2.1.5 Biological Membranes Flashcards
Role of the glycolipids and glycoproteins
Help to stabilise the membrane and allow to act as a receptor for signalling molecules and antibodies needed ( acts as a receptor)
are also antigens
Cholesterol role
Helps to regulate the fluidity of the membrane
Depending on if it is a warm or low temperature
Protein channel
The channel shields ions and polar molecules from the hydrophobic centre
Functions of membranes at the surface of the cell
A barrier between the cell and its environment
They are partially permeable
And all for cell signalling
Function of membranes within cells
Act as a membrane between organelle and cytoplasm
Can form vesicle’s to transport substances
Also site of chemical reactions - e.g inner membrane of the mitochondrion has lots of enzymes for respiration
What is the fluid mosaic structure
The idea that the bilayer is fluid due to the phospholipids constantly moving
Role of phospholipids
hydrophbic tails and hydrophillic head
The centre is hydrophobic so does not allow for water soluble substances in but fat soluble ones can go through
what is simple diffusion?
the net movement of molecules from a high to a low concentration until an equilibrium is reached
how is facilitated diffusion different then simple diffusion?
proteins are used to transport the molecules but still not ATP is used
On ions or molecules that are too large
what is a protein channel?
Is a transmembrane that is filled with water to allow water soluble molecules through the membrane
describe a protein carrier?
will bind to the molecule which causes a shape change in the molecule which allows it through to the other side
define osmosis
osmosis is the net movement of water from a high water potential to a low water potential through a partially permeable membrane
what is water potential?
this is the pressure that is made by water and is negative when their is more solute then water
describe active transport
Goes against the concentration gradient as it uses the carrier proteins to pump substances across the membrane . ATP provides the energy for the carrier protein to change shape
explain the function of membranes within cells
It provides an internal transport system
it is partially permeable so can control what goes into and out of other organelles
protection from cytoplasm when needed
3 factors that affect membrane permeability
temperature - denatures the membrane
phospholipids and proteins gain more kinetic energy to move apart
pH - changes tertiary structure of membrane proteins
Use of a solvent- may dissolve membrane
Outline how calorimetry could be used to find out the permeability of a membrane
- use plant tissue with a soluble pigment (e.g beetroot) so it is visible when the membrane is most permeable
- select calorimeter filter with complementary color
- use distilled water to set your calorimeter to zero
- high absorbance and low transmission = more pigment in solution
Define endocytosis and exocytosis
Active process
involved in bulk transport and transporting big particles by invaginating the particle into the membrane
factors that affect the rate of diffusion
temperature
diffusion distance
surface area
size of molecule
difference in concentration
