Bio 116 Exam 2
Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors?
Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site.
What do we do with NAD+ and FAD post-cellular respiration?
They can be reused in glycolysis, prep step, and the citric acid cycle
Which of the following is a characteristic feature of anabolic pathways?
They consume energy to build up polymers from monomers.
Which of the following statements best explains the ability of CAM plants to synthesize sugars in the daytime while keeping their stomata closed to reduce water loss?
They fix CO2 into organic acids during the night.
Which of the following statements best explains the ability of C4 plants to perform photosynthesis with no apparent photorespiration?
They use PEP carboxylase to initially fix CO2
Some enzymes can couple the hydrolysis of ATP to ion transport by having
changes during ATP hydrolysis alter the enzyme's shape, forcing ionic transport to occur.
A photosystem consists of which of the following structures?
chlorophyl molecules, reaction center complex, primary electron acceptor, light harvesting complexes
A ribosome has three binding sites for tRNA, the P site
holds the tRNA that carries the growing polypeptide chain
The A site
holds the tRNA that carries the next amino acid to be added to the chain
Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step __________.
enables the cell to recycle the reduced NADH to oxidized NAD+
Is energy released or gained when electrons move down the electron transport chain?
energy is RELEASED
You expect to see decoupled transcription and translation in ______.
eukaryotes
Is the breakdown of organic molecules endergonic or exergonic?
exergonic
The function of cellular respiration is to
extract usable energy from glucose
The function of cellular respiration is to __________.
extract usable energy from glucose
In the overall process of glycolysis and cellular respiration, _____ is oxidized and _____ reduced
glucose is OXIDIZED, oxygen is REDUCED
During the energy investment phase of glycolysis, __________.
glucose is phosphorylated before it is split into two three-carbon molecules
Which of the following metabolic processes normally occurs in most cells regardless of oxygen (O2) availability?
glycolysis
Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?
glycolysis and fermentation
In which reactions of cellular respiration does substrate-level phosphorylation occur?
in both glycolysis and the citric acid cycle
How do we derive this number?
2 ATP from glycolysis, 2 ATP from prep step and the citric acid cycle, 26/28 ATP from electron transport and chemiosmosis
Glycolysis results in the net production of which of the following sets of molecules per glucose molecule?
2 NADH, 2 pyruvate, and 2 ATP
A sample of double-stranded DNA contains 28% thymine. Approximately what percent of the nucleotides in this sample will be guanine?
22%
How many ATP are produced (from one glucose molecule: including glycolysis and aerobic respiration)?
30 or 32 ATP
Approximately how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C6H12O6) in aerobic cellular respiration?
30-32
For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle
4
Suppose a 150-base-pair, double-stranded DNA molecule consists of 15% thymine bases. How many total hydrogen bonds are holding the two strands together?
405
Glucose is the primary fuel for cellular respiration. Which of the following molecules can also be used by cellular respiration to generate ATP?
Amino acids, glycerol, and fatty acids can all be used in cellular respiration.
Which of the following correctly states the relationship between anabolic and catabolic pathways?
Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
During aerobic respiration, molecular oxygen is used for which of the following purposes?
At the end of the electron transport chain to accept electrons and form H2O
The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of __________.
allosteric regulation
ATP synthase at the inner mitochondrial membrane makes ATP and water from ADP and phosphate by coupling this to which other process?
allowing H+ to move down its electrochemical gradient
The E site
is the exit site, where discharged tRNAs leave the ribosome
transcription
is the synthesis of RNA using information in DNA
translation
is the synthesis of a polypeptide, using information in the mRNA
The 3′ end gets a
poly-A tail
Chemiosmosis
process in which energy stored in the form of a hydrogen gradient across a membrane is used to drive cellular work such as the synthesis of ATP
oxidative phosphorylation
production of ATP using energy derived from the redox reactions of an electron transport chain; the 3rd stage of respiration
When electrons are passed from one atom to a more electronegative atom, the more electronegative atom is ________.
reduced, and energy is released
Most of the electrons removed from glucose by cellular respiration are used for which of the following processes?
reducing NAD+ to NADH in glycolysis and the citric acid cycle and producing a proton gradient for ATP synthesis in the mitochondria
the genetic code is ____ but not _____
redundant but not ambiguous
Muscle tissues make lactate from pyruvate to do which of the following?
regenerate NAD+
An exergonic (spontaneous) reaction is a chemical reaction that __________.
releases energy when proceeding in the forward direction
In general, the hydrolysis of ATP drives cellular work by __________.
releasing free energy that can be coupled to other reactions
What is the function of the enzyme topoisomerase in DNA replication?
relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix
RNA splicing
removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence
mismatch repair
repair enzymes correct errors in base pairing
Binding of a repressor to the operator
shuts off transcription
The removal of introns is accomplished by
spliceosomes, a complex consisting of a variety of proteins and several small RNAs that recognize the splice sites
Carbon dioxide and oxygen enter and exit a leaf by diffusion. Which structure(s) on a leaf allow(s) this process to happen?
stomata
How does carbon dioxide enter the leaf?
stomata
Where does the Calvin cycle occur?
stroma of the chloroplast
The enzyme ______ compensates for replication-associated shortening of linear chromosomes.
telomerase
Which of the following reactions produces the majority of the CO2 released by the complete oxidation of glucose?
the citric acid cycle
When a cell is deprived of oxygen, which of the following processes will be inhibited first?
the electron transport chain
An operon is
the entire stretch of DNA that includes the operator, the promoter, and the genes that they control -The operon can be switched off by a protein repressor
Which of the following events takes place in the electron transport chain?
the harnessing of energy from redox reactions to generate a proton gradient
The light reactions of photosynthesis use _____ and produce _____.
water ... NADPH
exons
what the other regions are called because they are eventually expressed, usually translated into amino acid sequences
Output 19 of Pathway B is best identified as ______.
G3P
Which of the following processes occurs during the second phase, the reduction phase, of the Calvin cycle?
G3P Production
Which of the following reactions would be endergonic?
Glucose + fructose → sucrose
Is glucose being oxidized or reduced? What about oxygen?
Glucose = oxidized to carbon dioxide Oxygen= reduced to water
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
Glycolysis
Most of the ATP in cellular respiration is produced by the process of chemiosmosis. How does this process produce ATP?
H+ flows across the inner mitochondrial membrane through the enzyme ATP synthase
What represents the flow of electrons during photosynthesis?
H20 > NADPH > Calvin Cycle
In the light reactions, light energy is used to oxidize ____ to _____
H2O to O2
What are the 2 linked sets of reactions in photosynthesis?
Light dependent reactions & light independent reactions (Calvin Cycle)
the three stages of translation are
1. Initiation 2. Elongation 3. Termination
Accurate translation requires two steps
1. a correct match between a tRNA and an amino acid, done by the enzyme aminoacyl-tRNA synthetase 2. a correct match between the tRNA anticodon and an mRNA codon
An enzyme-catalyzed reaction has a ΔG of -20 kcal/mol under standard conditions. What will be the ΔG for the reaction if the amount of enzyme is doubled?
-20 kcal/mol
telomeres
-Eukaryotic chromosomal DNA molecules that have special nucleotide sequences. -Telomeres do not prevent the shortening of DNA molecules, but they do postpone the erosion of genes near the ends of DNA molecules -It has been proposed that the shortening of telomeres is connected to aging
transcription in eukaryote
-In a eukaryotic cell, the nuclear envelope separates transcription from translation -Eukaryotic RNA transcripts are modified through RNA processing to yield the finished mRNA -nucleus
Both PS I and PS II
-Light absorption -Reduction of primary electron acceptor
Photosynthesis II only
-Oxidation of water -Reduction of electron transport chain between the two photosystems
Photosynthesis I only
-Reduction of NADP+ -Oxidation of electron transport chain between the two photosystems
Chargaff's Rule
-The base composition of DNA varies between species -In any species the number of A and T bases is equal and the number of G and C bases is equal
Alteration of mRNA ends functions
-They seem to facilitate the export of mRNA to the cytoplasm -They help ribosomes attach to the 5′ end -They protect mRNA from hydrolytic enzymes
translation in prokaryotes
-occurs simultaneously as transcription inside the cytoplasm -translation of mRNA can begin before transcription has started
The two ribosomal subunits (large and small) are made of
-proteins -ribosomal RNA (rRNA)
A tRNA molecule consists of
-single RNA strand and looks like a cloverleaf -Anticodon & the 3' amino acid attachment end -Flexible pairing at the third base of a codon is called wobbleand allows some tRNAs to bind to more than one codon
What is the major goal of these processes?
1) Convert light energy to chemical energy 2) Fix inorganic carbon in organic molecules
If glucose is the sole energy source for cellular respiration in an animal, what proportion of the carbon dioxide exhaled is derived from oxidation of pyruvate to acetyl CoA?
1/3
If a cell produces on average 30 ATP molecules for each molecule of glucose that is completely oxidized to carbon dioxide and water, how many ATP molecules on average can the cell synthesize for each molecule of pyruvate oxidized to carbon dioxide and water?
12.5
The 5′ end receives a modified nucleotide
5′ cap
The nontemplate strand of a portion of a gene reads 5′-TTCACTGGTTCA-3'. What is the sequence of the resulting transcript for this portion?
5′-UUCACUGGUUCA-3'
What are the inputs of photosynthesis? The outputs?
6 CO2 + 12 H2O + light energy → C6H12O6 + 6 H2O + 6 O2
Which of these equations best summarizes photosynthesis?
6 CO2 + 6 H2O → C6H12O6 + 6 O2
How many codons specify amino acids and the start codons?
61 specify amino acids and the start codons , 3 are stop codons
Once a translation cycle starts, where would you expect to find a tRNA attached to a single amino acid?
A site
Output of calvin cycle
ADP, NADP+, G3P
As ATP begins to build up in a cell, metabolism slows down. How does this happen?
ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function.
Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible?
ATP can be regenerated by the addition of a phosphate group to ADP.
Which of the following statements best summarizes the metabolic results of photorespiration?
ATP is hydrolyzed, carbon dioxide is produced, and oxygen is consumed
Which of the following statements best describes the central role that ATP plays in cellular metabolism?
ATP provides energy coupling between exergonic and endergonic reactions.
Drugs known as uncouplers facilitate diffusion of protons across the membrane. With an uncoupler, what will happen to ATP synthesis and oxygen consumption if the rates of glycolysis and the citric acid cycle stay the same?
ATP synthesis will decrease; oxygen consumption will stay roughly the same.
G3P is used in which of the following processes?
All of the listed processes can use G3P.
How does ATP drive mechanical work inside a cell?
By binding to motor proteins
How does ATP drive transport work inside a cell?
By phosphorylating a transport protein
Which of the summary statements below best describes the results of the following reaction?C6H12O6 + 6O2 →→ 6CO2 + 6H2O + Energy
C6H12O6 is oxidized and O2 is reduced.
The electrons derived from this oxidation reaction in the Calvin cycle are used to reduce _____ to _____
CO2 to G3P
Input of calvin cycle
CO2, ATP, NADPH
Because ______ plants have Bundle-sheath cells, they are able to ________ separate their Calvin Cycle from high concentrations of _______.
C4; spatially; O2
In bacteria, which of the following proteins is responsible for removing nucleotides from the RNA primer that is used for initiation DNA synthesis?
DNA pol I
What catalyzes the formation of phosphodiester bonds between a DNA strand and a new nucleotide being added during DNA replication?
DNA polymerase
What provides electrons to the electron transport chain?
Electron carriers (NADH and FADH2)
If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?
Energy input into the organism must be occurring to drive the decrease in entropy.
Which of the following statements about enzyme function is correct?
Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.
Which of the following statements best describes enzyme function?
Enzymes increase the rate of chemical reactions by lowering activation energy barriers.
Which of the following statements about enzymes is true?
Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.
What would happen to cytoplasmic enzyme activity inside a cell with a normal cytoplasmic pH of 7.2 if you injected a chemical that would change the pH to 4.0?
Enzymes would probably denature.
Cells must regulate their metabolic pathways so that they do not waste resources. What is the most common mechanism that regulates cellular respiration in most cells?
Feedback inhibition of glycolysis
Fermentation by itself produces no ATP but keeps glycolysis going, which produces a small amount of ATP. How does fermentation do this?
Fermentation oxidizes NADH to NAD+ which facilitates the production of ATP in glycolysis
What is the correct sequence of compounds an electron would encounter if you begin from the very start of Photosystem II and use non-cyclic electron flow? I Ferredoxin II Water III NADPH IV G3P V Pheophytin
II-V-I-III-IV
termination in bacteria
In bacteria, the polymerase stops transcription at the end of the terminator and the mRNA can be translated without further modification
termination in eukaryotes
In eukaryotes, RNA polymerase II transcribes the polyadenylation signal sequence; the RNA transcript is released 10-35 nucleotides past this polyadenylation sequence
Which of the following statements best describes the electron transport chain?
It consists of a series of redox reactions.
What is the role of oxygen in the electron transport chain?
It is reduced to form water
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
It joins Okazaki fragments together.
Which statement about the citric acid cycle is true?
It makes ATP through substrate-level phosphorylation.
Which of the following statements best describes the primary role played by oxygen in cellular respiration?
It serves as the final acceptor for electrons from the electron transport chain.
The standard free energy for the complete oxidation of glucose to CO2 and water is -686 kcal/mol, and the standard free energy for the reduction of NAD+ to NADH is +53 kcal/mol. Which of the following statements best explains why only two molecules of NADH are formed in glycolysis when up to 12 molecules could theoretically be produced?
Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis.
polyribosome, polysome
Multiple ribosomes can translate a single mRNA simultaneously
Which of the following statements best describes what happens to a molecule of NAD+ (nicotinamide adenine dinucleotide) when it gains a hydrogen atom?
NAD+ becomes reduced.
Which of the following statements best describes a characteristic of NAD+?
NAD+ is reduced to NADH in glycolysis, pyruvate oxidation, and the citric acid cycle
After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of _____.
NADH
Upon completion of the citric acid cycle, most of the energy originally stored in each glucose molecule catabolized by cellular respiration is stored in which of the following molecules?
NADH
During the energy payoff phase of glycolysis, __________.
NADH and ATP are produced
Which of the following products result from the oxidation of pyruvate to acetyl-CoA?
NADH and CO2
In what molecules is the majority of the chemical energy from pyruvate transferred during the citric acid cycle?
NADH and FADH2
The electrons derived from this oxidation reaction in the light reactions are used to reduce _______ to _________
NADP+ to NADPH
The calvin cycle oxidizes the light-reactions product ______ to _______
NADPH to NADP+
In E. coli, a mutation in a gene called dnaB prevents the helicase from binding at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?
No replication fork will be formed.
Outputs of light reactions
O2, ATP, NADPH
Which of the following is a correct description of the events of cellular respiration and the sequence of events in cellular respiration?
Oxidation of glucose to pyruvate; oxidation of pyruvate; oxidation of acetyl-coA; oxidative phosphorylation
Which of the following processes produces the most ATP?
Oxidative phosphorylation
signal peptide
Polypeptides destined for the ER or for secretion are marked by a
Which of the following statements accurately describes differences between DNA replication in prokaryotes and DNA replication in eukaryotes?
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.
What is another name for the H+ (proton) gradient?
Proton-motive force
In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs?
Pyruvate is oxidized and decarboxylated and the removed electrons are used to reduce an NAD+ to an NADH
During the Calvin cycle, what happens during the carbon fixation phase?
The Calvin cycle incorporates each CO2 molecule, one at a time, by attaching it to a five-carbon sugar named ribulose bisphosphate.
The reactions of the Calvin cycle are not directly dependent on light, but they usually do not occur at night. Why?
The Calvin cycle requires products only produced when the photosystems are illuminated.
promoter
The DNA sequence where RNA polymerase attaches
Which of these statements about enzyme inhibitors is true?
The action of inhibitors may be reversible or irreversible.
Which of the following statements best describes how addition of a catalyst will affect a chemical reaction?
The catalyzed reaction will have the same ΔG as the uncatalyzed reaction.
Most of the NADH that delivers electrons to the electron transport chain comes from which of the following processes?
The citric acid cycle
Which part of the catabolism of glucose by cellular respiration requires molecular oxygen (O2) and produces CO2?
The combination of the citric acid cycle and electron transport
transcription initiation complex
The completed assembly of transcription factorsand RNA polymerase II bound to a promoter is called
Which of the following metabolic pathways produce(s) the most ATP, per glucose molecule metabolized, during cellular respiration?
The electron transport chain and oxidative phosphorylation
Which of the following statements is correct regarding ATP?
The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.
Substrate-level phosphorylation
The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism
The ATP synthase in a human cell obtains energy for synthesizing ATP directly from which of the following processes?
The flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme
What best characterizes the role of ATP in cellular metabolism?
The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA in DNA replication?
The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
How do the leading and the lagging strands differ?
The leading strand is synthesized in the same direction as the movement of the replication fork, whereas the lagging strand is synthesized in the opposite direction.
During which process is molecular oxygen produced in photosynthesis?
The light reactions by linear electron flow
The energy from the electrons in NADH and FADH2 fuel what process in the electron transport chain?
The pumping of H+ across the cristae of the mitochondrion
A reaction has a ∆G of +1 kcal/mol. Which of the following would most likely be true?
The reaction is nonspontaneous.
Which of the following statements best describes an exergonic reaction?
The reaction proceeds with a net release of free energy.
introns
These noncoding regions are called intervening sequences
Which of the following statements best describes catabolic pathways?
They are exergonic and provide energy that can be used to produce ATP from ADP and Pi.
A small amount of ATP is made in glycolysis by which of the following processes?
Transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation
What is the total production of ATP, NADH, and FADH2 in the citric acid cycle from one molecule of glucose?
Two ATP, six NADH, and two FADH2
What do cells require to sustain high rates of glycolysis under anaerobic conditions?
Under anaerobic conditions, cells depend on the low-efficient fermentation pathway to generate ATP.
Metabolic pathways are typically redox processes. In photosynthesis, what molecule is oxidized and what molecule is reduced?
Water is oxidized and carbon dioxide is reduced.
A corepressor is
a molecule that cooperates with a repressor protein to switch an operon off
nucleotide excision repair
a nuclease cuts out and replaces damaged stretches of DNA
Imagine a bacterial replication fork. Synthesis of which new strand(s) would be affected by mutations in the enzyme primase?
both leading and lagging strands
Gene
can be defined as a region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule
A decrease in entropy is associated with which of the following types of reaction?
dehydration
Inputs of light reactions
light, water, ADP, NADP+
Aminoacyl-tRNA synthetase is an enzyme whose function is to _____.
link a tRNA to its corresponding amino acid
Bound ribosomes
make proteins of the endomembrane system and proteins that are secreted from the cell
Transcription factors
mediate the binding of RNA polymerase and the initiation of transcription
Energy released from the electron transport chain is used to pump H+ ions into which location in eukaryotic cells?
mitochondrial intermembrane space
Free ribosomes
mostly synthesize proteins that function in the cytosol
Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation?
oxidation of NADH to NAD+
Chlorophyll molecules are in which part of the chloroplast?
thylakoid membranes
What is the purpose of fermentation reactions?
to regenerate NAD+ so glycolysis can continue
Which of the following components does not form part of the transcription initiation complex at a eukaryotic promoter?
transfer RNA
