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

3.2.3- Cell Transport Flashcards

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
What type of process is diffusion?
Passive process (doesn't require energy)
26
facilitated diffusion
a form of diffusion using an intrinsic protein.
27
When is facilitated diffusion required?
when substances cannot freely move across the membrane such as charged, large, water molecule.
28
What does facilitated diffusion require?
Carrier or channel proteins. Each protein is specific to the ion
29
Intrinsic proteins in facilitated diffusion
Have a specific tertiary structure and so do ions. They are complementary to one another.
30
Active Transport
the movement of ions or molecules across a cell membrane (from low to high concentrations). Requires energy released via respiration
31
Active transport in root hair cell
Mineral ions from soil actively transport into root. Required for growth
32
Active transport in the intestine
Glucose in intestine actively transports into blood, required for respiration
33
Channel proteins
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
Carrier proteins
Move large molecules and can change shape. Required for active transport and facilitated diffusion.
35
State 1 similarity and 1 difference between active transport and facilitated diffusion
Similarity- both require carrier proteins Difference- only facilitated needs channel proteins
36
Saturated
All intrinsic proteins are occupied so no more ions can move across the membrane
37
Explain the process of active transport
1.Molecule binds to the carrier protein If complementary to its shape 2.ATP donates a phosphate molecules 3. Carrier protein is phosphorylated 4. Phosphorylation changes the tertiary structure 5. The solute is moved AGAINST its gradient
38
Phosphorylation
the addition of a phosphate group to a molecule
39
How do we maximise diffusion rate?
Increase SA, steep concentration gradient, mitochondria, short diffusion pathway, more carrier/channel proteins
40
small intestine structure
Duodenum- most digestion (connected to stomach) ileum- absorption of nutrients & water (end of intestine)
41
What moves through the small intestine?
Vitamins and minerals, glucose, proteins
42
Why do substances have to be moved out of the ileum?
Have to be absorbed or the body will excrete it
43
Ileum adaptations
Increased surface area Large number of intrinsic proteins Conc gradient maintained
44
Increased SA
Villi and Microvilli mean that there is more space for diffusion and other forms of transport
45
Villi
Tiny finger-shaped structures that cover the inner surface of the small intestine/ileum
46
Microvilli
projections that increase the cell's surface area for absorption. On the epithelial cells
47
Large number of intrinsic proteins
More Channel and carrier proteins mean there's less chance of saturation and increased rate of facilitated diffusion and AT
48
Conc gradient is maintained
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
What is co-transport?
The coupled movement of one molecule with its concentration gradient and another against its conc gradient using a co-transporter protein
50
What does co-transport prevent?
Prevents glucose from being removed from our bodies
51
What is the sodium potassium pump?
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
What type of transport is Co-transport?
Type of indirect active transport
53
What happens in co-transport?
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
Osmosis
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
Difference between facilitated diffusion and active transport
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
Isotonic
when the concentration/ water potential of two solutions is the same
57
Hypotonic
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
Hypertonic
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
Where does osmosis occur?
across a selectively permeable membrane in cells
60
What is water potential?
Pressure created by water molecules measured in kPa. Any solutions have negative values
61
lysed cell
Hypotonic solutions- water moves into a cell, enlarges it and causes osmotic lysis
62
Normal cell
isotonic solution- water moves in and out and cells stays the same and maintains its shape.
63
Shrivelled cell
Hypertonic solution- water moves out the cell so it shrinks and shrivels
64
plasmolyzed cell
extreme water loss; cell membrane separates from cell wall because of a hypertonic solution
65
Flaccid cell
Isotonic solution- water moves in and out and stays the same
66
Turgid cell
Hypotonic solution- cell membrane pushed against cell wall and the vacuole swells.

A-Level Biology- Y12 (14 decks)

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