transport across membranes

Question 1

phospholipid bilayer is made up of..

Answer 1

one glycerol molecule attached to two fatty acid tails and a phosphate group. phosphate head is polar forming the hydrophilic head and the fatty acid tails form the hydrophobic region. Tails face each other, away from the water in cytoplasm and extracelluar fluid, forming a bilayer.

Question 2

what forms the fluid part of the cell membrane

Answer 2

movement of phospholipid bilayer

Question 3

what forms the mosaic part of the cell membrane

Answer 3

uneven distribution of proteins

Question 4

what does cholesterol do

Answer 4

decreases permeability of the membrane and increases the stability, more cholesterol=less fluidity of membrane

Question 5

what are channel proteins?

Answer 5

-pores within the membrane
-only allow specific charged ions and small molecules to move across by facilitated diffusion
-specific complementary molecules can pass through specific channel proteins

Question 6

carrier proteins

Answer 6

transport complementary charged/large molecules by facilitated diffusion and active transport

Question 7

role of receptor proteins?

Answer 7

act as receptors for specific complementary molecules

Question 8

glycoproteins

Answer 8

composed of carbohydrates and proteins. important in cell recognition and act as antigens
immune cells detect the specific shape of glycoproteins and recognise them as self
produced in the golgi-body

Question 9

what are aquaporins?

Answer 9

channel proteins specific to water

Question 10

what is diffusion?

Answer 10

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

Question 11

what type of process is diffusion?

Answer 11

passive-it does not require energy(ATP)

Question 12

what type of molecules can pass through the cell membrane via diffusion?

Answer 12

non-polar, small, lipid-soluble molecules

Question 13

fick’s law

Answer 13

RATE OF DIFFUSION=S.A X CONCENTRATION GRADIENT/DIFFUSION DISTANCE

Question 14

what is facilitated diffusion?

Answer 14

water-soluble , large or charged molecules pass through the cell membrane via channel or carrier proteins. they only transport complementary molecules

Question 15

what is osmosis?

Answer 15

net movement of water molecules from a higher water potential to a solution with lower water potential through a selectively permeable membrane

Question 16

highest water potential

Answer 16

0kPa

Question 17

what lowers the water potential

Answer 17

addition of solute

Question 18

what is water potential

Answer 18

free moving water molecules collide with the surface of the membrane and exert pressure , known as water potential

Question 19

what happens if water potential is higher outside the cell

Answer 19

water moves in via osmosis
animal cells swell and burst(lysis)
plant cells increase in mass and become turgid(cell wall prevents lysis)

Question 20

what happens if water potential is lower outside the cell

Answer 20

water moves out of the cell via osmosis
animal cells shrivel (crenatation)
plant cell membrane pulls away from the cell wall and become plasmolysed

Question 21

what is active transport?

Answer 21

net movement of molecules across a membrane from an area of lower concentration to an area of higher concentration using carrier proteins (and energy/ATP)

Question 22

how does the carrier protein transport the molecule?

Answer 22

molecule binds to the binding site of the carrier protein
hydrolysis of ATP releases energy and phosphorylates the protein
this causes the protein to change shape and transport the molecule across the membrane

Question 23

give an example of where exocytosis is used

Answer 23

to move enzymes and glycoproteins from the golgi apparatus to the cell surface membrane to secrete proteins

Question 24

exocytosis

Answer 24

ATP is required to move the vesicle to the cell membrane, it then fuses with the cell membrane and molecules are released

Question 24

endocytosis

Answer 24

cell membrane is pulled inwards to form a vesicle. This process requires the breakdown of ATP

Question 25

what type of process is osmosis

Answer 25

passive