cell membranes

Name of model proposed by singer and Nicholson 1972

Fluid mosaic model

Explain how the distinction of charged and uncharged parts determine the position a protein will take up in a membrane

Charged particles will associate with hydrophilic heads

Uncharged particles will associate with hydrophobic tails

For lipid soluble molecules mode of transport, component of the membrane through which it passes, factor affecting rate of transport

MoT: diffusion

Comp: PL bilayer

Factor: concentration gradient

For water soluble molecules in high external concentration

MoT: facilitate diffusion

Compon: channel/ carrier proteins

Factor: concentration gradient/ size of molecule/ pH

Water soluble molecules in low external concentration

MoT: active transport

Compon: carrier proteins

Factor: respiratory rate, ATP production/ pH

Explain the pattern of results of temp against colorimeter reading referring to cell membrane structure

Membrane proteins are stable between .. and .. (at low temps)

Appearance of the red pigment means that the tonoplast and cell membrane has been damaged between .. and … (high temp)

Meaning pigment has leaked out of cell/ sap vacuole/ change in membrane permeability/ damaged membrane

Proteins change shape and denature and come out of bilayer

Explain the difference in results if you were investigating the effect of ethanol on the permeability of the membrane

Dissolve phospholipids/ destroys cell membrane structure

So pigment leaks out

Suggest one problem in performing any investigation using blood

Blood clots/ infection

Explain why the time taken for the RBC to burst (haemolysis) occurred quickest when placed in distilled water

in distilled water Water has highest water WP

Water passed down water potential gradient- from high to low water potential

Passes into the cell by osmosis

A sample of RBC were placed in a concentration solution of sodium chloride draw a diagram to show the expected appearance of one of the blood cell after 5 minutes

Mark scheme says: crinkled cell, high WP inside cell, water passes out of cell causing shrinkage / distortion

Difference between this model and currently accepted fluid mosaic model

Have PL bilayer, hydrophobic takls and hydrophilic heads , have proteins

However for the F-M model proteins are embedded in the lipid layer, there are instrinsci proteins as well as extrinsic

Also the F-M model there are glycocyx, glycolipids, glycoproteins

An investigation was carried out on the uptake of pottasium ions by root tissue stete with reasons the variables that should be kept constant

Temperature or pH BECAUSE

they change enzyme activity, affect reaction rate

Explain why as the O concentration increases the rate of pottasium ions also increases

Active transport is the main method of transport of pottasium ions

Which is energy dependent, uses energy from ATP and oxygen is required for aerobic respiration for ATP production

Greater O concentration produces greater uptake

State the rate of uptake you would expect of a drop of cyanide solution had been added to each of the four solution

They would all be .. (the starting rate of ion uptake)

cyanide inhibits aerobic respiration which prevents or reduces ATP production when no oxygen is present there is still some uptake by diffusion which is a passive process

Explain why increasing the temp increases the permeability of the cell membrane and result in more .. being realised

PL and protein molecules movement increases as temp increases

Creates gaps between PL molecules

Protein loses tertiary structure as hydrogen bonds weaken/ break

Pores in membrane proteins get larger

More .. can escape more quickly

Methods of transport that transports individual molecules or ions

All methods except endocytosis and exocytosis (bulk) : D, FD, OSM, AT

Don’t understand the last question on the FA on membranes, it is too confusing but mention plasma membrane model: fluid mosaic model

Describe the function of the PL bilayer

Physical barrier, selectively permeable membrane allows diffusion or transport of small non polar molecules

Function of intrinsic or channel/ carrier proteins

Allows FD / AT/ transport of large or polar molecules or ions

Explain why no glycocalyx is present in the inner mitochondrial membrane

No need for recognition/ receptor

Explain why there are more carrier/ channel proteins in inner mitochondrial membrane than cell membrane

More FD/ active transport

Maybe transport of ATP

Evidence that P ions can occur both by AT and Diffusion explain how evidence supports this conclusion

Absorption is highest with oxygen which indicates active transport as this requires ATP

Also occurs in the abdomen e of oxygen which indicates diffusion as this is not dependent on respiration passive process

Explain how the properties of the head and the tail of the chlorophyll molecules results in its position in the PT memrbane

Hydrophobic tail and fatty acid hydrophobic regions of the memrbane

Head is hydrophilx

Suggest an adv of the position of the chlorophyll molecules

Holds chlorophyll head in optimum position for absorption of light

Explain how glucose is reabsorbed from the filtrate into the blood even at very high blood glucose levels

Na+ ions actively transported out of epithelial cell lowering the concentration of Na+ inside

Na+ in filtrate at higher concentrated than inside the cell

Na+ Co transported with glucose into epithelial cell

Glucose concentration in epithelila cell is higher than blood plasma

Glucose moves out of epithelial cell into blood by FD

Circulation maintains plasma concentration below that in epithelial cells maintains concentration gradient