The important properties of aton6sr,bba4z7 kxr v2z kdm-)s:h8g,nimal cell membranes are fluidity and permeability. Which molecule is responsible foa,vnrtzdzm:r o k2b )7 8hsgx-4k,sb6 r ensuring the membrane’s fluidity?

  Which statement correctly describes the cell mem9rf* 0p-mbkla 25p3 rah8cezd brane structure?

  Which structure represents a component responsible q 0tv4-801mv0//gskd u l5ulknib j qnfor reducing membrane fluidity? kqstl-n4/0vv uuigdqjm/kl b 8n15 00

  Which component of tt ckh cyml4a9i0(w* )zhe cell membrane is represented by structure X?

  Which of the following is not a function b g wwd-8bhkf8yl/;e0of cholesterol in cell membranes?

  The diagram shows a plasma membrane. Which letter indicatxzq;om(s8r/ozx36c( / ,ip btvvesrhmj- 5 d.es cholesterol?

  Which of these membrane pr;-hfj yrcvra6 .w5-aur; 0x ,dusq u.voteins carry out active transport?

Neuronal cells have special 1gxi 6z(5jr;(zxv,anysfk c) membrane properties that allow their axons to propagate action potential from one cell to another. The diagram below shows a portion of an axonal s)5nvfyr,j ik(x; z6xa 1g (czplasma 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), wmx0on xyx0c 34ngtf 12hich is native to the Arctic. Which statement about the composition of its plasma membranesxmc20ntxxf04 3 oyg1 n is correct?

  Which allows cells to stick)6pamg mll.q,h x74lh together to form tissues?

  Some acetylcholine released by a mxytoq0pd+b-;j z9 v0q h1j*u zotor neuron at the neuromuscular junction stimulates muscle contraction, while the remainder is rapidly removed from the synapse. Which processes are required for vd yx-;p+qj0u t1jbh*ozz09 q this to happen?

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

1.Outline the effects of placing a liver cell in awide8mau, fvy;u0y l9+ w;nt , 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 of membrane proteins j 5bj1 ehczzba o3281rzd8u1q?

  Which of the structures below can transport water molecules across the cell membeh o8i4cb a*1vu;;yrii)r8c o rrua;yi4 r8ch )1oo b;v*iic e8ane?

  Which statement describes endo l5) xbycyq+iy42jwd;cytosis?

  In an investigation into tx42( *c fblgra 1wxcj0he 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 beaker of distilled water and at 3 minute intervals, samples were taken from the solution surrounding the membrane balloons in each beakex0*jfwacrb 2 xlc1( 4gr, 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 osmosisnv;,w o /c-ugf in potato tissue (Solanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seeds (Helianthus annuus). Similar sized piec fc;w ou/-vg,nes 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 sodsn6d5w/ dd1 egium-dependent glucose transporters in the small intestine, an example of indirect actsw1 neg5dd/d 6ive transport?

  Which type of transport is represented by this diagram? dy1o.rd . 7n3apmey t3

  Which row about the different methodwcmz 5ec qp96m82b 6uvs of membrane transport is incorrect?

  Which evidence supported the .(thcgd/ 0pnlh n.w0kSinger-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 cell1 c-5fy6hgzpg,pzt z5i cs-9v’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 tg*gsuxu2 4ez/mb+1 rztw z./ the percentage of cholesterol found in the cell membrane of epithelial skin cells of dif/ suw.z42 zx z+utg/*emb1tgrferent 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).