Membranes - Diffusion , Osmosis, and 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

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
How do protein channels allow charged particles to move through the membrane?
They provide a hydrophilic channel for charged particles
26
What are the 5 factors which affect the rate of facilitated diffusion?
temperature concentration gradient membrane surface area membrane thickness number of channel proteins
27
Which type of movement of particles requires ATP?
Active transport Bulk transport
28
What does active transport require to occur?
ATP Carrier proteins
29
Why is active transport considered to be selective?
specific substances are transported by specific carrier proteins
30
Define endocytosis
the bulk transport of material into cells
31
Define pinocytosis
the bulk transport of liquids into cells
32
Define phagocytosis
the bulk transport of solids into cells, most commonly the process by which white blood cells engulf pathogens
33
Define exocytosis
the bulk transport of materials out of a cell
34
Does bulk transport require ATP?
Yes
35
Why would a molecule be moved by bulk transport?
It is too big for channel or carrier proteins
36
Name 3 things which are moved by bulk transport
Enzymes, hormones, bacteria
37
Outline how phagocytosis occurs
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
Outline how exocytosis occurs
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
Name an example of exocytosis
Excretion
40
Why are ions only able to cross a membrane through a protein channel?
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
What is the effect of a higher surface area to volume ratio on the rate of diffusion?
It increases the rate of diffusion
42
What is the symbol of water potential?
Ψ
43
What are the units of water potential?
kPa
44
What is water potential?
The pressure exerted by water molecules as they collide with a membrane or container
45
What is the Ψ of pure water?
0
46
Why does water potential decrease as solute is added?
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
What is a hypertonic solution?
having a higher concentration of solute relative to another solution
48
What is an isotonic solution?
having the same concentration of solute relative to another solution
49
What is a hypotonic solution?
having a lower concentration of solute relative to another solution
50
What is the usual water potential in animal cells?
About 50kPa
51
What would be the effect of placing a red blood cell in a hypotonic solution?
net movement of water into the cell cell swells and bursts causing haemolysis cell contents lost, haemoglobin released
52
What would be the effect of placing a red blood cell in a hypertonic solution?
net movement of water out of the cell cell shrinks and shrivels becomes darker in colour as haemoglobin is more concentrated crenation
53
What would be the effect of placing a plant cell in a hypotonic solution?
net movement of water into cell cell becomes turgid protoplast pushed against cell wall
54
What would be the effect of placing a plant cell in a hypertonic solution?
net movement of water out of cell contents shrink cell plasmolysed protoplast completely pulled away
55
When a plant cell is placed in a hypertonic solution, what fills the space between the cell wall and the protoplast?
the external solution with a more negative water potential
56
Why do plant cell walls not burst from osmosis?
they have strong cellulose walls - which are able to resist the hydrostatic pressure
57
What happens to the volume of cytoplasm when a plant cell is placed in a hypertonic solution?
volume of cytoplasm decreases
58
Define precision
the closeness of two or more measurements to each other
59
Define accuracy
the closeness of a measured value to a standard or known value
60
Define repeatbility
if you repeat the experiment, how close are you results to other results you have collected
61
Define reproducility
if someone else repeats the experiment how close are their results to yours
62
Describe the routes that water molecules take through the cell surface membrane
diffuse between phospholipids - move through aquaporins