The important properties of animal cell membranes are fluidity and permeabilittv 4th -;51ghf+oulwny. Which molecule is responsible for ensuring the membrane; +5fhnohl-ugvt 4wt1’s fluidity?

  Which statement correctly describes the cell membrane a2 bsaom49 :m(bwvs/dstructure?

  Which structure represents a componem*d6 *fglue fz 8o,1if yjp0:unt responsible for reducing membrane fluidityid8p1 : * gf6lfue,uzfj oy0m*?

  Which component of the cell mdn*9; b*nx,9sqz xwg dje-2wzembrane is represented by structure X?

  Which of the following is not a function of cholesterol in cell meqg-o3l qlw)ti1y o6q) mbranes?

  The diagram shows a plasma membrane. Which letter indieiaeoi*p5er9 4fg + t3cates cholesterol?

  Which of these membrane proteins carry out active y ye9 al.p0 hf/ve2)zztransport?

Neuronal cells have special n7 teb98hpg n3membrane properties that allow their axons to propagate action potential from one cell to ann 8gpebt n739hother. 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 (Ursus maritimus), /if b/nug7i/jrq04e dbmu5(n which is native to the Arctic. Which statement about the compositi75/ru0/ i/b(indqe bg mj 4nufon of its plasma membranes is correct?

  Which allows cells to stick together to fo7 w 7w9dxdnv.4j;zafc rm tissues?

  Some acetylcholine re.2u cbdu7k+ (7kul swwleased by a motor neuron at the neuromuscular junction stimulates muscle contraction, while the remainder is rapidly removed fwuu(. 2 cd7sku lw7+kbrom 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 z6y2zst;0vumdqy:u-dtyy2 so 381mpplacing a liver cell in a 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.gd0j7-mogz pa qmd. 7 function of membrane proteins?

  Which of the structures bu 3t.b2g z:gobut/ ja0elow can transport water molecules across the cell membrane?b2 .0tz 3tag: ogju/ub

  Which statement describes endoc tb,mt h 57;bwk3qva-nytosis?

  In an investigation into the effect of solute concentration on diffrbn9mb9ff-p1;fv gw -usion 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 br f9 ;fb-v9mg1 -nwpfsolution 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 (S 7-zm19dy 4n5/r av,aazfsinsolanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seedf ,vdmz/i -s74z a91ns5yrnaas (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-dependent glucosyi*+plez+1v w e transporters in the small intestine, an example of in+lewvi z *+py1direct active transport?

  Which type of transpo f8)r-qve 0 nk6tsnsj/ri9 e2a,1 msokrt is represented by this diagram?

  Which row about the different methods of membrane trae6tr4b k+ ij2glgeeu4t,j81u nsport is incorrect?

  Which evidence supporuvxk*mys1x8 3ted the 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 mosai2ba ec4u 5e z8e1.w0qqrc b:ufc 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 from a study on the pf5g. yy9pyyo0/ kobpi a7b+9s ercentage of cholesterol found i bo05oyk.y+s 7g/p9y pbfayi9n the cell membrane of epithelial 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).