Biology · Semester A TEKS 5A-11B
Medium
Lipids store roughly twice as much energy per gram as carbohydrates. Which property of lipid molecules best explains this?
ALong hydrocarbon chains contain many C–H bonds that can be oxidized to release energy
BThey are insoluble in water, so they take up much less space and can pack tightly when stored
CThey are able to form much longer repeating polymer chains than carbohydrate molecules can
DThey contain a great many more nitrogen atoms within each molecule than carbohydrate molecules do
Explanation
Lipid fatty-acid tails are long chains of carbon–hydrogen bonds. Oxidizing each C–H bond releases energy, so the more C–H bonds per gram, the more energy is stored. Carbohydrates have fewer C–H bonds per carbon because oxygen atoms are already attached. Water insolubility relates to *where* lipids are stored, not how much energy they hold. Lipids are not true polymers. Lipids contain almost no nitrogen — that is a feature of proteins and nucleic acids.
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