Exam 2

Question 1

Which statement about electron transport systems is TRUE?
a. During aerobic respira6on oxygen is always the terminal electron acceptor while during
anaerobic respira6on it is another (typically inorganic) compound.
b. Electron transport systems mediate transfer of electrons and conserve some of the energy
released during transfer and use it for synthesis of ATP.
c. Fermenta6on does not require a fully func6onal electron transport chain.
d. In electron transport systems, the electron carriers are membrane associated.
e. All of the above are correct.

Answer 1

E. All of the above are correct

Question 2

Which statement is FALSE?
a. RNA polymerase ini6ates transcrip6on aZer binding to the promoter sequence in DNA
b. The template for RNA polymerase is DNA and newly synthesized RNA molecules are parallel
and iden6cal to the template.
c. In complementary base pairing of DNA, adenine pairs with thymine and cytosine always pairs
with guanine
d. The promoters of posi6vely controlled operons require ac6vator proteins because the
promoters bind RNA polymerase weakly and use activator proteins to help RNA
polymerase recognize the promoter.
e. The codon on the RNA matches with the an6codon on the tRNA to direct the addi6on of the
correct amino acid to the growing polypeptide chain.

Answer 2

The template for RNA polymerase is DNA and newly synthesized RNA molecules are parallel
and identical to the template.

Question 3

When arginine is added to a culture growing exponentially in a medium without arginine, what occurs?

Answer 3

Growth continues but the production of enzymes required for he synthesis of arginine ceases

Question 4

Repression and induction of enzyme biosynthesis occurs at the level of

Answer 4

transcription

Question 5

In negative control of transcription, how does the presence of a co-repressor like the amino acids
tryptophan or arginine affect transcription?

Answer 5

The co-repressor causes the repressor to bind to the operator

Question 6

What is the importance of the stop codon UAG

Answer 6

It signals the ribosome to stop translating the mRNA

Question 7

Supercoiling is important for DNA structure, because

Answer 7

it condenses the DNA so that it can fit inside a cell

Question 8

In the process of transcription, promoters are specific sequences of ________ that are recognized by
________.

Answer 8

DNA / sigma factors

Question 9

Which of the following statements is true with respect to heterotrophic organisms?
a. They have the ability to use either preformed organic compounds as sources of carbon or they
can fix carbon dioxide from the atmosphere during photosynthesis.
b. They invariably ferment carbon-containing substrates.
c. They use preformed organic compounds as sources of carbon.
d. They prefer bacterial cells of the opposite sex during the process of reproduction.

Answer 9

They use preformed organic compounds as sources of carbon

Question 10

Which of the following statements regarding DNA and RNA synthesis is FALSE?

a. The overall direc6on of chain growth is from the 5ʹ to 3ʹ end.
b. The template strand is an6parallel to the newly synthesized strand.
c. An RNA primer is required to ini6ate both processes.
d. DNA is the template for both DNA and RNA synthesis

Answer 10

An RNA primer is required to initiate both processes

Question 11

In all cells, genes are composed of

Answer 11

deoxyribonucleic acids

Question 12

The two strand of the DNA double helix are held together by

Answer 12

hydrogen bonds between nucleotide bases

Question 13

An operon is a useful genetic element, because it

Answer 13

allows coordinated expression of multiple related genes in prokaryotes

Question 14

You experimentally change the DNA sequence directly upstream of a start codon of an operon in E.
coli to inves6gate the func6on of this region of DNA. Analysis reveals that aZer the change the same
amount of mRNA is made from the operon, but there are very few proteins made from the operon.
The DNA sequence you changed most likely encodes

Answer 14

A ribosome binding site

Question 15

during metabolism

Answer 15

catabolism and anabolism both occur and energy from catabolism is conserved as ATP and used in anabolism to make the macromolecules found in cells

Question 16

Which of the following might be used by a chemoorganotroph for energy

Answer 16

c2h3o2-

Question 17

if an oxidation reaction occurs

Answer 17

a different compound will be simultaneously reduced because electrons do not generally exist alone in solution

Question 18

What are stromatolites

Answer 18

fossilized remnants of ancient microorganisms that are about 3.5 billion years old

Question 19

The glycolysis pathway and the tricarboxylic acid (TCA) pathway are commonly referred to as central
metabolism. This is because

Answer 19

essentially all carbon sources (amino acids, lipids, aromatic compounds, etc.) are usually
metabolized by first transforming them into intermediates of these two pathways.

Question 20

Which of the following statements about transcrip6on of the lac operon in Escherichia coli is NOT
true?
a. RNA polymerase can be blocked by a repressor protein that binds to the operator region.
b. When the inducer is present, RNA polymerase transcribes three structural genes encoded by
the operon.
c. RNA polymerase binds to the operator region.
d. All the above

Answer 20

RNA polymerase binds to the operator region

Question 21

Which statement(s) concerning the Subsurface Origin Hypothesis is/are true?

a. So was the earliest electron acceptor
b. H2 andH2S were the earliest electron donors
c. Carbon dioxide was the earliest carbon source
d. Only (b) and (c)
e. All the above (a-c)

Answer 21

all the above

Question 22

How are codons and anticodons related

Answer 22

They are complimentary short sequences found in mRNA and tRNA respec6vely that
determine the sequence of amino acids in proteins.

Question 23

Which statement is FALSE?
a. In the tricarboxylic acid (TCA) pathway, acetyl~CoA derived from pyruvate is completely
oxidized to CO2with the forma6on of NADH.
b. Fermenta6on yields less ATP than respira6on.
c. When one molecule of glucose is completely oxidized by an aerobic bacterium through aerobic
respira6on, the net gain of ATP is 2.
d. In fermenta6on, electrons are used to reduce an organic compound derived from pyruvate,
which serves as a terminal electron acceptor.

Answer 23

When one molecule of glucose is completely oxidized by an aerobic bacterium through aerobic
respiration, the net gain of ATP is 2.

Question 24

Which intermediate compound(s) in the tricarboxylic acid (TCA) pathway is/are oZen used for
biosynthetic pathways as well as carbon catabolism?
a. α-ketoglutarate
b. oxaloacetate
c. acetyl~CoA
d. None of the above (a-c)
e. All of the above (a-c)

Answer 24

All the above

Question 25

The bottleneck created by the forma6on of a reduced electron carriers in central metabolism is
overcome in fermentation by the

Answer 25

oxidation of NADH back to NAD+

Question 26

Ribosomes are

Answer 26

complex molecular machines that translate the code of single strands of mRNA into sequences
of polypeptides during protein synthesis

Question 27

The pentose phosphate pathway

Answer 27

a. is used in anabolism to produce the nucleo6des found in RNA and DNA.
b. is used for the catabolism of sugars that have five carbons.

Question 28

Phototrophs obtain energy from the reduction of carbon dioxide

Answer 28

False

Question 29

DNA synthesis occurs continuously on the lagging strand, while on the leading strand DNA synthesis
occurs discontinuously.

Answer 29

False

Question 30

Transcription uses mRNA as a template to synthesize polypeptides.

Answer 30

False

Question 31

The glyoxylate cycle is an anabolic pathway that is a variation of the tricarboxylic acid cycle.

Answer 31

True

Question 32

Translation involves the 5’ to 3’ synthesis of mRNA from a DNA template

Answer 32

False

Question 33

As part of regulating the lac operon in Escherichia coli allolactose binds to a repressor protein and this
complex binds to lac operator blocking the transcription of genes required for lactose metabolism.

Answer 33

False

Question 34

During glycolysis substrate level phosphorylation conserves chemical bond energy in the form of ATP.

Answer 34

True

Question 35

Prokaryotes that are chemolithotrophs obtain their energy from the oxidation of inorganic
compounds.

Answer 35

True