26. Which of the following statements is FALSE regarding phospbolipids? A) Phosp

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26. Which of the following statements is FALSE regarding phospbolipids? A) Phospholipids commonly move laterally on one side of the lipid bilayer B) Phospholipids almost never move from one side to the other side of the lipid bilayer mgth of phospholipid fatty acid tails increases membrane fluidity/permeability move C) Increasing the len D Phospholipids with aurated fatty acid tails have fatty acid tails that are straight Which of the following is TRUE regarding unsaturated fatty acids? 27. A) Unsaturated fatty acids have double bonds between some of the carbons in their hydrocarbon tails B) Unsaturated fatty acids have straight hydrocarbon tails saurated 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 fuidity/permeability? acid tails B) decreasing the length of fatty acid tails in phospholipids C) decreasing the proportion of phospbolipids 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 D) Diffusion is a passive/spontaneous process. E) Diffusion requires ATP

Explanation / Answer

26) C) Increasing the length of the phospholipid fatty acid tails increases membrane fluidity/permeability.

27) A) Unsaturated fatty acids have double bonds between some of the carbons in their hydrocarbon chain.

28) D) Increasing the amount of cholesterol

Increase in cholesterol level will increase the hydrophobicity of the membrane thus making the membrane impermeable or less permeable.

29) A) Ions

Permeability depends mainly on the size and the degree of hydrophobicity of the molecule. Since ions are hydrophilic, these are replled by the hydrophobicity of the membrane.

30) D) Diffusion is a passive/spontaneous process.

Diffusion is the process of movement of molecules from high concentration gradient to a low concentration gradient. It is a passive, spontaneous process and does not require any energy

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