The important properties of animal cell membranes are flui 28fqwwb9 d* wo(soz.pdity and permeability. Which molecule is responsible for ensuring thewsoofq 89(*dzpw. 2w b membrane’s fluidity?

  Which statement correctly descjomeg-* u*l*yztz xms6 -2g2cribes the cell membrane structure?

  Which structure represents a component responokync*1s jxgr(;s +;fq0pr/ssible for reducing membrane fluidity?s*jq 0ns/;osc(+f1 ypxr kg; r

  Which component of the cell membrane is represented by structure thr )-;0-g *xsdpp yh7(ghqtjncd48 i X?

  Which of the following l j*33iibgp: jiwqy17v o;sj9 is not a function of cholesterol in cell membranes?

  The diagram shows a plasma l xtuz:;gi i ln6e )d.g5q45 )fn4ymunmembrane. Which letter indicates cholesterol?

  Which of these membrane proteins carry out ahe- , m;)io msh2w+pq,j2oaa yctive transport?

Neuronal cells have special membrane properties that allow their ax 8 k,mbys jaa )ytw4z61vt z,k2o:lsgo 7mt59xons to propagate action potential from one cell to another. The diagram b2:o)stoy5t,k8t z a64s1kg ,m yxabm9j7wvz lelow shows a portion of an axonal 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 maritimus), whichu17z7mg0 nsq s is native to the Arctic. Which statement about thum07q gssz71n e composition of its plasma membranes is correct?

  Which allows cells to sg a1bt 1 +zp6zw*gs+q:6 sm+ qyhbhz7ftick together to form tissues?

  Some acetylcholine released by a motor neo2,xrfd * *1taexyoi: uron at the neuromuscular junction stimulates muscle contraction, while the remainder is rapidly removed from thatoo2xy ex* rf1 i*d,:e 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 liver cell in a hruuhsjjo/ g0h;v b)zrj-q.87)cmzt.ypotonic 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 of memb u ucb5tco58x8rane proteins?

  Which of the structures belowg x xasqjmcm)5,ys 33ji:9xv( can transport water molecules across the cell membrajs9m, s v5 :)( gjxy3ia3qxmcxne?

  Which statement describes endocytosis?98tr:x 7 3 9lm0hji.gnj bqwnn

  In an investigation infq-.j vll-lmroe8h/ . to the effect of solute concentration on diffusion rate, starch solutions, of varying concentrations, were placed inside star l-mr/.e .lfv-qojhl 8ch permeable membrane balloons. Each balloon was put into a beaker 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 results of an experiment on osmosis in potato tissue (Solanuw9:qmgvq1sah2we(sw 7 bv g3x;1gb q0m t 0xbqq;s:gwgevb gw9 (1hvq2 w1 s3ma7uberosum), cactus 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-depen* q3+mccx 4zkng n,i1zw75lxwdent glucose transporters in the small intestine, an example of indirect active transpkqz4g,li wn*5z+ccxw73 mx 1nort?

  Which type of transport is represented by this di.n9yb4ig v:p ppe4d3ibxod:*ru;zx +agram?

  Which row about the different methods of membrane transport is incorrepnv;9*n y; vache nvi6(chxi h 060(nzct?

  Which evidence supported t30wa grb tm:/u4qlbnhj ww:0*he 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 plasma membrane.mjnw:z;os38h3h 9 hnn

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 st9ev9nr(6j1 uzxiyy 3kudy on the percentage of cholesterol found in the cell membrane of epithelial skin cells orjx y3i6nu k(9yvz 9e1f 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).