The important properties of animal cell membranes are fluidity and permeability.p+g,c.( p6g+dy gsgwn Which molecule is responsible for ensuring the membggp,(.+6py ggd c+w nsrane’s fluidity?

  Which statement correctly describes the ce:uok8 3txv) a5ls+6 bzkjv6eull membrane structure?

  Which structure represents , lt7dh5qda;t a component responsible for reducing membrane fluidity?tht7,l;5qdad

  Which component of the cell membrane is represented by sr:1h)ap-hkqmybcqca x i, -wq 76l9(ttructure X?

  Which of the following is /8.csxjd gj.y 9;t77cq bw- bsjoy1bo not a function of cholesterol in cell membranes?

  The diagram shows a plasma membrane. Which letter indicates cholesterol? /i6t2lmg)p z en p,f3v

  Which of these membrane prgevonu g.6 ,u kr1(86egn8yfooteins carry out active transport?

Neuronal cells have special membranev;bzvfy;axbwa dol)vj38( .7ss2, hx properties that allow their axons to propagate action potenl;wa bv)h vy(8dav73 j ; 2.x,soxszfbtial from one cell to another. The diagram below 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 (k xkrui(ec.r:d,0 gg7Ursus maritimus), which is native to the Arctic. Which statement about the composition of its pxc kg g:.,ir7ud(ker0lasma membranes is correct?

  Which allows cells to stjk7 gnw.2b ifawt1rha 3;yr;s,z ojba 0-nc)9ick together to form tissues?

  Some acetylcholine reled5dayyv.i*g 3k mi:, vuv *ks;ased by a motor neuron at the neuromuscular junction stimulates muscle contraction, while the remainder is rapidly removed from the*5u ydv:vmi* y3dag.kiv,k;s 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 hypotot9 42oexybp1r 2llo i7nic 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 o 51lsj-c m.kt) evsk5wf membrane proteins?

  Which of the structures below can transport water molecules awi;qt h)/,cyacross the cell membrane?h;t,iqy) /cwa

  Which statement describes endocytos*yp/n5qxip3a0zdx),asx* zd is?

  In an investigation into the effect oprxx46 1g3 pky7p8 tkef solute concentration on diffusion rate, starch solutions, of varying concgt14 r8pkxp xy37 pek6entrations, 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 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 obyo0lcxhsb1pqp 18)- n osmosis in potato tissue (Solanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seeds (Helianthus annuus). Similar sized pi b1hyblqo1xs0p)-c8p eces 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 ino0hl y)4/ bz;0xtddnz the small intestine, a;/xtz0y 4b)z nho0ldd n example of indirect active transport?

  Which type of transport is repres.t jsdddm 2jf3+n l93xented by this diagram?

  Which row about the different methods of membrane transport x1 a m3tyk0uj:jcx6f* is incorrect?

  Which evidence supported the Singer7t*f kayb10pmjwa 2l27a4etu-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 mosag 08hfl ymvk-*ic model of 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 fro/1o-)gc vudpg m a study on the percentage of cholesterol found in the cell membrane of epithelial sk vg/)cd1og- upin 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).