30 In order for animal cell plasma membranes to function correctly they must exhibit fluidity. Which of the below statements regarding the fluidity of animal cell plasma membranes are CORRECT? i. Phospholipids containing unsaturated fatty acids can be incorporated into the plasma membrane to help maintain fluidity. ii. Many proteins embedded in the cell membrane can move laterally through the phospholipid bilayer. iii. Cholesterol acts as a fluidity buffer by reducing fluidity at moderate temperatures and by reducing solidification of the phospholipid fatty acids at low temperatures. iv. Phospholipids flip between the inner and outer layers of the membrane bilayer more frequently than they flip laterally with phospholipids that neighbour them in the same layer. Select one alternative: Oi, ii and iv only Oi, ii and iii only Oii and iii only Oi and ii only

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Osmosis Water moving by diffusion across a membrane is called osmosis. Remember, diffusion is the movement of molecules from a high concentration to a lower concentration, in order to reach equilibrium. In the image below, the diamonds represent water and the circles represent solutes. Water will move by osmosis from the side with a higher concentration of water to a side with a lower concentration of water. In other words, water will move by osmosis from the side with a lower concentration of solute to the side with a higher concentration of solute. Water is attracted to solutes. 2. Use the following diagram to answer the questions below. Start by filling in the blanks for the missing % concentrations for beakers B and C. 150ml 100 Beaker A 0% Sugar 100% Water a) What is the solute concentration of: O Beaker A? O Beaker B? 150ml 100 Beaker B % Sugar 90% Water b) What is the solvent concentration of Beaker C? 150ml 100 Beaker C 40% Sugar % Water When we think about solutions in human…

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6. As a demonstration, an artificial cell consisting of an aqueous solution enclosed in a semi permeable membrane is placed into a beaker containing a different solution. The membrane is permeable to water and to monosaccharide's glucose and fructose but completely impermeable to the disaccharide sucrose. The concentration of each cell is described in the diagram below. 0.03M Sucrose 0.02M Glucose 0.01M Sucrose 0.01M Glucose 0.01M Fructose a. Which solute(s) will exhibit a net diffusion into the cell? Explain. b. Which solute(s) will exhibit a net diffusion out of the cell? Explain. C. Which solution is hypertonic, the cell or the solution? Explain.

A solution containing 3.58 x 1023 molecules/m3 of protein in water is separated from pure water by a membrane 3.20 μm thick.  The diffusion coefficient of the protein through the membrane is 7.15 x 10-18 m2/s.  On average, how many molecules cross 0.0240 μm2 of this membrane each second? [Answer as a positive number with 3 sig digits, but do not enter units with your answer]