Fluid mosaic model of membranes is fluid because of the phospholipid bilayer which has individual phospholipids that can move giving it a flexible shape
Fluid mosaic model of membranes is mosaic because of the intrinsic and extrinsicproteins of different shapes and sizes embedded in the bilayer
In membranes, cholesterol connects phospholipids and reduces fluidity to maintain mechanical Stability of the bilayer and resist effects of temperature change.
In membranes, glycolipids are used for cell signalling and cell recognition
In membranes, intrinsic proteins are electron carriers; channel proteins; carrier proteins
Membranes within cells provide an internal transport system. They are selectivelypermeable to regulate passage of molecules; provide a reaction surface; isolate organelles from the cytoplasm for specific metabolic reactions.
The cell surface membrane isolates cytoplasm from external environment; selectivelypermeable to regulate transport of substances; involved in cell signalling/recognition
Temperature affects membrane permeability
high temperature denatures the membrane proteins; phospholipid molecules have more kinetic energy and move further apart so membrane is more permeable
Ph affects membrane permeability as it changes the tertiary structure of membrane proteins so they are denatured
Solvent effects membrane permeability as some organic solvents may dissolve the membrane
Colorimetry can be used to investigate membrane permeability with temperature.
Results of beetroot investigation:
the higher the temperature, the higher the colorimeter value is.
More pigment leaked from the beetroot so the membrane become more permeable as temperature increased.
Simple diffusion is the netmovement of small,lipidsolublemoleculesfromanareaofhighconcentrationtoanareaoflowerconcentration,downaconcentrationgradient.
Simple diffusion is a passive process so requires no energy from ATP hydrolysis.
Facilitated diffusion the movementoflarger or polarmoleculesfromanareaofhigh concentrationtoanareaoflow concentrationviaspecificchannel or carrier proteins.
facilitated diffusion is a passive process
Channel proteins are pores allowing transport of ions
Osmosis is the netmovementofwatermoleculesfromanareaofhighwaterpotentialtoanareaoflowwaterpotentialacrossapartiallypermeablemembrane.
Water potential is the pressurecreatedbywatermolecules.
The water potential of pure water is 0kPa. The more solute is added the more negative the value of water potential.
When animal cells are placed in solution with a lower water potential:
water moves out by osmosis
Cell shrinks or shrivels up - known as crenation
When animal cells are placed in solution with the same water potential:
No net movement of water
cell stays the same shape
When animal cells are placed in solution with a higher water potential:
water moves in by osmosis
cell expands and may burst - known as cytolysis
When plant cells are placed in solution with a higher water potential:
water moves in by osmosis
cell begins to swell and push against cellwall - known as turgid
gives plants strength and shape
compartmentalisation within cells; keeps organelle contents separate from the cytoplasm
Cell signalling is communication between cells; where cells worktogether to trigger a response
Active transport is the movementofsubstancesagainsttheirconcentrationgradientacrossacellmembraneusingATPandproteincarriers
Exocytosis is the bulk transportofmolecules, toolargetopassthroughacell membrane, outofa cell
For the colorimeter experiment, cuvettes are used to find a Colorimeter value in the colorimeter
In exocytosis:
the cytoskeleton contracts; to move the vesicle to the plasma membrane; the membrane of the vesicle and plasma membrane fuse; releasing the contents of the vesicle
In the osmosis practical:
For sugar solution there is a higher water potential inside the potato; water moves out by osmosis; mass of potato decreases
for distilled water there is a higher water potential in the solution, water moves in by osmosis; mass of potato increases