The important properties of animal cell membranes are f rwh1la :,u,duluidity and permeability. Which molecule is responsible for ensuring the membrane’s fluidity ,dw,l1:aurhu?

  Which statement correctly describes the cell membr5kltmbe6, l7uane structure?

  Which structure represents a component reh:tpja 4 ug.3e 4re+jrsponsible for reducing membrane fluidity? e :p4ge+jtajh.3r r u4

  Which component of the cesle /c4a 9(rb90 t,i/fvsz tltyr:ra(ll membrane is represented by structure X?

  Which of the following is not a function of cholesterol in celly 1 6+ mj5kkomzy7+y6qdjd fk+ membranes?

  The diagram shows a plasma membrane. Which letter indicates cholesterol?ufb ul(6h 95du+qka w5

  Which of these membrane proteins carry wh 3cuje651y9ybk-u rout active transport?

Neuronal cells have special membrane properties that al05cfa zrtj *2 k:uckoo6yc 1o9low their axons to propagate action potential from one cel *:cyj oc oz9ku52afk10c o6rtl 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 (Ursus maritimus), which is native to thzf 1twvhr/- r7e Arctic. Which statement about the composition of its plasma membranes h7-f t wrv1/rzis correct?

  Which allows cells to stick together t laay ;wxmtt1l *wh7(sv) u/m,o form tissues?

  Some acetylcholine released by a motor neuron at the neu, 4ga/c ikf013h2dui scd8jz rromuscular junction stimulates muscle contraction, while the remainder is rapidly r41u32d/0d zfskgi har8cc,i jemoved 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 hypotc2gjwg 5-c.dlua0. wn onic 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 0/(6vfhbiaq :qmmk 7cof membrane proteins?

  Which of the structures below can transport wa al4:)xiq,qset:d zp;ter molecules across the cell membrane?l;d)tqa,s:e4q px zi:

  Which statement describes enda8gpoxl3:l k)35 b3nrg g( eapocytosis?

  In an investigation into the effect oks -3v zxxu08kf solute concentration on diffusion rate, starch solutions, of varying concentrations, were placed inside starch ks0x-kzv8 3uxpermeable 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 ofpmiw/ ).q:2c.b7d+/(pnztzamg xsw i an experiment on osmosis in potato tissue (Solanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seeds (Helianthus annuus). Similar w+qd72xztgipp.a/im mc (w)bzn .:s/ 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 gb82d nb xz,g1ylucose transporters in the small intestine, an example of indirect active trans 2yzdbbx ,81ngport?

  Which type of transport is represented by this diagram?ixkza0lh( y7( hyv3* c

  Which row about the different methods of membrane mlt:lcnm syhb*,:6 a0 transport is incorrect?

  Which evidence supported the Singer-Nicolslwfx:t 4ur/5xon 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 me 1rm2r 93( avhxzsyscz9ga *2umbrane.

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 percentage uaebrwz:18n 5 eo2-xi z4i95g6g f n:ycqca.dof cholesterol found in the cell membrane of epithelial skin:.9dzr o gi 2-g5xcu51f ibaqnea6yznc8we:4 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).