membranes

Question 1

what are membranes made of

Answer 1

phospholids in bilayers

Question 2

what is the head of a phodpholipid

Answer 2

polar (hydrophillic)

Question 3

what is the tail of a phospholipid

Answer 3

non polar (hydrophobic)

Question 4

what is the hydrophobic tail made of

Answer 4

fatty acids and lipids

Question 5

what is the model of the cell membrane called

Answer 5

fluid mosaic model

Question 6

how is the membrane fluid

Answer 6

some parts are not attached to any other part of the cell and so can move freely

Question 7

why is the membrane described as mosaic

Answer 7

because of the different sizes of phospholipids proteins and cholestrol

Question 8

what is the purpose of cholesterol in the membrane

Answer 8

makes membrane more rigid and stable

Question 9

what is the purpose of the glycoproteins/lipids

Answer 9

act as hormone receptors or cell to cell proteins

Question 10

what is an extrinsic protein

Answer 10

only in the half of the membrane which is hydrophillic

Question 11

what is an intrinsic protein

Answer 11

through all of the membrane

Question 12

how do small and non polar molecules get through the membrane

Answer 12

they diffuse through the lipid bilayer

Question 13

how do other molecules get through the membrane

Answer 13

some are too big or polar and so can’t go through the lipid bilayers, instead they go through hydrophillic channel or carrier proteins.

Question 14

what is the difference between a channel protein and a carrier protein

Answer 14

channel - have a hydrophilic pore which can be open and closed carrier - have a binding shape for the molecule. they change their shape to allow the molecule to cross the membrane

Question 15

what is diffusion

Answer 15

movement of molecules from an area of higher concentration to an area of lower concentration

Question 16

what is osmosis

Answer 16

movement of water molecules from an area go high concentration of water to an area of low concentration of water through a partially permeable membrane

Question 17

what is a solvent

Answer 17

a substance that a chemical can dissolve in

Question 18

what is a solute

Answer 18

the molecule that dissolves

Question 19

what is water potential

Answer 19

a measure of free energy of water molecules and the tendency of water to movw

Question 20

what is water potential measured in

Answer 20

kPa (kilopascals)

Question 21

water moves from a less negative………

Answer 21

water potential to a more negative water potential

Question 22

what is the water potential in a dilute solution

Answer 22

more water potential energy

Question 23

what is the water potential in a concentrated solution

Answer 23

less water potential energy

Question 24

what is solute potential

Answer 24

how easily water molecules move out of a solution the more solute present the tighter the water molecules are held

Question 25

what is pressure potential

Answer 25

pressure builds up within a plant cell due to the cell wall making the plant turgid. this pressure is pressure potential, resisting more water entry

Question 26

what is the sign (+ or -) of pressure potential

Answer 26

+

Question 27

water potential =

Answer 27

pressure potential + solute potential

Question 28

what does it mean in a cell is hypertonic (plant and animal)

Answer 28

(plant)it is plasmolyse, the cell membrane is pulling away from the cell wall (animal) it will crenate it means that to much water is leaving the cell when in a concentrated solution in order to balance the amount of water outside the cell to the amount of water inside the cell

Question 29

what does is mean if a cell is isotonic

Answer 29

it remains the same as water leaves in equal parts

Question 30

what does it mean if a cell is hypotonic (plant and animal)

Answer 30

there is more water outside the cell than there is inside so more water will try and enter but the pressure potential will increase (plant) the cell wall will push out making the cell turgid(animal) the cell will explode as it has no cell wall to protect it and cant cope with the pressure

Question 31

what is incipient plasmolysis

Answer 31

when the water potential outside and inside a cell is equal there is no net movement half of the cell is plasmolysed and half is not

Question 32

what is ficks law

Answer 32

rate of diffusion is in proportion to (surface area x concentration gradient) / length of diffusion pathway

Question 33

why is the rate of diffusion only ‘in proportion to’ and not equal to

Answer 33

because there are other factors that affect the rate of diffusion

Question 34

what other factors affect the rate of diffusion

Answer 34

tempertaure size of diffusing molecules chemistry of diffusing molecules (polar or non polar)

Question 35

what is active transport

Answer 35

molecules move from a low concentration to a high concentration against the concentration gradient

Question 36

what does active transport need to take place

Answer 36

ATP for energy