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Biology - biological molecules + cells > 3.2.3 Transport Across Cell Membranes > Flashcards

3.2.3 Transport Across Cell Membranes Flashcards

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1
Q

What’s diffusion

A

The movement of a substance (gas/liquid) from a high concentration to a low concentration.

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2
Q

What type of process is diffusion

What does it not require

A

It’s a passive process

It doesn’t require ATP

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3
Q

5 factors that affect the rate of diffusion

A 
Concentration gradient
Temperature
Surface area
Thickness of membrane
Distance
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4
Q

5 ways lungs are adapted to allow rapid oxygen exchange between air in the alveoli and blood in the capillaries around them

A

Many alveoli + capillaries so large surface area
Good blood supply around alveoli
Short diffusion path
Ventilation - maintains conc gradient
Flattened epithelium
Concentration gradient - faster diffusion

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5
Q

How can different substances cross a cell surface membrane

A

Diffusion
Osmosis
Active transport
Facilitated diffusion by carrier proteins

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6
Q

Why will only some things pass through plasma membranes

A

As they’re semi-permeable

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7
Q

3 factors that affect the permeability of the cell membrane

A

Temperature
pH
Ethanol

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8
Q

How does temperature affect the permeability of membranes

A

Denatures channel/transport proteins

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9
Q

What does ethanol do to membrane permeability

A

It causes permeability to increase as phospholipids are soluble in alcohol

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10
Q

What type of molecule must you be to diffuse through phospholipids

A

A small molecule (tight together) without a charge

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11
Q

What cells are more succeptible to water damage and why

A

Animal cells as they have no cell wall

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12
Q

What molecules need to use facilitated diffusion to pass through the bilayer

E.g

A

Molecules that aren’t soluble in lipids

Glucose, amino acids (too big), urea, ions

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13
Q

What does facilitated diffusion use

A

Proteins in the membrane

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14
Q

2 types of proteins involved in facilitated diffusion

A

Channel proteins

Carrier proteins

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15
Q

How do carrier proteins allow insoluble substance into cell

A

Changes shape

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16
Q

What type of process is using carrier proteins in facilitated diffusion

What isn’t used

A

Passive

ATP isnt used

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17
Q

Where does the energy come from in facilitated diffusion with carrier proteins

A

The molecules’ kinetic energy

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18
Q

What do carrier proteins have specific for certain substances

A

Binding sites

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19
Q

When substance is attached to carrier protein what does it do

A

Flips + changes shape

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20
Q

What’s a Channel protein like

A

Tube with hole in (tunnel) that’s full of fluid

21
Q

What molecules do channel proteins allow through

A

Larger molecules

22
Q

What’s needed for movement via channel proteins

A

Concentration gradient (high->low concentration)

23
Q

Define osmosis

A

The passive diffusion of water molecules down concentration gradient through a semi permeable membrane from high water potential -> low water potential

24
Q

What’s the movement like in isotonic solutions

What’s the cell like

A

No movement (equilibrium) as it has the same water potential as cell

Cell is normal (flaccid)

25
Q

What’s osmosis like in hypotonic solutions

What happens to cell

A

Hypotonic has higher water potential than cell so water goes into cell

It swells (turgid)

26
Q

What’s osmosis like in hypertonic solutions

What happens to cell

A

Hypertonic has lower water potential than cell so water leaves the cell

It shrivels (dehydrated + plasmolyzed)

27
Q

What are aquaporins

A

Proteins that transport water (in membrane)

28
Q

Define active transport

A

Movement of substances against a concentration gradient from low -> high concentration

29
Q

What does scribe transport require to work (2)

A

Energy from ATP

Transport proteins in membrane

30
Q

What pump is an example of active transport

A

Sodium-potassium pump

31
Q

How does the sodium potassium pump work (6)

A
  1. Sodium in cell bonds to transport protein
  2. ATP attatches to protein and is hydrolysed
  3. The releases energy
  4. Allowing protein to change shape to allow sodium out of cell
  5. Potassium ions outside cell bind to protein
  6. Phosphate group is released + protein returns to original allowing potassium into cell
32
Q

What’s ATP hydrolysed into

A

ADP + P

33
Q

What does energy released from hydrolysis of ATP in sodium-potassium pump allow

A

Allows protein to change shape to allow sodium out of cell

34
Q

What is moved in 1 cycle of the sodium-potassium pump

A

3 sodium out of cell

2 potassium’s into cell

35
Q

3 examples of active transport

A

In small intestine moves glucose to and from blood
Plants move minerals out of soil
Sodium-potassium pump

36
Q

What’s water potential (osmosis) measured in

A

KPa

37
Q

How many KPa is the highest water potential (pure water)

A

0KPa

38
Q

What numbers are lower water potentials

A

Negatives

39
Q

What proteins may osmosis involve

A

Aquaporins

40
Q

What are solutes

A

What is getting dissolved in a solvent to form a solution

41
Q

What curve can estimate an unknown value

A

Calibration curve

42
Q

What’s co-transport

What’s it a type of

A

Moving 2 Substances at the same time

Facilitated diffusion

43
Q

What’s the pump for co-transport in the small intestine

A

The sodium-glucose symporter

44
Q

What has to be done in the sodium-glucose symporte rbefore the molecules can be moved by the protein

A

Both sodium + glucose must bind

45
Q

What makes it easier for the other molecule to bind in the sodium-glucose symporter

A

The binding of 1 molecule

46
Q

What keeps the sodium-glucose symporter moving in the right direction

A

The sodium concentration gradient

47
Q

What would happen due to the sodium-glucose symporter if sodium levels in epithelial cells were allowed to accumulate

How would this allow the co-transport of glucose

A

Sodium would be actively pumped out of the epithelial cells and into the blood by Na/K+ pump

As this maintains the concentration gradient for glucose to pass into the blood via facilitated diffusion

48
Q

What’s the end of the small intestine called

A

The ileum

Biology - biological molecules + cells (16 decks)

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