Which of these molecular structures could be found in a lipid, but not in a carbohydrate, protein, or nucleic acid? a. a long chain of carbon, oxygen, and nitrogen atoms b. a long chain made only of carbon and hydrogen atoms c. a phosphate group joined to a chain of carbon atoms d. an amino group and a carboxyl group bonded together

B

Explanation:

Lipids are made of very long carbon chains connected to other carbons and hydrogen. These chairs can be connected to another molecule such as glycerol. Examples of lipids are triglycerides, cholesterol, and phospholipid that differ in the length of their chains and also the number of double bonds in these chains. These chains - that are the main characteristic that defines lipids - are hydrophobic.

The  molecular structures that could be found in a lipid, but not in a carbohydrate, protein, or nucleic acid is a long chain made only of carbon and hydrogen atoms.

Lipids and carbohydrates are composed of carbon, hydrogen and oxygen atoms.

Proteins and nucleic acids have nitrogen atoms.

However, even though lipids and carbohydrates have carbon, hydrogen and oxygen atoms, carbohydrates are mostly cyclic structures and not straight chain molecules like lipids and they do not have a long chain made only of carbon and hydrogen atoms.

Hence, only lipids have a long chain made only of carbon and hydrogen atoms.

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