The important properties of animal cell membranes are4gl3 65xtxl l9zwe9b t fluidity and permeability. Which molecule is responsibll39wex4t g6l9 lx 5tbze for ensuring the membrane’s fluidity?

  Which statement correctl/i rqc,6t:qg my describes the cell membrane structure?

  Which structure reprix2r- y+xq)jxesents a component responsible for reducing membrane fluidit jq-2)yxx+rx iy?

  Which component of the cell membrane is represented by9,b;fbm eu6(j 7emjx7 1d yuay structure X?

  Which of the following is not a function of zd ing2.1yuvs wx48( icholesterol in cell membranes?

  The diagram shows a plagutlt*1 j++bn td 6ze9sma membrane. Which letter indicates cholesterol?

  Which of these membrane proteins carry out actiq( n*9/kdamzjve transport?

Neuronal cells have special membrane properties that allow their axons t0s1vg m1lmk2gq 7eajd:/. 1 q:0tmzen ztf;czo propagate action potential from one cell to another. The diagram below shows a portion of an ax 7g1 mz;1:a/1tclqezkdq0 j .vs2tz:e0mgm nfonal plasma membrane.

1.1.State the role of a sodium-potassium pump in axon.
1.2.Describe the action of the sodium-potassium pump.
2.Distinguish between simple diffusion, facilitated diffusion and active transport.
3.Compare and contrast sodium-potassium pumps and potassium channels.

  The diagram shows a polar bear (Ursus marqe r5 z,b8poitw ab:+*itimus), which is native to the Arctic. Whicwz,*q8t:e ro+ 5abb pih statement about the composition of its plasma membranes is correct?

  Which allows cells to stick u( uparz+a 5dl g4o :+rks1vb*x5-gvn together to form tissues?

  Some acetylcholine released by a motor neuron at the neuromuscular junctiln1/oud 1n3) kybux*p5l frx ,on stimulates muscle contraction, while the remainder is rapidly removed from the15o3ku)nxb1 dlnp,yu*flx/ r synapse. Which processes are required for this to happen?

  
Which structure on the above diagram corresponds to the molecule below?

1.Outline the effects of placing a liv7+c9m r2pnde3 tj)jpb v:5f uger cell in a hypotonic solution.
2.Outline how the fluidity of membranes allows materials to be taken into cells or to be released from cells.
3.Compare and contrast four types of membrane transport. Include an example of each.

  Which of the following is not a function ofhinppu ,cm 78787qci ;x z.9tabjb xq5 membrane proteins?

  Which of the structures below can transport water molecules acrosnacp1 zhqk/6lpg5h 73s the cell membrk/3ah l1czh np7 g5p6qane?

  Which statement describes en2dx8rh1 s tv;odocytosis?

  In an investigation into deq0ng6wh 4qpvj9-*jthe effect of solute concentration on diffusion rate, starch solutions, of varying concentrations, were placed inside starch permeable membrane balloons. Each balloon was put into a beakee-q9 *n h q40gwdjjv6pr of distilled water and at 3 minute intervals, samples were taken from the solution surrounding the membrane balloons in each beaker, placed on spotting tiles and tested for the presence of starch. The time taken for a positive test to show was recorded for each trial.


The results are shown in the graph.

1.1.Identify the dependent and independent variable in this investigation.

1.2.State one variable, other than time of testing, that should be kept constant in this investigation to ensure the results are valid.

2.Describe a positive test for starch.

3.Explain why the method used in this study would not be appropriate for an investigation into the effects of solute concentration on active transport.

4.1.Samples taken from the 5% and 10% starch solution both tested positive for starch after 3 minutes. Suggest a way in which the experiment could be improved to provide a more accurate result.
The accuracy of the experiment could be improved by  ----待选择----increasingdecreasing  the frequency.

4.2.Predict the time taken for a positive starch test for a starch concentration of 3%.
A positive test for starch, at 3%, would take approximately    minutes.

5.Suggest modifications to the methodology that would make it suitable to investigate the effect of glucose concentration on the rate of diffusion.

  The graph shows the y s99ln-xpz9kresults of an experiment on osmosis in potato tissue (Solanum tuberosum), cactn 99-pz l9yskxus tissue (Carnegiea gigantea) and sunflower seeds (Helianthus annuus). Similar sized pieces of tissue were immersed in different solutions of sucrose for 30 hours.



1.Estimate the concentration of sucrose that is isotonic to the interior of the potato tissue.
The concentration of sucrose in the potato tissue is    mol dm$^{-3}$
2.Using the graph deduce, with a reason, the tissue that has the highest solute concentration.

3.Suggest one reason for the difference in internal solute concentration between the sunflower seed and cacti tissue.

4.The epidermis of the potato and cactus and the testa of the sunflowers seeds were removed. Suggest a reason for this.

5.Predict what the appearance of the cacti tissue would be like at 0.5 mol dm-3 sucrose solution.

6.1.State how percentage change in mass is calculated.

6.2.Explain why percentage change in mass is calculated rather than change in mass.

7.Explain why temperature has to be controlled in this study.

8.State one way in which this experiment could be made more reliable.

  How is the action of sodium-dependent glucose transporters in the small intest4/ +s b;mmlsftine, an examtlf+/mm4 ssb; ple of indirect active transport?

  Which type of transport is represente ym b/j+ l gcw--6vgg0d/f7gied by this diagram?

  Which row about the different methods of membrane trang /7g +uug/,3mm4ak2 9vl1zbmkslrtqsport is incorrect?

  Which evidence supported the Singer-N w8owf 0n3ch sxm*dr()icolson model of the plasma membrane?
I. Membrane fusion experiments revealed membrane proteins can diffuse from one position to another in the phospholipid bilayer.
II. Analysis of membrane proteins indicated that some surfaces of membrane proteins were hydrophobic.
III. Electron micrographs revealed the appearance of the membrane as two dark bands separated by a light band.

1.Draw and label the fluid mosaic model of g q0e+6e9oy tpkn2r2j a cell’s plasma membrane.

2.Distinguish between integral and peripheral proteins.

3.Compare and contrast the structure and function of glycoproteins and glycolipids in the plasma membrane.

The table shows the results from a study on the percentage of chole+6tx3ucy.-:xlcx dn a 9r,so wp 6as,fsterol found in the cell membrane of epithelial skin cells of different animn :6s o-3twcp,9fcl+dsxy6au .xrxa, als.

1.Calculate the mean percentage of cholesterol found in the cell membrane across all the animals listed in the table.
mean =__%
2.State one role of cholesterol in the cell membrane.
3.Suggest why arctic foxes have a greater mean percentage of cholesterol in their cell membranes than kangaroos.
4.Estimate, with a reason, the percentage of cholesterol that would be found in the cell membranes of polar bears.
5.Explain why the mass of cholesterol in the cell membranes is calculated as a percentage rather than a whole number.
6.Suggest why the cells studied may contain a higher percentage of cholesterol than shown in the table.
7.1Based on the data provided, suggest which animal in the study exhibits the highest fluidity in its epithelial skin cell membrane.
7.2Explain your answer to part (i).