MCB 150 Mastering Biology Exam #2

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For each molecule of glucose processed during glycolysis, the net yield is ____.

two molecules of NADH, two of ATP, and two of pyruvate

During pyruvate processing, two carbons from pyruvate combine with ____.

coenzyme A

Which of these enters the citric acid cycle?

acetyl CoA

acetyl CoA

In the citric acid cycle, ATP molecules are produced by _____.

substrate-level phosphorylation

Which of these is NOT a product of the citric acid cycle?
acetyl CoA

acetyl CoA

Why is ATP production during cellular respiration characterized as indirect?

ATP is not produced directly by the ETC but instead via the proton gradient generated during electron transport through the ETC.

What would be the most likely effect on the pH of the mitochondrial matrix of a drug that inhibits ATP synthase?

It would rise.

Which answer best explains why organisms that have an ETC as well as fermentation pathways seldom ferment pyruvate if the electron acceptor at the end of the ETC is available?

Fermentation is extremely inefficient in terms of the number of ATP molecules produced for each molecule of glucose metabolized

Net input for glycolysis

glucose, ADP, NAD+

Net output for glycolysis

Pyruvate, ATP, NADH

Net input for Acetyl CoA Formation

Pyruvate, NAD+, coenzyme A

Net output for Acetyl CoA Formation

CO2, acetyl CoA, NADH

Net input for citric acid cycle

NAD+, acetyl CoA, ADP

Net output for citric acid cycle

CO2, ATP, NADH, Coenzyme A

Which statement best explains why more ATP is made per molecule of NADH than per molecule of FADH2?

Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.

For each glucose that enters glycolysis, _____ acetyl CoA enter the citric acid cycle.


For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle


In cellular respiration, most ATP molecules are produced by _____.

oxidative phosphorylation

The final electron acceptor of cellular respiration is _____.


During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

NADH and FADH2 ... intermembrane space

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient

Complementary base pairing is possible only if two DNA strands align in antiparallel—instead of parallel—fashion. Which statement best explains why?

Only antiparallel strands create the geometry that allows complementary base pairs to form via hydrogen bonding.

The polarity of a DNA strand refers to the fact that ______.

the two ends of the strand have different chemical groups

The Hershey-Chase experiment answered the question of whether protein or DNA was the genetic material by learning whether ___

DNA or protein from a virus entered bacterial cells during infection

With regard to DNA packaging, prokaryotic chromosomes

use RNA to contribute to chromosomal packaging.

Which of the following is the correct order of the levels of DNA packaging in eukaryotic chromosomes?

nucleosome → chromatin fiber → looped domains → heterochromatin

The Meselson-Stahl experiment was designed to answer which question?

What part of newly replicated DNA comes from the parental molecule and what part is newly synthesized?

Each DNA strand in a double helix contains all the information needed to make a new identical double helix.


An enzyme called ________ relieves the supercoiling of the DNA caused by unwinding of double stranded DNA by ________.

topoisomerase; helicase

DNA melting temperature (Tm) is:

higher if the DNA strand is stabilized by salts in the buffer
higher if the DNA helix has more GC base pairs compared to AT base pairs.
the temperature at which all identical DNA molecules in a population are halfway unwound

Which one of the following statements about the organization of DNA is correct?

In eukaryotes, DNA is coupled with proteins called histones and other proteins to make up chromatin.
In bacteria, chromosomes are supercoiled.
There is a very high degree of similarity between histones of a given type among species that possess them.

Which one of the following statements about nucleases is correct?

Kornberg's treatment of eukaryotic DNA with nuclease resulted in free 8-polypeptide complexes wrapped in DNA.
When Kornberg treated eukaryotic DNA with nuclease followed by salt treatment, 146 bp oligonucleotides were present.

Which of the following statements about histones is incorrect?

Histones are found in bacteria, where they assist with the supercoiling of circular chromosomes.

Which one of the following statements about euchromatin is incorrect?

It is typically found at the periphery of the nucleus.

Telomerase is needed to ______

prevent the loss of DNA bases at the ends of linear chromosomes

What is a major difference between eukaryotic DNA replication and prokaryotic DNA replication?

Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

DNA in both daughter cells would be radioactive.

The primers used for DNA synthesis are ______.

short RNA sequences

Okazaki fragments are found ______.

only on the lagging strand

How many copies of DNA polymerase III are in the replisome?


The new DNA strand that grows continuously in the 5' to 3' direction is called the ________.

leading strand

The direction of synthesis of an RNA transcript is ______.

5' -----> 3'

Which of the following enzymes is responsible for specifically transcribing tRNA in eukaryotic cells?

RNA polymerase III

Which of the following is not associated with mRNA processing in eukaryotes?

removal of exons

David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). These two regions of the promoter _____.

bind the sigma subunit that is associated with RNA polymerase

During elongation, RNA polymerase has three prominent channels, or grooves. These channels provide sites for all of the following EXCEPT _____.

a site for the exit of the diphosphates removed from the nucleotide triphosphates

Put the following events of transcription in chronological order.
1. Sigma binds to the promoter region.
2. The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands.
3. Sigma binds to RNA polymerase.
4. Sigma is released.
5. Transcription begins

3, 1, 2, 5, 4

During mRNA splicing ______.

snRNPs that make up the spliceosome recognize and remove introns

Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus?

A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.
Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes.
A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.

5' caps and 3' poly(A) tails of eukaryotic mRNAs ______.

protect mRNA from degradation and enhance translation

Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?

Codons are a nearly universal language among all organisms.

The redundancy of the genetic code is a consequence of ______

having more codons than amino acids

With respect to RNA processing, which of the following is false?

It leads to the production of alternative gene products.
Some introns are removed by spliceosomes.
Some introns are self-splicing.
Prokaryotic mRNAs are polyadenylated at the 3' end.
Chemical modification occurs with tRNA transcripts.

Prokaryotic mRNAs are polyadenylated at the 3' end.

What is recognized by an aminoacyl tRNA synthetase?

one amino acid and the set of tRNAs that are coupled to that amino acid

How does the bacterial ribosome recognize where to start translation?

The small ribosomal subunit binds to a sequence in the mRNA just upstream of the start codon.

Ribosomes are very old structures, found in all organisms. As a result, molecular taxonomists are looking at relationships based upon which rRNA sequence(s)?

16S and 18S

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