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Wjec Biology As Unit 1 > 1.3 > Flashcards

1.3 Flashcards

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1
Q

Why do phospholipids form a bi-layer in water and describe how they’re arranged

A

Due to the hydrophilic head and hydrophobic tails
Polar heads face outwards interacting with water outside the cell and inwards interacting with the water in the cytoplasm

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2
Q

What is an extrinsic protein

A

Found on either surface of the bilayer

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3
Q

Function of extrinsic proteins

A

Act as receptors for hormones and as recognition sites

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4
Q

What is an intrinsic protein

A

Proteins that are found within the membrane and extend across both layers

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5
Q

What are the 2 kinds of intrinsic proteins

A

Channel and carrier

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6
Q

Why is the membrane said to be representative of the fluid-mosaic model?

A

Fluid - phospholipids are free to move

Mosaic - random assortment of protein molecules

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7
Q

Animal or plant cell membrane contains cholesterol and what does it do

A

Animal

Stabilises the membrane

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8
Q

Function of glycoproteins

A

Act as antigens

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9
Q

Function of glycolipids

A

Act as receptor sites for molecules eg hormones

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10
Q

What kind of molecules pass through simple diffusion

A

Non-polar molecules and small molecules

They can dissolve in the fatty acid tail and diffuse across the membrane

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11
Q

What is diffusion

A

The passive movement of molecules from a high concentration to a low concentration until they’re equally distributed

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12
Q

What does passive mean

A

Doesn’t require ATP

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13
Q

Does simple diffusion transport individual molecules

A

Yes

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14
Q

Factors affecting diffusion

A
  • concentration gradient
  • diffusion distance
  • surface area of the membrane
  • thickness of the exchange surface
  • increase in temperature
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15
Q

How does increase in concentration gradient affect rate of diffusion

A

More molecules can diffuse in a given time so collisions with membrane are more likey

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16
Q

How does decrease in diffusion distance increase rate of diffusion

A

Less time for molecules to diffe

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17
Q

How does increase in surface area of the membrane increase rate of diffusion

A

More molecules can diffuse in a given time

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18
Q

How does thickness of the exchange surface affect rate of diffusion

A

Increases with a shorter distance as less time is taken to diffuse

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19
Q

How does increase in temperature increase rate of diffusion

A

Molecules possess more kinetic energy so they move faster and collide with the membrane more frequently

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20
Q

Graph of simple diffusion is

A

Directly proportional

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21
Q

What kind of molecules pass through facilitated diffusion?

A

Polar, water soluble and large

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22
Q

What is facilitated diffusion

A

Passive transfer of molecules/ions down a concentration gradient, across a membrane, by transport proteins in the membrane

23
Q

Which kind of intrinsic protein allows charged molecules through

A

Channel

24
Q

Which kind of intrinsic protein allows large and water soluble molecules through

A

Carrier

25
Q

What is active transport

A

Movement of ions/molecules across the membrane from a low to high concentration against the concentration gradient, this is an ATP requiring process
Carrier proteins

26
Q

How does cyanide affect active transport?

A

Prevents aerobic respiration and ATP production

Without ATP active transport cannot occur

27
Q

Why does the graph of facilitated diffusion and active transport plateau after a while

A

The proteins are saturated

28
Q

What is co-transport

A

Type of facilitated diffusion that brings molecules + ions into cells together on the same carrier protein

29
Q

Example of co-transport

A

Glucose and sodium ions

Mechanism by which glucose is absorbed in the ileum of mammals

30
Q

What is osmosis

A

the net passive diffusion of water molecules across a selectively
permeable membrane from a region of higher water potential to a region of lower water potential.

31
Q

What is water potential

A

A measure of the tendency of water molecules to move from a high to low concentration of water

32
Q

What is pressure potential

A

represents the pressure exerted by the cell contents on the cell wall.
It can be OkPa or higher.

33
Q

What does a turgid plant cell mean

A

the plant cell can hold no more

water, as the cell wall cannot expand further.

34
Q

What is a hypertonic solution

A

Has a lower water potential than the solution inside the cells
Water flows out of the cell

35
Q

What is a hypotonic solution

A

Higher water potential than the solution inside the cell

Water flows into the cell

36
Q

What is an isotonic solution

A

Has the same water potential to the solution inside the cell

No net water movement

37
Q

What is solute potential

A

Concentration of dissolved substance in the cell vacuole

38
Q

When is a plant cell said to be flaccid and how does it happen

A

When plasmolysis is complete

When a plant cell is in a hypertonic solution so the vacuole shrinks and cytoplasm draws away from the cell wall

39
Q

What is the point of incipient plasmolysis

A

Point at which the cell membrane just begins to move away from the cell wall

40
Q

What is the pressure potential during incipient plasmolysis

A

0 kPa

41
Q

What is the solute potential during incipient plasmolysis

A

= water potential

42
Q

Why is being turgor important in plants - especially young seedlings

A

It provides support

Maintains their shape and holds them upright

43
Q

What % of cells are plasmolysed during incipient plasmolysis

A

50

44
Q

What will happen to red blood cells in a hypotonic solution

A

Haemolysis - burst

45
Q

What will happen to red blood cells in a hypertonic solution

A

Said to be crenated

46
Q

Why will animal cells burst but not plant

A

Lack of cell wall to resist bursting

47
Q

What are 3 factors that affect permeability of membrane

A

Temperature , pH and ethanol

48
Q

How does temperature and pH beyond normal range affect permeability

A

Denature the membrane’s proteins which makes gaps in the membrane and it is far more permeable

49
Q

How does ethanol increase permeability of the membrane

A

Dissolves the lipid components of the membrane and makes holes in it

50
Q

Which kind of transport doesn’t transport molecules or ions individually

A

Bulk - endocytosis and exocytosis

51
Q

What does endocytosis involve

A

Engulfing of the material by infolding of the plasma membrane bringing it into cell enclosed within a vesicle

52
Q

What are the 2 kinds of endocytosis

A

Phagocytosis- solid (that are too large)

Pinocytosis - liquid

53
Q

How does exocytosis work

A

Substances leave the cell after being transported through the cytoplasm in a vesicle

54
Q

Membrane width

A

7-8 nm

Wjec Biology As Unit 1 (7 decks)

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