endocytosis?

A

The bulk movement of material into a cell

36
Q

What is exocytosis?

A

Bulk movement out of a cell

37
Q

What is phagocytosis?

A

‘cell eating’ solid material

  • bacteria bins to receptors on membrane
  • membrane folds engulfing bacteria
  • membrane fuses with itself, forming a vesicle
  • vesicle moves through cytoplasm along microfilaments (ATP required)
  • vesicle fuses with a lysosome
38
Q

What is pinocytosis?

A

‘cell drinking’ liquid material

39
Q

What is bulk transport needed for?

A

Moving large molecules

40
Q

What happens during bulk transport?

A

Whole membrane changes and moves, vesicle membrane becomes part of the cell surface membrane

41
Q

How is active transport different to facilitated diffusion?

A
  • moves against the concentration gradient
  • uses energy (ATP)
  • specific molecules are passed one way
42
Q

What are the stages to cell signalling?

A
  • first message (eg: hormone)
  • second messenger (eg: cyclic AMP)
  • activation of energy (cascade effect)

OCR BIOLOGY (MODULE 2) (6 decks)

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