2.1.5 - membranes🧪

Question 1

roles of membranes within cells

Answer 1

separate organelle content from cell cytoplasm
provides large surface area for aerobic respiration
contains digestive enzymes
where reactions can occur

Question 2

roles of membranes on the surface of cells

Answer 2

separate contents from environments
control entry and exit of molecules
facilitated diffusion, active transport
cell recognition
cell adhesion
receptors

Question 3

fluid mosaic model

Answer 3

fluid - phospholipids are free to move within layer, giving the membrane fluidity
mosaic - comes from the variety of different sizes, shapes and positions of the proteins within the bilayer

Question 4

intrinsic proteins

Answer 4

proteins of the cell surface membrane that completely span the phospholipid bilayer from one side to another

Question 5

channel proteins

Answer 5

intrinsic protein that provide a hydrophilic channel to help passive movement

Question 6

carrier proteins

Answer 6

intrinsic protein that has an important role in passive and active transport

Question 7

glycoproteins

Answer 7

intrinsic proteins with an attached carbohydrate chains of varying lengths and shapes, they play a role in cell adhesions and have receptors (cell signalling)

Question 8

glycolipids

Answer 8

lipids attached to a carbohydrate sugar chain
antigens that can be recognised by the cells immune system

Question 9

diffusion

Answer 9

the net overall movement of particles from a region of high concentration to a region of lower concentration. passive.

Question 10

facilitated diffusion

Answer 10

diffusion across a membrane using channel or carrier proteins

Question 11

osmosis

Answer 11

diffusion of water from a high water potential to a low water potential, through a partially permeable membrane

Question 12

water potential

Answer 12

the pressure exerted by water molecules as they collide with a membrane or container, measued in kPa

Question 13

how does water potential link to concentration

Answer 13

the more concentrated a solution, the more negative the water potential

Question 14

temperature and membrane permeability

Answer 14

when temperature increases, the molecules have more kinetic energy and it will move more, making the membrane more fluid causing a loss of structure increasing permeability

high temperatures may also denature enxymes, increasing permeability

Question 15

solvents and membrane permeability

Answer 15

many organic solvents are less polar than water therefore dissolving membranes and disrupting cells
pure alcohols can destroy cells in the body
more fluid, and therefore more permeable

Question 16

factors which affect the rate of diffusion

Answer 16

surface area, thickness of membrane, concentration gradient

Question 17

active transport

Answer 17

energy requiring process that moves material across a cell membrane against the concentration gradient

Question 18

process of active transport

Answer 18

1. molecule binds to receptors in channel or carrier protein
2. (inside) atp binds to carrier protein and is hydrolysed
3. binding of phosphate molecule to carrier protein changes shape and opens up
4. molecule released to inside of the cell
5. phosphate molecule released and atp is reformed
6. carrier protein returns to original shape

Question 19

bulk transport

Answer 19

a form of active transport where large molecules or whole bacterial cells are moved into or out of acell

Question 20

endocytosis

Answer 20

bulk transport of material into cells

Question 21

two types of endocytsosis

Answer 21

phagocytosis and pinocystosis

Question 22

process of endocytosis

Answer 22

• cell surface membranes invaginates and enfolds the substance
• membrane fuses to form vesicle containing the substance
• vesicle pinches off and moves into the cytoplasm to transfer the material for further processing

Question 23

exocytosis

Answer 23

process by which a cell releases large anmounts of material

Question 24

process of exocytosis

Answer 24

1. vescile buds from trans of golgi apparatus
2. vescile moves along microtubles
3. vesicle and membrane fuse
4. contents of vesicle spill out of cell
5. vesicle becomes part of plasma membrane

Question 25

cytolysis

Answer 25

bursting of a cell

Question 26

effect of placing an animal cell in a higher water potential

Answer 26

water will move into the cell, increasing hydrostatic pressure inside cell, potentially bursting it.

Question 27

effect of placing an animal cell in a lower water potential

Answer 27

water will move out of the cell, as water travels down the wp gradient. this may cause crenation

Question 28

turgor pressure

Answer 28

the pressure that water molecules exert against the cell wall

Question 29

plasmolysed plant cell

Answer 29

cell has lost water and the cytoplasm has shrunk; the membrane has pulled away from the cell wall

Question 30

turgid cell

Answer 30

a plant cell has absorbed water and has cytoplasm that is pressing outwards on the cell wall.

Question 31

phospholipids

Answer 31

- form the basic structure of bilayer membrane - makes the membrane flexible - prevent the passage of water soluble molecules but allow the passage of lipid soluble molecules

Question 32

extrinsic proteins

Answer 32

found on the surface or embedded in one layer of the membrane, and provide mechanical support

Question 33

cholesterol

Answer 33

restricts movement ofbother membrane components, making membranes less fluid