Cellular Membranes Flashcards
Function of the Fluid Mosaic Model
Bilayered structure that;
- perform vital physiological roles
- form boundaries
- regulate molecules that enter and exit the cell
= lipids, carbohydrates and proteins make these possible
What do lipids do in the FMM
barrier for water soluble molecules
What separates two aqueous regions
Phospholipid bilayer
Integral membrane proteins
hydrophobic regions of amino acids that penetrate or cross the phospholipid bilayer
(Embedded)
Transmembrane proteins
Specific orientation - two faces on both sides of the phospholipid bilayer
Peripheral membrane proteins
Lack hydrophobic regions and are not embedded in the bilayer
Why are some proteins restricted in movement across the membrane and cause
They are anchored to components of the cytoskeleton or trapped within regions of the lipid rafts
= this causes unequal distribution of proteins = allowing specialisation of certain regions of the cell membrane
What is a glycoprotein
carbohydrate in the membrane is covalently bonded to proteins
What are plasma membrane glycoproteins responsible for
enables cells to be recognised by other cells and proteins
What are glycoproteins in the lipid membrane involved in
cell- cell interactions
What are the two cell adhesion molecules
Homotypic
Heterotypic
What is homotypic binding
occurs when both cell posses the same type of cell surface receptor and their interaction causes them to stick together
What is heterotypic binding
occurs between two different but complimentary proteins and resembles a plug socket
3 types of animal cell junctions
tight junctions
desmosomes
gap junctions
What are tight junctions in animal cells
specialised structures at the plasma membrane that link adjacent epithelial cells
function of tight junctions in animal cells
- restrict migration of membrane proteins and phospholipids
- prevent substances from moving through intracellular space
What are desmosomes in animal cells
act like spot welds on adjacent cells, holding them together
What are gap junctions in animal cells
connections that facilitate communication between cells
They are made up of protein channels called connexions, these span the plasma membranes of two adjacent cells and protrude them slightly
What is facilitated diffusion
molecules must travel through proteins to get into the cell - still diffusion
diffusion
the passive movement towards the state of equilibrium
Effects of diffusion rates
Effected by
Temp, size of molecule, electrical charge of molecule and concentration gradient
Osmosis
Diffusion of water across membranes
high (low solutes) —— low (high solutes)
What ae=re isotonic solutions
equal solute concentrations
What is a hypertonic solution
It has a greater total solute concentration than the solution
What is a hypotonic solution
It has a lower total solute concentration that the solution to which its being compared to
What two types of membrane proteins does Facilitated diffusion rely on
channel and carrier proteins
What are channel proteins
integral membrane proteins that form channels linked with polar amino acids
What type of amino acid faces the outside of the channel
nonpolar (hydrophobic)
how is the potassium ion channel activated
a change in voltage across the membrane
Carrier proteins
allow diffusion in both directions
Facilitated diffusion using carrier proteins
involves opening a channel and binding the transported substance
How can the concentration gradient be kept during facilitates diffusion
by metabolising the transported substance once it enters the cell
What is needed for active transport
ATP
Three different protein driven systems that are involved in active transport
Uniport, Symport, Antiport
Uniport transporters
move a single solute such as calcium ions, in one direction
Symport transporters
move two solutes in the same direction
Antiport transporters
move two solutes in different directions, one into the cell the other out
Primary active transport
The sodium potassium pump
What cations use primary active transport
Sodium, potassium and calcium
Secondary active transport
these systems use established gradients to move substances
it uses ATP indirectly
example of symport system
intestinal cells, which move glucose up its concentration gradient whilst moving sodium ions down their ion concentration gradient
How does the secondary active transport system work
ATP molecules are consumed to establish the ion gradient
The gradient is then used to move the substances either Symport or Antiport
What is the process endocytosis
brings macromolecules, particles and other cells into the eukaryotic cell
Three types of endocytosis
Phagocytosis, Pinocytosis and receptor mediated endocytosis
Phagocytosis
common amongst unicellular protists
White blood cells use this to defend the body against invading foreign cells
Pinocytosis
vesicle formation where the vesicles are far smaller
it dissolves substances and fluids brought into the cell
Pinocytotic in humans
single layer of cells separating blood capillaries from surrounding tissue uses this to acquire fluid from the blood
Receptor mediated endocytosis
is specific
Receptor proteins are exposed on the outside of the cell in regions called coated pits. Clathrin form the coats of the pits
What is Exocytosis
process by which materials packages in the vesicle are secreted from the cell
Functions of membrane
- organising chemical reactions
- information processing
- energy transformation
Functions of membrane
- organising chemical reactions
- information processing
- energy transformation
