Mr Allsop- cell membranes Flashcards
What is the general role of the cell membrane
Separates contents from outside/cytoplasm.
Cell recognition and signalling
Hold components of some metabolic pathways in place.
What are polar molecules
Partially charged as they have an uneven share of electrons.
Cannot move through middle layer of membrane as are insoluble in fat.
What is the phospholipid bilayer
Has two layers
Hydrophilic head- attracted to water
Hydrophobic tail -face inwards away from water .
Middle layer is fat
Gas , small polar molecules can diffuse through gap but large polar molecules, charged molecules cannot diffuse.
What are non polar molecules
Uncharged
Soluble in fat- can cross membrane but is hydrophobic
What is the fluid mosaic model
(Things move)
Membrane composed of phospholipid bilayer within various molecules floating around.
Lipid bilayer- lipid molecule with hydrophobic heads in contact with watery exterior.
What is glycoprotein
Protein attached to carbohydrate.
Role in cell adhesion and as receptors for signalling. (Receptors of insulin/glucagon are glycoproteins both affect uptake/storage of glucose by cells)
What is glycolipid
Attach to phospholipid
Lipids with carbohydrate attached by glycosidic bond. Maintains stability of cell membrane. Connect to form tissue
(Antigens)
What is glycocalyx
‘Sugar coat’
Formed from carbohydrate chains.
Attracted to lipids of proteins in membrane.
What is colesterol
Lipid
Regulates fluidity and stability of membrane .
In between phospholipid molecules to stop them getting to close when the temperature decreases.
Helps animals resist temperature change.
What are intrinsic proteins
Trans membrane
Some are channel proteins (allow charged ions to pass through )
Some are carrier proteins ( change shape to allow large molecules to be pushed through)
Role of membranes within a cell
Inner membrane of mitochondria, crustal give large surface area for aerobic respiration.
Digestive enzymes- plasma membrane of epithelial cells of small intestine, breakdown of certain types of sugars
What is a peripheral protein
Part of the bilayer
what is an integral protein
Goes through the whole bio layer
what are the factors effecting membrane permeability ?
membrane integrity is vital to selective permeability.
temperature, proportion of cholesterol, proportion of saturated and unsaturated fats, presence of solvents.
what happens to protein’s in the membrane as temperature increases
the phospholipid bilayer moves constantly which increases the kinetic energy, making the membrane higher in fluidity but this means there is less membrane integrity and in very high temp the hydrogen and ionic bonds will break making the enzymes denature and changes the tertiary membrane permanently.
what is unsaturated fatty acids
‘kinks in the tails’ of phospholipid biolayer.
2 covalent bonds .
allows fluidity when temperature decreases, stops it solidifying.
what is saturated fatty acids
viscous phospholipid biolayer (compact)
one covalent bond
no room for fluidity
good for high temp as stops it separating
what does the amoeba do
pseudopods ‘ fake feet’ - project to get phagocytes.
organic solvents (ethanol)
dissolves lipids/ membranes
antiseptic- disrupts cell surface membrane of bacteria so kills it. sometimes destroys cells
drunkenness- slightly breaks down membrane- affects nerve impulse.
what is diffusion
the net movement of particles from a high concentration to a low concentration down the concentration gradient.
what is net movement
goes mainly one direction but does go in both.
what is a transport system
remove diffusing molecules to maintain concentration gradient.
what is simple diffusion
molecules like co2/02 and small/ soluble lipids pass through membrane unassisted .
passive process- doesn’t require energy.
large lipids can pass through as they dissolve in the fatty bilayer.
what is facilitated diffusion
water/ polar/ lipid-insoluble molecules can’t pass through so rely on carrier proteins/ channel proteins.
carrier protein- glucose/amino acids - they change shape to allow them to pass through.
channel proteins- water/ions as they can’t pass through bilayer.
