Chapter 3 Test Bank AP Bio

Which functional groups shown in figure 3.4 are present in all amino acids>

(e) C and D (COOH and NH2)

One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3) Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3) and a hydrogen ion (H+) thus, H2CO<-->HCO3+H+ If the pH of the blood drops, one would expect

(e) the HCO3 to act as a base and remove excess H+ with the formation of H2CO3

When an ionic compound such as sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of particles (molecules or ions)

1 Lof 1.0 MNaCl

One liter of a solution of pH 2 has how many more hydrogen ions (H+) than 1 L of a solution of pH 6

10,000 times more

A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be composed of

120 thymine ad 120 adenine molecules

If a DNA ample were composed of 10% thymine, what would be the percentage of guanine?

40

Upon chemical analysis, a particular polypeptide was found to contain 100 amino acids. How many peptide bonds are present in this protein

99

Which of the following effects is produced by the high surface tension of water

A water strider can walk across the surface of a small pond

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O → H2CO3. Carbonic acid (H2CO3) is a weak acid. Respiring cells release CO2. What prediction can we make about the pH of blood as that blood first comes in contact with respiring cells

Blood pH will decrease slightly

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2_H2O<-->H2CO3. Carbonic acid is a weak acid. Respiring cells release CO2 into the bloodstream. What will be the effect on the pH of blood as that blood first comes into contact with respiring cells?

Blood pH will decrease slightly

which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers

Why does ice float in liquid water

Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water

A .01 M solution of a substance has a pH of 2. What can you conclude about this substance?

It is a string acid that ionizes completely in water

Which of the following statements are true regarding the chemical reaction illustrated in figure 3.11?

It results in a peptide bond

Which of the following takes place as an ice cube cools a drink

Kinetic energy in the drink decreases

the R group or side chain of the amino acid serine is -CH2-OH. The R group or side chain of the amino acid leucine is -CH2CH-(CH3)2. Where would you expect to find these amino acids in a globular protein in a aqueous solution

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

If 14C-labeled uracil is added to the growth medium of cells, what macro molecules will be labeled?

RNA

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

The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called

a hydrogen bond

Waterʹs high specific heat is mainly a consequence of the

absorption and release of heat when hydrogen bonds break and form

Normal hemoglobin is a tetramer, consisting of two molecules of B hemoglobin and two molecules of a hemoglobin. In sickle cell, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle cell hemoglobin exhibits

altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered

Polysaccharides, triacylglycerides, and proteins are similar in that they

are synthesized from sub-units by dehydration reactions

Which two functional groups are always found in amino acids?

carboxyl and amino

Water molecules are able to form hydrogen bonds with

compounds that have polar covalent bonds

If the pH of a solution is increased from pH 5 to pH 7, it means that the

concentration of OH- is 100 times greater than what it was at pH 5

A new organism is discovered in the forests of Costa Rica. Scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 from a gibbon, 49 from a rat, and 5 from a frog. These data suggest that the new organism is more closely related to

frogs than humans

What gives rise to the cohesiveness of water molecules

hydrogen bonds

Which type of bond must be broken for water to vaporize

hydrogen bonds

Which of the following statements are true regarding the molecule illustrated in figure 3.9

molecules of this type are usually liquid at room temp

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

polar covalent bonds

If cells are grown in a medium containing radioactive 35S, which of these molecules will be labeled?

proteins

The two molecules shown in figure 3.1 are best describes as

structural isomers