Chapter 2

Choose the incorrect statement: a. Electrons are found outside the nucleus at certain energy levels (shells). b. For any atom, the number of protons plus the number of electrons equals the atomic mass. c. The atomic number equals the number of protons in the nucleus. d. Electrons have negligible mass.

Covalent bonds a. form when two or more atoms share electrons. b. result from the mutual attraction of oppositely charged ions. c. form between a hydrogen atom on one water molecule and an oxygen atom on another water molecule. d. involve the transfer of electrons.

Choose the incorrect statement: a. Peptide bonds are formed through hydrolysis. b. Vitamins sometimes help an enzyme convert substrate to product. c. The primary structure of a protein is the precise sequence of amino acids. d. Quaternary structure results from attractive forces between the subunits of a protein.

Hydrogen bonds a. are stronger than either ionic or covalent bonds. b. form between a slightly positively charged hydrogen atom and a slightly negatively charged atom nearby. c. maintain the shape of proteins and DNA. d. \(b\) and \(c\)

Carbohydrates a. consist of chains of amino acids. b. supply our cells with energy. c. contain glycerol. d. function as enzymes.

Triglycerides a. have one molecule of glycerol and three fatty acids. b. are poor sources of energy. c. are saturated when there are two or more double bonds linking carbon atoms. d. are major components of plasma membranes.

Enzymes a. speed up chemical reactions and are consumed in the process. b. function only in decomposition reactions. c. are usually nonspecific and therefore capable of binding to many different substrates. d. have locations, known as active sites, to which the substrate binds.

Choose the incorrect statement: a. The base uracil is found in RNA but not in DNA. b. The two chains of RNA are held together by hydrogen bonds between the bases. c. Nucleotides are the monomers of nucleic acids. d. DNA molecules contain genes, which specify the sequence of amino acids in proteins.

Choose the incorrect statement: a. Most biochemical reactions in the human body occur around \(\mathrm{pH} 7\) b. Buffers prevent dramatic changes in pH. c. \(\mathrm{HCl}\) is an important buffering system in the blood. d. Burning of fossil fuels causes acid rain.

Changes in temperature or \(\mathrm{pH}\) can cause a protein to lose its three- dimensional shape and become nonfunctional. This process is called ________.