7C PEQs

Vascular endothelial growth factor (abbreviated VEGF and pronounced "Veg-F") is a peptide signaling molecule related to platelet-derived growth factor. VEGF is important in the formation of the circulatory system because its signaling pathway causes the formation of blood vessels in developing embryos during normal development. Tumors also produce and secrete VEGF, causing nearby blood vessels to branch and grow to form new blood vessels that supply these tumors. Given what you know about the different kinds of cell signaling and VEGF, which statement is true? A. VEGF is a paracrine signaling molecule because it binds to receptors on nearby cells, at the site where new blood vessels are needed. B. Because the effect of VEGF is on nearby blood vessels, it must signal in relatively short distances, which is characteristic of paracrine signaling. C. VEGF is an endocrine-signaling molecule because it is released from platelets into the bloodstream and is carried throughout the body, causing widespread activation of platelet-derived growth factor receptors on cells in a variety of tissues. D. VEGF is an endocrine-signaling molecule because it circulates through the bloodstream inside of platelets.

A. VEGF is a paracrine signaling molecule because it binds to receptors on nearby cells, at the site where new blood vessels are needed.

Structures known as microvilli are associated with: A. increased surface area for nutrient absorption. B. adhesion to the extracellular matrix. C. communication between cells. D. increased rates of cell division.

A. increased surface area for nutrient absorption.

Shown are four ligands (M, H, K, and L) and their corresponding receptors along with three genes (U, V, and W), whose activity the receptor controls through signal transduction. The arrows indicate gene activation, the T-bars indicate gene repression. If either U or V is required to activate W, which ligands result in W being active? Select all that apply. A. ligand M B. ligand L C. ligand H D. None of the other answer options are correct. E. ligand K

A. ligand M C. ligand H E. ligand K

(2) Dilated pupils, inhibited digestive activity, increased respiratory rate, and release of glucose from the liver are all signs of activity of: A. the sympathetic division of the autonomic system. B. the somatic nervous system. C. the parasympathetic division of the autonomic system. D. both divisions of the autonomic nervous system.

A. the sympathetic division of the autonomic system.

The graphs shown represent relationships between circulating levels of luteinizing hormone (LH) and testosterone in normal men. Which of the graphs indicate negative feedback regulation of testosterone on LH? A. Graph 1 B. Graphs 2 and 3 C. Graph 3 D. Graph 4 E. Graphs 1 and 2

B. Graphs 2 and 3

Imagine you genetically engineered a neuron to produce voltage-gated Na+ and K+ channels that opened at the same time in response to a change in voltage. How would that change the recording shown in the figure? A. The peak would occur over a longer period of time. B. No action potential would be generated. C. Threshold values would increase. D. The peak voltage would be higher. E. The period of hyperpolarization would be longer.

B. No action potential would be generated. The simultaneous movement of positively charged ions into and out of the cell would result in a change in membrane potential that would not reach threshold potential and no action potential would be generated.

What would happen to a signaling pathway if phosphatases had reduced levels of function? A. There would be no change in the persistence of the response to the pathway. B. The response to the signal would persist longer after activation. C. Phosphatases function in termination of signals activated by kinases. D. Without termination, the cellular response would persist.The response to the signal would be shorter after activation.

B. The response to the signal would persist longer after activation.

The outward movement of K+ ions from inside a neuron (Mark all that apply) A. generates excitatory postsynaptic potentials B. repolarizes the membrane potential C. establishes resting membrane potential D. generates inhibitory postsynaptic potentials

B. repolarizes the membrane potential C. establishes resting membrane potential D. generates inhibitory postsynaptic potentials

Imagine you created a toxin such that binds to the sodium-potassium pump. The toxin binds immediately to the sodium-potassium pump at the peak of the action potential but does not alter the function of sodium and potassium channels. Which of the processes would the toxin prohibit in the neuron? Select all that apply. A. the hyperpolarization phase of an action potential B. returning to resting potential after the hyperpolarization phase of an action potential C. maintaining resting potential D. the depolarization phase of an action potential

B. returning to resting potential after the hyperpolarization phase of an action potential C. maintaining resting potential

Low levels of iodine will cause a decrease in the synthesis of which of the following? (Select all that apply) A. TRH B. Thyroglobulin C. T4 D. TSH E. T3

C. T4 E. T3

Which of the answer choices is an example of negative feedback altering homeostatic control? A. The production of oxytocin (a hormone) increases in a pregnant woman's body as oxytocin levels in her body rise. B. A person with a bacterial infection runs a fever and his body temperatures rises and stays elevated for several days. C. A person's heart rate remains elevated over the course of a long run. D. The concentration of salt in a person's urine increases after that person eats a large bag of salty chips.

D. The concentration of salt in a person's urine increases after that person eats a large bag of salty chips. After a person eats a bag of chips, salt concentration in the blood increases above set point. This would cause an opposite response by the kidneys to remove excess salt from the blood.

Which of the answer choices is an example of the effector's role in maintaining homeostasis? A. decrease in body temperature on a cold day B. increased body temperature during a workout C. vasodilation on a cold winter day D. increased sweating on a hot summer day

D. increased sweating on a hot summer day The effector receives a signal form the sensor causing it to change its activity. In this case, sweat glands have received a signal to sweat in response to the stimulus of heat.

A cell in a chick embryo is tested to determine whether it is a stem cell of some kind. These tests find: 1. The SR receptor is present 2. DIV genes are on 3. The DIFF (skin) genes are blocked 4. TF of the neural pathway is in the cytoplasm 5. Transducer 2 of the skin pathway is not phosphorylated For the following statement answer True or False: Based on these results, this cell will differentiate into a skin cell.

False

Referring to the graph shown, indicate whether the statement is true or false. The changes in voltage seen at point 2 and point 4 in the figure are caused by similar movements, in the same direction, of the same ions across the membrane. True False

False

Referring to the graph shown, indicate whether the statement is true or false. The changes in voltage shown in the figure are due to ligand-gated ion channels opening and closing along the axon. True False

False

The magnitude of the action potential is correlated with the strength of the stimulating input. True False

False

Referring to the graph shown, indicate whether the statement is true or false. The trace (blue) line in the figure is following the voltage change as it moves down the axon. True False

False All cells with membranes that experience action potentials have the characteristic shape shown in the graph. When threshold potential is reached, through a stimulus, such as an EPSP or multiple EPSPs, an action potential will fire, and the membrane potential becomes more positive. This begins by the influx of sodium ions into the cell at point 2 in the graph. As the voltage changes, voltage-gated potassium ion channels open and potassium ions leave the cell. At point 3, there is no more influx of sodium ions, and potassium ions are still leaving. Potassium ions continue to leave the cell at point 4, and there is a change in membrane potential to below resting membrane potential. The sodium-potassium pump restores resting membrane potential, and then the membrane can depolarize again.

Referring to the graph shown, indicate whether the statement is true or false. All voltage changes along the plasma membrane of an axon have the characteristic shape shown above. True False

True

Referring to the graph shown, indicate whether the statement is true or false. An excitatory postsynaptic potential (EPSP) of sufficient strength to reach threshold occurred at point 1 on the figure. True False

True

Referring to the graph shown, indicate whether the statement is true or false. The voltage differences shown in the figure are measured across the plasma membrane. True False

True

Aldosterone is a hormone secreted by the adrenal cortex, and insulin is a peptide secreted by the pancreas. Refer to the figures shown. When aldosterone contacts a target cell, it binds to an intracellular receptor and migrates to the nucleus. Insulin binds to extracellular receptors on the plasma membrane. What is the most likely reason for this difference? A. Aldosterone is lipid-soluble and, therefore, easily crosses the phospholipid bilayer of the plasma membrane. B. Aldosterone is too small to bind extracellular receptors on the plasma membrane. C. Insulin is too large to interact chemically with DNA. D. Aldosterone is hydrophilic and, therefore, must enter the aqueous environment of the cytoplasm to have an effect.

A. Aldosterone is lipid-soluble and, therefore, easily crosses the phospholipid bilayer of the plasma membrane. Aldosterone is derived from cholesterol and is hydrophobic. Aldosterone can cross the plasma membrane, while insulin is hydrophilic and cannot cross the plasma membrane.

If a mutation occurred in the cadherin gene so that the cytoplasmic domain no longer attached to the cytoskeleton, which of the following would occur? A. Cadherins in desmosomes would no longer be anchored to intermediate filaments. B. Cadherins in desmosomes would no longer be anchored to microfilaments. C. Cadherins in hemidesmosomes would no longer be anchored to intermediate filaments. D. Cadherins in adherens junctions would no longer be anchored to microtubules.

A. Cadherins in desmosomes would no longer be anchored to intermediate filaments. Cadherin cytoplasmic domain binds to microfilaments in adherens junctions and to intermediate filaments in desmosomes.

When a doctor suspects that a patient may have diabetes, she will often have the patient take a glucose challenge test. After the patient drinks a large amount of sugary solution, his blood is drawn, and the circulating levels of glucose in the blood are determined. Review the graph shown. Which curve do you expect from a patient with diabetes? A. Curve B B. Curve C C. Curve A

A. Curve B Depending on the type of diabetes, patients either fail to produce insulin or are unresponsive to insulin. A patient that drinks a sugary drink will not be able to absorb the glucose into their cells; therefore, the glucose concentration will increase over time, as shown in Curve B. A peak seen in Curve A means that the response to glucose levels is slower, but still decreases over time after the drink.

A stem cell is fate determined once it has received the Self Renewal signal. As result, which genes are newly expressed? (Check all that apply) A. ID genes B. SR genes C. DIV genes D. DIFF (neural) genes E. DET genes F. DIFF (skin) genes

A. ID genes C. DIV genes E. DET genes

Some people have low levels of calcium circulating in the blood, a condition known as hypocalcemia. While for many this disorder has little to no effect, for some it can be life-threatening. How could low levels of calcium harm an individual? A. Low levels of calcium would result in fewer signals sent between the presynaptic and postsynaptic cell. B. Low levels of calcium would cause sustained depolarization of the presynaptic cell. C. Low levels of calcium would not have any effect on synaptic transmission.

A. Low levels of calcium would result in fewer signals sent between the presynaptic and postsynaptic cell. Extracellular calcium is important because as an action potential reaches the axon terminal of the presynaptic neuron, voltage-gated calcium channels open. An increase in cytosolic calcium causes the vesicles carrying neurotransmitters to bind and release neurotransmitters into the synaptic cleft. If there is not enough circulating calcium to enter the presynaptic cell and facilitate release of neurotransmitter, then many functions controlled by the nervous system may not occur.

A stem cell continuously expresses the DIV and ID genes. Which of the following could cause this inhibition of differentiation? (Mark all that apply) A. The skin pathway receptor is not able to autophosphorylate when the skin signal is present. B. The neural signal is over expressed. C. The neural pathway transducer P1 acts as a phosphatase that would target transducer P2 of the skin pathway. D. The neural pathway transducer P2 is always phosphorylated.

A. The skin pathway receptor is not able to autophosphorylate when the skin signal is present.

Suppose there is a mutation in a laminin-binding integrin gene that causes a loss of function in the cytoplasmic domains of the integrin. Which one of the outcomes would you expect to observe as a result of this mutation? A. The strength of tissues would decrease because the integrin could no longer associate with intermediate filaments. B. The integrin would adhere to laminin and the cytoplasmic domain would adhere to microtubules instead of microfilaments. C. The integrin would function normally because the extracellular domain is responsible for binding to laminin.

A. The strength of tissues would decrease because the integrin could no longer associate with intermediate filaments.

Blood glucose begin to increase after a meal. As a result, glucagon levels must _________ while insulin levels must ________ in order to maintain metabolic homeostasis. A. decrease; increase B. decrease; stay the same C. increase; decrease D. stay the same; increase

A. decrease; increase

Learning and memory involve changes in neural circuits within specific regions of the brain. At the cellular level, repeated stimulation of a presynaptic neuron may result in learning if:Select all that apply. A. the postsynaptic cell becomes more responsive to subsequent stimulation. B. the amount of neurotransmitter released from postsynaptic vesicles of the stimulated cell decreases. C. the postsynaptic cell produces action potentials with greater maximum voltage. D. molecular or structural changes occur at the synapse. E. the stimulated cell produces action potentials with greater maximum voltage.

A. the postsynaptic cell becomes more responsive to subsequent stimulation. D. molecular or structural changes occur at the synapse

(1) Gap junctions are a complex of integral membrane proteins called connexins arranged in a ring. In plasmodesmata, the plasma membranes of the two connected cells are actually continuous. Gap junctions and plasmodesmata have what feature in common? A. They are both found in plant cells. B. They both allow direct transport of materials between cells. C. They both are made up of protein subunits located in the plasma membrane. D. They both attach to the cytoskeleton.

B. They both allow direct transport of materials between cells.

Macrophage cells undergo a process called phagocytosis in which material is brought into a cell in the form of membrane vesicles and then transported along microtubules toward the cell center. Assuming that the centrosome is near the cell center, you can predict that these vesicles are moving to the _____ end of microtubules using the motor protein _____. A. plus end; dynein B. minus end; dynein C. minus end; kinesin D. plus end; kinesin

B. minus end; dynein Dynein is a minus end-directed motor protein that carries vesicles along microtubules.

An interneuron may receive multiple stimuli from the same sensory neuron over a very short period of time. The firing rate of the receiving neuron is proportional to the number of signals received from the sensory neuron over time. Of which process is this an example? A. action potential B. temporal summation C. hyperpolarization D. spatial summation

B. temporal summation

Phosphatases are a family of enzymes that remove phosphate groups from specific proteins; these phosphate groups had been added to the proteins by protein kinases. Vanadate is an inhibitor of phosphatases in eukaryotic cells. What effect would vanadate have on the response of cells to signals received by receptor kinases? A. The response of the cell would be shorter than it normally would. B. The signal would still bind the receptor, so there would be no effect. C. The response of the cell would last longer than it normally would.

C. The response of the cell would last longer than it normally would. Phosphatases remove phosphate groups added by kinases and terminate their activating effect. Without phosphatases, phosphorylation and activation would persist.

In a study of tadpole coloration, you noticed that a certain percentage of tadpoles in a population displayed a decreased ability to shift from dark coloration at night to light coloration during the day. These individuals were studied and found to have the normal number of melanophores and these melanophores produced normal amounts of melanin pigment granules. You remember reading that pigment granule transport in melanophores involves the cytoskeleton. Which part of the cytoskeleton would you suggest investigating as a potential source of the faulty color adjustment in these tadpoles? A. microfilaments B. intermediate filaments C. microtubules

C. microtubules Melanophores are moved along microtubules by kinesin and dynein during the color shifts in amphibian epithelial cells.

Imagine that you are talking with one of your friends about your biology course. He states that the somatic nervous system is subdivided into sympathetic and parasympathetic components and is responsible for involuntary responses. Is this statement correct? A. Yes, this statement is correct. The somatic nervous system has both sympathetic and parasympathetic components and controls involuntary responses. B. No, although the somatic nervous system does have both sympathetic and parasympathetic subdivisions, it is responsible for voluntary responses. C. No, although the somatic nervous system controls involuntary responses, it is the autonomic nervous system that is subdivided into parasympathetic and sympathetic components. D. No, the somatic nervous system is responsible for voluntary responses and is not subdivided into sympathetic and parasympathetic components.

D. No, the somatic nervous system is responsible for voluntary responses and is not subdivided into sympathetic and parasympathetic components.

The figure shows how normal signaling works with a Ras protein acting downstream of a receptor kinase. You examine a cell line in which Ras is always activated even in the absence of a signaling molecule. This causes constant activation of the kinases in the MAP kinase pathway. Which condition would be most likely to turn off this abnormally active signaling pathway? A. The addition of a drug that prevents the dimerization of the receptor kinase. B. The addition of a drug that increases the binding affinity of Ras for MAP kinase enzymes in the cytoplasm. C. The addition of a drug that prevents the phosphorylation of the receptor kinase D. The addition of a drug that prevents the final kinase from interacting with its target protein in the nucleus.

D. The addition of a drug that prevents the final kinase from interacting with its target protein in the nucleus. If Ras is constantly active, something else downstream in the pathway would have to be blocked to stop the pathway.

Epithelial cells that line the digestive system are responsible for absorption and secretion of materials across the cell's plasma membrane. If a mutation occurred in the claudin gene that make up tight junctions, which of the following would occur? A. Transport of materials will decrease between cells. B. Transport of digestive enzyme-filled vesicles will not occur within cells. C. Transport of materials will not change. D. Transport of materials will increase between cells.

D. Transport of materials will increase between cells.

Your core body temperature set point has just decreased. As a result you... A. Feel cold and sweat B. Feel cold and shiver C. Feel hot and shiver D. None of the above E. Feel hot and sweat

E. Feel hot and sweat

When iodine intake is too low, the anterior pituitary gland _____. A. decreases triiodothyronine production B. increases thyroxine production C. decreases TSH production D. decreases thyroxine production E. increases TSH production

E. increases TSH production