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A Level: Biology > Biological Membranes > Flashcards

Biological Membranes Flashcards

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1
Q

Name four components of the fluid mosaic Model of cell surface membrane

A

Fluid- phospholipids and proteins are free to move relative to each other - gives membrane flexibility

Mosaic- proteins are scattered and randomly arranged between the phospholipids

Intrinsic proteins- extended throughout the bilayer

Extrinsic proteins, partly embedded in bilayer they sit inside or outside the cell

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2
Q

Name all the parts of the plasma membrane

A 
Glycolipid
Glycoprotein
Channel protein (intrinsic)
Cholesterol
Phospholipid bilayer
Carrier protein (intrinsic)
Phosphate head-hydrophilic 
Fatty acid tails-hydrophobic
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3
Q

What is the difference between a polar molecule and an ion

A

Ions have a full charge - molecules which have lost or gained electrons (Cl-)

Polar molecules- have an uneven distribution of charge across them (H20)

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4
Q

Describe the phospholipids the form the bilayer

A

Hydrophobic fatty acid tails pointing inwards and hydrophilic phosphate heads pointing outwards

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5
Q

What is the purpose of the hydrophobic region

A

To ensure that the fatty acids don’t come into contact with the water

And to separate aqueous regions from the inside and outside of the cell

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6
Q

What is the purpose of the phospholipid

A

To prevent legs molecules from leaving or entering the cell

Allows flexibility

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7
Q

What is cholesterol

A

A steroid molecule which fits within the bilayer between the fatty acid tails

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8
Q

What is the job of cholesterol

A

Increases the packing of the membrane and so reducing fluidity

Stabilises the membrane

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9
Q

What are the two main groups of proteins

A

Intrinsic proteins, eg channel proteins

Extrinsic proteins eg enzymes

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10
Q

Describe intrinsic proteins

A

embedded through both layers of the bilayer

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11
Q

Describe extrinsic proteins

A

Present on only one side of the bilayer

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12
Q

What is the job of channel proteins

A

To transport ions by facilitated diffusion, allow specific ions through, can be gated so can open and close in specific circumstances

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13
Q

What is the job of a carrier proteins

A

Only allow specific large molecules to pass through , when it binds it changes the shape and transfers the molecule to the other side of the membrane

( active transport of water soluble molecules and charged ions uses ATP)

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14
Q

What does gated mean and what does this apply to

A

Can open and close in specific circumstances

Channel proteins

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15
Q

What are:
A) glycoproteins
B) glycolipids

A

Glycoproteins are proteins with a carbohydrate chain attached

Glycolipids are lipids with carbohydrates attached

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16
Q

What are glycoproteins used in

A

Cell adhesion and receptors for cell signalling

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17
Q

What are glycolipids used for

A

Cell antigens used to recognise cells as self or non self

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18
Q

What is the role of the cell surface membrane:

A
  • separates cell content from external environment
  • cell signalling
  • cell recognition
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19
Q

What are the jobs of membranes inside of cells

A
  • compartmentalisation
  • site of chemical reaction
  • provides an attachment site for enzymes
  • form vesicles for the transport of proteins
  • attachment site for pigment
  • membranes allow cellular compartment to have different conditions
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20
Q

What is cell signalling

A

The process that leads to communication and coordination between cells, so they can work together to trigger a response

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21
Q

What occurs during cell signalling

A

A receptor in the cells plasma membrane picks up signals

The signal will be in the form of a hormone or chemical mediators binding to the receptor

The binding to receptor brings about the appropriate response within the cell

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22
Q

Describe the structure and function of hormone receptors

A

protein and glycoproteins receptors found sticking out from target cells have a specific shape which is complimentary only to the shape of a specific hormone

The hormone binds to the receptor allowing the cell to respond appropriately

23
Q

What is insulin

What’s it job

A

A blood based hormone

To lower blood glucose concentration levels

24
Q

What happens when blood glucose levels gets too high

A

The pancreas secretes insulin which is carried in the blood

insulin binds to the insulin
receptor on liver or muscle cells which causes a chemical to be released which causes more glucose transport proteins to be inserted into the membrane increasing facilitated diffusion of glucose into cells

Also activated enzymes that convert glucose into glycogen for storage

25
Q

What do histamines do

A

When the skin is damaged they are released to increase blood flow to an area making capillaries more permeable to phagocytes

26
Q

What is diffusion

A

The net passive movement of particles down a concentration gradient from higher to lower concentration

27
Q

Does Diffusion require ATP

A

No because it is a passive process

28
Q

When will diffusion stop

A

One in equilibria am is reached

29
Q

What molecules use diffusion

A

Small lipid soluble and nonpolar molecules

30
Q

Name six factors which affect the rate of diffusion

What is this known as

A

Temperature

Concentration gradient

Stirring motion

Surface area

Diffusion distance

Size of molecule

(Ficks Law)

31
Q

What is facilitated diffusion

A

Net Passive movement of polar molecules or ions from a high area of concentration to an area of lower concentration down a gradient across a membrane via a carrier or channel protein

32
Q

Give examples of what…. allow through during facilitated diffusion

Channel proteins
Carrier proteins

A

Specific ions

Large molecules (glucose n amino acids)

33
Q

Define active transport

A

Movement of molecules or ions against a concentration gradient from a lower to a higher concentration using ATP and a carrier protein

34
Q

What transport protein is used in active transport

A

Carrier protein

35
Q

What does atp do to the carrier protein

A

ATP changes the shape of the carrier protein to ensure one way flow

36
Q

What is endocytosis

A

The bulk movement of substances into the cell with ATP, substances have part of the membrane surrounding them which then pinches off to form a vesicles inside of the cell

37
Q

Explain the process of endocytosis

A

Cell surface membrane bends onwards when it comes into contact with material

The membrane engulfs the material, it fused together and the vesicle is formed

The vesicle pinches off and moved into the cytoplasms

Vesicle moves towards a lysosome where the bacteria is digested

38
Q

What is exocytosis

A

The bulk movement of substances out of the cell with ATP, inside the cell vesicles containing substances fuse with the plasma membrane releasing material outside the cell

39
Q

Explain the process of exocytosis

A

Vesicles dude with the membrane, the contents are released outside the cell, this vesicle would be formed by the Golgi apparatus

40
Q

Define osmosis

A

The movement of water molecules form a dilute to a concentrated solution across a partially permeable membrane

41
Q

What is the water potential

A

A measure of the tendency of water molecules to diffuse from one place to another

42
Q

What is the units for water potential

A

KiloPascals (kPa)

43
Q

What is the water potential of pure water

A

0kPA

44
Q

The more dilute dissolved in water…..

A

The lower the water potential (more negative)

Because more molecules cluster around the solute and so are not free to move

45
Q

Which has the higher water potential:

  • 10kpa
  • 20kpa
A

-10kpa is higher

46
Q

What occurs in osmosis in terms of water potential

A

Water moved from an area of higher water potential to lower water potential

47
Q

What is an isotonic solution

A

The solution surrounding the cell has the same water potential as the cell

48
Q

What is a hypertonic solution

A

the cell has a higher water potential than The solution surrounding the cell

49
Q

What is a hypotonic solution

A

The inside of the cell has lower water potential than the outside of the cell

50
Q

What’s the word used to describe a …… in a plant and animal cell

Isotonic solution

A

Animal: normal
Plant: flaccid

51
Q

What’s the word used to describe a …… in a plant and animal cell

Hypotonic solution

A

Animal- lysed

Plant- turgid

52
Q

What’s the word used to describe a …… in a plant and animal cell

Hypertonic solution

A

Animal- shrivelled (crenated)

Plant-shrivelled (plasmolysed)

53
Q

How does temperature affect membrane structure

A

The higher the temperature the more kinetic energy the phospholipids have so they move more

Membrane becomes too fluid and loses its structure - increasing permeability

Proteins can become denatured

54
Q

Name a organic solvent which can dissolve membranes

A

Alcohol

A Level: Biology (18 decks)

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