7. Which statement about primary active transporters is correct?(A) They use the electrochemical gradient of another ion to drive solute transport.(B) They directly hydrolyze ATP to move substrates against their concentration gradients.(C) They transport substrates only down their concentration gradients.(D) They function exclusively as symporters in biological membranes.(E) They do not require energy input for substrate transport.

8. Lipids, sugars, and amino acids can be chiral. Which statement about their stereochemical properties in nature is correct?(A) All naturally occurring amino acids in proteins are chiral and have the L-configuration.(B) Fatty acids in biological membranes are predominantly chiral and exist mainly as L-enantiomers.(C) Naturally occurring sugars and amino acids both predominantly adopt the L-configuration.(D) Most monosaccharides in biological systems have the D-configuration, and glycerol-based membrane lipids are synthesized from sn-glycerol-3-phosphate with defined stereochemistry.(E) Biological systems contain racemic mixtures of sugars, amino acids, and lipids due to spontaneous chemical reactions.

相關試題

相關試卷