3.2.3 Transport across cell membranes Flashcards
what is the cell surface membrane
a barrier between the cell and its environment
controls what enters and leaves the cell
partially permeable
why does the cell membrane have a Fluid Mosaic Structure
fluid- phospholipids are able to move
mosaic- made up of many components such as the phospholipid bilayer, glycoproteins and glycolipids
how are phospholipids arranged
they are arranged in a bilayer
what is meant by hydrophobic
it repels water
what is meant by hydrophilic
it attracts water
what part of the phospholipid is hydrophopic
the fatty acid tail
what part of the phospholipid is hydrophilic
the phosphate head
what type of molecules are allowedd to move through the phospholipid bilayer by
non-polar molecules
lipid soluble molecules
small molecules
what does the bilayer restrict
the movement of large/polar molecules
what do channel proteins allow the movement of
allow the movement of water-soluble/ polar molecules
what do carrier proteins allow the movement of
movement of molecules against concentration gradient using ATP
what is cholestral made up of
lipid
what is the role of cholestral
the make the membrane rigid by restricting the lateral movement of phospholipids
where in the cell membrane is cholestral found
they bind to the hydrophobic tail
what happens to the cell membrane when the temperature is increased
thee membrane permeability increases
explain what happens to the cell membrane when the temperature is really really high (45 degrees)
phospholipids have more kinetic energy
-the bilayer starts to melt
- the membrane become more permeable
- water in the cell expands
- channel and carrier proteins denature.
- so the cant control what goes in and out
explain what happens to the cell membrane when the temperature are below 0 degrees
-phospholipids dont have enough energy
-so unable to move as they are packed together
what are the 5 ways molecules can move across the membrane
-simple diffusion
-facilitated diffusion
-active transport
-osmosis
-co-transport
how do molecules move into the membrane by simple diffusion
from high concentration to low concentration down the concentration gradient
across the membrane
is diffusion an active or passive process
passive
what does facilitated diffuision use
carrier proteins
protein channels
describe how molcules move through carrieer proteins
- they attach to the carrier protein
- protein changes shape
- molecule is released to opposite side of membrane
what do channel proteins allow the movement of
charged particles
how does a high concentration gradient affect the rate of simple diffucion
-faster rate of diffusion
- so that equilibrium is reached
what is the effect of a thin exchange surface on the rate of diffusion
- a thin exchange surface
(means particles have short distance to travel)
so faster rate of diffusion
what is the affect of a large surface during simple diffusion
the rate of diffusion is faster
why does the presence of microvilli increase the surface area for faster diffusion
allows more particles to exchange in the same amount of time
what is the effect of microvili on the rate of diffusion
they increase it
what does facilittated diffusion depend on
the number of carrier or channel proteins
what happens when carrier proteins and chaneels are in use
facilitated diffusion cant happen quickly
what does many carrier proteins and channels allow
faster rate of facilitated diffusion
describe thee movement of water molecules across a partially permeable membrane
water moves down water potential gradient
from an area of high water potential to areas of low water potential
how does the water potential decrease
when a solute is added
what is the water potential of pure water
0
two solutions with the same water potential is referred to as..?
isotonic
what factors affect the rate of osmosis
-the water potential gradient
- tickness of the exchange surface
-surface are of the exchange surface
what is active transport
-movement of molecules against a concentration gradient
-requiring energy in the form of ATP
-low to high conc
is active transport an active or passive proccess
active process
what proteins is usually involved in active transport
carrier protein
expalin how molecules are actively transported across the membrane
-molecule attaches to carieer protein
- protein changes shape
and ATP splits into ADP + Pi . the energy changes the tertiary structure of protein.
to allow solutes to be transported
what effects the rate of active transport
speed of individual carrier proteins
-number of carrieer proteins
- rate of respiration
when the speed of the carrier proteins are increased what happens to the rate of active transport
they work faster
what happens when there are more carrieer proteins
active transport occurs at a faster rate
what happens when respiation is inhibited
no ATP produced
no active transport
