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biology > 4 transport across cell membranes > Flashcards

4 transport across cell membranes Flashcards

1
Q

what is the cell surface membrane made up of?

A

phospholipids

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2
Q

explain the fluid mosaic model

A

phospholipids form a bilayer that constantly moves around relative to one another in a fluid structure
protein molecules in bilayer unevenly distributed forming a mosaic

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3
Q

what is the function of the phospholipid bilayer?

A

to allow lipid soluble substances to enter and leave the cell

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4
Q

name what components are within the phospholipid bilayer

A

phospholipids
cholesterol
channel proteins
carrier proteins
receptor proteins
enzymes
glycoproteins
aquaporins

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5
Q

what does the phospholipid bilayer allow through by simple diffusion?

A

lipid soluble molecules (non polar)

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6
Q

what is the function of cholesterol in the phospholipid bilayer?

A

decreases permeability and increases stability

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7
Q

what is the function of a channel protein?

A
  • only allow specific charged ions or small molecules to move across the membrane by facilitated diffusion
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8
Q

what is the function of a carrier protein?

A

help with the transport of ions/ polar molecules/ large molecules by facilitated diffusion and active transport

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9
Q

what could bind to receptor proteins?

A

insulin/hormones

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10
Q

do all cells have the same receptor proteins?

A

no

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11
Q

what is the function of a glycoprotein in a phospholipid bilayer?

A

important in cell recognition often acting as antigens
identify cells as self or non self

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12
Q

where are glycoproteins produced?

A

golgi body

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13
Q

do all cells have glycoproteins on their cell surface membrane?

A

yes

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14
Q

what is an aquaporin?
what can a cell with lots of aquaporins do?

A

special type of channel protein specific to water
a cell with lots of aquaporin can carry out osmosis easily

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15
Q

what can movement of substances into or out of cells occur by?

A

simplediffusion
facilitated diffusion
osmosis
active transport
co transport
exo/endocytosis

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16
Q

does simple diffusion require ATP?

A

no

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17
Q

define diffusion

A

the net movement of molecules from an area or higher concentration to a lower concentration across a partially permeable membrane

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18
Q

give an example of what simple diffusion can help move through the membrane

A

O2
oestrogen

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19
Q

give the equation for ficks law

A

rate of diffusion =
surface area x conc grad/diffusion distance

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20
Q

what factors affect the rate of diffusion?

A

temperature
surface area
conc gradient
diffusion distance

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21
Q

how does temperature affect the rate of diffusion?

A

increased kinetic energy leads to faster rate of diffusion

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22
Q

how does surface area affect the rate of diffusion?

A

larger surface area provides more space for molecules to pass through- faster diffusion

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23
Q

how does concentration gradient affect the rate of diffusion?

A

as concentration difference increases, rate of diffusion increases

24
Q

how does diffusion distance affect the rate of diffusion?

A

the shorter the diffusion distance the faster the molecules will travel through

25
Q

what part of the phospholipid bilayer is hydrophobic and hydrophilic?

A

hydrophobic tails
hydrophilic heads

26
Q

why cant hydrophilic substances pass through the tails of the bilayer?

A

because the fatty acid tails are non polar and repel polar molecules

27
Q

how do water soluble molecules move through the membrane?

A

through channel or carrier proteins via facilitated diffusion

28
Q

does facilitated diffusion require ATP?

A

no

29
Q

define osmosis

A

the net movement of water molecules from higher water potential to a solution lower water potential through a partially permeable membrane

30
Q

what is water potential?

A

the pressure exerted on the membrane due to free moving water molecules colliding with it

31
Q

what is water potential measured in?

A

kPa

32
Q

what solution has the highest water potential?

A

pure water

33
Q

how many kPa does pure water have?

A

0

34
Q

why does water have 0kPa?

A

because all water molecules are free moving

35
Q

what happens when you add a solute to a solution?

A

the water potential becomes more negative

36
Q

why does adding a solute to a solution make it have a more negative water potential?

A

H2o is a dipole so is attracted to charges on solutes, decreasing the amount of free moving water molecules so less pressure exerted onto membrane

37
Q

which way does water move when the inside of a cell has a higher water potential than outside?

A

down water potential gradient/moves to inside the cell

38
Q

which way does water move when the inside of a cell has a lower water potential than outside?

A

down water potential gradient/moves to outside the cell

39
Q

what can happen to an animal cell when there is a higher water potential inside the cell than outside?

A

swelling and lysis

40
Q

what can happen to a plant cell when there is a higher water potential inside the cell than outside?

A

swelling and increased mass
NOT lysis

41
Q

why don’t plant cells undergo lysis if water is moving into the cell b osmosis?

A

cellulose prevents lysis

42
Q

what is lysis?

A

bursting

43
Q

what can happen to an animal cell when there is a higher water potential outside the cell than inside?

A

crenation (shrivelling)

44
Q

what can happen to a plant cell when there is a higher water potential outside the cell than inside?

A

cells plasmolyse (cell membrane pulls away from cell wall)

45
Q

what does isotonic mean?

A

no net movement of water in or out of cells

46
Q

what is active transport?

A

transportation of molecules against a concentration gradient (from low concentration to high concentration)

47
Q

what does active transport use to tranport molecules?

A

ATP
carrier proteins

48
Q

how does active transport use carrier proteins and ATP to transport molecules against a concentration gradient?

A
  1. molecule binds to specifically complementary binding site on carrier protein
  2. ATP hydrolysed into ADP + Pi releasing small amounts of energy/phosphorylating protein
  3. carrier proteins tertiary structure changes, transporting molecule across
49
Q

what are two types of active transport?

A

exo and endocytosis

50
Q

briefly describe the process of exocytosis

A

uses golgi vesicles to move large quantity of molecules to be secreted form inside the cell to outside of the cell

51
Q

briefly describe the process of endocytosis

A

cell surface membrane ‘pulled’ inwards creating a vesicle

52
Q

what do exocytosis and endocytosis require ATP for?

A

movement/creation of vesicles

53
Q

what happens to transport across membranes if aerobic respiration stops?

A

active transport can’t occur due to less ATP being made

54
Q

what happens to transport across membranes if the tertiary structure of a carrier protein changes?

A

active transport and facilitated diffusion inhibited as molecule is no longer specifically complementary

55
Q

describe how amino acids are absorbed from the ileum into the blood

A
  1. Na+ actively transported out of epithelial cell into the blood by NaK pump
  2. creating a conc grad of Na+
  3. Na+ and amino acid enter by facilitated diffusion
  4. Na+ moves into the cell down its conc grad
  5. amino acids move into the cell against their conc grad
  6. amino acids move into the blood by facilitated diffusion

biology (23 decks)

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