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Biology Module 2 - Own Flashcards > Membranes - Diffusion , Osmosis, and Active Transport > Flashcards

Membranes - Diffusion , Osmosis, and Active Transport Flashcards

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1
Q

Define diffusion

A

The net movement of particles from an region of higher concentration to a region of lower concentration

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2
Q

Is diffusion active or passive?

A

Passive

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3
Q

Define passive transport

A

Movement of substances that does not require energy

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4
Q

Define osmosis

A

The movement of water from a region of high water potential to a region of low water potential across a partially permeable membrane

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5
Q

Define facilitated diffusion

A

Diffusion across a plasma membrane through protein channels

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6
Q

Is facilitated diffusion passive?

A

Yes

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7
Q

Is osmosis passive or active?

A

Passive

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8
Q

Define active transport

A

The movement of molecules from an area of low concentration of that molecule to an area of high concentration of that molecule. This movement requires ATP

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9
Q

What sort of molecules tend to move via diffusion across a membrane?

A

small molecules (e.g. gases)
lipid soluble molecules
non-polar molecules

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10
Q

How does water tend to move across membranes?

A

Through aquaporins (via osmosis)

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11
Q

Why can steroid hormones easily cross a membrane by simple diffusion?

A

They are lipid soluble
- They are non-polar

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12
Q

Which 2 factors affect the rate of diffusion?

A

Temperature

Concentration difference

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13
Q

What effect does an increase in temperature have on the rate of diffusion?

A

It increases the rate of diffusion

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14
Q

What effect does a greater difference in concentration of two regions have on the rate of diffusion?

A

It increases the rate of diffusion

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15
Q

Why does a higher temperature increase rate of diffusion?

A

higher temperature means particles have more kinetic energy and move at higher speeds

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16
Q

Why is it easier for oxygen to diffuse across a membrane than water?

A

oxygen molecules are small and non-polar whereas water molecules are polar
the hydrophobic interior of the phospholipid bilayer repels the charged molecules
water is only partially charged so is still able to diffuse through the membrane, though only slowly

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17
Q

What 4 factors affect the rate of diffusion across a membrane?

A

temperature
concentration gradient
surface area
thickness of membrane

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18
Q

An increase in surface area of an exchange surface has what effect on rate of diffusion?

A

increases rate of diffusion

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19
Q

An increase in membrane thickness has what effect on the rate of diffusion?

A

Decreases rate of diffusion

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20
Q

Why are membranes containing protein channels selectively permeable?

A

Most protein channels are specific to one molecule or ion
- Therefore only these specific molecules/ions are able to move across the membrane

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21
Q

What does facilitated diffusion allow to move across a membrane?

A

larger molecules
lipid insoluble molecules
small charged particles

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22
Q

Give an example of a small charged particle that moves across membranes via facilitated diffusion

A

Na+

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23
Q

Give an example of a large molecule that moves across membranes via facilitated diffusion

A

Glucose or amino acids

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24
Q

What happens to carrier proteins when a specific molecule binds to them?

A

They change shape

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25
Q

How do protein channels allow charged particles to move through the membrane?

A

They provide a hydrophilic channel for charged particles

26
Q

What are the 5 factors which affect the rate of facilitated diffusion?

A

temperature
concentration gradient
membrane surface area
membrane thickness
number of channel proteins

27
Q

Which type of movement of particles requires ATP?

A

Active transport

Bulk transport

28
Q

What does active transport require to occur?

A

ATP

Carrier proteins

29
Q

Why is active transport considered to be selective?

A

specific substances are transported by specific carrier proteins

30
Q

Define endocytosis

A

the bulk transport of material into cells

31
Q

Define pinocytosis

A

the bulk transport of liquids into cells

32
Q

Define phagocytosis

A

the bulk transport of solids into cells, most commonly the process by which white blood cells engulf pathogens

33
Q

Define exocytosis

A

the bulk transport of materials out of a cell

34
Q

Does bulk transport require ATP?

A

Yes

35
Q

Why would a molecule be moved by bulk transport?

A

It is too big for channel or carrier proteins

36
Q

Name 3 things which are moved by bulk transport

A

Enzymes, hormones, bacteria

37
Q

Outline how phagocytosis occurs

A

the cell surface membrane invaginates when it comes into contact with a bacterium
the membrane then enfolds around the bacterium forming a vesicle around it
the vesicle then pinches off and moves into the cytoplasm towards lysosomes

38
Q

Outline how exocytosis occurs

A

vesicles are usually formed by the golgi apparatus
vesicles move towards and fuse with the cell surface membrane
contents of the vesicle are then released outside of a cell

39
Q

Name an example of exocytosis

A

Excretion

40
Q

Why are ions only able to cross a membrane through a protein channel?

A

protein channels provide a hydrophilic channel through the membrane
ions cannot pass through membranes without them due to the hydrophobic centre of the phosphoplipid bilayer

41
Q

What is the effect of a higher surface area to volume ratio on the rate of diffusion?

A

It increases the rate of diffusion

42
Q

What is the symbol of water potential?

A

Ψ

43
Q

What are the units of water potential?

A

kPa

44
Q

What is water potential?

A

The pressure exerted by water molecules as they collide with a membrane or container

45
Q

What is the Ψ of pure water?

A

0

46
Q

Why does water potential decrease as solute is added?

A

when a substance is dissolved in water the kinetic energy of the water is lowered
because water molecules aggregate around the solute
movement of water molecules is partially impeded
so a lower pressure is exerted

47
Q

What is a hypertonic solution?

A

having a higher concentration of solute relative to another solution

48
Q

What is an isotonic solution?

A

having the same concentration of solute relative to another solution

49
Q

What is a hypotonic solution?

A

having a lower concentration of solute relative to another solution

50
Q

What is the usual water potential in animal cells?

A

About 50kPa

51
Q

What would be the effect of placing a red blood cell in a hypotonic solution?

A

net movement of water into the cell
cell swells and bursts
causing haemolysis
cell contents lost, haemoglobin released

52
Q

What would be the effect of placing a red blood cell in a hypertonic solution?

A

net movement of water out of the cell
cell shrinks and shrivels
becomes darker in colour as haemoglobin is more concentrated
crenation

53
Q

What would be the effect of placing a plant cell in a hypotonic solution?

A

net movement of water into cell
cell becomes turgid
protoplast pushed against cell wall

54
Q

What would be the effect of placing a plant cell in a hypertonic solution?

A

net movement of water out of cell
contents shrink
cell plasmolysed
protoplast completely pulled away

55
Q

When a plant cell is placed in a hypertonic solution, what fills the space between the cell wall and the protoplast?

A

the external solution with a more negative water potential

56
Q

Why do plant cell walls not burst from osmosis?

A

they have strong cellulose walls
- which are able to resist the hydrostatic pressure

57
Q

What happens to the volume of cytoplasm when a plant cell is placed in a hypertonic solution?

A

volume of cytoplasm decreases

58
Q

Define precision

A

the closeness of two or more measurements to each other

59
Q

Define accuracy

A

the closeness of a measured value to a standard or known value

60
Q

Define repeatbility

A

if you repeat the experiment, how close are you results to other results you have collected

61
Q

Define reproducility

A

if someone else repeats the experiment how close are their results to yours

62
Q

Describe the routes that water molecules take through the cell surface membrane

A

diffuse between phospholipids
- move through aquaporins

Biology Module 2 - Own Flashcards (23 decks)

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