AP Biology Unit 1 Multiple Choice

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2+H20 ➡️ H2CO3. Carbonic acid (H2CO3) is a weak acid. If CO2 is bubbled into a beaker containing pure, freshly-distilled water, which of the following graphs correctly describes the results?

Graph: pH steadily decreases as time progresses

Which of the following is responsible for the cohesive property of water?

Hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule

Some green sea turtle females deposit their eggs in nests that are dug on warm, tropical beaches. Researchers have studied the effects of temperature on the hatching rate and the proportion of female to male hatchlings produced at different average nest temperatures in Suriname. At temperatures below 23°C or above 33°C the eggs do not develop. Which of the following best describes the results shown in Figure 1?

Warmer nests produce more female sea turtles than do cooler nests

Which is the best description of a carbonyl group?

a carbon atom joined to an oxygen by a double covalent bond (C=O)

Which of the following statements is true regarding the moleceule illustrated above? (Fat)

a diet rich in this molecule may contribute to atherosclerosis

Which of the following descriptions best fits the class of molecules known as nucleotides?

a nitrogenous base, a phosphate group, and a pentose sugar

Which of the following contains nitrogen in addition to carbon, oxygen, and hydrogen?

an amino acid such as glycine

About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?

carbon, hydrogen, nitrogen, oxygen (CHON)

The tertiary structure and function of a polypeptide is principally determined by the

interactions between amino acids present in the polypeptide

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by

polar covalent bonds

At which bond would water need to be added to achieve hydrolysis of the peptide, back to its component amino acid?

separate the amino group (NH2) and carboxyl group (C=O) of different amino acids

Which of the following describes the hydrolysis of carbohydrates?

the addition of a water molecule breaks a covalent bond between sugar monomers

Which of the following statements is false for the class of biological molecules known as lipids?

they are soluble in water

Which of the following best estimates the population size of the sea lions in 2000 based on the data shown in Figure 1?

175,000

Assume that acid rain has lowered the pH of a particular lake to pH 4.0. What is the hydroxyl ion concentration of this lake?

1x10^-10 mol of hydroxyl ion per liter of lake water

Which of the following pairs of functional groups characterizes the structure of an amino acid?

Carboxyl and Amino

The amino acid in Figure 1 is found in a region of a polypeptide that folds away from water. Which part of the amino acid most likely contributes to the hydrophobic behavior of this region of the polypeptide?

Methyl (CH3) group

Sometimes atoms form molecules by sharing two pairs of valence electrons. When this occurs, the atoms are said to be joined by

a double covalent bond

The R-group, or side chain, of the amino acid serine is -CH2-OH. The R-group, or side chain, of the amino acid alanine is -CH3. Where would you expect to find these amino acids in a globular protein in aqueous solution?

alanine would be in the interior, and serine would be on the exterior of the globular protein

What is the chemical mechanism by which cells make polymers from monomers?

dehydration reactions

The function of each protein is a consequence of its specific shape. What is the term used for a change in a protein's three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds?

denaturation

There are 20 different amino acids. What makes one amino acid different from another?

different side chains (R groups) attached to an alpha (a) carbon

A typical bag of fertilizer contains high levels of nitrogen, phosphorus, and potassium but trace amounts of magnesium and calcium. Which of the following best matches the fertilizer component with the molecule in which it will be incorporated by organisms in the area?

nitrogen will be incorporated into nucleic acids

Hydrophobic substances such as vegetable oil are

nonpolar substances that repel water molecules

A covalent chemical bond is one in which

outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms

Humans produce sweat as a cooling mechanism to maintain a stable internal temperature. Which of the following best explains how the properties of water contribute to this physiological process?

the high heat of vaporization of water allows the body to remove excess heat through a phase change of water from liquid to gas

All of the following statements concerning saturated fats are true except

they have multiple double bonds in the carbon chains of their fatty acids

Which of the following statements is true about buffer solutions?

they maintain a relatively constant pH when either acids or bases are added to them