A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?
ATP is transported into the cell from the circulatory system.
Other cells take over, and the muscle cells that have used up their ATP cease to function.
Catabolic processes are activated that generate more ATP.
He or she has to sit down and rest.
A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases, although they do not often hydrolize ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If resting muscle cell's cytosol has a free calcium ion concentration of 10^(-7) while the concentration in the SR is 10^(-2), then how is the ATPase acting?
ATPase activity must be opening a channel for the calcium ions to diffuse back into the SR along the concentration gradient.
ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
ATPase activity must be powering an inflow of calcium from the outside of the cell into the SR.
ATPase activity must be transferring Ⓟi to the SR to enable this to occur.
Cell membranes are asymmetrical. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?
The two sides of a cell membrane face different environments and carry out different functions.
Since the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical.
Since cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical.
Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane's asymmetrical nature.
Fatty acids usually have an even number of carbons in their structures. They are catabolized by a process called beta-oxidation. The end products of the metabolic pathway are acetyl groups of acetyl CoA molecules. These acetyl groups ________.
directly enter the energy-yielding stages of glycolysis.
directly enter the electron transport chain.
are directly decarboxylated by pyruvate dehydrogenase.
directly enter the citric acid cycle.
If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence ______.
In solution, why do hydrolysis reactions occur more readily than condensation reactions?
Hydrolysis raises G, or Gibbs free energy.
Hydrolysis increases entropy and is endergonic.
Hydrolysis increases entropy and is exergonic.
Hydrolysis decreases entropy and is exergonic.
Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?
As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.
Living organisms are able to transform energy into entropy.
Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is exactly balanced by an increase in the entropy of the universe.
Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time.
Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this probably mean?
Proton pumps are necessary to all cell membranes.
Cells of each domain evolved proton pumps independently when oceans became more acidic.
Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.
The membranes of winter wheat are able to remain fluid when it is extremely cold by _____.
increasing the percentage of cholesterol molecules in the membranes
decreasing the number of hydrophobic proteins in the membrane
cotransport of glucose and hydrogen
increasing the percentage of unsaturated phospholipids in the membrane
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 ______.
a reaction with a positive delta G
an endergonic reaction coupled to an exergonic reaction
Which of the following processes includes all others?
transport of an ion down its electrochemical gradient
Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
It requires the presence of membrane-enclosed cell organelles found only in eukaryotic cells.
It is found in prokaryotic cells but not in eukaryotic cells.
It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.
It produces much less ATP than does oxidative phosphorylation.
A localized group of organisms that belong to the same species is called a
Organisms interact with their environments, exchanging matter and energy. For example, plant chloroplasts convert the energy of sunlight into
the energy of motion
carbon dioxide and water
the potential energy of chemical bonds
The main source of energy for producers in an ecosystem is
Which of the following types of cells utilize deoxyribonucleic acid (DNA) as their genetic material but do not have their DNA encased within a nuclear envelope?
To understand the chemical basis of inheritance, we must understand the molecular structure of DNA. This is an example of the application of which concept to the study of biology?
the cell theory
Once labor begins in childbirth, contractions increase in intensity and frequency until delivery. The increasing labor contractions of childbirth are an example of which type of regulation?
a bioinformatic system
When the body's blood glucose level rises, the pancreas secretes insulin and, as a result, the blood glucose level declines. When the blood glucose level is low, the pancreas secretes glucagon and, as a result, the blood glucose level rises. Such regulation of the blood glucose level is the result of
The elongation of the leading strand during DNA replication
Proceeds away from the replication fork
Depends upon the action of DNA polymerase
Proceeds in the 3' to 5' direction
Does not require a template strand
What does the reactivity of an atom depend on?
Number of valence shells in the atom.
Number of orbitals found in the atom.
Number of electrons in each orbital in the atom.
Presence of unpaired electrons in the outer valance shell of the atom.
Presence of the hybridized orbitals in the atom.
A covalent chemical bond is one in which...
electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged.
protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms.
outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shell of both atoms.
outer-shell electrons of an atom are transferred to the inner electron shells of another atom.
the inner-shell electrons of one atom are transferred to the outer-shell of another atom.
Which of the following is the best example of gene expression?
A frog adapts to variation in its environmental temperature.
Mouse fur color results from pigment formed by gene-encoded enzymes.
DNA is replicated during the S phase of the cell cycle.
What results from an unequal sharing of electrons between atoms?
A nonpolar covalent bond.
A polar covalent bond.
An ionic bond.
A hydrogen bond.
A hydrophobic interaction.
Which bonds must be broken for water to vaporize?
Nonpolar covalent bonds
Polar covalent bonds
One liter of a solution of pH has how many more hydrogen ions (H+) than 1L of a solution of pH 6?
4 times more
400 times more
4,000 times more
10,000 times more
100,000 times more
Observe the structure of glucose and fructose in the figure. These two molecules are...
Polymers of polysaccharides, fats and proteins are all synthesized from monomers by which process?
Connecting monosaccharides together (condensation reactions)
The addition of water to each monomer (hydrolysis)
The removal of water (dehydration reactions)
Ionic bonding of the monomers
The formation of disulfide between monomers
The 20 different amino acids found in polypeptides exhibit different chemical and physical properties because of different
Carboxyl groups attached to an alpha (α) carbon
Amino groups attached to an alpha (α) carbon
Side chains (R groups)
Alpha (α) carbons
The tertiary structure of a protein is the...
bonding together of several polypeptide chains by weak bonds.
order in which amino acids are joined in a polypeptide chain.
unique three-dimensional shape of the fully folded polypeptide.
organization of a polypeptide chain into a a-helix or B-pleated sheet.
Which of the following best describes the flow of information in eukaryotic cells?
DNA → RNA → Proteins
RNA → Proteins → DNA
Proteins → DNA → RNA
RNA → DNA → Proteins
DNA → Proteins → RNA
Which of the following are nitrogenous bases found in DNA?
Which of the following types of molecules are the major structural components of the cell's membrane?
The movement of a substance across a biological membrane against its concentration gradient with the help of energy input is...
The sodium-potassium is called an electrogenic pump because it...
Pumps equal quantities of Na+ and K+ across the membrane.
Pumps hydrogen ions out of cells.
Contributes to the membrane potential.
Ionizes sodium and potassium atoms.
Is used to drive the transport of other molecules against a concentration gradient.
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
Which of the following statements regarding ATP is (are) correct?
ATP serves as a main energy shuttle inside cells.
ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants.
The regeneration of ATP from ADP and phosphate is an endergonic reaction.
In addition to ATP, what are the end products of glycolysis?
CO2 and H2O
CO2 and pyruvate
NADH and pyruvate
CO2 and NADH
H2O, FADH2, and citrate
The primary role of oxygen in cellular respiration is to...
Yield energy in the form of ATP as it is passed down the respiratory chain.
Act as an acceptor for the electrons and hydrogen.
Combine with carbon, forming CO2.
Combine with lactate, forming pyruvate.
Catalyze the reactions of glycolysis.
From the perspective of the cell receiving the message, the three stages of cell signaling are...
The paracrine, local, and synaptic stages
Signal reception, signal transduction, and cellular response
Signal reception, nucleus disintegration, and new cell generation
The alpha, beta, and gamma stages
Signal reception, cellular response, and cell division
Which of the following is/are true of ligand-gated ion channels?
They are important in the nervous system.
They lead to changes in sodium and calcium concentration in cells.
They open or close in response to a chemical signal.
Which of the following is true of the process of meiosis?
Two diploid cells result
Four diploid cells result
Four haploid cells result
Four autosomes result
Four chiasmata result
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
There is considerable genetic variation in garden peas.
Traits are inherited in discrete units, and are not the results of "blending".
Recessive genes occur more frequently in the F1 than do dominant ones.
Genes are composed of DNA.
An organism that is homozygous for many recessive traits is at a disadvantage.
The leading and the lagging strands differ in that
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
The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.
The leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together.
RNA polymerase and DNA polymerase differ in that
RNA polymerase uses RNA as a template and DNA polymerase uses a DNA template
RNA polymerase binds to single-stranded DNA and DNA polymerase binds to double-stranded DNA
RNA polymerase is much more accurate than DNA polymerase
RNA polymerase can initiate RNA synthesis but DNA polymerase requires a primer to initiate DNA synthesis.
RNA polymerase does not need to separate the two strands of DNA in order to synthesize an RNA copy, whereas DNA polymerase must unwind the double helix before it can replicate the DNA.
A frameshift mutation could result from...
a base insertion only
a base deletion only
a base substitution only
deletion of three consecutive bases
either an insertion or a deletion of a base
Thylakoids are present in chloroplasts.
The presence of cholesterol in the plasma membranes of some animals
enables the membrane to stay fluid more easily when cell temperature drops.
enables the animal to remove hydrogen atoms from saturated phospholipids.
enables the animal to add hydrogen atoms to unsaturated phospholipids.
makes the membrane less flexible, allowing it to sustain greater pressure from within the cell.
makes the animal more susceptible to circulatory disorders.
According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
They can move laterally along the plane of the membrane.
They frequently flip-flop from one side of the membrane to the other.
They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
They are free to depart from the membrane and dissolve in the surrounding solution.
They have hydrophilic tails in the interior of the membrane.
What kinds of molecules pass through a cell membrane most easily?
large and hydrophobic
small and hydrophobic
monosaccharides such as glucose
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
an amino acid
Molecules with which functional groups may form polymers via dehydration reactions?
Which of these molecules is not formed by dehydration reactions?
Which of these classes of biological molecules consist of both small molecules and macromolecular polymers?
Which of the following is not a polymer?
How many molecules of water are needed to completely hydrolyze a polymer that is 11 monomers long?
Which of the following are polysaccharides?
The bonding of two amino acid molecules to form a larger molecule requires which of the following?
Removal of a water molecule
Addition of a water molecule
Formation of a glycosidic bond
Formation of a hydrogen bond
Both removal of a water molecule and formation of a hydrogen bond
Upon chemical analysis, a particular polypeptide was found to contain 100 amino acids. How many peptide bonds are present in this protein?
What methods may be used to elucidate the structures of purified proteins?
analysis of amino acid sequence of small fragments
One of the primary functions of RNA molecules is to
transmit genetic information to offspring.
function in the synthesis of proteins.
make a copy of itself, thus ensuring genetic continuity.
act as a pattern or blueprint to form DNA.
form the genes of higher organisms.
The element present in all organic molecules is
Differences among organisms are caused by...
large differences in elemental composition from organism to organism.
differences in the types and relative amounts of organic molecules synthesized by each organism.
differences in the elements that bond with carbon in each organism.
differences in the sizes of the organic molecules in each organism.
differences in inorganic compounds present in each organism.
A carbon atom is most likely to form what kind of bond(s) with other atoms?
covalent bonds and hydrogen bonds
ionic bonds, covalent bonds, and hydrogen bonds
Why are hydrocarbons insoluble in water?
The majority of their bonds are polar covalent carbon-to-hydrogen linkages.
The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.
They are hydrophilic.
They exhibit considerable molecular complexity and diversity.
They are lighter than water.
How many structural isomers are possible for a substance having the molecular formula C₄H₁₀?
Which of the following statements correctly describes cis-trans isomers?
They have variations in arrangement around a double bond.
They have an asymmetric carbon that makes them mirror images.
They have the same chemical properties.
They have different molecular formulas.
Their atoms and bonds are arranged in different sequences.
Research indicates that ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules that
have identical chemical formulas but differ in the branching of their carbon skeletons.
are mirror images of one another.
exist in either linear chain or ring forms.
differ in the location of their double bonds.
A compound contains hydroxyl groups as its predominant functional group. Which of the following statements is true concerning this compound?
It lacks an asymmetric carbon, and it is probably a fat or lipid.
It should dissolve in water.
It should dissolve in a nonpolar solvent.
It won't form hydrogen bonds with water.
It is hydrophobic.
Which two functional groups are always found in amino acids?
Why are human sex hormones considered to be lipids?
They are essential components of cell membranes.
They are not soluble in water.
They are made of fatty acids.
They are hydrophilic compounds.
They contribute to atherosclerosis.
All of the following contain amino acids except...
Which of the following descriptions best fits the class of molecules known as nucleotides?
A nitrogenous base and a phosphate group.
A nitrogenous base and a pentose sugar.
A nitrogenous base, a phosphate group, and a pentose sugar.
A phosphate group and an adenine or uracil.
A pentose sugar and a purine or pyrimidine.
A primary objective of cell fractionation is to...
view the structure of cell membranes.
sort cells based on their size and weight.
determine the size of various organelles.
separate the major organelles so that their particular functions can be determined.
separate lipid-soluble from water-soluble molecules.
All of the following are part of a prokaryotic cell except...
a cell wall
a plasma membrane
an endoplasmic reticulum
Which of the following is a major cause of the size limits for certain types of cells?
Limitation on the strength and integrity of the plasma membrane as cell size increases.
The difference in plasma membranes between prokaryotes and eukaryotes.
Evolutionary progression in cell size; more primitive cells have smaller sizes.
The need for a surface area of sufficient area to support the cell's metabolic needs.
Rigid cell walls that limit cell size expansion.
Which organelle or structure is absent in plant cells?
Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
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 endoplasmic reticulum
the Golgi apparatus
Which organelle is the primary site of ATP synthesis in eukaryotic cells?
Which of the following is true for anabolic pathways?
They do not depend on enzymes.
They are usually highly spontaneous chemical reactions.
They consume energy to build up polymers from monomers.
They release energy as they degrade polymers to monomers.
Which of the following is the smallest closed system?
Which of the following is true of metabolism in its entirety in all organisms?
Metabolism depends on a constant supply of energy from food.
Metabolism depends on an organisms adequate hydration.
Metabolism uses all of an organism's resources.
Metabolism consists of all the energy transformation reactions in an organism.
A chemical reaction that has a positive ΔG is correctly described as...
Why is ATP an important molecule in metabolism?
Its hydrolysis provides an input of free energy for exergonic reactions.
It provides energy coupling between exergonic and endergonic reactions.
Its terminal phosphate group contains a strong covalent bond that, when hydrolyzed, releases free energy.
Its terminal phosphate bond has higher energy than the other two.
It is one of the four building blocks for DNA synthesis.
Which of the following statements is true concerning catabolic pathways?
They combine molecules into more energy-rich molecules.
They supply energy, primarily in the form of ATP, for the cell's work.
They are endergonic.
They are spontaneous and do not need enzyme catalysis.
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
It is used to power yet more cellular work.
It is used to store energy as more ATP.
It is used to generate ADP from nucleotide precursors.
It is lost to the environment.
The active site of an enzyme is the region that
binds allosteric regulators of the enzyme.
is involved in the catalytic reaction of the enzyme.
binds noncompetitive inhibitors of the enzyme.
is inhibited by the presence of a coenzyme or a cofactor.
For the enzyme-catalyzed reaction shown in the figure, which of these treatments will cause the greatest increase in the rate of the reaction, if the initial reactant concentration is 1.0 micromolar?
doubling the activation energy needed
cooling the reaction by 10°C
doubling the concentration of the reactants to 2.0 micromolar
doubling the enzyme concentration
increasing the concentration of reactants to 10.0 micromolar, while reducing the concentration of enzyme by 1/2
This question is based on the reaction A + B ↔ C + D shown in the figure. Which of the following terms best describes the forward reaction in the figure?
endergonic, ∆G > 0
exergonic, ∆G < 0
endergonic, ∆G < 0
exergonic, ∆G > 0
chemical equilibrium, ∆G = 0
The oxygen consumed during cellular respiration is involved directly in which process or event?
accepting electrons at the end of the electron transport chain
the citric acid cycle
the oxidation of pyruvate to acetyl CoA
the phosphorylation of ADP to form ATP
Where are the proteins of the electron transport chain located?
mitochondrial outer membrane
mitochondrial inner membrane
mitochondrial intermembrane space
In any ecosystem, terrestrial or aquatic, what group(s) is (are) always necessary?
autotrophs and heterotrophs
producers and primary consumers
In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during...
both photosynthesis and respiration
neither photosynthesis nor respiration