Transport across membranes

Question 1

what does partially permeable mean

Answer 1

lets some moelcules in but not others

Question 2

what are the 3 types of transport across momebranes

Answer 2

active transport
osmosis
difficult (simple/facilitated)

Question 3

what is the membrane structure

Answer 3

composed of phospholipids , proteins and carbohydrates

Question 4

fluid moasic model what does it mean

Answer 4

describe the arranegment of moelcules in the membrane
fluid - the phospholipid layer is flexible as constantly moving
moasic - many different proteins, carbohydrates all of different shapes and szies

Question 5

what is a bilayer

Answer 5

phospholipid moelcules form a continous, double layer

Question 6

what types of proteins are there and what do they do

Answer 6

• channel proteins and carrier proetins - allow larger moelcules and ions pass through
• receptor proteins - all cell to detect chemicals released from other cells

Question 7

what is glycoprotein

Answer 7

protein have a carbohydrate atatched

Question 8

what is a glycolipid

Answer 8

lipid with carbohydrate attached

Question 9

what is cholesterol role

Answer 9

• gives membrane stabilitu
• type of lipid
• fits between the phospholipids
• binds to hydrophobic tail
• causing them to pack closely together
• restricts moevemnt of phospholipid - makes membrane less fluid and more rigid
• helps to maintain shape of animal cells
• also has a hydrophobic region, able to create further barrier

Question 10

phospholipid role

Answer 10

• barrier to dissolved substance

- as center is hydrophobic so doesn’t allow water through

Question 11

phospholipid structure

Answer 11

• hydrophilic head
• hydrophobic tail
• so moelcules arrange into a bilayer
• head facing outwards on either side

Question 12

what is the membrane like below 0

Answer 12

• not much energy
• packed cloesly together
• rigid membrane
• channel proteins/carrier denature
• increasing perm of membrane
• ice crystals pierce membrane - highly perm when thaws

Question 13

what is the membrane like between O and 45

Answer 13

• phospholipids can move around
• not tightly packed together
  membrane partially permeable
• temperature increases the phospholipids move more energy
• increases perm of mem

Question 14

what is the membrane like above 45

Answer 14

• phospholipid bilayer starts to break down
• becomes more perm
• water inside expands
• putting pressure on mem
  channel/carrier proteins denature cant control what leaves/enter
• increasing perm

Question 15

what is diffiussion

Answer 15

net movement of particles from area of higher conc to area of lower conc

Question 16

what is simple diffiusion

Answer 16

when moelcules directly diffuse through a cell membrane

Question 17

what effetcs ROD

Answer 17

• conc m
• thickens
• SA

Question 18

what is facilitated diffusion

Answer 18

• large/charged molecules diffuse through carrier proteins/channel proteins in cell membrane

Question 19

how does a carrier protein work in facilitated diffusion

Answer 19

1. larger mol attached to carrier protein
2. protein changes shape
3. releases molecule on opp side of mem

Question 20

how does a channel protein work in facilitated diff

Answer 20

charged particles diffuse through

different channel proteins facilitated diffusion of different charged particles

Question 21

what affects the rate of FD

Answer 21

conc m

number of channel/carrier proteins

Question 22

what is osmosis

Answer 22

diffusion of water moelcules across partially permeable membrane from area of high water potential to an area of low water potential

Question 23

what is water potential

Answer 23

likelihood of water moelcules to diffuse out

Question 24

what is isotonic

Answer 24

water pot same

Question 25

what is hypotonic

Answer 25

net movement into cell

Question 26

hypertonic?

Answer 26

net movement water out of cell

Question 27

what is active transport

Answer 27

uses energy to move moelcules and ions across membrane against a concentration gradient

Question 28

what proteins are used in active transport

Answer 28

carrier proteins and co-transporters

Question 29

how does carrier protein work in AT

Answer 29

• molecule attaches to carrier protein
• protein changes shape
• moves moelcules across mem

Question 30

where does AT get its energy

Answer 30

hydrolysis of ATP

Question 31

what is a co-transporter

Answer 31

type of carrier protein, binds to two moelcules at a time. the conc gradient of one mol is used to move the other mol against its own conc m

Question 32

describe the process of co-transport and the absorbtion of glucose in the illeum

Answer 32

1. Na+ AT out of epithelial cells in illeum into blood by sodium potassium pumo
2. creates conc m , now higher conc of Na+ in the lumen of illeum than inside the cell
3. this causes sodium ions to diffuse from lumen of ileum into epithelial cell down conc gradient
   (via sodium-glucose co-transporter protein)
4. co transporter carrier glucose into cell with the sodium. as a result conc of glucose inside cell increse
5. glucose diffuse sout of the cell, into the blood down conc m through protein channel via faciliated diff