Membranes 🧋

Question 1

What is the roles of membranes

Answer 1

Compartmentalise
Signalling (detect change in environment)
Controlling transporting

Question 2

How does phospholipid structure aid cell membrane

Answer 2

Acts as a barrier, stops water soluble molecules from leaking out and getting in unwanted

Question 3

how to phospholipids contribute to membrane formation

Answer 3

aqueous environment means heads point outward creating bi layre

Question 4

what type of reaction holds bilayer toghether

Answer 4

weak hydrophobic reactions between tails

Question 5

how is fluidity beneficial to membrane function

Answer 5

allows for spontaneous breaking and reforming of membranes

Question 6

how thick is the bilayre

Answer 6

approximately 7.5 nm

Question 7

how do unsaturated fatty acid tails effect membranes

Answer 7

make it less stable and more fluid as less packed togheter

Question 8

when would unsaturated fatty acid tails be useful

Answer 8

in extreme environments

Question 9

why do phospolidips get chemically modified

Answer 9

to act as signalling molecules

Question 10

how art phospilids chemically modified

Answer 10

moving within bilayer to activate other molecules
or being hydrolysed which releases smaller water soluble molecules that bind to specific receptors in cytoplasm

Question 11

role of glycolipids

Answer 11

maintain stability of cell membrane and to facilitate cellular recognition

Question 12

what do glycolipids act as

Answer 12

cell markers or antigens that can be recognised by immune cells

Question 13

impact of shorter fatty acids

Answer 13

increase fluidity, less viscous

Question 14

why are phospholipids fluid

Answer 14

due to them being in constant movement relative to one another

Question 15

what is the fluid mosaic model

Answer 15

phospholipids free to move, creat viscous layre, proteins randomly arranged in bilayer, free to move within layre relative to each other

Question 16

intergal (transmembrane proteins)

Answer 16

permantely attached and span across bilayer

Question 17

peripheral proteins

Answer 17

temporarily attached and associate with surface of membrane

Question 18

what structure do transmembrane proteins adopt

Answer 18

single helical or beta barrels forming channels

Question 19

glycoproteins

Answer 19

intrinsic proteins with a carbohydrate attached, have a role in adhesion and signal transduction

Question 20

how do glycoproteins act as a receptor

Answer 20

binding site for chemical signal

Question 21

cholesterol

Answer 21

maintains integrity and mechanical stability

Question 22

how does cholesterol affect fluidity

Answer 22

binds to fatty acid tail increasing packing of the membrane therefore reducing fluidity of membrane

Question 23

what does cholesterol make membranes less permeable to

Answer 23

very small water soluble molecules that would otherwise pass freely

Question 24

active transport

Answer 24

low to high conc active process requiring atp

Question 25

active transport step 1

Answer 25

molecule binds to receptor in channel of carrier protein outside cell, inside cell atp binds to carrier protein and is hydrolysed

Question 26

active transport step 2

Answer 26

binding of phosphate molecule to carrier protein causes protein to change shape, molecule is then realesed inside of cell

Question 27

active transport step 3

Answer 27

phosphate molecule is realesed from carrier protein and recombines with adp to form atp, so carrier protein returns to original shape

Question 28

is active transport selective

Answer 28

yes, specific substances are transported by specific carrier proteins

Question 29

bulk transport

Answer 29

active movement of large molecules

Question 30

endocytosis

Answer 30

is bulk transport of materials into cells

Question 31

phagocytosis

Answer 31

endocytosis for solids

Question 32

pinocytosis

Answer 32

endocytosis for liquids

Question 33

endocytosis process

Answer 33

cell surface membrane invaginates when it comes into contact with material, membrane unfolds intill fuses forming a vesicle, which pinches off and moves into cytoplasm for further processing inside cell

Question 34

exocytosis

Answer 34

vesicles move towards and fuse with cell surface membrane, contents of vesicle then realised outside of cell

Question 35

energy in diffusion

Answer 35

particles have KE so movement is random and unequal, particles collides slowing process down, not requiring energy as would be supplied to slowly

Question 36

facilitated diffusion

Answer 36

movement down a gradient across a membrane through protein channels

Question 37

can polar molecules travel through

Answer 37

no except for water as its so small

Question 38

can non polar molecules travel through

Answer 38

yes, but large polar ions cannot pass through

Question 39

can ions pass through

Answer 39

no

Question 40

carrier proteins

Answer 40

integral glycoproteins which bind to a solute and undergo change of shape, only bind to specific molecule, can go against conc gradient using atp

Question 41

which form of protein transport is slower

Answer 41

carrier protein 1000 molecules per second

Question 42

channel proteins

Answer 42

intergral lipoproteins, with fixed shape. only go along conc gradient

Question 43

what do channel proteins transport

Answer 43

ions and they are ion selective

Question 44

effect of alcohol

Answer 44

dissolve membrane, disrupting cells. membrane becomes more permeable and fluid and interactions cannot happen as normal

Question 45

effect of hot tempetures

Answer 45

more KE and move more, so membrane becomes more fluid and loses structure. proteins denature at high temps and if temp increases cell will completely break down

Question 46

effect of cold temps

Answer 46

water expands and ice crystals can pierce membranes, proteins can deform, permeability of membrane increases

Question 47

what helps to regulate membranes in hot temps

Answer 47

cholesterol which regulates membrane fluidity at high temps stabilising membrane and raising melting point

Question 48

solute

Answer 48

substance dissolves in solent to form a solution

Question 49

concentration

Answer 49

mass os solute in given volume of aqueous solution

Question 50

hypotonic

Answer 50

lower solute than ...

Question 51

hypertonic

Answer 51

higher solute than

Question 52

isotonic

Answer 52

same levels of solute

Question 53

what is water potential

Answer 53

pressure created by water molecules as they collide with membrane or container units : kPa

Question 54

water potential of pure water

Answer 54

o kPa which is highest value

Question 55

what do solutes do to w.p

Answer 55

reduce it

Question 56

water potential in plant cells

Answer 56

w.p = solute potential + pressure potential

Question 57

water potential in animal cells

Answer 57

water potential = solute potential

Question 58

cytolysis

Answer 58

cell full of water then burst as cell surface membrane unable to stretch

Question 59

crenation

Answer 59

cell shrinks as water moves out of cell

Question 60

turgor pressure

Answer 60

pressur exerted on cell wall when cell full of water

Question 61

plasmolyse

Answer 61

plant cell protoplast shrinks and pulls away fro cell wall