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56 terms

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?

glucose
NADH + H+
G3P
acetyl CoA
pyruvate
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
FADH2
CO2
NADH + H+
ATP
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.
2
For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle
6
In cellular respiration, most ATP molecules are produced by _____.
oxidative phosphorylation
The final electron acceptor of cellular respiration is _____.
oxygen
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.
True
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?
2
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