transport across membranes

Question 1

what is diffusion

Answer 1

the net movement of particles from an area of higher concentration to an area of lower concentration

Question 2

what are the properties of diffusion

Answer 2

no membrane required
no ATP required (passive)
continues until equilibrium occurs
diffusion of different particles independent
random movement of particles

Question 3

what factors affect the rate of diffusion

Answer 3

temperature
concentration gradient
surface area of membrane
diffusion distance
size of molecule/ion

Question 4

how does temperature affect rate of diffusion

Answer 4

increases kinetic energy therefore rate of diffusion increases

Question 5

how does concentration affect rate of diffusion

Answer 5

increase concentration gradient increases rate of diffusion

Question 6

how does surface area of membrane affect rate of diffusion

Answer 6

increase surface area means higher rate of diffusion

Question 7

how does diffusion distance affect rate of diffusion

Answer 7

smaller distance means faster rate of diffusion

Question 8

what is the effect of sizes of molecules/ions on rate of diffusion

Answer 8

smaller size means higher rate of diffusion

Question 9

what are the properties of simple diffusion

Answer 9

only for lipid-soluble, non-polar molecules
can pass through phospholipid bilayer
examples:hormones, oxygen and carbon dioxide

Question 10

what is facilitated diffusion

Answer 10

diffusion via channel or carrier proteins and no ATP is required (passive)

Question 11

what goes through specific channel proteins

Answer 11

ions

Question 12

what goes through specific carrier proteins

Answer 12

polar or water soluble molecules eg glucose or amino acids

Question 13

How do carrier proteins work?

Answer 13

binding of molecule causes carrier protein to change shape and change of shape therefore causes amino acid to be released on other side of membrane

Question 14

what is osmosis

Answer 14

the net movement of water from area of higher water potential to lower water potential through a semi permeable membrane until equilibrium

Question 15

what is water potential

Answer 15

concentration of water

Question 16

what is the highest water potential

Answer 16

0 and this is for pure water

Question 17

what are the properties of osmosis

Answer 17

passive process
continues until equilibrium
follows movement of solute as water potential decreases
random movement of particles

Question 18

what happens when theres a lower water potential inside an animal cell but higher outside

Answer 18

water enters the cell and because the plasma membrane cant stretch the cell cytolyses

Question 19

what happens when theres a higher water potential inside animal cell and lower outside

Answer 19

water leaves cell and cell cremates

Question 20

what happens when theres a lower water potential inside plant cell but higher outside

Answer 20

water enters the cell and because the plasma membrane supported by cell wall cell becomes turgid

Question 21

what happens when theres a higher water potential inside cell

Answer 21

water leaves the cell and cell becomes plasmolysed

Question 22

what is plasmolysis

Answer 22

plasma membrane of plant comes away from cell wall

Question 23

what is flaccid

Answer 23

when all cells in a tissue are plasmolysed

Question 24

what membranes are there inside cells

Answer 24

surrounding vesicles, lysosomes, smooth and rough endoplasmic reticulumn, golgi, mitochondria and chloroplasts

Question 25

whats the role of outside cell membranes

Answer 25

acts as a barrier
semi-permeable
cell recognition
cell signalling

Question 26

what is the role of inside cell membranes

Answer 26

compartmentalisation
semi-permeable
site of metabolic pathways

Question 27

what is meant by fluid mosaic model of cell

Answer 27

randomly arranged proteins in constant motion and hydrophillic heads facing outwards and hydrophobic tails facing inwards

Question 28

what is the role of phospholipid bilayer

Answer 28

its two layers of phospholipids which ONLY allows lipid soluble molecules to pass through

Question 29

what is the role of protein channels

Answer 29

allows ions to diffuse through by facilitated diffusion

Question 30

what is the role of carrier proteins

Answer 30

allows polar molecules to diffuse via facilitated diffusion

Question 31

what is the role of glycolipids and glycoproteins

Answer 31

acts as cell recognition

Question 32

what is an intrensic protein

Answer 32

protein that spans whole of bilayer

Question 33

what is an extrensic protein

Answer 33

any protein that doesnt span whole of bilayer

Question 34

what is the role of intrensic proteins

Answer 34

may be involved in cell signalling because proteins can have a multitude of tertiary structures which means that they can be complementary to particular molecules eg hormones which can bind to them on outside of plasma membrane and then cause series of reactions to occur within cytoplasm

Question 35

what is the role of cholesterol

Answer 35

binds to lipid tails of phospholipid molecule and causes them to pack more tightly and phospholipid bilayer becomes less fluid and more rigid

Question 36

how does temperature affect permeability

Answer 36

increase in temp increases kinetic energy of phospholipids and proteins and at certain temperatures plasma membrane ruptures and proteins denature

Question 37

how does solvent concentration affect permeability

Answer 37

increase in solvent concentration means more lipid dissolved and at certain concentration cell rupture occurs