The important properties of animal cell membranes are fluidxl4vn;qqp6 *kity and permeability. Which molecule is respon l k;vqnxq*4p6sible for ensuring the membrane’s fluidity?

  Which statement correctly descr0 c3c9km0gxx kb.p zs4ibes the cell membrane structure?

  Which structure represents axcju 75 m2+qf-iw,0prrdjr,j component responsible for reducing membrane fluiditwim5f+, d-j,pq7j jr0r 2urc xy?

  Which component of the cell membrane is represented by stru5mh9wfj2,f:7oiwpsv5 ru (j ail+5tb cture X?

  Which of the following id-a i/ )2:,o dj5ob:p surxsnzs not a function of cholesterol in cell membranes?

  The diagram shows a plasma me1h2mpf p. -syjmbrane. Which letter indicates cholesterol?

  Which of these membrane pro* frwm1i h1+wnteins carry out active transport?

Neuronal cells have special membrane powm5 bp u4v+1p4wb ;wjroperties that allow their axons to propagate action potential from one cell to another. The diagram below shows a portion of an axonpow4umj; w b v+514bpwal 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 ms*/pg5xhwa +jm+ +f)l *vyl dqaritimus), which is native to the Arctic. Which statement about the composition of its plasma membranes is corr *gsfd/lvyx *hw5++m )+qpaj lect?

  Which allows cells to stick togexax7;.bw hax9i7qeo,0sx *pt ther to form tissues?

  Some acetylcholine released by a motor neuron avj hs,610m r0nfgj.y sg5 b4qft the neuromuscular junction stimulates muscle contraction, while the remainder is rapidly removed from 6s0j4 f1yjq5 h vgm0br .g,fnsthe 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 hypotonic solj3 0z -cnefal88*otf,z wh9oyution.
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 ah im (jgk ;8eo3/x- (7fthpuxfunction of membrane proteins?

  Which of the structures below cc/ 5kip(e3lu*4rjxb3jm i: ocan transport water molecules across the cell membrane?j*oc jm354brl/pecii3 :kxu (

  Which statement describes endo;x jd:j mv,7afb98xw mcytosis?

  In an investigation into the effect of solute concentration on diffusk j(5:hqt9xddjcd / ;xion 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 weretkjc:(ddh j 9q;/xx d5 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 experim:7d3bopjrmptp dpz ( xy)v.8/ent on osmosis in potato tissue (Solanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seeds (Helianthus annuus). Spjd7r/mb pv yt)xo: p3 .pdz8(imilar 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 glucoseqp 1oevh+z61z-3 dh*h6 vhyng transporters in the small intestine, an example of indirect az h-eo6q+ hvdhyn*1g6ph v1 3zctive transport?

  Which type of transport is reld 5i8e8j5lzyj5 zsk 7prkd4dsy 27.ppresented by this diagram?

  Which row about the different methods aq(:wrin0fxp xo(m62of membrane transport is incorrect?

  Which evidence supported the Singer-Nicolson model of the plasma 4+cg7r7bpj3 x njex6 emembrane?
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 o igu 20zrm51tcuq27i mosaic 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 percentage p(5;+)pxvphxsyls/ j of cholesterol found in the cell membrane of epithelial skin cells of different(x+;px ssv)py5j/ lhp 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).