Mr Allsop- cell membranes

Question 1

What is the general role of the cell membrane

Answer 1

Separates contents from outside/cytoplasm.
Cell recognition and signalling
Hold components of some metabolic pathways in place.

Question 2

What are polar molecules

Answer 2

Partially charged as they have an uneven share of electrons.
Cannot move through middle layer of membrane as are insoluble in fat.

Question 3

What is the phospholipid bilayer

Answer 3

Has two layers
Hydrophilic head- attracted to water
Hydrophobic tail -face inwards away from water .
Middle layer is fat
Gas , small polar molecules can diffuse through gap but large polar molecules, charged molecules cannot diffuse.

Question 4

What are non polar molecules

Answer 4

Uncharged
Soluble in fat- can cross membrane but is hydrophobic

Question 5

What is the fluid mosaic model

Answer 5

(Things move)
Membrane composed of phospholipid bilayer within various molecules floating around.
Lipid bilayer- lipid molecule with hydrophobic heads in contact with watery exterior.

Question 6

What is glycoprotein

Answer 6

Protein attached to carbohydrate.
Role in cell adhesion and as receptors for signalling. (Receptors of insulin/glucagon are glycoproteins both affect uptake/storage of glucose by cells)

Question 7

What is glycolipid

Answer 7

Attach to phospholipid
Lipids with carbohydrate attached by glycosidic bond. Maintains stability of cell membrane. Connect to form tissue
(Antigens)

Question 8

What is glycocalyx

Answer 8

‘Sugar coat’
Formed from carbohydrate chains.
Attracted to lipids of proteins in membrane.

Question 9

What is colesterol

Answer 9

Lipid
Regulates fluidity and stability of membrane .
In between phospholipid molecules to stop them getting to close when the temperature decreases.
Helps animals resist temperature change.

Question 10

What are intrinsic proteins

Answer 10

Trans membrane
Some are channel proteins (allow charged ions to pass through )
Some are carrier proteins ( change shape to allow large molecules to be pushed through)

Question 11

Role of membranes within a cell

Answer 11

Inner membrane of mitochondria, crustal give large surface area for aerobic respiration.
Digestive enzymes- plasma membrane of epithelial cells of small intestine, breakdown of certain types of sugars

Question 12

What is a peripheral protein

Answer 12

Part of the bilayer

Question 13

what is an integral protein

Answer 13

Goes through the whole bio layer

Question 14

what are the factors effecting membrane permeability ?

Answer 14

membrane integrity is vital to selective permeability.
temperature, proportion of cholesterol, proportion of saturated and unsaturated fats, presence of solvents.

Question 15

what happens to protein’s in the membrane as temperature increases

Answer 15

the phospholipid bilayer moves constantly which increases the kinetic energy, making the membrane higher in fluidity but this means there is less membrane integrity and in very high temp the hydrogen and ionic bonds will break making the enzymes denature and changes the tertiary membrane permanently.

Question 16

what is unsaturated fatty acids

Answer 16

‘kinks in the tails’ of phospholipid biolayer.
2 covalent bonds .
allows fluidity when temperature decreases, stops it solidifying.

Question 17

what is saturated fatty acids

Answer 17

viscous phospholipid biolayer (compact)
one covalent bond
no room for fluidity
good for high temp as stops it separating

Question 18

what does the amoeba do

Answer 18

pseudopods ‘ fake feet’ - project to get phagocytes.

Question 19

organic solvents (ethanol)

Answer 19

dissolves lipids/ membranes
antiseptic- disrupts cell surface membrane of bacteria so kills it. sometimes destroys cells
drunkenness- slightly breaks down membrane- affects nerve impulse.

Question 20

what is diffusion

Answer 20

the net movement of particles from a high concentration to a low concentration down the concentration gradient.

Question 21

what is net movement

Answer 21

goes mainly one direction but does go in both.

Question 22

what is a transport system

Answer 22

remove diffusing molecules to maintain concentration gradient.

Question 23

what is simple diffusion

Answer 23

molecules like co2/02 and small/ soluble lipids pass through membrane unassisted .
passive process- doesn’t require energy.
large lipids can pass through as they dissolve in the fatty bilayer.

Question 24

what is facilitated diffusion

Answer 24

water/ polar/ lipid-insoluble molecules can’t pass through so rely on carrier proteins/ channel proteins.
carrier protein- glucose/amino acids - they change shape to allow them to pass through.
channel proteins- water/ions as they can’t pass through bilayer.

Question 25

what is an aquaporin

Answer 25

channel where water passes through.

Question 26

how does diffusion work in the alveolus

Answer 26

oxygen in blood cells continually are pumped away so there is a lower concentration of oxygen in the blood than alveolus, so maintains a concentration gradient as new deoxygenated cells enter.

Question 27

how do carrier proteins work

Answer 27

they are a specific shape that normally carry one specific molecule so when that molecule comes it opens to allow conformational change ( shape change) so solute comes out other end.

Question 28

what is active transport

Answer 28

movement from a low to high concentration against the concentration gradient.
requires energy in the form of ATP which is produced by respiration in the mitochondria.

Question 29

describe how active transport opens carrier proteins

Answer 29

ATP binds to the end of the carrier protein causing a hydrolysis reaction (addition of water) that forms ADP and a phosphate which allows for conformational change and substance passes through.

Question 30

what is endocytosis

Answer 30

large substances enter by invagination so is trapped in the membrane.
this is possible because of the fluidity in membrane.

Question 31

what is exocytosis

Answer 31

vesicles fuse to plasma membrane and releases its contents in the cytoplasm as the membrane changes shape ‘pumping it in’

Question 32

what are the two types of endocytosis and what do they do?

Answer 32

phagocytosis- ‘cell eating’ .
it traps food/solid substances.
pinocytosis- ‘cell drinking’
vesicle traps liquid to be taken into cell.

Question 33

What is crenation

Answer 33

In an animal cell when there is a solution of low water potential a water potential gradient is established so water moves down the concentric gradient , out of the cell causing it to shrink ( crenation)

Question 34

What is plasmolysis

Answer 34

In a plant cell when it is placed into a hypertonic (high solute concentration. Low water potential) Cytoplasm shrinks and membrane pulls away when placed in hypertonic solution. As the cell wall is strong so dokey change shape.

Question 35

What is cytolysis

Answer 35

In an animal cell when it is placed into a hypotonic solution (lots of water , little solute) water enters cell lowering potential gradient making it burst as it has no cell wall.

Question 36

What is haemolysis

Answer 36

Red blood cells burst

Question 37

What happens when a plant cell is placed into a hypotonic solution ( little solute )

Answer 37

Water moves in down potential gradient. Which causes cell to swell increasing turgour pressure but won’t burst as it has a cell wall.