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BIOLOGY A-LEVEL > 2B Cell Membranes > Flashcards

2B Cell Membranes Flashcards

Cell membrane structure, diffusion, osmosis & active transport

1
Q

What are all plasma membranes made of?

A

phospholipid b

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2
Q

What are phospholipids made of?

A

1x phosphate group bound by phosphodiester bond to 1x glycerol boundby ester bond 2x fatty acids.

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3
Q

what is the phospholipid bilayer made of?

A

hydrophilic heads and hydrophobic tails

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4
Q

is a polar molecule lipid or water soluble

A

water soluble

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5
Q

is a non- polar molecule lipid or water soluble

A

lipid soluble

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6
Q

is a hydrophobic tail polar or non polar

A

they are non polar as they are water insoluble so lipid soluble

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7
Q

is a hydrophilic head polar or non polar

A

polar because it is water soluble as it attracts water

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8
Q

what is the effect of more C=C bonds on the movement of proteins within the phospholipid bilayer?

A

more C=C bonds in protein = more unsaturated (bent) so proteins move easier in the bilayer.

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9
Q

why is the plasma membrane model called a fluid mosaic model?

A
  • fluid because molecules move laterally in the membrane as phospholipids move freely
  • mosaic because proteins are distributed randomly through bilayer
  • model because its an agreed structure based on experimental and chemical evidence
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10
Q

In a phospholipid what is the bond between the glycerol and fatty acids

A

ester bond

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11
Q

In a phospholipid what is the bond between phosphate and glycerol?

A

phospho-diester bond

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12
Q

Name 3 roles of the plasma membrane

A
  • control movement of substances in and out of the cell
  • increase cell surface area for quicker rate of reactions
  • separate organelles
  • hold enzymes
  • hold electron carriers for ATP production
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13
Q

Role of channel proteins in plasma membrane

A

To allow ions and large molecules to pass through

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14
Q

Role of glycolipids in plasma membrane

A

Cell Recognition site

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15
Q

Role of glycoproteins in plasma membrane

A

cell recognition site

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16
Q

Role of carbohydrate molecules in plasma membrane

A

provides cell energy and is a recognition site

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17
Q

Role of cholesterol in plasma membrane

A

Regulates cell fluidity to reduce lateral movement of molecules (animal cells only).
Makes more ridged less fluid due to no cell wall present.

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18
Q

Role of peripheral proteins in plasma membranes

A

They act as cell external enzyme or receptor

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19
Q

Role of hydrophobic tails in plasma membranes

A

fatty acids and are Non polar molecule (lipid soluble) so is a barrier to polar molecules so repels water.

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20
Q

Role of hydrophilic heads in plasma membranes

A

polar so are water soluble and attract polar molecules phosphates. face the aqueous environment

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21
Q

define diffusion

A

Net movement of molecules from a high concentration region to low concentration so down the concentration gradient.

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22
Q

What are the two types of diffusion?

A

Simple and Facilitated

23
Q

Why is diffusion a passive process?

A

because it is down the concentration gradient

24
Q

Ficks law equation (Rate of diffusion)

A

ROD = (SA x difference in concentration) / length of diffusion path

25
Q

Factors that affect the rate of diffusion

A
  • SA of membrane
  • distance between regions
  • temperature
  • steepness of concentration gradient
  • number of proteins (only Facilitated)
26
Q

Which type of diffusion require proteins?

A

Facilitated diffusion

27
Q

What is simple diffusion?

A

The direct diffusion of non polar (lipid soluble) moleculesfrom high to low concentration without the use of energy

28
Q

What molecules type use facilitated diffusion?

A

polar, water soluble, charged or large.

29
Q

What are the two types of proteins that are involved in facilitated diffusion?

A

Carrier (large molecules) and channel (charged)

30
Q

how do carrier proteins work in facilitated diffusion?

A
  • Large molecules attach to carrier protein binding sites
  • Carrier protein changes shape to release the molecule on the other side of the membrane.
31
Q

What is channel proteins role in facilitated diffusion?

A

For charged particles to pass through the channel protein pores in the membrane to diffuse through.

32
Q

Define osmosis

A

The diffusion of water from an area of high to low water potentials across a partially permeable membrane.

33
Q

What is water potential?

A

The potential (likelihood) for water molecules to diffuse out or into a solution

34
Q

ψ meaning

A

water potential

35
Q

What is the water potential of pure water?

A

ψ = 0

36
Q

What is isotonic?

A

Where the water potential of two substances are the same so it’s in equilibrium (no net movement)

37
Q

What factors affect rate of osmosis?

A
  • Surface area of exchange surface
  • thickness of exchange surface
  • water potential gradient ( difference between regions )
38
Q

How do you make a serial dilution for potato cells?

A
  • 10cm3 of the 2M sucrose, add 5cm3 of serial 1 into 5cm3 distilled water.
  • Add 5cm3 of solution to next boiling tube with 5cm3 distilled water
  • every addition halves the sucrose concentration.
39
Q

What is it called when the ψ is higher externally than internally?

A

Hypotonic (Osmosis in)

40
Q

What is it called when the ψ is lower externally than internally?

A

hypErtonic (water Exits)

41
Q

What is plasmolysis?

A

When a plant cell membrane detaches from the cell wall due to hypertonic solutions (shrinks due to osmosis out of the cell)

42
Q

What is active transport?

A

The movement of molecules and ions against a concentration gradient from low to high, requiring the use of energy/

43
Q

How is energy released for Active transport?

A

ATP is generated in respiration that hydrolysed to release ADP+Pi+energy. This energy is used to power active transport.

44
Q

What is the name of the protein used in active transport?

A

Carrier proteins 2 types: counter and co-transport (co = more important)

45
Q

What are co-transporter proteins?

A

Used in active transport and are a type of carrier protein.
Transport more than 1 molecule at the same time (eg glucose and Na+ in the small intestine absorption of glucose).

46
Q

What are counter transporter proteins used for?

A

Used to pump one solute out at the same time as pumping another in. Eg. Na+&K+ pump in small intestine.

47
Q

Describe how co-transporters work in active transport.

A
  • 2 molecules bind to the receptor sites on the protein at the same time.
  • The concemtration of 1 of these molecules is used to move the other molecule past the membrane against its gradient.
    eg. Glucose is moved by the gradient of sodium ions in the SI absorption of glucose.
48
Q

What are 3 factors that affect the rate of active transport (3x limiting factors)?

A
  • Energy (ATP) available from cellular respiration/efficiency of respiration
  • The number of carrier proteins
  • The speed of the carrier proteins
49
Q

What does ATP bind to during active transport?

A

ATP binds to the carrier protein and splits into ADP and Pi which releases energy, making the carrier protein change shape (and release the molecules on the other side of the membrane.)

50
Q

What processes use co-transporter proteins?

A

Facilitated diffusion and active transport

51
Q

State the 3 steps of the glucose/amino acids absorption in the small intestine into blood

A

1) Na+ and K+ pump (sodium into blood, potassium into cell) = counter active transport
2) Na+ and glucose/amino acids into the epithelial cell via facilitated diffusion co-transport, glucose/amino acids against concentration gradient with the sodium.
3) Facilitated diffusion of glucose/amino acids into the blood via channel proteins.

52
Q

How does glucose enter the blood through the epithelial cells?

A

Glucose enters via facilitated diffusion through channel proteins into the blood (likewise for amino acids)

53
Q

How does sodium and glucose enter the epithelial cell from the lumen of ileum in glucose absorption? (stages 2/3)

A

Through co transport facilitated diffusion via sodium-glucose co-transporter proteins.

54
Q

What is an epithelial cell?

A

Very abundant in the body and cover blood vessels. Vital in cell membrane transportation.

BIOLOGY A-LEVEL (8 decks)

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