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Biology > Bio Unit 1.3 - Cell Membranes and Transport > Flashcards

Bio Unit 1.3 - Cell Membranes and Transport Flashcards

1
Q

Why are the hydrophilic heads pointing in important in the phospholipid bilayer?

A

Interacts with water in the cytoplasm

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2
Q

Why are the hydrophilic heads pointing out important in the phospholipid bilayer?

A

Interacts with water surrounding the cell

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3
Q

Which way do hydrophobic tails point?

A

Toward each other, to centre of membrane

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4
Q

What does the phospholipid component of the bilayer allow to cross?

A

Allows lipid soluble molecules across but not water soluble molecules

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5
Q

Extrinsic Proteins (on surface of bilayer)

A

Provide structural support and form recognition sites (by identifying cells) and receptor sites hormone attachment

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6
Q

Intrinsic Protein (extends across both layers)

A

Include transport proteins which use active/passive transport to move molecules/ions across cell membrane

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7
Q

2 reasons why phospholipid bilayer is known as ‘fluid-mosaic’ model

A
  1. Fluid - individual phospholipid molecules can move within layer relative to one another
  2. Mosaic - proteins embedded in bilayer vary in shape and size and in their distribution
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8
Q

What do both plant and animal cells contain in their cell membrane?

A

Sterols, glycoproteins, glycolipids

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9
Q

What is the sterol in animal membrane?

A

Cholesterol

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10
Q

What does cholesterol do?

A

Occurs between phospholipid molecules, making membrane more stable to high temperatures and more fluid at low temperatures

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11
Q

What is the carbohydrate layer around animal cells and what does it do?

A

Glycocalyx - works as hormone receptors

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12
Q

How can small molecules travel across the membrane? (O2 and Co2)

A

Move between phospholipid molecules and diffuse across membrane

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13
Q

How do lipid soluble molecules (vitamin A) move across?

A

Dissolve in phospholipid and diffuses across membrane. The phospholipid layer is hydrophobic so lipid soluble molecules move through easier.

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14
Q

How do water soluble molecules pass through the membrane?

A

Must pass through intrinsic proteins forming water filled channels across the membrane (why cell surface is selectively permeable)

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15
Q

Where do glycoproteins connect to?

A

Extrinsic Proteins

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16
Q

Diffusion

A

The passive movement of a molecule/ion down a concentration gradient from a region of high concentration to a region of low concentration until they are equally distributed

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17
Q

How does concentration gradient affect rate of diffusion?

A

Greater difference in concentration of molecules in two areas - more molecules diffuse in given time

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18
Q

What affects rate of diffusion?

A

Concentration gradient, thickness of exchange surface, surface area of membrane

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19
Q

Other irregular factors that might affect rate of diffusion?

A

Size of molecule, nature of diffusing molecules, temperature

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20
Q

Facilitated Diffusion

A

Passive transfer of molecules down a concentration gradient across a membrane by channel or carrier protein molecules in the membrane

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21
Q

Where does facilitated diffusion occur?

A

Sites on membrane where transport proteins are present (numbers limit rate of facilitated diffusion.)

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22
Q

2 types of facilitated diffusion?

A

Channels proteins and Carrier Proteins

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23
Q

Channel Protein facilitated diffusion

A

Molecules with pores lined with polar groups, channels are hydrophilic so water soluble ions can pass through

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24
Q

Carrier Protein facilitated diffusion

A

Allows diffusion of larger polar molecules (sugars and amino acids)

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25
Q

How does carrier protein f.d work?

A

Molecules attaches to its binding site, protein changes shape and releases molecule on the other side of membrane before resuming original shape

26
Q

Do carrier proteins allow active transport?

A

Yes

27
Q

What different molecules do channel and carrier proteins transport?

A

Channel-water soluble
Carrier - soluble and insoluble

28
Q

Active Transport

A

Movement of molecules against a concentration gradient using energy from hydolysis of ATP made by cell respiration

29
Q

Features of active transport

A
  1. Low to high concentration
  2. Requires energy from ATP
  3. Occurs through intrinsic carrier proteins
  4. Rate is limited by availability of carrier proteins
30
Q

Process of Active Transport through Carrier Protein

A
  1. molecule combines with specific carrier protein outside the membrane
  2. ATP transfers phosphate group to the carrier protein on inside of membrane
  3. Carrier protein changes shape and takes molecule across membrane
  4. Molecule released into cytoplasm
  5. Phosphate ion is released from carrier molecule back to cytoplasm and forms ATP
  6. Carrier protein returns to original shape
31
Q

Effect of cyanide?

A

Respiratory inhibitor, will prevent aerobic respiration and without production of ATP active transport cannot take place

32
Q

Co transport

A

A transport mechanism in which facilitated diffusion brings molecules and ions (glucose and Na+ ions) across cell membrane together (on the same transport protein molecule) into cell

33
Q

Why is glucose and sodium co transport important?

A

Significant for absorbing these substances across cell membranes and into the blood in the ileum and kidney nephron

34
Q

Process of co-transport

A
  1. Glucose/Sodium ions bind to carrier protein in cell membrane
  2. Carrier changes shape and deposits both inside the cell (facilitated diffusion)
  3. Both substances separately diffuse through cytoplasm to the opposite membrane
  4. Glucose passes into blood by facilitated diffusion
  5. Sodium ions carried out of epithelial cell via active transport by same carrier that moves potassium in
35
Q

Why is sodium level low in epithelial cell?

A

S0 more sodium ions can move in and bring in more glucose (so facilitated diffusion can continue)

36
Q

Water Potential

A

measure of free energy of water molecules and the tendency of water to move (kPa)

37
Q

Osmosis

A

The net passive diffusion of water molecules across a selectively permeable membrane from a region of higher water potential to a region of lower water potential

38
Q

What is water potential of pure water?

A

Zero

39
Q

What does addition of solute to pure water do to water potential?

A

Lowers it into a negative value

40
Q

Higher concentration impact on water potential

A

More concentrated, fewer water molecules free to move, pull on water molecules greater, water potential more negative

41
Q

Solute Potential

A

Measure of osmotic strength of a solution. The reduction of water potential due to the presence of solute molecules

42
Q

More solute impact of solute potential?

A

more solute, more tightly water molecules are held, lower tendency of water to move out therefore higher concentration has more negative solute potential

43
Q

Pressure potential

A

Pressure of when water enters cell by osmosis and expands the vacuole, pushing against the cell wall. Cell wall can only expand a little so pressure outwards builds up, resisting entry of more water (cell becomes turgid)

44
Q

What does pressure potential increase?

A

Increases tendency of water to move out

45
Q

Potential Equation

A

Solute potential + Pressure potential = Water potential

46
Q

If water potential of external solution is less negative than inside solution?

A

External solution is hypotonic to cell and water flows in.

47
Q

If water potential externally is more negative than inside then?

A

External solution is hypertonic to cell and water flows out

48
Q

Same water potentials externally and internally?

A

External solution and cell are isotonic

49
Q

Plasmolysis

A

Retraction of cytoplasm and cell membrane from cell wall as cell loses water by osmosis

50
Q

Incipient Plasmolysis

A

Cell membrane and cytoplasm are partially detached from cell wall due to insufficient water to make cell turgid

51
Q

After playmolysis…

A

Flaccid

52
Q

Turgid

A

Cytoplasm pushes against cell wall

53
Q

Why is pressure potential not considered in animal cells?

A

No cell wall to be pushed against

54
Q

Hameolysis

A

Bursting of (eg. red blood cells) without a cell wall after water enters through osmosis

55
Q

When will red blood cell burst?

A

In pure water (too much water moves in)

56
Q

When will cell shrink?

A

In concentrated solution (too much water moves out)

57
Q

Endocytosis

A

active process of cell membrane engulfing material, bringing it into cell in a vesicle

58
Q

Exocytosis

A

active process of vesicle fusing with cell membrane , releasing the molecule it contains

59
Q

2 types of endocytosis

A

Phagocytosis and Pinocytosis

60
Q

Phagocytosis

A

Uptake of solid material too large to be taken in by diffusion
Granulocytes engulf bacteria, a lysosome fuses with vesicle formed and enzymes digest cells, products absorbed into cytoplasm

61
Q

What does the cell membrane have to do when exocytosis and endocotosis take place?

A

Change shape and requires energy (uses ATP produced by respiration)

62
Q

Pinocytosis

A

Uptake of liquid by the same mechanism (vesicles are smaller though)

Biology (7 decks)

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