When biologists wish to study the internal ultrastructure of cells, they can achieve the finest resolution by using
a transmission electronic microscope.
advantage of light microscopy over electron microscopy is that
microscopy allows one to view dynamic processes in living cells.
What is the reason that a modern electron microscope (TEM) can resolve biological images to the subnanometer level, as opposed to tens of nanometers achievable for the best super-resolution light microscope?
Electron beams have much shorter wavelengths than visible light
The volume enclosed by the plasma membrane of plant cells is often much larger than the corresponding volume in animal cells. The most reasonable explanation for this observation is that
plant cells contain a large vacuole that reduces the volume of the cytoplasm
Which of the following is a major cause of the size limits for certain types of cells?
the need for a surface area of sufficient area to support the cell's metabolic needs
Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
Recent evidence shows that when chromosomes decondense during interphase, their DNA molecules do not intermingle. Instead, they occupy distinct territories within the nucleus. Considering the structure and location of the following structures, which is most likely to be involved in chromosome location?
the nuclear matrix
Which type of organelle or structure is primarily involved in the synthesis of oils, phospholipids, and steroids?
smooth endoplasmic reticulum
Which structure is the site of the synthesis of proteins that may be exported from the cell?
Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. Which of the following organelles contains these hydrolytic enzymes in animal cells?
Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large and complex lipids. Which cellular organelle must be involved in this condition?
The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and therefore abundant in liver cells?
Which organelle is the primary site of ATP synthesis in eukaryotic cells?
Which plant cell organelle contains its own DNA and ribosomes?
In a plant cell, DNA may be found
in the nucleus, mitochondria, and chloroplasts.
What types of proteins are not synthesized in the rough ER?
Cyanide binds with at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the cyanide will be found within the
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
Which of the following is (are) true for anabolic pathways?
They consume energy to build up polymers from monomers
Which of the following is an example of potential rather than kinetic energy?
a molecule of glucose
Which of the following is true for all exergonic reactions?
The reaction proceeds with a net release of free energy.
A chemical reaction that has a positive ΔG is correctly described as
Why is ATP an important molecule in metabolism?
It provides energy coupling between exergonic and endergonic reactions.
Which of the following statements is true concerning catabolic pathways?
They supply energy, primarily in the form of ATP, for the cell's work.
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's
Which of the following statements regarding enzymes is true?
Enzymes increase the rate of a reaction by lowering the activation energy barrier.
The active site of an enzyme is the region that
is involved in the catalytic reaction of the enzyme.
Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses?
in or near the active site
When you have a severe fever, what grave consequence may occur if the fever is not controlled?
change in the tertiary structure of your enzymes
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction
loses electrons and loses potential energy.
When electrons move closer to a more electronegative atom, what happens?
The more electronegative atom is reduced, and energy is released.
Which of the following statements describes the results of this reaction?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C6H12O6 is oxidized and O2 is reduced.
Where does glycolysis take place in eukaryotic cells?
The ATP made during glycolysis is generated by
The oxygen consumed during cellular respiration is involved directly in which process or event?
accepting electrons at the end of the electron transport
Why are carbohydrates and fats considered high energy foods?
They have a lot of electrons associated with hydrogen.
During glycolysis, when each molecule of glucose is catabolized to two molecules of pyruvate, most of the potential energy contained in glucose is
retained in the two pyruvates.
In addition to ATP, what are the end products of glycolysis?
NADH and pyruvate
Why is glycolysis described as having an investment phase and a payoff phase?
It uses stored ATP and then forms a net increase in ATP.
During aerobic respiration, electrons travel downhill in which sequence?
food → NADH → electron transport chain → oxygen
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
In cellular respiration, the energy for most ATP synthesis is supplied by
a proton gradient across a membrane.
The primary role of oxygen in cellular respiration is to
act as an acceptor for electrons and hydrogen, forming water.
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the
creation of a proton-motive force.
Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis)
The synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient, is an example of
an endergonic reaction coupled to an exergonic reaction.
You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave her body?
It was converted to heat and then released
Where does the Calvin cycle take place?
stroma of the chloroplast
When oxygen is released as a result of photosynthesis, it is a direct by-product of
splitting water molecules.
In the thylakoid membranes, what is the main role of the antenna pigment molecules?
concentrate photons within the stroma
Which of the events listed below occurs in the light reactions of photosynthesis?
Light is absorbed and funneled to reaction-center chlorophyll a.
Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will have the most direct effect on which of the following processes?
the synthesis of ATP
What does the chemiosmotic process in chloroplasts involve?
establishment of a proton gradient across the thylakoid membrane
In a plant cell, where are the ATP synthase complexes located?
thylakoid membrane and inner mitochondrial membrane
Which of the following statements best describes the relationship between photosynthesis and respiration?
Photosynthesis stores energy in complex organic molecules, whereas respiration releases it.
Where are the molecules of the electron transport chain found in plant cells?
thylakoid membranes of chloroplasts
In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during
both photosynthesis and respiration
Generation of proton gradients across membranes occurs during
both photosynthesis and respiration
Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?
They protect against oxidative damage from excessive light energy.
The reactions that produce molecular oxygen (O2) take place
the light reactions alone.
Where do the enzymatic reactions of the Calvin cycle take place?
stroma of the chloroplast
What is the primary function of the Calvin cycle?
synthesize simple sugars from carbon dioxide
The phylogenetic distribution of the enzyme rubisco is limited to
all known photoautotrophs, both bacterial and eukaryotic
Plants photosynthesize only in the light. Plants respire
both in light and dark.
The light reactions of photosynthesis supply the Calvin cycle with
ATP and NADPH.
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
At which phase are centrioles beginning to move apart in animal cells?
If cells in the process of dividing are subjected to colchicine, a drug that interferes with the formation of the spindle apparatus, at which stage will mitosis be arrested?
Why do chromosomes coil during mitosis?
to allow the chromosomes to move without becoming entangled and breaking
Which of the following is (are) required for motor proteins to function in the movement of chromosomes toward the poles of the mitotic spindle?
ATP as an energy source
Why do neurons and some other specialized cells divide infrequently?
They have been shunted into G0.
All cell cycle checkpoints are similar in which way?
They activate or inactivate other proteins.
For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?
It interferes with rapidly dividing cells.
You have a series of cells, all of which were derived from tumors, and you first need to find out which ones are malignant. What could you do?
Karyotype samples to look for unusual size and number of chromosomes.
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related
disruption of mitotic spindle formation.
One difference between cancer cells and normal cells is that cancer cells
continue to divide even when they are tightly packed together.
Which of the following is a true statement about sexual vs. asexual reproduction?
In sexual reproduction, individuals transmit 50% of their genes to each of their offspring
At which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype?
The human X and Y chromosomes
include genes that determine an individual's sex.
Which of the following is true of a species that has a chromosome number of 2n = 16
Each cell has eight homologous pairs.
A given organism has 46 chromosomes in its karyotype. We can therefore conclude which of the following?
Its gametes must have 23 chromosomes.
If a cell has completed the first meiotic division and is just beginning meiosis II, which of the following is an appropriate description of its contents?
It has half the amount of DNA as the cell that began meiosis.
How do cells at the completion of meiosis compare with cells that have replicated their DNA and are just about to begin meiosis?
They have half the number of chromosomes and one-fourth the amount of DNA.
Independent assortment of chromosomes is a result of
the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.
A human cell containing 22 autosomes and a Y chromosome is
How do we describe transformation in bacteria?
assimilation of external DNA into a cell
In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?
DNA contains phosphorus, whereas protein does not.
Which of the following investigators was/were responsible for the following discovery?
In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?
sequence of bases
What is meant by the description "antiparallel" regarding the strands that make up DNA?
The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand
Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?
DNA polymerase III
To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
endonuclease, DNA polymerase I, DNA ligase
What is the function of DNA polymerase III
to add nucleotides to the 3' end of a growing DNA strand
A new DNA strand elongates only in the 5' to 3' direction because
DNA polymerase can only add nucleotides to the free 3' end
What is the function of topoisomerase?
relieving strain in the DNA ahead of the replication fork
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
It joins Okazaki fragments together.
Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?
They cannot repair thymine dimers.
What is a ribozyme?
an RNA with enzymatic activity
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the
bonding of the anticodon to the codon and the attachment of amino acids to tRNAs
Why might a point mutation in DNA make a difference in the level of protein's activity
It might substitute an amino acid in the active site.
Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
a deletion of two nucleotides
What is the effect of a nonsense mutation in a gene?
It introduces a premature stop codon into the mRNA.
A frameshift mutation could result from
either an insertion or a deletion of a base.
Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
a base-pair deletion
Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?
a base deletion near the start of a gene
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in
a polypeptide missing an amino acid.