26. Which of the following statements is FALSE regarding A) Phospholipids common

Question

26. Which of the following statements is FALSE regarding A) Phospholipids commonly move laterally on one side of the lipid bilayer almost never move from one side to the other side of the lipid bilayer. B) Phospholipids increases membrane fluidity/permeability. C) Increasing the length of phospholipid fatty acid tails D) Phospholipids with saturated fatty acid tails have fatty acid tails that are straight. E) Phospholipids have both a polar end and a nonpolar end. 27. Which of the following is TRUE regarding unsaturated fatty acids? A) Unsaturated fatty acids have double bonds between some of the carbons in their hydrocarbon tails. ) Unsaturated fatty acids have straight hydrocarbon tails C Unsaturated fatty acids have the maximum number of hydrogen atoms in their hydrocarbon tails. D) Unsaturated fatty acids solidify easily at room temperature. E) none of the above 28. Which of the following modifications would result in a DECREASE in membrane fluidity/permeability? A) increasing the proportion of phospholipids with unsaturated fatty acid tails B) decreasing the length of fatty acid tails in phospholipids C) decreasing the proportion of phospholipids with saturated fatty acid tails D) increasing the amount of cholesterol E) all of the above 29. Lipid bilayers are LEAST permeable to which of the following types of molecules? A) ions B) small, uncharged polar molecules C) large, uncharged polar molecules D) hydrophobic molecules E) water 30. Which of the following statements is TRUE about diffusion across a cell membrane? A) Diffusion requires an input of energy. B) Diffusion always requires the use of a transport protein. C) Diffusion occurs when molecules move from low concentration to high concentration. D) Diffusion is a passive/spontaneous process E) Diffusion requires ATP

Explanation / Answer

26. (B) Flippases are lipid transporter proteins that aid in the movement of phospholipids from the inner leaflet to outer and vice versa (flip-flop transition). All the other options are correct.

27. (A) Unsaturated fatty acids have atleast one double bond anywhere in their hydrocarbon chain. They also stay Liquid at room temperature due to the presence of kinks. All the other options are incorrect about unsaturated fatty acids.

28. the question is incorrect. all the options lead to an increase in fluidity.

29. (A) and (C) lipid bilayers are almost impervious to large uncharged polar molecules like glucose and sucrose as well as ions. this is why transport of these molecules inside the cell occurs by either facilitated diffusion or active transport with help of channel proteins.

30. (D) Diffusion is a passive process since no energy is expended in the transport. it's also spontaneous since the movement of one solute is independent of the concentration gradient of other solutes.

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