Unit 2 - Factors Affecting Membrane Structure Flashcards
in a membrane, what are constantly moving?
phospholipids
what does temperature do to phospholipids
increase in temp gives the mobile phospholipids more energy, to move more
more kinetic energy to phospholipids, the more
fluid the membrane is, and it begins to lose its structure
eventually break down completely
loss of structure
increases permeability
particles enter easier
which molecules denature as temp rises?
carrier and channel proteins, so transport is affected
water is a
polar solvent
essential to formation of phospholipid bilayer
what substances dissolve membranes?
organic solvents, like ketones, ethanol (alcohols) benzene
all non polar or not very polar
how do antiseptic wipes work
alcohol in them dissolve the membranes of bacteria which kills them
alcohols can enter the bilayer and
get between phospholipids, disrupting structure
active exchanges across a membrane require
metabolic energy
define diffusion
the net overall movement of particles across a partially permeable membrane
from an area of high to low concentration
diffusion will happen until
there is an equilibrium between the two areas
what slows diffusion that the particles do
collisions between particles slows them down
as diffusion distance increases
diffusion rate decreases, as more collisions have taken place over the longer distance
factors affecting rate of diffusion x2
temperature
concentration difference
concentration difference in diffusion
net movement is larger so increases diffusion
why can’t ions travel easily across the membrane (they still can though)
the hydrophobic tail interior of the bilayer repels any positive or negative charge
rate of diffusion of ions or molecules is affected by. x2
surface area, thickness of membrane
thinner membrane = quicker diffusion
in facilitated diffusion, polar molecules and ions can pass in the bilayer through
channel proteins
membranes with channel proteins are ___ because channel proteins are ______
selectively permeable, specific to one molecule or ion
rate of facilitated diffusion is dependant on x5
temperature
membrane surface area
membrane thickness
number of channel proteins
concentration gradient difference
active transport defintion
movement of molecules or ions into or out of a cell from an area of low concentration to high
metabolic energy is
supplied by ATP, adenosine triphosphate
steps of active transport x6
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
what is bulk transport
large molecules are too large to fit in carrier or channel proteins, so are moved by bulk transport
endocytosis
bulk transport into cells
types of endocytosis x2
phagocytosis, pinocytosis
phagocytosis is for
solids
pinocytosis is for
liquids
process of endocytosis x4
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
exocytosis
vesicles move towards and fuse with the cell surface membrane where contents moves out
atp is needed for the vesicles
to move along the exoskeleton,
shape change of cells to engulf,
and fusion of the cell membrane and vesicle
osmosis is
the movement of water across a partially permeable membrane from an area of high water potential to low and is passive
concentration defintion
the amount solute in a certain volume of aqueous solution
water potential definition
the pressure exerted by water molecules as they collide with container or membrane
symbol for water potential
psi
what is the psi of are water at RTP
0kpa
what is rtp
-25*c, 100atm
all solutions have a
negative water potential
adding a solute decreases the psi
so pure is 0 which is highest
osmosis happens until
equilibrium is reached
hydrostatic pressure is
osmosis of water into a solution increases volume. in a closed system, this leads to an increase of pressure. this pressure is hydrostatic pressure
hydrostatic pressure units
same as water potential, kPa
when an animal cell, with a thin cell membrane is put into a higher water potential,
water enters
will burst and break called cytolysis
animal cell placed in a lower water potential
water moves out cell
crenation occurs
cell membrane “puckers”
pressure in plant cells
turgor
water hydrostatic pressure against cell wall (made of cellulose)
as turgor increases
it resists entry of further water
cell is now turgid
plant cells in a lower water potential
water is lost by osmosis
Reduction of volume of cytoplasm
pulls the cell membrane away from cell wall
=plasmolysed
