The important properties of animag :k,st7n4ppk l cell membranes are fluidity and permeability. Whi,s: ntpgk74pkch molecule is responsible for ensuring the membrane’s fluidity?

  Which statement correctly describes the cell mem (qy/shgq) k)qbrane structure?

  Which structure represents a(. rzgtm(gp u8 component responsible for reducing membrane fluidity? g8prg .(umzt(

  Which component of the cell membrane is represented s4mlah *,y94npts m f4by structure X?

  Which of the following is not a zi) 0c s+,9ej grcg:swfunction of cholesterol in cell membranes?

  The diagram shows a plasma membrane. Which letter indicates cholest ewo.empe4- w1dz8n/pabiquuh,+a)l,2 i,xn erol?

  Which of these membrane proteins carry out active t2wcggd94;s xz 7kkz /cransport?

Neuronal cells have special membrane properties that+ p pahq(:osi- allow their axons to propagats (ophpa:q-+i e action potential 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), w q):is1fwk+ohxa -k d,m;asq6hich is native to the Arctic. Which statem) ;mo -fikqds, 6wak:qsh+a1xent about the composition of its plasma membranes is correct?

  Which allows cells to stick together to fozum1bi- /vv6yrm tissues?

  Some acetylcholine rem.1mn ai0 +boeleased by a motor neuron at the neuromuscular junction stimulates muscle contraction, while the remainder is rapidly removed from the synapse. Which processes are required for this to ha m+a0e 1noim.bppen?

  
Which structure on the above diagram corresponds to the molecule below?

1.Outline the effects of pusr4lr-5xgg p53c6q 8-pj-rqd4 ssyblacing 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 3)2vmtrmx 7eq a function of membrane proteins?

  Which of the structu6jl lez1c5v +etmjgp 3, xvf:,res below can transport water molecules across the cell membrane?65xt:3mj fgj+ vcvp, eez, l1l

  Which statement describes endocytos z,t43 a6vzl/88r jfypib(ffb is?

  In an investigation into the effect of solute concentration ybsg4o .7x(va ubo 7qoi,qq44on 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, s4vqb7 x.uo agyoq(4b 74o,sqiamples 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 of an experiment on osmosis in potato tissue (Sola8s3 atewb l93lnum tuberosum), cactus tissue (Carnegiea gigantea) and sunflower seeds (Helianthus annuus). Similar sized pieces of tissue were immebl 3l3wsa t98ersed 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 tr6f,cd 6i in2ihe small intestine, an example of indirect active transport?i,f6 62irdn ci

  Which type of transport is representedjgby(tk, .ik(g ,1hd x8:ne4cum : sbo by this diagram?

  Which row about the different methods of membrane transport is incorrechgaoip 5y 9g54t?

  Which evidence supported the pvve2;j p; +efw06jxugigp8n2vao:*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 mosaic model of a cell’s plasma membran4:fl2. u; 6dbia3ci5i fskvave.

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 percentagemxspr0 urw3/1 of cholesterol found in the cell membrane of epithelial skin cells of different animals.3pw0rus1m/rx

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).