4 transport across cell membranes

Question 1

what is the cell surface membrane made up of?

Answer 1

phospholipids

Question 2

explain the fluid mosaic model

Answer 2

phospholipids form a bilayer that constantly moves around relative to one another in a fluid structure
protein molecules in bilayer unevenly distributed forming a mosaic

Question 3

what is the function of the phospholipid bilayer?

Answer 3

to allow lipid soluble substances to enter and leave the cell

Question 4

name what components are within the phospholipid bilayer

Answer 4

phospholipids
cholesterol
channel proteins
carrier proteins
receptor proteins
enzymes
glycoproteins
aquaporins

Question 5

what does the phospholipid bilayer allow through by simple diffusion?

Answer 5

lipid soluble molecules (non polar)

Question 6

what is the function of cholesterol in the phospholipid bilayer?

Answer 6

decreases permeability and increases stability

Question 7

what is the function of a channel protein?

Answer 7

• only allow specific charged ions or small molecules to move across the membrane by facilitated diffusion

Question 8

what is the function of a carrier protein?

Answer 8

help with the transport of ions/ polar molecules/ large molecules by facilitated diffusion and active transport

Question 9

what could bind to receptor proteins?

Answer 9

insulin/hormones

Question 10

do all cells have the same receptor proteins?

Answer 10

no

Question 11

what is the function of a glycoprotein in a phospholipid bilayer?

Answer 11

important in cell recognition often acting as antigens
identify cells as self or non self

Question 12

where are glycoproteins produced?

Answer 12

golgi body

Question 13

do all cells have glycoproteins on their cell surface membrane?

Answer 13

yes

Question 14

what is an aquaporin?
what can a cell with lots of aquaporins do?

Answer 14

special type of channel protein specific to water
a cell with lots of aquaporin can carry out osmosis easily

Question 15

what can movement of substances into or out of cells occur by?

Answer 15

simplediffusion
facilitated diffusion
osmosis
active transport
co transport
exo/endocytosis

Question 16

does simple diffusion require ATP?

Answer 16

no

Question 17

define diffusion

Answer 17

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

Question 18

give an example of what simple diffusion can help move through the membrane

Answer 18

O2
oestrogen

Question 19

give the equation for ficks law

Answer 19

rate of diffusion =
surface area x conc grad/diffusion distance

Question 20

what factors affect the rate of diffusion?

Answer 20

temperature
surface area
conc gradient
diffusion distance

Question 21

how does temperature affect the rate of diffusion?

Answer 21

increased kinetic energy leads to faster rate of diffusion

Question 22

how does surface area affect the rate of diffusion?

Answer 22

larger surface area provides more space for molecules to pass through- faster diffusion

Question 23

how does concentration gradient affect the rate of diffusion?

Answer 23

as concentration difference increases, rate of diffusion increases

Question 24

how does diffusion distance affect the rate of diffusion?

Answer 24

the shorter the diffusion distance the faster the molecules will travel through

Question 25

what part of the phospholipid bilayer is hydrophobic and hydrophilic?

Answer 25

hydrophobic tails hydrophilic heads

Question 26

why cant hydrophilic substances pass through the tails of the bilayer?

Answer 26

because the fatty acid tails are non polar and repel polar molecules

Question 27

how do water soluble molecules move through the membrane?

Answer 27

through channel or carrier proteins via facilitated diffusion

Question 28

does facilitated diffusion require ATP?

Answer 28

no

Question 29

define osmosis

Answer 29

the net movement of water molecules from higher water potential to a solution lower water potential through a partially permeable membrane

Question 30

what is water potential?

Answer 30

the pressure exerted on the membrane due to free moving water molecules colliding with it

Question 31

what is water potential measured in?

Answer 31

kPa

Question 32

what solution has the highest water potential?

Answer 32

pure water

Question 33

how many kPa does pure water have?

Answer 33

0

Question 34

why does water have 0kPa?

Answer 34

because all water molecules are free moving

Question 35

what happens when you add a solute to a solution?

Answer 35

the water potential becomes more negative

Question 36

why does adding a solute to a solution make it have a more negative water potential?

Answer 36

H2o is a dipole so is attracted to charges on solutes, decreasing the amount of free moving water molecules so less pressure exerted onto membrane

Question 37

which way does water move when the inside of a cell has a higher water potential than outside?

Answer 37

down water potential gradient/moves to inside the cell

Question 38

which way does water move when the inside of a cell has a lower water potential than outside?

Answer 38

down water potential gradient/moves to outside the cell

Question 39

what can happen to an animal cell when there is a higher water potential inside the cell than outside?

Answer 39

swelling and lysis

Question 40

what can happen to a plant cell when there is a higher water potential inside the cell than outside?

Answer 40

swelling and increased mass NOT lysis

Question 41

why don't plant cells undergo lysis if water is moving into the cell b osmosis?

Answer 41

cellulose prevents lysis

Question 42

what is lysis?

Answer 42

bursting

Question 43

what can happen to an animal cell when there is a higher water potential outside the cell than inside?

Answer 43

crenation (shrivelling)

Question 44

what can happen to a plant cell when there is a higher water potential outside the cell than inside?

Answer 44

cells plasmolyse (cell membrane pulls away from cell wall)

Question 45

what does isotonic mean?

Answer 45

no net movement of water in or out of cells

Question 46

what is active transport?

Answer 46

transportation of molecules against a concentration gradient (from low concentration to high concentration)

Question 47

what does active transport use to tranport molecules?

Answer 47

ATP carrier proteins

Question 48

how does active transport use carrier proteins and ATP to transport molecules against a concentration gradient?

Answer 48

1. molecule binds to specifically complementary binding site on carrier protein 2. ATP hydrolysed into ADP + Pi releasing small amounts of energy/phosphorylating protein 3. carrier proteins tertiary structure changes, transporting molecule across

Question 49

what are two types of active transport?

Answer 49

exo and endocytosis

Question 50

briefly describe the process of exocytosis

Answer 50

uses golgi vesicles to move large quantity of molecules to be secreted form inside the cell to outside of the cell

Question 51

briefly describe the process of endocytosis

Answer 51

cell surface membrane 'pulled' inwards creating a vesicle

Question 52

what do exocytosis and endocytosis require ATP for?

Answer 52

movement/creation of vesicles

Question 53

what happens to transport across membranes if aerobic respiration stops?

Answer 53

active transport can't occur due to less ATP being made

Question 54

what happens to transport across membranes if the tertiary structure of a carrier protein changes?

Answer 54

active transport and facilitated diffusion inhibited as molecule is no longer specifically complementary

Question 55

describe how amino acids are absorbed from the ileum into the blood

Answer 55

1. Na+ actively transported out of epithelial cell into the blood by NaK pump 2. creating a conc grad of Na+ 3. Na+ and amino acid enter by facilitated diffusion 4. Na+ moves into the cell down its conc grad 5. amino acids move into the cell against their conc grad 6. amino acids move into the blood by facilitated diffusion