Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A LEVEL - Biology (P2) > 2B - Cell Membranes > Flashcards

2B - Cell Membranes Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What are the different types of membrane?

A
  • Cell membranes

* Organelle membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Do all cells have a cell membrane?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What type of cells also contains organelle membranes?

A

Eukaryotic cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the function of cell surface membranes?

A

Control what goes in and out of cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What term is used to describe the way in which cell membranes control what goes in and out of cells?

A

Partially permeable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the types of molecule in cell membranes?

A
  • Lipids (mainly phospholipids)
  • Proteins
  • Carbohydrates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do carbohydrates fit in the cell membrane?

A

They attach to proteins or lipids (glycoproteins and glycolipids).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the model used to describe cell membranes?

A

Fluid mosaic model

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the fluid mosaic model.

A
  • Continuous phospholipid bilayer -> These are constantly moving (thus “fluid”)
  • Cholesterol molecules are inside the bilayer
  • Channel, carrier and receptor proteins are either fixed or can move through the bilayer
  • Polysaccharides attach to some proteins and lipids to form glycoproteins and glycolipids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Name all of the individual components of a cell membrane.

A
  • Phospholipids
  • Cholesterol
  • Proteins -> Channel, Carrier and Receptor
  • Glycoproteins
  • Glycolipids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the role of receptor proteins in the cell-surface membrane?

A
  • Allow the cell to detect chemicals released from other cells.
  • These chemicals signal for the cell to respond in some way.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Give an example of how receptor proteins work.

A

Insulin binds to receptor proteins on liver cells, which tells them to absorb glucose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Explain why the cell-surface membrane can be described as having a fluid mosaic structure.

A
  • “Fluid” -> The phospholipids (and some other molecules) in the bilayer can move around freely.
  • “Mosaic” -> The phospholipids, proteins and other molecules are arranged in a mosaic-like pattern.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the role of phospholipids in cell-surface membranes?

A

Arrange themselves in a bilayer, which acts as a barrier for water-soluble substances.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why do phospholipids arrange themselves in a bilayer in cell-surface membranes?

A
  • Have a hydrophilic head and hydrophobic tail

* In water, a bilayer forms with the heads facing out and the tails facing in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why does the phospholipid bilayer in cell-surface membranes not allow water-soluble substances to pass through it?

A

The centre of the bilayer is hydrophobic (that’s where the hydrophobic tails are).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which parts of a phospholipid molecule are hydrophobic and hydrophilic?

A
  • Hydrophobic - Tail

* Hydrophilic - Head

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What type of molecule is cholesterol?

A

Lipid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

In what type of cell membrane is cholesterol found?

A

All types, except bacterial cell membranes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Where in the cell-surface membrane is cholesterol found and what does this do?

A
  • Between phospholipid molecules

* This restricts the movements of the phospholipids, making the membrane less fluid and more rigid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the role of cholesterol in cell-surface membranes?

A
  • The cholesterol between phospholipids restricts their movement and makes the membrane more rigid
  • This maintains the shape of cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

In which cells is cholesterol in the membrane especially important?

A

Cells that aren’t supported by other cells (e.g. RBCs floating freely in the blood)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What experiment can be used to investigate how temperature affects cell membrane permeability?

A

Beetroot in water experiment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe an experiment to investigate the effect of temperature on cell membrane permeability (beetroot).

A

1) Cut 5 equal sized pieces of beetroot and rinse.
2) Add the pieces to 5 test tubes and add 5cm3 of water to each.
3) Place each tube in a water bath at a different temperature (e.g. 10C, 20C, 30*C, etc.) and for the same length of time.
4) Remove the beetroot and keep only the coloured water.
5) Use a colorimeter to measure the absorption of each sample - The higher the absorbance, the more pigment is released, so the higher the membrane permeability.
6) Draw a graph of the results.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is a colorimeter and what must be done when using it?

A

• A device that passes light through liquid and measures how much is absorbed.• First, it must be calibrated at 0 by taking a measurement with pure water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe how cell membrane permeability changes with temperature.

A

• There is a minimum permeability at a certain temperature (e.g. 0C).
• Below this temperature (below 0C), permeability increases rapidly.
• Above that temperature (0 - 45C), permeability increases gradually. Eventually (above 45C), it increases rapidly.
(See diagram pg 37 of revision guide)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Explain membrane permeability below 0*C.

A

• Permeability increases rapidly as temperature decreases.
BECAUSE:
• Channel and carrier protein deform
• Ice crystals may form, piercing the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Explain membrane permeability 0 - 45*C.

A

• Permeability increases as temperature increases.
BECAUSE:
• Phospholipids gain energy, move around faster and are less tightly packed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Explain membrane permeability above 45*C.

A

• Permeability increases rapidly as temperature increases.
BECAUSE:
• Phospholipid bilayer starts to melt
• Water inside the cell expands, putting pressure on the membrane
• Channel and carrier proteins denature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Name 2 factors that may affect the permeability of cell membranes.

A
  • Temperature

* Solvent concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is diffusion?

A
  • The net movement of particles from an area of higher concentration to an area of lower concentration.
  • It is a passive process.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

In diffusion, do particles only move from high to low concentration?

A

No, they move both ways, but the NET movement is from high to low concentration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

For how long does diffusion happen?

A

Until the particles are evenly distributed throughout the liquid or gas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

When answering a diffusion question, what is it important to mention?

A

It is a PASSIVE process.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Does diffusion / facilitated diffusion require energy?

A

No, it is a passive process.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

When can diffusion happen across a membrane?

A

When:
• Going from high to low concentration
• The particles can move freely through the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Why can oxygen and CO2 easily diffuse through cell membranes?

A
  • Small -> Can pass between phospholipids

* Non-polar -> Soluble in lipids + can dissolve in the hydrophobic bilayer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What are the two types of diffusion?

A
  • Simple diffusion

* Facilitated diffusion

39
Q

What is the difference between simple and facilitated diffusion?

A

Simple diffusion doesn’t require any carrier proteins or channel proteins, while facilitated diffusion does.

40
Q

Why is there a need for facilitated diffusion through cell membranes?

A
  • Larger molecules -> Would diffuse extremely slowly

* Charged particles -> Are water soluble and the bilayer is hydrophobic

41
Q

What is facilitated diffusion?

A
  • When carrier and channel proteins move particles across a membrane from an area of higher concentration to an area of lower concentration.
  • It is a passive process.
42
Q

What are the two types of protein used in facilitated diffusion?

A
  • Carrier proteins

* Channel proteins

43
Q

What type of particle do carrier and channel proteins move across cell membranes?

A
  • Carrier proteins -> Large molecules

* Channel proteins -> Charged particles

44
Q

Can one carrier/channel protein facilitate the diffusion of every molecule?

A

No, different carrier/channel proteins facilitate the diffusion of different molecules/charged particles.

45
Q

Do diffusion and facilitated diffusion happen up or down a concentration gradient?

A

Down

46
Q

How does a carrier protein work?

A

1) A large molecule attaches to the protein.
2) Protein changes shape.
3) This releases the molecule on the other side of the membrane.
(See diagram pg 38)

47
Q

How does a channel protein work?

A

1) Proteins form pores in the membrane.
2) Charged particles can diffuse through these.
(See diagram pg 38)

48
Q

Remember to revise facilitated diffusion diagrams.

A

Pg 38 of revision guide.

49
Q

What is another set of terms for cell-surface membranes and organelle membranes?

A

External and internal membranes

50
Q

What factors affect the rate of diffusion?

A

1) Concentration gradient
2) Thickness of exchange surface
3) Surface area

51
Q

How does the rate of diffusion change over time and why?

A
  • As diffusion happens, the difference in concentration between both sides decreases until it reaches equilibrium.
  • So the rate slows down over time.
52
Q

Give an example of an exchange surface adapted for diffusion.

A
  • Epithelial cells in the small intestines -> Have microvilli (projections formed by the cell-surface membrane folding)
  • Increase the surface area
53
Q

What factors affect the rate of facilitated diffusion?

A

1) Concentration gradient

2) Number of carrier/channel proteins

54
Q

Why does the number of carrier/channel proteins affect the rate of facilitated diffusion?

A

Once all of the proteins in the membrane are in use, facilitated diffusion cannot happen any faster, even if you increase the concentration gradient. So only increasing their number will speed up facilitated diffusion.

55
Q

Give an example of an exchange surface adapted for facilitated diffusion.

A
  • Kidney cells -> Have lots of aquaporins (channel proteins that allow the facilitated diffusion of water)
  • These allow the kidneys to reabsorb lots of water
56
Q

What is osmosis?

A

The diffusion of water molecules across a partially permeable membrane, from high to low water potential.

57
Q

What is water potential?

A

A measure of how likely water molecules are to diffuse out of a solution.

58
Q

What does a high water potential mean?

A

Water is very willing to move away from that solution.

59
Q

What solution has the highest water potential?

A

Pure water (0KPa)

60
Q

What is the unit for water potential?

A

Kilopascals (KPa)

61
Q

What is unusual about water potential?

A

It is usually negative, so the water potential of 0KPa is actually the highest.

62
Q

What is the term for two solutions having the same water potential?

A

Isotonic

63
Q

In terms of water potential, what do hypotonic, hypertonic and isotonic mean?

A
  • Hypertonic - Lower water potential
  • Hypotonic - Higher water potential
  • Isotonic - Same water potential
64
Q

Which water potential is higher, -200 or -400KPa?

A

-200KPa

65
Q

What does hypertonic mean?

A

Having a higher solute concentration.

66
Q

What does hypotonic mean?

A

Having a lower solute concentration.

67
Q

What factors affect the rate of osmosis?

A

1) Water potential gradient
2) Thickness of exchange surface
3) Surface area of exchange surface

68
Q

What is a serial dilution?

A

When samples of several different concentrations of a solution are made by taking a sample of the previous and adding water to make the next.

69
Q

Describe how you would obtain solutions of 2M, 1M 0.5M, 0.25M and 0.125M sucrose solution when given some 2M sucrose solution.

A

1) Line up 5 test tubes.
2) Add 10cm3 of the 2M sucrose solution to the first.
3) Add 5cm3 from this one and add it to the next tube. Then add 5cm3 of distilled water to make 1M.
4) Repeat step 3 another 3 times to get solutions of 0.5M, 0.25M and 0.125M.

70
Q

Describe how you can make a solution of a particular concentration when given a solution of known concentration.

A

1) Start with a solution of known concentration.
2) Find the scale factor by dividing this concentration by the target concentration.
3) You now know that the target solution must be that many times weaker than the original.
4) Look at the volume that you need and divide it by the SF to find the amount of the original solution you need.
5) Fill the rest of the volume required with distilled water.

71
Q

Use the scale factor method to make 15cm3 of 0.4M of sucrose solution when given a 1M sucrose solution.

A
  • SF = 1M / 0.4M = 2.5
  • 15cm3 / 2.5 = 6cm3
  • Therefore, use 6cm3 of the 1M solution and 9cm3 of distilled water.
72
Q

Describe an experiment to find the water potential of some potato cells.

A

1) Use a cork borer to cut potatoes into identical length cylinders
2) Place the cylinders into groups of 3 and measure the mass of each group using a mass balance
3) Put each group into a different concentration of sucrose solution
4) Leave for 20 minutes
5) Remove the potato and dry each piece with a paper towel
6) Weigh each group and calculate % change in mass
7) Draw a calibration curve of sucrose concentration (x) against % change in mass (y)
8) Read at which concentration there is no change in mass
REMEMBER: This is a concentration, not the water potential. You will need to look up the water potential value that corresponds to this sucrose concentration.

73
Q

What is the graph draw when calculating the water potential of some potato cells called?

A

Calibration curve

74
Q

In the experiment to find the water potential of some potato cells, is it enough to read off the concentration at which the graph crosses the x-axis?

A

No, this is the CONCENTRATION of the cells, not their WATER POTENTIAL. You need to look up the water potential that corresponds to that sucrose solution concentration.

75
Q

What is active transport?

A

The movement of molecules and ions across a membrane from low to high concentration requiring energy.

76
Q

What molecules are required in active transport?

A

Carrier proteins

77
Q

In what types of transport are channel and carrier proteins used?

A
  • Carrier - Facilitated diffusion + Active transport

* Channel - Facilitated diffusion

78
Q

Are channel proteins involved in active transport?

A

No, only carrier proteins.

79
Q

What are the 2 main differences between facilitated diffusion and active transport?

A

1) AT moves solutes from low to high concentration, while FD moves them from high to low
2) AT requires energy, while FD is passive.

80
Q

Where does the energy used in active transport come from?

A
  • ATP is produced by respiration.

* It undergoes hydrolysis to split into ADP and Pi, releasing energy for active transport.

81
Q

What is it called when two different molecules are moved by a protein across a membrane, using the concentration gradient of one to move the other?

A

Co-transport

82
Q

What type of molecule is a co-transporter?

A

Carrier protein

83
Q

What is co-transport?

A

When two different molecules are moved by a protein across a membrane, using the downward concentration gradient of one to move the other against its concentration gradient.

84
Q

Describe the process of co-transport.

A

1) 2 different molecules bind to the co-transporter.

2) One goes from high to low concentration, and this is used to move the other from low to high concentration.

85
Q

Give an example of co-transport.

A
  • Sodium ions and glucose

* Sodium ions move down their concentration gradient, moving glucose against its concentration gradient.

86
Q

What factors affect the rate of active transport?

A

1) Speed of carrier proteins
2) Number of carrier proteins
3) The rate of respiration + Availability of ATP

87
Q

Is the rate of active transport affected by the concentration gradient?

A

No

88
Q

What type of transport is co-transport most closely related to?

A

Active transport

89
Q

What example of co-tranport do you need to know about?

A

The absorption of glucose in the mammalian ileum.

90
Q

What is the ileum?

A

The final part of the small intestine.

91
Q

Where is glucose absorbed into the bloodstream?

A

The small intestine.

92
Q

Why is the process of absorbing glucose into the bloodstream different in the ileum?

A
  • The ileum is the final part of the small intestine.
  • The concentration of glucose is too low for glucose to diffuse into the blood (since most has been absorbed by then).
  • Therefore, co-transport is used instead.
93
Q

Describe the absorption of glucose into the blood in the ileum.

A

1) Na+ ions move from ileum epithelial cells into the blood by active transport -> Using a sodium-potassium pump.
2) This creates a concentration gradient between the ileum and the cells.
3) Na+ ions can diffuse from the ileum into the cells via sodium-glucose co-transporter proteins.
4) The co-transporter takes glucose with it from low to high concentration.
5) This increases the glucose concentration of the cells.
6) Glucose can now move into the blood by facilitated diffusion from high to low concentration -> Using a channel protein.

94
Q

Remember to practice drawing out the diagram for absorption of glucose in the ileum.

A

Pg 43 of revision guide.

A LEVEL - Biology (P2) (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions