Question

8. Protons are unable to cross the lipid bilayer because: a) the lipid bilayer is too hydrophilic b) protons are nonpolar c) protons are too small d) the lipid bilayer is only permeable to polar substances e) none of the above

 9. The side chain of an amino acid labeled ‘basic’ is most likely ______ at cellular pH and it therefore ______ water. Fill in the blanks with the word pair that correctly completes the sentence. a) negatively-charged; b) positively-charged; c) positively-charged; d) negatively-charged; e) positively-charged; repels attracts repels attracts forms ionic bonds with

Answer 1

(8) e) none of the above

protons are charged, they cannot cross the hydrophobic core of the membrane

(9) b) positively-charged; attracts

Side chain of a basic amino acid will be positively charged at physiological pH

Hence it is polar and charged it attracts water molecules