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Bio Prelims - Michelle > Unit 2 - Diffusion/osmosis/active transport > Flashcards

Unit 2 - Diffusion/osmosis/active transport Flashcards

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

Which 2 factors affect the rate of diffusion?

A

Temperature
Concentration difference

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12
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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13
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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14
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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15
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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16
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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17
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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18
Q

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

A

Decreases rate of diffusion

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19
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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20
Q

What does facilitated diffusion allow to move across a membrane?

A

-larger molecules
-lipid insoluble molecules
-small charged particles

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21
Q

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

A

Na+

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22
Q

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

A

Glucose or amino acids

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23
Q

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

A

They change shape

24
Q

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

A

They provide a hydrophilic channel for charged particles

25
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

26
Q

Which type of movement of particles requires ATP?

A

Active transport
Bulk transport

27
Q

What does active transport require to occur?

A

ATP
Carrier proteins

28
Q

Describe how active transport occurs with aid of a carrier protein

A

-molecules/ions bind to receptors in the channel of the carrier protein
-ATP binds to the opposite side of the carrier protein
-ATP is hydrolysed to form ADP and phosphate
-the phosphate molecule binds to the phosphate molecule to the carrier protein causes the protein to change shape
-carrier protein opens, allowing molecules through
-phosphate molecule is released and recombines with ADP to form ATP
-carrier protein returns to original shape

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

How can the effect of surface area on the rate of diffusion be investigated?

A

-agar made with phenolpthalein and NaOH is pink as NaOH is alkai
-cubes of different sizes are placed in HCl
-In HCl the cubes will go colourless
-Leave for 5 minutes
-measure the volume of cube that is still pink
-calculate % diffusion

42
Q

How can the effect of temperature on the rate of diffusion be investigated?

A

-an artificial cell is made from dialysis tubing
-solution is placed in cell
-cell is placed in water bath at different temperatures
-indicators can be used to see the rate of diffusion (e.g. iodine for starch or benedict’s solution for glucose)

43
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

44
Q

What is a hypertonic solution?

A

having a higher concentration of solute relative to another solution

45
Q

What is an isotonic solution?

A

having the same concentration of solute relative to another solution

46
Q

What is a hypotonic solution?

A

having a lower concentration of solute relative to another solution

47
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

48
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

49
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

50
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

51
Q

Why do plant cell walls not burst from osmosis?

A

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

52
Q

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

A

-volume of cytoplasm decreases

53
Q

How can the concentration of a potato be determined?

A

-weight pieces of equal size potato
-place in different concentrations of solution
-leave potato for the same time
-blot potato dry and reweigh
-calculate % change in mass
-plot on graph
-where line of best fit crosses 0 on x-axis shows concentration of potato

54
Q

Define precision

A

the closeness of two or more measurements to each other

55
Q

Define accuracy

A

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

56
Q

Define repeatbility

A

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

57
Q

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

A

-diffuse between phospholipids
-move through aquaporins

Bio Prelims - Michelle (26 decks)

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