unit 4 review questions ap bio
if the concentration of potassium in the cytoplasm of a nerve cell with a resting membrane potential of -70 mV were elevated above normal, the new resting potential would
be -69 mv or higher
when would b cells produce effector cells?
between 0 and 7 days
when would you find antibodies being produced?
between 3 and 7 days and between 28 and 35 days.
repolarization occurs, sodium gates close, and some potassium gates reopen
c
Which of the following best represents two different signaling pathways that share a second messenger?
c (shared dot)
what is the narrow opening of the human uterus called?
cevix
during the menstrual cycle, what is the main source of progesterone in females?
corpus luteum
the cells are involved in cell mediated immunity and destroy virally infected cells
cytotoxic t cells
the cells are involved in cell mediated immunity, and they respond to class 1 mhc molecule antigen complexes
cytotoxic t cells
the membrane is unable to respond to any further stimulation, regardless of intensity
d
the membrane is at resting potential
e
which of these best describes the mentrual cycle?
it refers specifically to changes that occur in the endometrium of the uterus
hormone that triggers ovulation
lh
where do synaptic vesicles discharge their contents by exocytosis?
presynaptic membrane
The diagram above shows a developing worm embryo at the four-cell stage. Experiments have shown that when cell 3 divides, the anterior daughter cell gives rise to muscle and gonads and the posterior daughter cell gives rise to the intestine. However, if the cells of the embryo are separated from one another early during the four-cell stage, no intestine will form. Other experiments have shown that if cell 3 and cell 4 are recombined after the initial separation, the posterior daughter cell of cell 3 will once again give rise to normal intestine. Which of the following is the most plausible explanation for these findings?
A cell surface protein on cell 4 signals cell 3 to induce formation of the worm's intestine.
The graph above shows changes in glucagon and insulin secretions at different concentrations of blood glucose. Which of the following feedback mechanisms is best supported by the data?
A low glucose level causes the release of glucagon, which stimulates the release of more glucose from tissues, which in turn lowers the amount of glucagon being released.
Which of the following best describes the production of DMSP by coral and coral symbionts?
A negative feedback mechanism that reverses the environmental change
Two types of cells, alpha and beta cells, produce signaling molecules that affect blood sugar levels in opposite ways (Figure 1). Epinephrine is a chemical, often released during periods of exercise, that ultimately causes an increase in blood sugar levels in the body. Based on Figure 1, which of the following best explains how exercise causes blood glucose levels to rise?
Epinephrine activates alpha cells, causing the release of glucagon, and inhibits beta cells, blocking the release of insulin.
Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?
Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP
Based on the data, which of the following best represents how the mice with the implanted hESC-b cells use negative feedback to return blood glucose levels to normal if blood glucose levels increase?
Increased insulin secretion by hESC-b cells increased glucose uptake by body cells decreased insulin secretion by hESC-b cells
The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system?
After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels.
Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production?
As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.
Melanocytes are skin cells that can become cancerous and develop into a cancer known as melanoma. Some cancerous melanocytes have developed resistance to the drugs currently used to treat melanoma. As a result, researchers are investigating the effects of a new compound (drug X) on four different melanoma cell lines. Researchers analyzed cell survival in two cell lines (Figure 1) and oxygen consumption in the presence of drug X in all four cell lines (Figure 2). Figure 3 shows the proposed mechanism by which drug X affects cells. Which of the following best describes the data in Figure 1 ?
At a concentration above 10 μM, drug X reduces melanoma cell survival.
The diagram above depicts the negative feedback loop which regulates the Calcium ion concentration in the blood. According to the diagram, what will happen if blood calcium levels drop below the set point?
Calcium ions will be released from the bones.
Figure 1 shows a model of the endocrine signaling pathway that regulates ovulation. Which of the following observations would provide evidence of a positive feedback mechanism in this system?
Estrogen from the ovaries stimulates the hypothalamus and anterior pituitary to secrete more GnRHGnRH, LHLH, and FSHFSH.
Which of the following conclusions is best supported by the data presented in Figure 1 ?
Implanted hESC-b cells are effective at regulating blood glucose levels in the absence of mouse b-cells.
Based on the data, which of the following best represents how the mice with the implanted hESC-β cells use negative feedback to return blood glucose levels to normal if blood glucose levels increase?
Increased insulin secretion by hESC-β cells → increased glucose uptake by body cells → decreased insulin secretion by hESC-β cells
Cortisol is a hormone produced in response to stress, including starvation, in humans. Which of the following is most likely an immediate effect of a starvation-induced increase in cortisol secretion?
Increased mobilization of fatty acids from fat cells
Insulin is a protein hormone that is secreted in response to elevated blood glucose levels. When insulin binds to its receptors on liver cells, the activated receptors stimulate phosphorylation cascades that cause the translocation of glucose transporters to the plasma membrane. Based on the information provided, which of the following best describes the role of insulin in this liver cell signal transduction pathway?
It acts as a ligand.
Which of the following modifications to the experimental design would improve the reliability of the results presented in Figure 1 ?
Measuring blood glucose levels in a group of mice that were not given STZ
Air is less dense at very high elevations, so less oxygen is available than in the denser air at sea level. Based on the model in Figure 1, if a person travels from sea level to a high elevation location, which of the following correctly predicts the response to the decreased blood oxygen level?
More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes.
Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling?
Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.
Which of the following statements best predicts the effect of a mutation that results in a loss of the glucocorticoid receptor's ligand binding function?
The glucocorticoid receptor will remain associated with the accessory proteins.
The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Which of the following outcomes will most likely result from the irreversible binding of GDP to the G protein?
The intracellular concentration of glycogen will increase.
Thyroxin is a hormone that increases metabolic activities within various tissue targets. Low levels of circulating thyroxin trigger the secretion of thyroid-stimulating hormone (TSH) from the anterior pituitary. TSH secretion then stimulates thyroxin production and release by the thyroid gland. The increased level of circulating thyroxin inhibits further secretion of TSH from the anterior pituitary. Based on the information provided, which of the following can most likely be concluded about the TSH-thyroxin loop?
The negative feedback mechanism would maintain relatively constant levels of thyroxin throughout tissue targets.
Blood vessels are surrounded by cells called smooth muscle cells. Nitric oxide triggers a signaling cascade in smooth muscle cells that causes the cells to relax (Figure 1). Which of the following is represented by the gradual increase in thickness of the arrows from the top to the bottom of Figure 1 ?
The number of signaling molecules that are produced or activated increases with each step in the pathway.
Which of the following best describes the scientists' findings concerning the density of symbionts presented in Figure 2 ?
The symbiont density at 32°C32°C was different from the density at 27°C27°C on days 55 and 1010 of the experiment.
n contrast to type 1 diabetes, where there is no insulin production, type 2 diabetes is characterized by a failure of body cells to respond normally to insulin. Based on the results of the experiment, which of the following best predicts the effectiveness of using hESC-b implantation to treat type 2 diabetes?
The treatment would fail because insulin produced by implanted hESC-b cells will not stimulate glucose uptake by body cells.
Trypsinogen is split by the enzyme enterokinase to form an activated molecule of the protease trypsin. Which of the following would confirm that the activation of trypsin is an example of how a positive feedback mechanism can amplify a biological process?
The trypsin produced by the reaction is capable of splitting and activating additional trypsinogen molecules.
the sodium gates open
a
hormone secreted by the growing follicle
estrogen
what is the breakdown and discharge of the soft uterine tissues that occurs if no egg is fertilized?
menstruation
fertilization of human eggs usually takes place in the
oviduct
Based on the data in Figure 2, which of the following best justifies the researchers' claim that hESC-b implants can functionally replace the mouse's naturally occurring b-cells?
)The mouse with an hESC-b implant successfully regulated blood glucose levels after STZ treatment but not after the implant was removed.
when would memory cells be produced?
Between 0-7 and 28-35 days
saltatory conduction is a term applied to conduction of impulses
along myelinated nerve fibers
what are antigens?
foreign molecules that trigger the generation of antibodies
the anterior pituitary hormone that stimulates the maturation of the follicle in the ovary during the beginning of the menstrual cycle
fsh
hypothalamic hormone that stimulates the secretion of gonadotropins by the anterior pituitary
gnrh
which cell type interacts with both the humoral and cell mediated immune pathways
helper t cells
Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model (Figure 1) in which CDK5, a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the presynaptic membrane.To test their model, the researchers used a modified version of green fluorescent protein (GFP). In slightly alkaline conditions, GFP exhibits a bright green fluorescence. In acidic conditions, GFP exhibits no fluorescence. Using standard techniques, the gene encoding is easily introduced into living cells. By engineering the expression of GFP in laboratory-cultured nerve cells, the researchers found that a bright green fluorescence was exhibited only when a presynaptic neuron was given a certain stimulus.Which of the following observations best supports the hypothesis that negatively regulates neurotransmitter release?
inhibition of cdk5 activity in neurons increases the movement of synaptic vesicles to the plasma membrane in response to a specific stimulus
which of the following is the best explanation for the fact that most transduction pathways have multiple steps?
multiple steps provide for greater possible amplification of a signal
repolarization of the membrane of a neuron after an action potential is a consequence of which of the following?
na+ channels inactivating, K+ channels opening
the sodium potassium pump of neurons pumps
na+ out of the cell and k+ into the cell
a person with aids would be unlikely to suffer from which of the following diseases?
rehumatoid arthritis
in the sequence of permeability changes that depolarizes and the repolarizes the membrane of a neuron during an action potential, which of the following changes occurs first?
sodium gates open
Integration of simple responses to certain stimuli, such as the patellar reflex, is accomplished by which of the following?
spinal cord
a receptor protein in a membrane that recognizes a chemical signal is most similar to
the active site of an allosteric enzyme that binds to a specific substrate
which of the following is a correct statement about a resting neuron?
the membrane potential is more negative than the threshold potential
because most receptors are membrane proteins, which of the following is usually true?
they change their conformation after binding with signal polypeptides