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A-level AQA Biology > Chapter 2B: Transport > Flashcards

Chapter 2B: Transport Flashcards

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1
Q

What are the functions of cell membranes? (5)

A
  1. keeping all cellular components inside the cell
  2. partially permeable - lets certain mol. in and out of cell
  3. isolating organelles from the rest of the cytoplasm (allowing cellular processes to occur separately e.g- ER has a membrane)
  4. site of biochemical reactions (e.g- enzymes on inner membrane of mitochondria for respiration)
  5. allowing cells to change shape
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2
Q

What are the main two components of a plasma cell membrane?

A

proteins

phospholipid bilayer

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3
Q

What is the structure of a phospholipid?

A

phosphate head which is a polar molecule

2x fatty acid tail chain is non-polar

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4
Q

What 3 structures can be formed when phospholipids are placed in water and in what conditions?

A

-bilayer (water on two sides)
-monolayer (water/air interface)
-micelle (water/air interface)
draw structures!!!!

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5
Q

Can water soluble molecules pass directly through the membrane and why/why not?

A

water soluble mol. will NOT be able to pass through the membrane because they will not be able to pass through the hydrophobic fatty acid part of phospholipid bilayer

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6
Q

Can lipid soluble molecules pass directly through the membrane?

A

lipids are insoluble so no water will be near it so it can pass through the hydrophobic phospholipid part of membrane

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7
Q

Is the membrane flexible and why is this useful?

A

Phospholipids are held together by weak forces between the molecules making up the bilayer, the molecules can slide past each other and change position in the bilayer,
so it can allow the cell to change shape

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8
Q

What is the name of the model that the cell membrane is based off and why?

A

fluid-mosaic model
fluid because it exists in water and individual phospholipid molecules and proteins can diffuse within their monolayer and thus move around.
mosaic- different sized proteins randomly dotted around the membrane

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9
Q

What 3 types of proteins exist in the membrane (in terms of position)?

A
  • extrinsic: outside membrane
  • intrinsic: goes fully through the membrane
  • partially intrinsic: goes partially through the membrane
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10
Q

What are glycoproteins?

A
  • chains of carbohydrates that are attached to proteins

- chains that go straight out of cell

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11
Q

What are the functions of glycoproteins? (3)

A
  1. act as recognition sites (receptors) for HORMONES and NEUROTRANSMITTERS
  2. allow cells to recognise each other - lymphocytes can recognise each other (antigens)
  3. help cells to attach to each other to form tissues
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12
Q

What part of a glycoprotein/lipid acts as the receptor?

A

the carbohydrate part

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13
Q

What is a glycolipid?

A

carbohydrates bound to a lipid

curved branch

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14
Q

What are the functions of glycolipids? (3)

A
  • acts as a recognition site for specific CHEMICALS
    (e. g medication, alcohol)
  • helps maintain stability of membrane
  • helps attach to each other to form tissues
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15
Q

How do glycolipids help maintain stability of the membrane?

A

they weigh down certain phospholipids to prevent them from moving too much

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16
Q

What is the function of cholesterol in the cell membrane?

A
  • provides strength to membrane
  • prevent water loss
  • prevents ion loss
  • reduces fluidity at high-temps
  • reduces lateral movement of molecules in the membrane
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17
Q

What is a property of cholesterol?

A

they are VERY hydrophobic

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18
Q

What is lateral movement and why is this harmful?

A

when the top part of the phospholipid bilayer moves in one direction and the bottom part moves the other way
but this could destroy an intrinsic protein

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19
Q

What is diffusion?

A

it is the net movement of molecules in a fluid from an area of high concentration to an area of low concentration (down a concentration gradient). it is a passive process, no energy is required

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20
Q

What factors affect the rate of diffusion? (3)

A
  1. concentration gradient- higher the conc. gR, the higher the rate of diffusion
  2. thickness of exchange surface- thinner the material, the lower the distance that has to be travelled by particles, faster the rate
  3. surface area- larger the SA, faster the rate
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21
Q

How is the energy provided for passive transport processes?

A

by the inherent kinetic energy of the particles that are constantly moving in random directions, these particles collide with each other

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22
Q

What are the properties of a particle that allows it to diffuse faster?

A

smaller, can pass through the membrane and fit through the gaps more easily
lipid soluble, so that it can pass through the hydrophobic, non-polar fatty acid part of membrane
polarity, more polar a mol. is , it cannot pass through the non-polar part of the fatty layer chain

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23
Q

What are some examples of polar molecules?

A

water
ions
other charged particles

24
Q

What are the two types of diffusion and with what particles?

A

simple diffusion- lipid soluble and uncharged molecules
facilitated diffusion- travel through protein channels
only SPECIFIC water soluble and polar molecules and larger

25
Q

What type of proteins are involved in facilitated diffusion?

A

carrier proteins
channel proteins
both have to fully intrinsic

26
Q

What is simple diffusion?

A

lipid soluble, non-polar molecules cross through the phospholipid bilayer from high to low concentration, it is a passive process

27
Q

What is facilitated diffusion via channel proteins?

A

occurs through intrinsic proteins
larger, polar- water soluble- molecules can travel through the channel
the proteins are selective and only accept specific molecules

28
Q

How can specific molecules travel through channel proteins?

A

channels are selective, only open in the presence of a specific mol. the inherent energy of the mol. causes the lip (gate) of the protein to open

29
Q

What is facilitated diffusion via carrier proteins?

A

specific molecules bind to the external surface of the carrier protein which causes a change in shape
the shape change results in the molecule to be released into the cytoplasm from an are of high to low concentration

30
Q

What does the rate of facilitated diffusion depend on? (2)

A
  1. concentration gradient- higher the conc. gR, the faster the rate of facilitated diffusion, as equilibrium is reached, the rate slows down
  2. number of channel proteins/carrier proteins- once all proteins are in use, rate cannot increase, even if conc. GR is increased
31
Q

What is the effect of heat on the permeability of a cell membrane?

A

if temperature increases too much, then the proteins in the membrane will denature, which will create large holes in the membrane so substances can leak outside of the holes, so permeability INCREASES with temp.

32
Q

How does putting honey on a cut kill bacteria. Honey contains a high concentration of sugar? (in terms of water potential)

A

Water potential is higher in the bacteria than in honey
so water leaves cell by osmosis
loss of water stops metabolic reactions so it dies

33
Q

How can a specific monoclonal antibody bind to a protein?

A

the monoclonal antibody will have a complementary shape to the protein due to its specific tertiary structure so it can bind to the protein

34
Q

What is an advantage of having stomata that can close?

A

because water is lost through the stomata, but closure prevents water loss so water content of the cell is maintained and reduces wilting

35
Q

How can CO₂ be enter through the top of the leaf (with no stomata)?

A

CO₂ can enter through the upper surface via the cuticles

36
Q

Why do stomata close when the light is off?

A
  • less photosynthesis can occur (less light)
  • so to prevent water loss, close the stomata
  • also build up of CO₂ in the leaf because respiration occurs so conc. gradient of CO₂ out of cell, so to prevent losing CO₂ (maybe)
37
Q

Why do red blood cells have more cholesterol than cell lining ileum cells?

A

this is because red blood cells are free, not supported by other cells so cholesterol is used to maintain its shape

38
Q

How do you describe water potential?

A

a concentrated solution, has less water potential

a dilute solution has more water potential

39
Q

What is osmosis?

A

it is the net movement of water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane

40
Q

What are solutes, solvents and solutions?

A

solute- any substance dissolved in a substance
solvent- able to dissolve other substances
solution- solute + solvent

41
Q

What is water potential, unit and symbol?

A

it is the potential of water molecules to move

measured in kPa (kilopascals) and symbol is: Ψ

42
Q

What determines the movement of water molecules?

A

the pressure that is exerted by the water mol.

43
Q

What is the water potential of pure water?

A

0

which is the highest Ψ possible

44
Q

If you increase the conc., what happens to the water potential and WHY?

A

addition of a solute to the pure water will decrease the water potential into the negative figures
because, the solute molecules attract water (polar) and lower their potential to move

45
Q

What is a hypotonic solution?

A
  • more water

- less solute than inside the cell

46
Q

What is a hypertonic solution?

A
  • less water

- more solute than inside the cell

47
Q

If you put a cell in hypotonic solution, what would happen?

A

water would move into the cell
from an area of high water potential to an area of low water potential across the partially permeable membrane by osmosis

48
Q

If you put a cell in a hypertonic solution, what would happen?

A

water would move out of the cell
from an area of high water potential to an area of low water potential across the partially permeable membrane by osmosis

49
Q

If you put a plant cell in a hypotonic solution, what would happen?

A

water would move in

cell would be turgid

50
Q

If you put a plant cell in a hypertonic solution, what would happen?

A

water would move out

cell would become flaccid/plasmolysed

51
Q

If you put an animal cell in a hypertonic solution, what would happen?

A

water would move out

cell would become crenated

52
Q

If you put an animal cell in a hypotonic solution, what would happen?

A

water would move in

cell would swell, and can undergo lysis (burst)

53
Q

What is plasmolysis?

A

when the cytoplasm pulls away from the cell wall

54
Q

How are red blood cell transported around the body and why?

A

red blood cells are transported in plasma which is isotonic, to prevent them from bursting or shrivelling

55
Q

Why do plant cells not need to be kept in isotonic solutions?

A

this is because they are kept intact by their cell wall, alternating between a turgid and plasmolysed state

A-level AQA Biology (6 decks)

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