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A-Level Biology- Y12 > 3.2.3- Cell Transport > Flashcards

3.2.3- Cell Transport Flashcards

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1
Q

What is the fluid mosaic model?

A

describes the arrangement of the molecules that make up a cell membrane and its structure

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2
Q

Why is it called the fluid mosaic model?

A

The phospholipid bilayer fluid as molecules move in membrane and proteins scattered in mosaic pattern. Selectively permeable

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3
Q

Semipermeable

A

some substances can pass directly through the cell membrane by passive or active transport

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4
Q

Hydrophilic head

A

Attracted to water

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5
Q

hydrophobic tails

A

water hating

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6
Q

Can lipid soluble substances (O2 & CO2) pass through the phospholipid bilayer?

A

Yes. Small and dissolve in lipids

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7
Q

Can Fatty acids pass through the phospholipid bilayer?

A

Yes. Same properties as the membrane

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8
Q

Can large molecules pass through the membrane?

A

No. They are too large to fit through the selective barrier

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9
Q

Can water soluble ions pass through the membrane?

A

No. They are I water so are repelled by hydrophobic tail

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10
Q

Can polar molecules pass through a membrane?

A

No. Charged molecules like to interact with the head and don’t like the non-polar inside

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11
Q

Phospholipid bilayer

A

Barrier. Prevents passage of large or polar/hydrophilic substances.

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12
Q

Intrinsic proteins

A

Extend from one side of the membrane to the other. Channels that pass through the bilayer and allow passage of specific molecules

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13
Q

Extrinsic proteins

A

Proteins on the surface of the bilayer. Allow cell to cell interactions, recognition, signalling and cell adhesion

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14
Q

Glycoprotein

A

A protein with one or more carbohydrates covalently attached to it (a carbohydrate chain).

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15
Q

Glycolipid

A

a lipid with one or more covalently attached carbohydrates (a carbohydrate chain).

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16
Q

Cholesterol

A

Between phospholipid molecules. Hydrophobic. Increases strength and stability while reducing fluidity.

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17
Q

Explain how 3 features of a plasma membrane adapt it for its functions. (6)

A
  • Phospholipid bilayer acts as a barrier- To prevent polar substances from entering the cell

Membrane contains cholesterol- Increases the strength and stability of the membrance

Glycoproteins- Act as receptors

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18
Q

Diffusion

A

the movement of particles from an area of high to low concentration down a concentration gradient until equilibrium is met

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19
Q

3 factors affecting diffusion

A

concentration gradient, temperature, surface area

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20
Q

Fick’s Law- description

A

a relationship between the rate of diffusion at constant temperature and 3 variables.

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21
Q

Fick’s Law

A

Rate of diffusion is proportional to SA x Diff in conc gradient / length of diff pathway

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22
Q

What happens to rate of diffusion when conc gradient increases?

A

Diffusion rate increases. This is because there is a greater difference between the 2 concs so more space for the molecules to move.

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23
Q

What happens to diffusion rate when length of diffusion pathway increases?

A

the longer the pathway the lower the diffusion rate as there is a further distance for molecules to travel

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24
Q

What happens to diffusion rate when surface area increases?

A

increases the rate of diffusion as there is more surface for substance movement

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25
Q

What type of process is diffusion?

A

Passive process (doesn’t require energy)

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26
Q

facilitated diffusion

A

a form of diffusion using an intrinsic protein.

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27
Q

When is facilitated diffusion required?

A

when substances cannot freely move across the membrane such as charged, large, water molecule.

28
Q

What does facilitated diffusion require?

A

Carrier or channel proteins. Each protein is specific to the ion

29
Q

Intrinsic proteins in facilitated diffusion

A

Have a specific tertiary structure and so do ions. They are complementary to one another.

30
Q

Active Transport

A

the movement of ions or molecules across a cell membrane (from low to high concentrations). Requires energy released via respiration

31
Q

Active transport in root hair cell

A

Mineral ions from soil actively transport into root. Required for growth

32
Q

Active transport in the intestine

A

Glucose in intestine actively transports into blood, required for respiration

33
Q

Channel proteins

A

have a hydrophilic channel that certain molecules or ions (water soluble) can use as a tunnel. Water filled tubes. Selective due to specific quarternary structure

34
Q

Carrier proteins

A

Move large molecules and can change shape. Required for active transport and facilitated diffusion.

35
Q

State 1 similarity and 1 difference between active transport and facilitated diffusion

A

Similarity- both require carrier proteins

Difference- only facilitated needs channel proteins

36
Q

Saturated

A

All intrinsic proteins are occupied so no more ions can move across the membrane

37
Q

Explain the process of active transport

A

1.Molecule binds to the carrier protein If complementary to its shape

2.ATP donates a phosphate molecules

  1. Carrier protein is phosphorylated
  2. Phosphorylation changes the tertiary structure
  3. The solute is moved AGAINST its gradient
38
Q

Phosphorylation

A

the addition of a phosphate group to a molecule

39
Q

How do we maximise diffusion rate?

A

Increase SA, steep concentration gradient, mitochondria, short diffusion pathway, more carrier/channel proteins

40
Q

small intestine structure

A

Duodenum- most digestion (connected to stomach)

ileum- absorption of nutrients & water (end of intestine)

41
Q

What moves through the small intestine?

A

Vitamins and minerals, glucose, proteins

42
Q

Why do substances have to be moved out of the ileum?

A

Have to be absorbed or the body will excrete it

43
Q

Ileum adaptations

A

Increased surface area

Large number of intrinsic proteins

Conc gradient maintained

44
Q

Increased SA

A

Villi and Microvilli mean that there is more space for diffusion and other forms of transport

45
Q

Villi

A

Tiny finger-shaped structures that cover the inner surface of the small intestine/ileum

46
Q

Microvilli

A

projections that increase the cell’s surface area for absorption. On the epithelial cells

47
Q

Large number of intrinsic proteins

A

More Channel and carrier proteins mean there’s less chance of saturation and increased rate of facilitated diffusion and AT

48
Q

Conc gradient is maintained

A

Muscle layer increases the rate of digestion. More glucose in the lumen compared to the blood means glucose can diffuse and conc gradient is maintained

49
Q

What is co-transport?

A

The coupled movement of one molecule with its concentration gradient and another against its conc gradient using a co-transporter protein

50
Q

What does co-transport prevent?

A

Prevents glucose from being removed from our bodies

51
Q

What is the sodium potassium pump?

A

an active transport mechanism in the plasma membrane. Type of carrier protein transporting 3 sodium ions out of the cell and 2 potassium ions into the cell. Maintains internal concentrations

52
Q

What type of transport is Co-transport?

A

Type of indirect active transport

53
Q

What happens in co-transport?

A

Na+ is actively transported out of epithelial cell into blood- reducing concentration of sodium ions. More Na+ ions then diffuse down the conc gradient from the lumen and into the epithelial cell. A co-transporter protein is used to move glucose or amino acids into epithelial cells against the conc gradient. The glucose then moves by facilitated diffusion into blood.

54
Q

Osmosis

A

The net movement of water molecules from region of higher water potential to a region of lower water potential through a partially/semi-permeable membrane

55
Q

Difference between facilitated diffusion and active transport

A

Facilitated diffusion is a PASSIVE PROCESS and does not require energy, while active transport needs energy.

FD uses carrier and channel proteins

AT uses carrier only

56
Q

Isotonic

A

when the concentration/ water potential of two solutions is the same

57
Q

Hypotonic

A

Having a lower concentration of solute & higher water potential surrounding the cells/outside the cells compared to within them. Water moves into the cell

58
Q

Hypertonic

A

Having a higher concentration of solute & lower water potential outside the cell than inside the cell. Water moves out of cell from a pure water solution to a less pure water solution.

59
Q

Where does osmosis occur?

A

across a selectively permeable membrane in cells

60
Q

What is water potential?

A

Pressure created by water molecules measured in kPa. Any solutions have negative values

61
Q

lysed cell

A

Hypotonic solutions- water moves into a cell, enlarges it and causes osmotic lysis

62
Q

Normal cell

A

isotonic solution- water moves in and out and cells stays the same and maintains its shape.

63
Q

Shrivelled cell

A

Hypertonic solution- water moves out the cell so it shrinks and shrivels

64
Q

plasmolyzed cell

A

extreme water loss; cell membrane separates from cell wall because of a hypertonic solution

65
Q

Flaccid cell

A

Isotonic solution- water moves in and out and stays the same

66
Q

Turgid cell

A

Hypotonic solution- cell membrane pushed against cell wall and the vacuole swells.

A-Level Biology- Y12 (14 decks)

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