The important properties of animal cell membranes are fluidity+3g:m)ywbga7nfq31 3 g l dyqx and permeability. Which molecule is r+3 y: fn3bq7l )ga gd13gxyqmwesponsible for ensuring the membrane’s fluidity?

  Which statement correctgp n a/5m7my(2xfyd t*ly describes the cell membrane structure?

  Which structure represents a component respo2as hz7jqq9v2nsible for reducing membrane fluidity? 2s9qjz2a 7hq v

  Which component of the cell membrane is represented by9 )qhv lo4sys) structure X?

  Which of the following is not a function of cholesterol in ce04xwy1ye;e *m q zn4vtll membranes?

  The diagram shows a plasma membrane. Which l ip+o5utdfmvigj6;4:c) ogr -etter indicates cholesterol?

  Which of these membrane proteins carr30.qe mz98 vtq,xa oyoy out active transport?

Neuronal cells have special membrane properties that allow their axons to pbfao;e p+ j25mropagate action potential from one cell to another. The diagram below shows a por apj+5me b;of2tion 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 pd3(iyvv,b7g mpvg ;7holar bear (Ursus maritimus), which is native to the Arctic. Which statemendgy ( h3b7;,vgipm vv7t about the composition of its plasma membranes is correct?

  Which allows cells to stick togetherflrp p5i,l c.5 to form tissues?

  Some acetylcholine released by a motor kkor,04niken0.alw *2 eqp/j neuron at the neuromuscular junction stimul 4w0ke*kkrinn/ pa,. ejq lo02ates muscle contraction, while the remainder is rapidly removed from the 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 hypotonvul9m(ug*0 rp0ap cu ;ffp-;oo u2o9lic 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 of6+yu.+co57:w e rfya .nzxiok4s r9bqs) 8fl t membrane proteins?

  Which of the structures bq5fu l*z 2qokwzcpe *9,sd37eelow can transport water molecules across the cell membra25 zfe*ou3lqkc* w9 7p sd,qezne?

  Which statement describe72i:( ipn6.btez h algs endocytosis?

  In an investigation into the effect of solute concentration on +t 9 1/whzuc4;dyknhuyhs. y5)tj wt(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 jc;yhk/ 51nyu td+z4)w h sut.y9(whttaken 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 experimef5es58 /jygxxi i; 4ofnt on osmosis in potato tissue (Solanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflowex yi5/o 4ifg x8s;5jfer 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 sodia:xa8c)ye82vqnja :m 9w lmu3vu g /+qum-dependent glucose transporters in the small intestine, an example of indirec wq9e/) c82nlaguvj:3umamq xyv8:+at active transport?

  Which type of transport is represented by this qc 13h);har)rkmpaf 6diagram?

  Which row about the differ0m;o en khlpb+ ys(b86 cqp0a9ent methods of membrane transport is incorrect?

  Which evidence supported the Singer-Nicol6:p g7x 2c-8 ih1v ko37w2 lsxrlejmmkson 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 cecg)g ,;gll8ju ll’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 re td7as nk0x/9gsults from a study on the percentage of cholesterol found in the cell membrane of epithelial skin cells of diffg7 s0dakn x9t/erent 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).