Answers to Test & Quantitative
and Thought Questions
The four basic cell types are epithelial, muscle,
nervous, and connective.
Steady-state requires energy input, but equilibrium
Muscles carry out the response (removing the hand
from the stove).
Circadian rhythms are typically entrained by the light/
dark cycle, but in the absence of such cues, the rhythms
“free run” with their own endogenous cycle length.
Intracellular ﬂ uid volume is greater than the sum of
plasma and interstitial ﬂ
Quantitative and Thought Questions
No. There may in fact be a genetic difference, but
there is another possibility: The altered skin blood
ﬂ ow in the cold could represent an
undergone by each Eskimo during his or her lifetime
as a result of performing such work repeatedly.
This could occur in many ways. For example, suppose
that an individual were to become dehydrated.
What would happen to his or her plasma sodium
? Initially, the loss of ﬂ uid would result
in an increased sodium concentration, even though
the absolute amount of sodium may not have changed
much. The increase in sodium concentration would
trigger endocrine and renal responses designed to return
the sodium concentration to normal. Another example
occurs during mountain climbing. At high altitude, a
person who is not acclimatized to low oxygen pressures
will hyperventilate (i.e., greatly increase the rate and
depth of breathing) to get more oxygen into his or her
blood. One consequence of hyperventilation, though, is
that more of the carbon dioxide in the body is exhaled.
Carbon dioxide tends to produce hydrogen ions in the
blood (Chapter 14). Thus, ascent to high altitude leads
to alkaline blood, which must then be compensated for
by renal, endocrine, and other responses.
The continued creation of new free radicals is a chain
reaction, and contributes to the potentially damaging
effects of a given free radical.
This is a dehydration reaction. The reverse reaction
would be hydrolysis.
Uracil is found in RNA; thymine is found in DNA.
Transcription refers to the conversion of a gene’s DNA
into RNA; translation is the conversion of mRNA
Allosteric modulation occurs at a site separate from
the ligand-binding site. The resulting change in three
dimensional structure of the protein may enhance or
reduce the ability of the protein to bind its ligand.
Catabolism refers to the breakdown of fatty acids into
usable forms for the production of ATP.
Quantitative and Thought Questions
Nucleotide bases in DNA pair A to T and G to C.
Given the base sequence of one DNA strand as:
a. The complementary strand of DNA would be:
b. The sequence in RNA transcribed from the ﬁ rst
strand would be:
Recall that uracil U replaces thymine T in RNA.
The triplet code G-T-A in DNA will be transcribed
into mRNA as C-A-U, and the anticodon in tRNA
corresponding to C-A-U is G-U-A.
If the gene were only composed of the triplet exon
code words, the gene would be 300 nucleotides in
length because a triplet of three nucleotides codes for
one amino acid. However, because of the presence
of intron segments in most genes, which account for
75 to 90 percent of the nucleotides in a gene, the
gene would be between 1200 and 3 nucleotides long;
moreover, it would also contain termination codons.
Thus, the exact size of a gene cannot be determined
by knowing the number of amino acids in the protein
the gene codes.
A drug could decrease acid secretion by (1) binding
to the membrane sites that normally inhibit acid
secretion, which would produce the same effect as the
body’s natural messengers that inhibit acid secretion;