Unit 2 - Factors Affecting Membrane Structure

Question 1

in a membrane, what are constantly moving?

Answer 1

phospholipids

Question 2

what does temperature do to phospholipids

Answer 2

increase in temp gives the mobile phospholipids more energy, to move more

Question 3

more kinetic energy to phospholipids, the more

Answer 3

fluid the membrane is, and it begins to lose its structure
eventually break down completely

Question 4

loss of structure

Answer 4

increases permeability
particles enter easier

Question 5

which molecules denature as temp rises?

Answer 5

carrier and channel proteins, so transport is affected

Question 6

water is a

Answer 6

polar solvent
essential to formation of phospholipid bilayer

Question 7

what substances dissolve membranes?

Answer 7

organic solvents, like ketones, ethanol (alcohols) benzene
all non polar or not very polar

Question 8

how do antiseptic wipes work

Answer 8

alcohol in them dissolve the membranes of bacteria which kills them

Question 9

alcohols can enter the bilayer and

Answer 9

get between phospholipids, disrupting structure

Question 10

active exchanges across a membrane require

Answer 10

metabolic energy

Question 11

define diffusion

Answer 11

the net overall movement of particles across a partially permeable membrane
from an area of high to low concentration

Question 12

diffusion will happen until

Answer 12

there is an equilibrium between the two areas

Question 13

what slows diffusion that the particles do

Answer 13

collisions between particles slows them down

Question 14

as diffusion distance increases

Answer 14

diffusion rate decreases, as more collisions have taken place over the longer distance

Question 15

factors affecting rate of diffusion x2

Answer 15

temperature
concentration difference

Question 16

concentration difference in diffusion

Answer 16

net movement is larger so increases diffusion

Question 17

why can’t ions travel easily across the membrane (they still can though)

Answer 17

the hydrophobic tail interior of the bilayer repels any positive or negative charge

Question 18

rate of diffusion of ions or molecules is affected by. x2

Answer 18

surface area, thickness of membrane
thinner membrane = quicker diffusion

Question 19

in facilitated diffusion, polar molecules and ions can pass in the bilayer through

Answer 19

channel proteins

Question 20

membranes with channel proteins are ___ because channel proteins are ______

Answer 20

selectively permeable, specific to one molecule or ion

Question 21

rate of facilitated diffusion is dependant on x5

Answer 21

temperature
membrane surface area
membrane thickness
number of channel proteins
concentration gradient difference

Question 22

active transport defintion

Answer 22

movement of molecules or ions into or out of a cell from an area of low concentration to high

Question 23

metabolic energy is

Answer 23

supplied by ATP, adenosine triphosphate

Question 24

steps of active transport x6

Answer 24

1) molecule or ion binds to the receptors in the channel of a carrier protein, which is specific

2) on the inside, ATP binds to carrier protein, and Is hydrolysed into ADP and phosphate

3) The phosphate molecule binds to the carrier protein and changes its shape

4) ion/molecule enters cell

5) phosphate unattached from carrier protein and rejoins he ADP to remake ATP

6) carrier protein returns to original shape

Question 25

what is bulk transport

Answer 25

large molecules are too large to fit in carrier or channel proteins, so are moved by bulk transport

Question 26

endocytosis

Answer 26

bulk transport into cells

Question 27

types of endocytosis x2

Answer 27

phagocytosis, pinocytosis

Question 28

phagocytosis is for

Answer 28

solids

Question 29

pinocytosis is for

Answer 29

liquids

Question 30

process of endocytosis x4

Answer 30

1) cell surface membrane invaginates
(bends inwards) when comes into contact w molecule
2) membrane enfolds material until it fuses
3) forming a vesicle
4) vesicle pinches off and moves into cytoplasm

Question 31

exocytosis

Answer 31

vesicles move towards and fuse with the cell surface membrane where contents moves out

Question 32

atp is needed for the vesicles

Answer 32

to move along the exoskeleton,
shape change of cells to engulf,
and fusion of the cell membrane and vesicle

Question 33

osmosis is

Answer 33

the movement of water across a partially permeable membrane from an area of high water potential to low and is passive

Question 34

concentration defintion

Answer 34

the amount solute in a certain volume of aqueous solution

Question 35

water potential definition

Answer 35

the pressure exerted by water molecules as they collide with container or membrane

Question 36

symbol for water potential

Answer 36

psi

Question 37

what is the psi of are water at RTP

Answer 37

0kpa

Question 38

what is rtp

Answer 38

-25*c, 100atm

Question 39

all solutions have a

Answer 39

negative water potential
adding a solute decreases the psi
so pure is 0 which is highest

Question 40

osmosis happens until

Answer 40

equilibrium is reached

Question 41

hydrostatic pressure is

Answer 41

osmosis of water into a solution increases volume. in a closed system, this leads to an increase of pressure. this pressure is hydrostatic pressure

Question 42

hydrostatic pressure units

Answer 42

same as water potential, kPa

Question 43

when an animal cell, with a thin cell membrane is put into a higher water potential,

Answer 43

water enters
will burst and break called cytolysis

Question 44

animal cell placed in a lower water potential

Answer 44

water moves out cell
crenation occurs
cell membrane “puckers”

Question 45

pressure in plant cells

Answer 45

turgor
water hydrostatic pressure against cell wall (made of cellulose)

Question 46

as turgor increases

Answer 46

it resists entry of further water
cell is now turgid

Question 47

plant cells in a lower water potential

Answer 47

water is lost by osmosis
Reduction of volume of cytoplasm
pulls the cell membrane away from cell wall
=plasmolysed