One of the most pronounced differences between animal and plant cells is
animal cells alone have one or more large vacuoles.
animal cells have a nucleolus.
animal cells alone have their nuclear chromatin attached to the spindle fibers during mitosis.
plant cells alone have rough endoplasmic reticulum.
plant cells alone have relatively thick, rigid cell walls.
Which of the following organelles would only be found within a cell that was both eukaryotic and autotrophic?
rough endoplasmic reticulum
After being formed by the ribosomes located on the endoplasmic reticulum, what is the next organelle to which a protein could be transported?
Which of the following are involved with the movement or transport of materials and organelles throughout the cell?
all of the choices are true
As they flow over rotten logs as a fluid sheet, slime molds appear to lack any partitioning into cell units; however, slime molds do become cellular when they change form to produce spores. And the surface of some parasitic flatworms and some insect tissues are a "syncytium" or layer of living material that contains many nuclei and cell organelles but lacks partitioning by cell membranes. These tissues consume food and produce wastes. In light of the cell theory that "all living things are composed of cells," then
these tissues are not living because they are not cellular.
these tissues are obviously a bridge between nonliving and primitive living cells.
the general concept of life-is-cellular still holds because these organisms still utilize cells sometime in their life, but this shows that cell membrane partitions can be abandoned.
this proves that a "vital force" beyond cell chemistry can give life to substances.
All of the choices are true.
Which is NOT a reason for the small size of cells?
As the linear dimensions of a cell increase, the volume increases twice as fast as the surface area.
Nutrients and wastes must enter and leave the cell through the plasma membrane.
The nucleus can only control a certain amount of cytoplasm.
The increased number of organelles requires that eukaryotic cells be smaller than prokaryotic cells.
Materials must be able to move quickly and efficiently through the cytoplasm.
A high-powered microscope that produces an image from scattered secondary electrons is the
bright-field light microscope.
transmission electron microscope (TEM).
scanning electron microscope (SEM).
Which statement is NOT true about bacteria?
Their cell wall is made of a slime layer that is the same as in plant cell walls.
Some are photosynthetic.
Some are motile due to flagella
They are all prokaryotes.
They have a cell wall that contains peptidoglycan.
An amino sugar called N-acetylmuramic acid is an important building block of the cell wall of some bacteria. Penicillin prevents this amino sugar from being incorporated into the bacterial cell wall. Therefore,
penicillin affects bacteria but not eukaryotes because eukaryotic cell walls are different.
bacterial cells that had already formed their cell walls would be unaffected.
penicillin would stop the growth of active colonies of susceptible bacteria.
penicillin would have no affect on a plant cell wall
All of the choices are correct.
Most bacteria live in a solution that is hypotonic relative to the cytoplasm of the bacteria. The cell wall of a bacterium is a peptidoglycan polymer that is tightly cross-linked. This would therefore function to
regulate the flow of most molecules into and out of the bacterial cell.
provide a rigid wall that prevents the cell from swelling.
provide a rigid wall that prevents the cell from shrinking.
confirm a close relationship to plant cells that have a similar structure and live in hypotonic solutions.
make all bacteria fairly uniform in metabolic chemistry.
Which of the following is NOT offered as evidence in support of the endosymbiotic theory, the belief that a eukaryotic cell has evolved as a "committee" of prokaryotic cells?
Mitochondria and chloroplasts are similar in size and structure to some species of bacteria.
The ribosomes of chloroplasts and mitochondria are similar to eubacteria.
Mitochondria and chloroplasts can actively break away from eukaryotic cells and live on their own.
Mitochondria and chloroplasts have their own DNA coding separate from the eukaryotic nucleus.
All of the choices offer support of the endosymbiotic theory.
The nucleus is NOT important as the site of
synthesis of ribosomal subunits.
All of these take place in the nucleus
Cell biologists have introduced radioactively labeled carbohydrates, fats and amino acids to living cells, allowed time for cell metabolism, and then disrupted the cells in a blender and separated out the various cell organelles from the cytoplasm. They found the radioactive molecules could soon be detected as part of various cellular compounds, although the visible cell structures appeared unchanged. This leads us to conclude that
these "food" molecules are used only for energy.
most cell components are constantly being broken down and rebuilt.
radioactivity was transferred from the introduced molecules to the resident stable molecules.
molecules diffuse at random through the cytoplasm and into cell organelles.
radioactivity has an unusual role in metabolism of living cells.
Which is a true statement about ribosomes?
Ribosomes contain DNA and protein.
Ribosomes are active in carbohydrate synthesis.
Ribosomal subunits leave the nucleus after being formed by the nucleolus.
Polyribosomes are the subunits of ribosomes.
Ribosomes are only found associated with the endoplasmic reticulum in prokaryotic cells.
Which of these is NOT part of the endomembrane system of the cell?
Which is NOT true concerning the Golgi complex?
It consists of a stack of saccules.
Golgi complexes may have an inner face and an outer face.
Molecules are modified within the lumen of Golgi saccules.
Lysosomes are vesicles that bind to enter the Golgi saccules.
Golgi apparatus contains enzymes.
The springtail is a very common small insect that lives in rotten logs, rich soil, and other humid places. Its cuticle is water repelling (hydrophobic) except for a strange organ, the collophore, on its ventral side. Because it lacks the excretory organs of other insects, the springtail has this organ in contact with the water (it is responsible for ion balance and secretion of wastes). If we examined the cell structure of this collophore, we would expect to find a high number of
Each time the water in a cell freezes slowly, long sharp crystals spear through the membrane structures of the cell. However, in the frozen state, virtually no chemical reactions occur. The most likely explanation for the bad taste of meat that has "freezer burn" from repeated freezing is the destruction of
the Golgi bodies and their vesicles.
lysosomes and resultant autodigestion.
rough endoplasmic reticulum causing the release of ribosomes.
ribosomes causing them to break into subunits.
the nuclear membrane causing mixing of nucleoplasm and cytoplasm.
From your knowledge of the size of cell components and the process of centrifugation, what is the order (from first to last) that the nucleus and organelles will be extracted?
ribosomes-mitochondria and chloroplasts-nucleus-soluble cytoplasm
nucleus-mitochondria and chloroplasts-ribosomes-soluble cytoplasm
nucleus-mitochondria and chloroplasts-soluble cytoplasm-ribosomes
mitochondria and chloroplasts-nucleus-soluble cytoplasm-ribosomes
soluble cytoplasm-ribosomes-mitochondria and chloroplasts-nucleus
Cells that make up salivary glands would
be expected to contain a relatively large
smooth endoplasmic reticulum
Which of the following is the reason plants wilt on a hot summer day?
loss of water
lack of turgor pressure
heat weakens the plant cell walls
both loss of water and therefore lack of turgor pressure.
reduced photosynthetic activity
Which of the following functions does the lipid bilayer component of the cell membrane NOT provide for the cell?
controls the exchange of matter and chemical information between one cell and adjacent cells or environment
provides an impermeable, self-sealing membrane capable of dividing or fusing the cell without breaking
provides the matrix into which are inserted proteins that facilitate the exchange of matter between the inside and outside of the cell
clearly defines a boundary preventing an equilibrium between the outside and inside of the cell
provides a fluid and flexible boundary that insulates the interior from the variations in humidity, food, and other external conditions
Which statement is NOT true about the proteins in the plasma membrane?
Proteins may be attached to the inner surface of the plasma membrane.
The hydrophobic portion of a protein is embedded within the membrane.
Some peripheral proteins are connected to cytoskeletal filaments.
Integral proteins are responsible for membrane functions.
Glycoproteins contain carbohydrate chains that are oriented toward the inner surface of the membrane.
Red blood cells come in many "blood types" including type A, type B, type AB, type O [lacking proteins A and B], Rh positive, and Rh negative [lacking Rh factor] and many others. If blood is transfused, the recipient detects any new or "foreign" proteins. These blood type proteins are
in the plasma where they have been secreted by the red blood cells.
inside the red blood cell cytoplasm.
on the outer surface of the red blood cell membrane.
evenly distributed throughout the cell contents and plasma.
in the red blood cell nucleus.
Freshwater protozoans react to a/an _____ environment by removing water through _____.
hypertonic, turgor pressure
hypotonic, turgor pressure
isotonic, a contractile vacuole
hypertonic, a contractile vacuole
hypotonic, a contractile vacuole
Which is NOT true about plant cell walls?
All plant cells have a primary cell wall.
Primary cell walls contain cellulose and microfibrils.
Secondary cell walls are located just inside the primary cell wall.
Lignin, a strengthening substance, is found in secondary cell walls.
Cell walls are penetrated by extensions of cytoplasm that connect adjacent cells' cytoplasms.
In speculating upon the origin of early cells and the cell membrane, which of the following statements is/are NOT plausible?
Due to similarities in basic structure, the endoplasmic reticulum, Golgi body, vesicles, and other "cytomembranes" may have arisen as invaginations of the cell membrane.
As long as a phospholipid-production mechanism is present, these molecules would naturally arrange themselves in two layers with the hydrophobic tails on the inside away from water.
It would be nearly impossible to have a cell without a cell membrane.
All of the choices are plausible.
None of the choices are plausible.
All life forms currently have a basic cell membrane so we presume that the earliest forms of life had this "fence" isolating the internal organization from the external chaos. It is likely that the primordial environment was acidic. In such a case, the cell membrane would have to include
a sodium (Na+) pump.
a proton (H+) pump.
mitochondria underneath in order to provide energy for active transport.
an acid-proof cell wall.
a totally nonpermeable membrane
A feature common to most transmembrane proteins is
a phosphorylated exterior domain.
a structure consisting almost exclusively of β-sheets.
an amino acid sequence rich in acidic residues.
an α-helical region of about 20 to 25 hydrophobic amino acids.
The membrane of an animal cell would be impermeable to all of the following EXCEPT
I. a large and primarily polar protein
II. a small lipid based molecule
I and II only
I and III only
All of the following statements regarding membranes are correct EXCEPT
Polar heads of phospholipids are located on the periphery of the cell membrane.
Cell surface receptor proteins transfer small polar substances into the cell.
Peripheral proteins may display enzymatic functions.
Phospholipids are amphipathic.
Glycoproteins are involved in cell-to cell recognition.
Which of the following signaling mechanisms represent a correctly matched pair?
endocrine- neural communication
synaptic- intravenous communication
paracrine- communication with nearby, surrounding cells
gap junction- communication via hormones
receptor- substrate communication
What is the function of structure E?
transport across the plasma membrane
stabilization of the phospholipids
structural support of the cell
detection of environmental change
Using the yeast signal transduction pathways, both types of mating cells release the mating factors.These factors bind to specific receptors on the correct cells,
which induce changes in the cells that lead to cell fusion.
which produce more of the a factor in a positive feedback.
then one cell nucleus binds the mating factors and produces a new nucleus in the opposite cell.
stimulating cell membrane disintegration, releasing the mating factors that lead to new yeast cells.
which in turn releases a growth factor that stimulates mitosis in both cells.
What is most likely to happen to an animal's target cells that lack receptors for local regulators?
They might compensate by receiving nutrients via a factor.
They could develop normally in response to neurotransmitters instead.
They could divide but never reach full size.
They might not be able to multiply in response to growth factors from nearby cells.
Hormones would not be able to interact with target cells
Which of the following is a likely explanation of why natural selection favored the evolution of signals for sexual reproduction?
Even in the simplest organisms, sexual reproduction required several coordinated responses by cells.
Multicellular eukaryotes required signals that were responded to by multiple organ systems.
Cells of several kinds of mating types needed to sort themselves to allow self-recognition.
Rooted plants required chemical diffusible signals that could travel throughout the organism.
Hormones required a mechanism for introducing changes in their target tissues.
In an experiment to track the movement of growth factor molecules from secretion to the point of receptor binding in a particular species of mammal, a student found a 20-fold reduction in mm traveled when in the presence of an adrenal hormone. This is in part attributable to which of the following?
The growth factor is a paracrine signal.
The growth factor depends on osmosis.
The mammal only carries growth factor through the lymph.
The growth factor is an exocrine signal.
The growth factor is an endocrine signal.
When a neuron responds to a particular neurotransmitter by opening gated ion channels, theneurotransmitter is serving as which part of the signal pathway?
Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP?
It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
It would activate only the epinephrine system.
It would be able to carry out reception and transduction but would not be able to respond to a signal.
It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
It would employ a transduction pathway directly from an external messenger.
Which of the following is true of transcription factors?
They regulate the synthesis of DNA in response to a signal.
They transcribe ATP into cAMP.
They initiate the epinephrine response in animal cells.
They control gene expression.
They regulate the synthesis of lipids in the cytoplasm.
Because most receptors are membrane proteins, which of the following is usually true?
They lead to changes in intracellular ion concentration.
They open and close in response to protein signals.
They are only attached to one membrane surface: exterior or interior.
They preferentially bind with lipid or glycolipid signal molecules.
They change their conformation after binding with signal polypeptides.
Since steroid receptors are located intracellularly, which of the following is true?
The receptor molecules are themselves lipids or glycolipids.
The steroid/receptor complex can cross the plasma membrane.
The unbound steroid receptors are quickly recycled by lysosomes.
The concentration of steroid receptors must be relatively high in most cells.
The receptor molecules are free to move in and out of most organelles.
Receptor tyrosine kinases (RTKs) are found at high levels on various cancer cells. A protein,Herceptin, has been found to bind to an RTK known as HER2. This information can now be utilized in breast cancer treatment if which of the following is true?
If Herceptin is found in the breast lymph nodes of the patient.
If HER2, administered by injection, is in sufficient concentration.
If the patient's cancer cells have detectable HER2.
If the patient's genome codes for the HER2 receptor.
If the patient's genome codes for the manufacture of Herceptin.
The receptors for a group of signaling molecules known as growth factors are often
ligand-gated ion channels.
G protein-coupled receptors.
receptor tyrosine kinases
Sutherland discovered that epinephrine signals
a decrease in levels of cAMP as a result of bypassing the plasma membrane.
lower blood glucose by binding to liver cells.
interactions with insulin inside muscle cells.
interactions directly with glycogen phosphorylase.
elevation of cytosolic concentrations of cyclic AMP.
Which of the following is the best explanation for the inability of a specific animal cell to reduce the Ca2+ concentration in its cytosol compared with the extracellular fluid?
blockage of the synaptic signal
loss of transcription factors
insufficient ATP levels in the cytoplasm
low oxygen concentration around the cell
low levels of protein kinase in the cell
The toxin of Vibrio cholerae causes profuse diarrhea because it
modifies a G protein involved in regulating salt and water secretion.
decreases the cytosolic concentration of calcium ions, making the cells hypotonic.
binds with adenylyl cyclase and triggers the formation of cAMP.
signals IP3 to act as a second messenger for the release of calcium.
modifies calmodulin and activates a cascade of protein kinases.
Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?
G protein-coupled receptor signaling
ligand-gated ion channel signaling
adenylyl cyclase activity
receptor tyrosine kinase activity
Which of the following most likely would be an immediate result of growth factor binding to its receptor?
protein kinase activity
protein phosphatase activity
An inhibitor of phosphodiesterase activity would have which of the following effects?
block the response of epinephrine
decrease the amount of cAMP in the cytoplasm
block the activation of G proteins in response to epinephrine binding to its receptor
prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm
block the activation of protein kinase A
Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of
activated G proteins
If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound
that activates epinephrine receptors.
that increases cAMP production in liver cells.
to block the G protein activity in liver cells.
that increases phosphorylase activity.
that keeps sugar molecules from crossing the plasma membrane of liver cells
An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum?
Which of the following statements is true of signal molecules?
When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules.
In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium.
In most cases, signal molecules interact with the cell at the plasma membrane and then enter the cell and eventually the nucleus.
Toxins such as those that cause botulism and cholera interfere with the ability of activated G proteins to hydrolyze GTP to GDP, resulting in phosphodiesterase activity in the absence of an appropriate signal molecule.
Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.
Which of the following is a correct association?
kinase activity and the addition of a tyrosine
phosphodiesterase activity and the removal of phosphate groups
GTPase activity and hydrolysis of GTP to GDP
phosphorylase activity and the catabolism of glucose
adenylyl cyclase activity and the conversion of cAMP to AMP
One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vessels and increase of blood in the penis, facilitating erection. Since cGMP is inhibited, the signal is prolonged. The original signal that is now inhibited would have
hydrolyzed cGMP to GMP.
hydrolyzed GTP to GDP.
removed GMP from the cell.
A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following?
lower cytoplasmic levels of cAMP
an increase in receptor tyrosine kinase activity
a decrease in transcriptional activity of certain genes
an increase in cytosolic calcium concentration
a decrease in G protein activity
In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following would provide evidence that this is related to cell signaling?
Growth factor ligands do not bind as efficiently to receptors.
Their lower hormone concentrations elicit a lesser response.
cAMP levels change very frequently.
Enzymatic activity declines.
ATP production decreases.
If an adult person has a faulty version of the human analog to ced-4
of the nematode, which of the following is most likely to result?
activation of a developmental pathway found in the worm but not in humans
a form of cancer in which there is insufficient apoptosis
webbing of fingers or toes
excess skin exfoliation
Why has C. elegans proven to be a useful model for understanding apoptosis?
The animal has as many genes as complex organisms, but finding those responsible is easier than in a more complex organism.
The nematode undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development.
This plant has a long-studied aging mechanism that has made understanding its death just a last stage.
While the organism ages, its cells die progressively until the whole organism is dead.
All of its genes are constantly being expressed so all of its proteins are available from each cell.