The important properties of anim 2fyv /n.os/f j:xaf-1ykz ja0al cell membranes are fluidity and permeability. Which molecule is responsible for ensuring the membrane’s fluidityv.2/ - y1knxy s:zff 0/aojfaj?

  Which statement correctly na156ss61wcy vvj9vnxpnaan /)m +(bdescribes the cell membrane structure?

  Which structure represents a compodd g:,xr dh87qnent responsible for reducing membrane fluidity?g 8d:,hdqr7xd

  Which component of the cell membrane is representedt h5 .zyehpmx0 lcb/nj:87s s. by structure X?

  Which of the following is not a function of cholester(zrb 9fph(-hmol in cell membranes?

  The diagram shows a plasma membrane. Which letter k 1*z wrbdf3cz1v+4t 1- l-oe 2oeyrcmindicates cholesterol?

  Which of these membrab3rl5pwb- vv)tr0 9 )zenw/s4 -kukqcne proteins carry out active transport?

Neuronal cells have special membrane properties that all:)8hu- hec egy)fbbt8ow their axons to propagate action potential from one cell to anoth-88 yhb)ebh:gt eu) fcer. 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 nativgo*-t nj p,vrn;q44b*brlv 4ee to the Arctic. Which statement about the composition of its plasma membranes is correc o-vrpnb gt*rq4,n*lej4v ;b 4t?

  Which allows cells to stick together 6v i 6sqkth 0yud+xivvk *zc1hp3)(:g to form tissues?

  Some acetylcholine released by a motor neuron at the neuromusculydlvre //cxf ui1 .86gzzn)4a ar junction stimulates muscle contraction, while the remainder uylxic8nz6/. r4az f dgv)1/eis 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 hypotonic solutiy-t z48xga 1j2)q8sc5oufhdw0s+ lcz on.
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 following0 du/bqa-ff7z is not a function of membrane proteins?

  Which of the structures below can transport water molecules across the cey8 uxnrg w/7: sfyii;geg-(y8ll membranegyi w ui;ynsyg 78x8(:/gfr -e?

  Which statement describes endocytosis?v/dgbl)qox/ 4

  In an investigation into the effect of solute concentration on diffoj-,ke0br m) jusion 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 t e r)job,-jmk0he 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 tvkf5g st: n67results of an experiment on osmosis in potato tissue (Solanum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seeds (Heliank:tstngv 67 5fthus 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 glucose transporters in the small intheu+jru-q n:-estine,n: ujq+uh r--e an example of indirect active transport?

  Which type of transport is represented by this diagracpc (m (()w*npticiv* m?

  Which row about the differe2c gcwg 5*a)gnnt methods of membrane transport is incorrect?

  Which evidence supported the Singer-Nicolson modezme+d w sxjc7) 3h,gd-l 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 model2;f:. zgssqgtd ,yfj * 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 of c wni ,ax36 lg+65/yz1jgpz csgholesterol found in the cell membrane of epithelial skin cells of differcgp,nl+/z g65wy 1x gs3iazj6 ent 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).