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BIOLOGY AS OCR > Biological Membranes > Flashcards

Biological Membranes Flashcards

1
Q

Outline the phospholipid bilayer

A

1- hydrophobic fatty acid tails ( face Inwards )

2- hydrophilic heads ( on the outside )

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2
Q

What’s the difference between saturated and unsaturated fatty acid tails ?

(4)

A

Saturated fatty acids are straight chained
-no double bonds

  • unsaturated fatty acid tails have kinks in them preventing them form packing closely together
  • at least one C=C
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3
Q

What’s a phospholipid ?

A
  • hydrophilic (head)
  • hydrophobic ( tail )
  • glycerol -2 fatty acid chains and a phosphate group ( hydrophilic )
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4
Q

Why is the fluid mosaic model used to describe the cell membrane ?
(2)

A
  • Bilayer = fluid ( constantly moving

- protein molecule scattered through the molecule like tiles in a Mosaic .

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5
Q

What can diffuse through the bilayer ?

A

Lipid soluble small molecules

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6
Q

What is the function of plasma membrane ?

4

A
  • barrier between cell and outside
  • partially permeable allows it to let some molecules in and other out
  • recognition by other cells
  • cell communication
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7
Q

What is the function of membranes within cells ?

5

A
  • divide the organelle and cytoplasm
  • form vesicles
  • control what enters and leaves the organelle
  • membranes within organelle =barrier between membrane and rest of the organelle ( thylakoids membranes )
  • site of chemical reactions
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8
Q

What is cholesterol ?

A
  • cholesterol is a lipid
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9
Q

What is the function of cholesterol and where does is fit ?

3

A

Function : maintain fluidity
(Buffer for temperature )

  • cholesterol fits between the phospholipid, causing them to pack more closely = less fluid and more rigid
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10
Q

What is the function of glycolipids , Glycoproteins ?

4

A
  • stabilise the membrane by forming hydrogen bonds with surrounding water molecules
  • sites where drugs , hormones , antibodies bind
  • receptors (cell signalling )
  • antigens- involved in immune response .
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11
Q

How do Neurones have specialised membranes ?

2

A
  • protein channels ( move ions so electrical impulses are conducted )
  • Myelin sheath
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12
Q

How to White blood cells have specialised membranes ?

1

A
  • special protein receptors to recognise antigens / foreign cells
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13
Q

How are root hairs cells specialised ( membrane wise) ?

1

A
  • many carrier proteins ( active transport of nitrate ions )
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14
Q

What can pass via simple diffusion ?

3

A
  • O2
  • CO2
  • lipid soluble molecules (steroids )
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15
Q

How do water molecules pass through the membrane ?

2

A
  • some diffuse through the bilayer

- Specific water channels- Aquaporins

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16
Q

How is the concentration maintained ?

1

A
  • many of the molecules are used up in metabolic reactions to keep molecules moving
17
Q

What factors make diffusion faster ?

5

A 
1- high temp 
2-large SA
3-Small size of diffusing molecules 
4-concentration gradient = steep
5-small diffusion distance
18
Q

Where does water move in Osmosis ?

1

A
  • high water potential to low water potential
19
Q

What is it called when a plant cell is completely filled with water? How does this effect osmosis?
(2)

A
  • Turgid

Cell wall high pressure ( less water can come in now )

20
Q

What happens when an animal cell bursts?

1

A
  • Cytolysed
21
Q

What is it called when the plant cell shrinks ?

A
  • plasmolysed
22
Q

What happens when animal cells shrink ?

1

A
  • no water leads to the cell being Crenated
23
Q

What’s active transport ?

1

A
  • movement of substances against concentration gradient
24
Q

What kind of transport is endo/exocytosis ?
What does It require ?
(2)

A
  • bulk active transport

- requires ATP

25
Q

How does the sodium potassium pump work ?

5

A

1-3 Na+ bind to cytoplasmic side of protein
2-ATP=ADP+P
Phosphorus binds to protein
3-phosphorylation of the protein = conformational change so Na+ is released on to the outside
4-2 K+ binds to sure in the outside
5- Phosphorus is released = shape change and k+ is released into the cell

26
Q

What’s endocytosis ?

1

A

Bulk transport into cell via vesicles

27
Q

What’s the process of exocytosis ?

3

A
  • vesicles moves to membrane
  • membrane fuses with the vesicles walls
  • fused sites opens and contents are released to the outside
28
Q

What happens to the Phospholipid bilayer when temp decrease ?
(3)

A

1- saturated fatty acids = compressed
2- unsaturated fatty acids maintain fluidity ( kink in tails)
3-cholesterol = buffet prevents the tails from getting to close and hence prevents the membrane form being too rigid

29
Q

What happens when you increase the temp ( bilayer ) ?

2

A
  • phospholipids gain KE

- Permeability increase

30
Q

What happens to proteins in higher temperature ?

4

A
  • large molecule vibrate
  • H bonds break
  • ionic bonds break
  • Unfold to give primary structure = denatured
31
Q

What do proteins do in the membrane ?

A
  • pores / channels
  • carrier
  • extrinsic and intrinsic proteins
  • facilitated diffusion
  • diffusion
32
Q

How does cell signalling work ?

5

A 
1- release signal via exocytosis
2-Glycoproteins / lipids = receptors 
3-shape receptor (signal is specific )
4-conformational change of glycoproteins or glycolipid 
5-molecule enters cell
33
Q

How do vesicles work ?

3

A

1-microtubules provide pathway
2-vesicles move across this pathway
3-ATP used

34
Q

Where does the sodium potassium pump work ? Cell ?

1

A
  • Neurones
35
Q

How does water move into the plant ?

1

A

Osmosis

36
Q

How do you make experiment more reliable ?

1

A
  • repeat and find average
37
Q

How do you make experiment more accurate ? (1)

A

Smaller gap between measurements of independent variable ( ie : smaller gap between concentrations )

BIOLOGY AS OCR (12 decks)

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