Chapter 3

Which functional group has a double bond and forms organic acids? a. carboxyl b. amino c. hydroxyl d. carbonyl e. sulfhydryl

Which of the following characteristics is not common to carbohydrates, lipids, and proteins? a. They are composed of a carbon backbone with functional groups attached. b. Monomers of these molecules undergo dehydration synthesis to form polymers. c. Their polymers are broken apart by hydrolysis. d. The backbones of the polymers are primarily polar molecules. e. The molecules are held together by covalent bonding.

Cellulose is to carbohydrate as: a. amino acid is to protein. b. lipid is to fat. c. collagen is to protein. d. nucleic acid is to DNA. e. nucleic acid is to RNA.

Maltose, sucrose, and lactose differ from one another: a. because not all contain glucose. b. because not all of them exist in ring form. c. in the number of carbons in the sugar. d. in the number of hexose monomers involved. e. by the linkage of the monomers.

The term secondary structure refers to a protein's: a. sequence of amino acids. b. structure that results from local interactions between different amino acids in the chain. c. interactions with a second protein chain. d. interaction with a chaperonin. e. interactions with carbohydrates.

The first and major effect in denaturation of proteins is that: a. peptide bonds break. b. \(\alpha\) helices unwind. c. \(\beta\) sheet structures unfold. d. tertiary structure is changed. e. quaternary structures disassemble.

RNA differs from DNA because: a. RNA may contain the pyrimidine uracil, and DNA does not. b. RNA is always single-stranded when functioning, and DNA is always double- stranded. c. the pentose sugar in RNA has one less \(\mathrm{O}\) atom than the pentose sugar in DNA. d. RNA is more stable and is broken down by enzymes less easily than DNA. e. RNA is a much larger molecule than DNA.

Identify the following structures as a carbohydrate, fatty acid, amino acid, or polypeptide: a. ('The \(R\) indicates an organic group.) b. \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) c. (glycine) 20 d. \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{16} \mathrm{COOH}\)

Lipoproteins are relatively large, spherical clumps of protein and lipid molecules that circulate in the blood of mammals. They are like suitcases that move cholesterol, fatty acid remnants, triglycerides, and phospholipids from one place to another in the body. Given what you know about the insolubility of lipids in water, which of the three kinds of lipids would you predict to be on the outside of a lipoprotein clump, bathed in the fluid portion of blood?

Explain how polar and nonpolar groups are important in the structure and functions of lipids, proteins, and nucleic acids.

How do you think the primary structure (amino acid) sequence of proteins could inform us about the evolutionary relationships of proteins?