The important properties of animal cx3 4awhvs.,+: zfyfm u6k84p*ccne hd*s ig;uell membranes are fluidity and permeability. Whizf+m43y gh4a h:ksu6*;vc,wp n ufse .8xdic*ch molecule is responsible for ensuring the membrane’s fluidity?

  Which statement correctyg;qf8 /b ydmr-)8 ezzv p98zzly describes the cell membrane structure?

  Which structure represents a component responsible for reducing m e*hw;ws+ z6aczel h5+embrane fluidityw ah l;ew++6 he*czsz5?

  Which component of the cell membrane is represe ./ce ee7jtzop:mg d6+nted by structure X?

  Which of the following v alkt6o7-wbw )yu.k;is not a function of cholesterol in cell membranes?

  The diagram shows a plasma membrane. Which letter indicates chole:msjyz, c*vy6 ;dgs 9)llr.u9g co 8ibsterol?

  Which of these membrane proteinssx c4m0niz2 -k carry out active transport?

Neuronal cells have special membrane properties that a2aa jw81j :ifac+4wb 1j/jlw6xckn: i llow their axons to propagate action potential from one cell to another. The diagram below shows a portion of an axonal pilf4bjci x:1nw1 6kwjjacj +a:wa8/2 lasma 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 m(rmwadjfw.16 aritimus), which is native to the Arctic. Which statement about the cormja16d. f w(wmposition of its plasma membranes is correct?

  Which allows cells to stick together to form tissutd: /t1vj yrbo1gxh) )es?

  Some acetylcholine released e8)e hr;l7alc+6v qqsby a motor neuron at the neuromuscular junction stimulates muscle contraction, while the remainder is rapidly removed from the synapse. Which process v;+hrel escql 7q6)8aes are required for this to happen?

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

1.Outline the effects of placing a liver cell in a hypotonic soluw*ze;-g krgeere6g /;tion.
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 of ma xkflbf* jg 76n.mr+6*vr 7twembrane proteins?

  Which of the structures below can transport water mol5 /n(ypqw 8 flqem9:i3ms/nwiecules across the cell membras/wq/yfi: ein8l5(q39pn w mmne?

  Which statement describes endoc-em /1 6 bij2vl5iicxfp95r ufytosis?

  In an investigation into the effect of solutcl)frtb8v0 5k5s4 j p1 i1ldvce concentration on diffusion rate, starch solutions, of varying concentrations, were placed inside starch permeable membrane balloons. Each balloon was put into a beaker of distilled water and at 3 minute intervals, samples were taken from thecb)4d815 lli1v5 j0p ksfv ctr 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 results8 1hs/uezxgu1 of an experiment on osmosis in potato tissue (Solanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seeds (Helianthus annuus). Similar sized pieces of tissue were immersed in different so1zu esxu8/ g1hlutions 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 tradi17; y hnh+ig1c nbf+nsporters in the small intestine, an example of indirec cgb1n+idy+h;f17i nht active transport?

  Which type of transport is represented by thutf20 5xnbf,;*lml6t o x fsdr9+o go1s2hab ;is diagram?

  Which row about the different methods of membrane transport is infu2.rcd 0hk 1ecorrect?

  Which evidence supported th1jcn sndb:(l;e Singer-Nicolson 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 a cell’s ploq r7vz3j e owdt1*k436tbqv1 asma 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 cholesmn(eb7c7jt h(terol found in the cell membrane of epitheb( (hm7ec tnj7lial skin cells of different animals.

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).