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88 questions
All of the following are part of a prokaryotic cell except
DNA
a cell wall.
a plasma membrane.
ribosomes.
an endoplasmic reticulum.
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 are capable of having a much higher surface-to-volume ratio than animal cells.
plant cells have a much more highly convoluted (folded) plasma membrane than animal cells.
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 evolution of larger cells after the evolution of smaller cells
the difference in plasma membranes between prokaryotes and eukaryotes
the evolution of eukaryotes after the evolution of prokaryotes
the need for a surface area of sufficient area to allow the cellʹs function
Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules?
lipids
starches
proteins
steroids
Under which of the following conditions would you expect to find a cell with a predominance of free ribosomes?
a cell that is secreting proteins
a cell that is producing cytoplasmic enzymes
a cell that is constructing its cell wall or extracellular matrix
a cell that is digesting food particles
Which type of organelle is primarily involved in the synthesis of oils, phospholipids, and steroids?
ribosome
lysosome
smooth endoplasmic reticulum
mitochondrion
Which structure is the site of the synthesis of proteins that may be exported from the cell?
rough ER
lysosomes
plasmodesmata
Golgi vesicles
In animal cells, hydrolytic enzymes are packaged to prevent general destruction of cellular components. Which of the following organelles functions in this compartmentalization?
chloroplast
lysosome
central vacuole
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
the lysosome
membrane-bound ribosomes
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?
rough ER
smooth ER
Golgi apparatus
nuclear envelope
Which of the following produces and modifies polysaccharides that will be secreted?
lysosome
vacuole
mitochondrion
Golgi apparatus
Which of the following contains its own DNA and ribosomes?
lysosome
vacuole
mitochondrion
Golgi apparatus
Grana, thylakoids, and stroma are all components found in
vacuoles
chloroplasts.
mitochondria.
lysosomes.
[check all that apply] Organelles other than the nucleus that contain DNA include
ribosomes
mitochondria
chloroplasts
Which of the following are capable of converting light energy to chemical energy?
chloroplasts
mitochondria
peroxisomes
Golgi bodies
A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from
a bacterium.
an animal, but not a plant.
a plant, but not an animal.
a plant or an animal.
The mitochondrion, like the nucleus, has two or more membrane layers. How is the innermost of these layers different from that of the nucleus?
The inner mitochondrial membrane is highly folded.
The two membranes are biochemically very different.
The space between the two layers of the nuclear membrane is larger.
The inner membrane of the mitochondrion is separated out into thylakoids.
Why isnʹt the mitochondrion classified as part of the endomembrane system?
It only has two membrane layers.
Its structure is not derived from the ER.
It is not involved in protein synthesis.
Motor proteins provide for molecular motion in cells by interacting with what types of cellular structures?
sites of energy production in cellular respiration
membrane proteins
ribosomes
cytoskeletons
Which of the following statements about the cytoskeleton is true?
Microfilaments are structurally rigid and resist compression, while microtubules resist tension (stretching).
Movement of cilia and flagella is the result of motor proteins causing microtubules to move relative to each other.
The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic of all of these extracellular structures?
They must block water and small molecules in order to regulate the exchange of matter and energy with their environment.
They must permit information transfer between the cellʹs cytoplasm and the nucleus.
They are constructed of materials that are largely synthesized in the cytoplasm and then transported out of the cell.
[select all that apply] A cell lacking the ability to make and secrete glycoproteins would most likely be deficient in its
nuclear DNA.
extracellular matrix.
Golgi apparatus.
Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells?
peroxisomes
desmosomes
gap junctions
Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through
plasmodesmata.
tight junctions.
gap junctions.
Which of the following types of molecules are the major structural components of the cell membrane?
phospholipids and cellulose
nucleic acids and proteins
phospholipids and proteins
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.
Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?
by increasing the percentage of unsaturated phospholipids in the membrane
by increasing the percentage of cholesterol molecules in the membrane
by decreasing the number of hydrophobic proteins in the membrane
In order for a protein to be an integral membrane protein it would have to be which of the following?
hydrophilic
hydrophobic
amphipathic
Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
The double bonds form kinks in the fatty acid tails, forcing adjacent lipids to be further apart.
Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in membranes.
Unsaturated fatty acids permit more water in the interior of the membrane.
Which of the following is true of integral membrane proteins?
They lack tertiary structure.
They are loosely bound to the surface of the bilayer.
They are usually transmembrane proteins.
They are not mobile within the bilayer.
Of the following functions, which is most important for the glycoproteins and glycolipids of animal cell membranes?
facilitated diffusion of molecules down their concentration gradients
active transport of molecules against their concentration gradients
maintaining the integrity of a fluid mosaic membrane
maintaining membrane fluidity at low temperatures
a cellʹs ability to distinguish one type of neighboring cell from another
Which of these are not embedded in the lipid bilayer at all?
transmembrane proteins
integral proteins
peripheral proteins
integrins
Which of these often serve as receptors or cell recognition molecules on cell surfaces?
transmembrane proteins
integral proteins
peripheral proteins
glycoproteins
Which of the following is true of the evolution of cell membranes?
Cell membranes have stopped evolving now that they are fluid mosaics.
Cell membranes cannot evolve if proteins do not
As populations of organisms evolve, different properties of their cell membranes are selected for or against.
An individual organism selects its preferred type of cell membrane for particular functions.
Why are lipids and proteins free to move laterally in membranes?
The interior of the membrane is filled with liquid water.
There are no covalent bonds between lipid and protein in the membrane.
Hydrophilic portions of the lipids are in the interior of the membrane.
There are only weak hydrophobic interactions in the interior of the membrane.
What kinds of molecules pass through a cell membrane most easily?
large and hydrophobic
small and hydrophobic
large polar
ionic
Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
It exhibits a specificity for a particular type of molecule.
It requires the expenditure of cellular energy to function.
It works against diffusion.
It has few, if any, hydrophobic amino acids.
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
CO2
an amino acid
glucose
K+
starch
Which of the following statements is correct about diffusion?
It is very rapid over long distances
It requires an expenditure of energy by the cell.
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
Water passes quickly through cell membranes because
the bilayer is hydrophilic.
it moves through hydrophobic channels.
water movement is tied to ATP hydrolysis.
it moves through aquaporins in the membrane.
Chloride ion channels are membrane structures that include which of the following?
gap junctions
aquaporins
hydrophilic proteins
Cystic fibrosis is a genetic disease in humans in which chloride ion channels in cell membranes are missing or nonfunctional. Which of the following would you expect to be a problem for someone with nonfunctional chloride channeling?
inadequate secretion of mucus
buildup of excessive secretions in organs such as lungs
sweat that includes no NaCl
mental disability due to low salt levels in brain tissue
Cystic fibrosis is a genetic disease in humans in which chloride ion channels in cell membranes are missing or nonfunctional. If a young male child has cystic fibrosis, which of the following would affect his fertility?
inability to make sperm
incomplete maturation of the testes
failure to form genital structures appropriately
incorrect concentrations of ions in semen
A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water, equal to the volume of blood lost, is transferred directly into one of his veins. What will be the most probable result of this transfusion?
It will have no unfavorable effect as long as the water is free of viruses and bacteria.
The patientʹs red blood cells will shrivel up because the blood fluid is hypotonic compared to the cells.
The patientʹs red blood cells will swell because the blood fluid is hypotonic compared to the cells.
Celery stalks that are immersed in fresh water for several hours become stiff and hard.
Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are
hypotonic to both fresh water and the salt solution.
hypertonic to both fresh water and the salt solution.
hypertonic to fresh water but hypotonic to the salt solution.
A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of water containing 0.02 molar glucose. Assuming that glucose is not actively transported into the cell, which of the following terms describes the tonicity of the external solution relative to the cytoplasm of the cell?
turgid
hypertonic
hypotonic
flaccid
isotonic
Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?
The animal cell is in a hypotonic solution, and the plant cell is in an isotonic solution
The animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution.
The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.
You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule enters the cell?
blood or tissue type of the patient
non-polarity of the drug molecule
lack of charge on the drug molecule
similarity of the drug molecule to other molecules transported by the target cells
In which of the following would there be the greatest need for osmoregulation?
an animal connective tissue cell bathed in isotonic body fluid
a terrestrial animal such as a snake
a red blood cell surrounded by plasma
a lymphocyte before it has been taken back into lymph fluid
When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?
the cell will burst
the cell membrane will lyse
plasmolysis will shrink the interior
the cell will become turgid
Which of the following membrane activities require energy from ATP hydrolysis?
facilitated diffusion.
movement of water into a cell
Na+ ions moving out of the cell
Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?
simple diffusion
facilitated diffusion
active transport pumps
exocytosis
What is the voltage across a membrane called?
water potential
chemical gradient
membrane potential
electrochemical gradient
If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium ions into the cell, which of the following is most likely true?
The sodium ions are moving down their electrochemical gradient while glucose is moving up.
A substance that blocked sodium ions from binding to the cotransport protein would also block the transport of glucose.
Potassium ions move across the same gradient as sodium ions.
Ions diffuse across membranes down their
chemical gradients.
concentration gradients.
electrical gradients.
electrochemical gradients.
The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?
It will be on the cytoplasmic side of the ER.
It will be on the side facing the interior of the ER.
It could be facing in either direction because the orientation of proteins is scrambled in the Golgi apparatus.
It doesnʹt matter, because the pump is not active in the ER.
Proton pumps are used in various ways by members of every kingdom of organisms. What does this most probably mean?
Proton pumps must have evolved before any living organisms were present on the earth.
Proton pumps are fundamental to all cell types.
The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism
Cells with proton pumps were maintained in each Kingdom by natural selection.
White blood cells engulf bacteria through what process?
exocytosis
phagocytosis
pinocytosis
osmosis
Which of the following is a statement of the first law of thermodynamics?
Energy cannot be created or destroyed.
The entropy of the universe is decreasing
Kinetic energy is stored energy that results from the specific arrangement of matter.
For living organisms, which of the following is an important consequence of the first law of thermodynamics?
The energy content of an organism is constant.
The organism ultimately must obtain all of the necessary energy for life from its environment.
The entropy of an organism decreases with time as the organism grows in complexity.
Organisms are unable to transform energy
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?
Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time.
Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is balanced by an increase in the entropy of the universe.
As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth.
Whenever energy is transformed, there is always an increase in the
free energy of the system.
free energy of the universe
entropy of the system
entropy of the universe.
Which of the following statements is a logical consequence of the second law of thermodynamics?
If the entropy of a system increases, there must be a corresponding decrease in the entropy of the universe.
If there is an increase in the energy of a system, there must be a corresponding decrease in the energy of the rest of the universe.
Every energy transfer requires activation energy from the environment.
Every chemical reaction must increase the total entropy of the universe.
Which of the following statements is representative of the second law of thermodynamics?
Conversion of energy from one form to another is always accompanied by some gain of free energy.
Heat represents a form of energy that can be used by most organisms to do work.
Without an input of energy, organisms would tend toward decreasing entropy.
Cells require a constant input of energy to maintain their high level of organization.
Which of the following types of reactions would decrease the entropy within a cell?
dehydration reactions
hydrolysis
respiration
digestion
The organization of organisms has become increasingly complex with time. This statement
is consistent with the second law of thermodynamics.
requires that due to evolution, the entropy of the universe increased.
is based on the fact that organisms function as closed systems.
Which of the following is considered an open system?
an organism
liquid in a corked bottle
a sealed terrarium
food cooking in a pressure cooker
Which of the following is true for all exergonic reactions?
The products have more total energy than the reactants.
The reaction proceeds with a net release of free energy.
Some reactants will be converted to products.
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.
Which of the following is most similar in structure to ATP?
an anabolic steroid
a DNA helix
an RNA nucleotide
an amino acid with three phosphate groups attached
When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell?
It is released as an excretory waste.
It can only be used to regenerate more ATP.
It can be added to other molecules in order to activate them
What must be the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in DNA and RNA?
The sugar molecule is different
There is no difference.
The number of phosphates is three instead of one.
Which of the following statements is (are) true about enzyme-catalyzed reactions?
The reaction is faster than the same reaction in the absence of the enzyme.
The free energy change of the reaction is opposite from the reaction in the absence of the enzyme.
The reaction always goes in the direction toward chemical equilibrium.
How can one increase the rate of a chemical reaction?
Increase the activation energy needed.
Cool the reactants.
Decrease the concentration of the reactants
Add a catalyst.
Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in
bringing glucose and fructose together to form sucrose.
the release of water from sucrose as the bond between glucose and fructose is broken.
breaking the bond between glucose and fructose and forming new bonds from the atoms of water.
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reactionʹs
entropy.
activation energy.
heat content.
free-energy
A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because
the starch solution has less free energy than the sugar solution.
the hydrolysis of starch to sugar is endergonic
the activation energy barrier for this reaction cannot be surmounted.
Which of the following statements regarding enzymes is true?
Enzymes decrease the free energy change of a reaction.
Enzymes increase the rate of a reaction.
Enzymes change the direction of chemical reactions.
Enzymes are permanently altered by the reactions they catalyze.
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 the products of the catalytic reaction.
is inhibited by the presence of a coenzyme or a cofactor.
According to the induced fit hypothesis of enzyme catalysis, which of the following is correct?
The binding of the substrate depends on the shape of the active site
The binding of the substrate changes the shape of the enzymeʹs active site.
Some enzymes change their structure when activators bind to the enzyme
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
allosteric inhibition
competitive inhibition
saturation of the enzyme activity
insufficient cofactors
Which of the following is true of enzymes?
Enzymes may require a nonprotein cofactor or ion for catalysis to take speed up more appreciably than if the enzymes act alone.
Enzyme function is increased if the three-dimensional structure or conformation of an enzyme is altered.
Enzyme function is independent of physical and chemical environmental factors such as pH and temperature.
Enzymes increase the rate of chemical reaction by lowering activation energy
Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n)
competitive inhibitor of the enzyme
noncompetitive inhibitor of the enzyme.
cofactor necessary for enzyme activity.
In order to attach a particular amino acid to the tRNA molecule that will transport it, an enzyme, an aminoacyl-tRNA synthetase, is required, along with ATP. Initially, the enzyme has an active site for ATP and another for the amino acid, but it is not able to attach the tRNA. What must occur in order for the final attachment to occur?
The ATP must first have to attach to the tRNA.
The binding of the first two molecules must cause a 3-dimensional change that opens another active site on the enzyme.
The hydrolysis of the ATP must be needed to allow the amino acid to bind to the synthetase.
Competitive inhibitors block the entry of substrate into the active site of an enzyme. On which of the following properties of an active site does this primarily depend?
the ability of an enzyme to form a template for holding and joining molecules
the enzymeʹs ability to stretch reactants and move them toward a transition state
the enzyme providing an appropriate microenvironment conducive to a reactionʹs occurrence
the enzyme forming covalent bonds with the reactants
When you have a severe fever, what may be a grave consequence if this is not controlled?
destruction of your enzymesʹ primary structure
removal of amine groups from your proteins
change in the folding of enzymes
removal of the amino acids in active sites
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as
feedback inhibition
allosteric inhibition.
reversible inhibition.
If an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to
add more of the enzyme.
heat the solution to 90°C.
add more substrate.
add an allosteric inhibitor.
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