The important properties of animal cell membranes are fluidity and permeabilit6ss+ i,2hcr yg,zqe-dy. Which molecule is responsible for ensuring the memb2s,i -,6d + hgreqczysrane’s fluidity?

  Which statement correctly describes the cell membqh7i n1+gd6h.y y al1yox3.pk rane structure?

  Which structure represents a b/-.hzpz:rw r component responsible for reducing membrane fluidit-.przw /rhz:by?

  Which component of the cell membrane is represented by strot/5t a6k f(jiv 73lkwucture X?

  Which of the followinxxm4 - qgqbq 68*6.iq*qoce;5 nnd cfug is not a function of cholesterol in cell membranes?

  The diagram shows a plasma mefy,j; g wg5ic:mbrane. Which letter indicates cholesterol?

  Which of these membrane proteins carry out active tra 7rc18 nwdt7 35fipto dwan1nlmae4k2jh3q41 nsport?

Neuronal cells have special membrane properties that (93ytag acnx/ t6mw e2 (mqm6yqoj.i6allow their axons to propagate action potentia. 6gw qmj(q aicte(/ t6a3y xy6on92mml from one cell 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 nat sqc;sq- nhg:nd.gh +mbp4p-2ive to the Arctic. Which statement about the composition of its plasma membranes:s+hgq4pgn.nc pq dmhs ;b--2 is correct?

  Which allows cells to stick together to form tissyhy.1 hp gj2iq j5q4g,ues?

  Some acetylcholine released by a motor neuron at the neuromuscular junch-rmh73j 2uvction stimulates muscle contraction, while the remainde7c humv32-jrhr 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 effectbo4xo 1kj,-y/ wb.xyfs of placing 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 fuhzn7lin899 2csx fp/ pnction of membrane proteins?

  Which of the structures behvz5j ;y;w :ys;1ngzw low can transport water molecules across the cell membng5y;zvj;sh 1:y zww ;rane?

  Which statement describes endocyt9nt ti 7s1j8t tap1n,sosis?

  In an investigation into t*k9x1pjh9 (io0dgmafa1g6e4u ubw d/ he 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 beaker, placed on spotth ao (gj961bwdxi9fek0 a g4m*/p1uduing 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 (S0my1p db ugp g+xfn+.9olanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seeds (Helianthus annuus). Similar sized pieces of tissue were i+ +bp9pug.n1fmx0g yd mmersed 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 ,dc82ccuqeu4x 2m vvsk9 nj81sodium-dependent glucose transporters in the small intestineucckv x2c8 1 8n2,dsmvj9uq4e, an example of indirect active transport?

  Which type of transport is represented by this diagraiwv.lb03 pj6b m?

  Which row about the diffeel*9zsm, qoz xum;2 .s7- ,abhjqa4iwrent methods of membrane transport is incorrect?

  Which evidence supported the Singer-Nicolson motsavj 0nv ds./7q 92sac*cv0idel 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 -xbxqy p5z 4u yuz5o58cell’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 oc; u4yu530 stff8 hyhin the percentage of cholesterol found in the cell membrane of epithelial30hsuc5ffyt 84 yu hi; 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).