Unit 1 (Chapter 3, Test Yourself Questions)

Question 1

Molecules that are found in living cells and contain the element __________ are considered organic molecules.

Answer 1

Carbon

Question 2

The versatility of carbon that allows it to serve as the backbone for a variety of different molecules is due to

Answer 2

The ability for it to form 4 covalent bonds and the ability for it to form covalent bonds with many different types of atoms.

Question 3

Which of the following type(s) of bonds are nonpolar?

C—C

C—O

C—H

both a and b

both a and c

Answer 3

E

Question 4

A polysaccharide that is commonly found in animal cells and stores energy is

Answer 4

Glycogen

Question 5

In contrast to other fatty acids, essential fatty acids

Answer 5

cannot be synthesized by a living organism and are necessary for survival.

Question 6

The monomers of proteins are __________, and these are linked by polar covalent bonds commonly referred to as __________.

Answer 6

amino acids, peptide bonds

Question 7

A __________ is a portion of protein with a particular structure and function.

Answer 7

domain

Question 8

A DNA molecule contains 30% G. What percentage of its bases are A?

Answer 8

20%

Question 9

Explain the similarities and differences between molecules that are isomers.

Answer 9

Isomers are molecules with the same chemical formula but with different structures and arrangements of their atoms. There are two major types of isomers: structural isomers and stereoisomers. Because many chemical reactions in biology depend on the actions of enzymes, which are often highly specific with respect to the spatial arrangement of atoms in a molecule, one isomer of a pair may have biological functions, and the other may not.

Question 10

What is the difference between a saturated and an unsaturated fatty acid? How do the structural differences contribute to differences in their properties?

Answer 10

Saturated fatty acids are saturated with hydrogens and have only single (C−C) bonds, whereas unsaturated fatty acids have one or more double (C=C) bonds. The double bonds in unsaturated fatty acids alters the shape, resulting in one or more kinks in the chain. Saturated fatty acids are unkinked and are better able to stack tightly together. Fats containing saturated fatty acids have a higher melting point than those containing mostly unsaturated fatty acids; consequently, saturated fats tend to be solids at room temperatures, and unsaturated fats are usually liquids at room temperature.

Question 11

A core concept of biology is that structure determines function. What does this mean for organic molecules such as carbohydrates, lipids, and proteins?

Answer 11

The structures of all these macromolecules determine their functions. For example, the structure of a protein determines its three-dimensional shape. This, in turn, allows a protein to interact specifically with certain other molecules. Also, protein domains have specific structures that determine their functions. A single protein may have multiple domains, allowing that protein to perform a fairly complex function, such as activating genes in response to hormone binding. Likewise, the structures of different lipids determine such functional characteristics as male/female differences, cellular membrane formation, and energy storage. The different structures of polysaccharides determine their usefulness as energy stores or as components of plant cell walls