FL 9 - bio/biochem Flashcards
A scientist exposes yeast cells to a chemical that causes drastic, irreversible conformational changes in gamma-tubulin. Later, the scientist observes that these cells are unable to complete mitosis. At which stage of this process will these cells initially fail?
A. Prophase
B. Metaphase
C. Anaphase
D. None of the above; yeast cells normally do not undergo mitosis.
A. Prophase
Gamma-tubulin is a component of the centriole, which acts as a center of microtubule reorganization. This protein forms a stable “base” for alpha and beta tubulin dimers to bind; this is a necessary process in the formation of microtubules, including the mitotic spindle. Disrupting the conformation of gamma-tubulin will prevent the binding of these dimers, so mitosis will fail as soon as the spindle apparatus begins to form during prophase.
A student researcher plans to study the effects of removing the endoplasmic reticulum from a cell. He discusses this idea with the professor overseeing his research, who informs him that the cells would almost immediately die. Why might the professor believe this?
A. Without the ER, the cell would be unable to synthesize a variety of essential proteins.
B. After removal of the ER, the cell would be unable to convert cholesterol into a vital steroid hormone precursor.
C. Removal of the ER might disrupt the outer leaflet of the nuclear envelope, potentially releasing the contents of the nucleus into the cell and triggering apoptosis.
D. The ER is directly involved in the aerobic production of ATP, so its removal would immediately render the cell energy-deficient.
C. Removal of the ER might disrupt the outer leaflet of the nuclear envelope, potentially releasing the contents of the nucleus into the cell and triggering apoptosis.
The membrane of the endoplasmic reticulum is an extension of the outer leaflet of the nuclear envelope. Its removal would greatly diminish overall nuclear integrity, likely causing that organelle to lyse. As this would almost certainly trigger apoptosis, it is the most accurate and immediate of the choices given.
Which of these predictions accurately describes the relationship between the result of a Gram staining procedure and the qualities of a bacterial species’ outer wall and membrane?
A. Cells with no outer membrane and a thick cell wall will stain positively in Gram’s iodine.
B. Cells with an outer membrane and a thin cell wall will stain positively in Gram’s iodine.
C. Cells with no outer membrane and a thin cell wall will stain negatively in Gram’s iodine.
D. Cells with an outer membrane and a thick cell wall will stain negatively in Gram’s iodine.
A. Cells with no outer membrane and a thick cell wall will stain positively in Gram’s iodine.
Gram positive bacteria have a thick peptidoglycan wall but entirely lack an outer membrane. This allows them to stain purple, as the complexes formed between crystal violet and Gram’s iodine are unable to exit through the thick cell wall.
Post-transcriptional modification allows for a single gene to produce a variety of mRNA transcripts, and thus, to form multiple distinct protein products. This is accomplished through the process of _______.
Post-transcriptional modification allows for a single gene to produce a variety of mRNA transcripts, and thus, to form multiple distinct protein products. This is accomplished through the process of splicing.
The ductus arteriosus is a fetal circulatory adaptation that shunts blood directly from the pulmonary artery to the aorta. In a fetus, this is beneficial, as it bypasses underdeveloped lungs that are not yet required for gas exchange. However, many babies are born with a condition known as “patent ductus arteriosus,” in which this shunt remains open after birth. When examining a 3-month-old male with this condition, one would expect to observe:
A. a PCO2 in the aorta that is higher than expected.
B. a PO2 in the pulmonary artery that is lower than expected.
C. a PO2 in the aorta that is higher than expected.
D. none of the above, as the pulmonary artery and aorta carry blood with roughly the same levels of CO2 and O2.
A. a PCO2 in the aorta that is higher than expected.
In adults and healthy infants, the pulmonary artery carries deoxygenated blood from the heart to the lungs to undergo gas exchange. If this low-O2, high-CO2 blood is allowed to mix with aortic blood, the main adverse consequence will be a lowering of oxygen concentration in the aorta. Additionally, the high levels of CO2 from the pulmonary artery will likely spread to the aorta, which normally contains minimal amounts of carbon dioxide.
A pharmacologist is testing the vasoconstrictive effects of caffeine on thermoregulation. He theorizes that, in cold weather, caffeine consumption can have a warming effect on the body by promoting the constriction of smooth muscle in arterioles. In what way is this hypothesis incorrect?
A. As capillaries have the largest combined surface area of all vessel types, they are the structures that would undergo the majority of overall vasoconstriction.
B. Blood vessels contain cardiac muscle, not smooth muscle.
C. Vasodilation, not vasoconstriction, warms the body when ambient temperatures are low.
D. None of the above; this theory is perfectly accurate.
D. None of the above; this theory is perfectly accurate.
Arteries, arterioles, veins, and venules contain walls with a layer of smooth muscle. When this muscle constricts in vessels near the body’s surface, blood is shunted away from the colder external environment. In this fashion, vasoconstriction helps to keep blood near the body’s warmer core.
The renin-angiotensin system is a regulatory system that helps control blood pressure. A critical catalyst within this system is angiotensin-converting enzyme (ACE), which transforms angiotensin I to angiotensin II. Drugs known as ACE inhibitors prevent the action of this enzyme. All of the following statements about the renin-angiotensin system are false EXCEPT:
A. even in an individual taking an ACE inhibitor, blood pressure can still change due to ADH.
B. inhibiting the renin-angiotensin system prevents any increases in blood pressure.
C. activation of the renin-angiotensin system results in vasodilation.
D. the renin-angiotensin system is directly activated when the salt content in the body exceeds a certain threshold.
A. even in an individual taking an ACE inhibitor, blood pressure can still change due to ADH.
The renin-angiotensin system regulates blood pressure by stimulating the release of aldosterone, which increases sodium reabsorption. Water naturally follows the ion movement, thus increasing blood pressure and decreasing urine output. If this system were disabled, blood pressure could still be regulated by antidiuretic hormone, which operates through a mechanism independent of the renin-angiotensin system. Instead of directly involving sodium reabsorption, ADH functions by increasing the permeability of the collecting duct to water.
The renin-angiotensin system directly responds to decreased blood pressure, specifically a drop in blood flow to the kidneys. It is not immediately activated by high salt osmolarity.
Diabetes insipidus (DI) is characterized by a deficiency of antidiuretic hormone. What effect would this have on a DI patient’s urine?
A. The patient’s urine would be hypertonic.
B. The patient’s urine would be hypotonic.
C. The patient’s urine would be isotonic to the urine of a healthy individual.
D. The patient’s urine would be dark in color.
B. The patient’s urine would be hypotonic.
Antidiuretic hormone (ADH) promotes the retention of water in the body. Without it, excess water is excreted, yielding hypotonic urine.
Which of these choices correctly identifies the function of a specific antibody?
I. IgA – present in mucosal areas to prevent colonization by pathogens
II. IgE – binds to allergens, causing the release of histamine
III. IgM – part of the early humoral response, secreted as a pentamer
IV. IgD – responsible for the majority of the humoral response
A. I only
B. I and III
C. I, II, and III
D. I, III, and IV
C. I, II, and III
IgA is an antibody found in the mucous membranes that helps prevent initial colonization by pathogens. IgE is primarily involved in the response to allergens, while IgM is responsible for the initial humoral response.
A urologist is able to remove microscopic samples from particular regions of a mammalian nephron. One particular sample, Sample 1, contains simple cuboidal epithelial cells that lack any “brush border” or microvillus-based lining. The most likely origin of Sample A is the:
A. collecting duct.
B. glomerulus.
C. proximal convoluted tubule.
D. distal convoluted tubule.
D. distal convoluted tubule.
Simple cuboidal epithelia are well-suited for solute transport and absorption. The two regions of the nephrons that are most likely to possess such a lining are the proximal and distal convoluted tubules. However, the PCT (which is especially specialized for reabsorption of glucose, amino acids, and other vital solutes) is lined with a brush border of microvilli. This is a unique characteristic in comparison to other parts of the nephron.
The DCT does not contain a brush border.
As a baseball pitcher throws fastballs, what prevents the surfaces of his arm bones from rubbing against each other?
A. Tendons
B. Skeletal muscle
C. The epiphyseal plate
D. Hyaline cartilage
D. Hyaline cartilage
Hyaline cartilage covers the bones at the point of contact in joints.
Which of the following statements correctly describes motor neurons?
A. Motor neurons are afferent and enter the spinal cord on the ventral side.
B. Motor neurons are afferent and enter the spinal cord on the dorsal side.
C. Motor neurons are efferent and enter the spinal cord on the ventral side.
D. Motor neurons are efferent and enter the spinal cord on the dorsal side.
C. Motor neurons are efferent and enter the spinal cord on the ventral side.
Efferent means to exit, while afferent means to enter. The dorsal side of the spinal cord receives signals, while the ventral side sends signals out. The mnemonic SAME DAVE (sensory afferent, motor efferent; dorsal afferent, ventral efferent) can help you memorize this.
A student is analyzing two images of distinct muscle types, observed through a microscope at his physiology lab.
The muscle type in A differs from B in that:
I. A is smooth muscle while B is cardiac muscle.
II. they possess different numbers and types of cell-cell junctions.
III. A contains structured sarcomeres, while B does not.
A. I only
B. II only
C. I and II only
D. I, II, and III
C. I and II only
Both muscle types appear to be uninucleate; at the very least, a single cell does not seem to contain a large number of nuclei. Additionally, cells in type B are branched and more irregular than those in type A. From this information, we can conclude that type A is smooth muscle, while type B is cardiac muscle (I). Cardiac fibers contain more gap junctions to allow for the continuous propagation of a contraction signal (II).
An elderly male patient arrives at a clinic complaining of erectile dysfunction. Due to a family history of heart disease, he is hesitant to start taking Viagra. An alternate treatment regimen might prescribe supplements to increase the levels of which neurotransmitter?
A. Dopamine
B. Norepinephrine
C. Acetylcholine
D. Serotonin
C. Acetylcholine
The parasympathetic nervous system is responsible for delivering impulses to the male genitals. These signals relax certain smooth muscles, allowing blood to flow into the penis during an erection. The parasympathetic system also delivers acetylcholine to all its effectors. Therefore, increasing the body’s acetylcholine levels could help this patient with erectile dysfunction.
What branch of the nervous system causes orgasm? What neurotransmitter is used?
The sympathetic nervous system, which secretes norepinephrine on most of its effectors, controls the orgasm.
You can remember this using the mnemonic “P is for point, S is for shoot.” (P, meaning parasympathetic and S, sympathetic)
PEEP, or positive end-expiratory pressure, refers to the pressure in the airway at the end of expiration. Patients with chronic respiratory conditions such as pulmonary edema or COPD often attempt to increase PEEP in order to prevent alveolar collapse and prolong gas exchange. Usually a subconscious effort, this is sometimes accomplished by forced exhalations through pursed lips. Which of the patients below is attempting to increase his or her PEEP?
A. An asthmatic patient gasping sharply during inhalation
B. A one-month premature infant grunting during exhalation
C. An emphysema patient with reduced alveolar elasticity coughing up thick sputum
D. A trauma patient with pneumothorax taking shallow, rapid breaths
B. A one-month premature infant grunting during exhalation
The question stem states that increasing PEEP keeps alveoli inflated and allows gas exchange to occur. Premature infants are often unable to produce surfactant, putting them in danger of respiratory failure secondary to alveolar collapse. Grunting increases the pressure against which the infant must exhale, which forces some of the collapsed alveoli to inflate.
Dendritic cells are often credited as being the link between the innate and adaptive immune systems. These cells are capable of sampling the membranes of somatic cells using a process called “nibbling.” The dendritic cell then carries the cellular sample to the nearest lymph node and presents the antigen to another immune cell, in a process that involves direct membrane contact and utilizes MHC. Assuming the sampled cell was subject to a novel intracellular infection, the dendritic cell most likely interacts with:
A. a helper CD4+ T cell.
B. a macrophage.
C. a memory B cell.
D. a cytotoxic CD8+ T cell.
A. a helper CD4+ T cell.
Dendritic cells present antigens, in the context of MHC, to immature CD4+ T cells. The T cell will become activated if it has affinity for the antigen/MHC presented by the dendritic cell. An activated CD4+ T cell will produce a unique cytokine profile to regulate other immune cells and facilitate an effective response to the pathogen.
Although cytotoxic T cells are capable of recognizing MHC loaded with antigen, they respond by perforating (or destroying) the presenting cell. While this is an effective way to kill an infected somatic cell, it would be counterproductive to the objective of the dendritic cell, which is to inform the immune system of a foreign invader.
Which of the following is true?
A. Trypsin cleaves sugars into monosaccharides and disaccharides.
B. The duodenum is less acidic than the stomach due to bicarbonate ions released by the pancreas.
C. Goblet cells in the digestive system epithelium secrete enzymes needed for digestion.
D. Chief cells in the stomach directly release pepsin for the breakdown of protein.
B. The duodenum is less acidic than the stomach due to bicarbonate ions released by the pancreas.
In the small intestine, the digestive system acts to decrease the acidity of the environment. To facilitate this, the pancreas releases bicarbonate along with enzymes that raise the pH to 6.
Trypsin cleaves proteins, while amylase cleaves sugars.
Goblet cells secrete mucus to protect the stomach lining from abrasion due to low pH.
Chief cells release the zymogen pepsinogen, which is then cleaved in the acidic environment of the stomach for activation.
Injuries to cartilaginous tissue, such as torn and stretched ligaments, can often take quite some time to heal. Which statement best explains why injuries to this type of connective tissue heal so slowly?
A. Cartilage does not contain cells, only fibers; therefore, cells must migrate from other parts of the body to repair it.
B. Cartilaginous fibers must be exposed to an enzyme to assure full tensile strength, and the mechanical stress placed on healing cartilaginous tissue tends to disrupt the action of this enzyme.
C. Cartilage relies on diffusive rather than direct vascular delivery of nutrients, and repairing cells therefore have a hard time sustaining increased activity.
D. Cartilaginous fibers are slow to divide, and an injury only slightly increases the reproduction rate of such fibers.
C. Cartilage relies on diffusive rather than direct vascular delivery of nutrients, and repairing cells therefore have a hard time sustaining increased activity.
Cartilage is not vascularized, and therefore cannot easily obtain the nutrients necessary to rebuild damaged tissues. Instead, it must rely on diffusion from the surrounding ECM.
Which of these statements regarding cults is NOT false?
A. They have practices that fall outside of what society considers to be normal.
B. They are led by an individual rather than by a multitude.
C. They can never become major religions.
D. They often survive and grow, but only to a certain point.
A. They have practices that fall outside of what society considers to be normal.
By definition, cults revolve around practices that are considered either abnormal or outright unacceptable.
Freud’s psychoanalytic theory separates human personality into three main “structures,” or components. Which of these choices accurately describes one of these components?
A. The superego drives the individual to accomplish moral aims, and in doing so, often counteracts the id.
B. The id balances input from the ego and the superego and tends to dominate in day-to-day adult life.
C. The ego is more unconscious in nature than either the id or the superego.
D. The ego represents the most base, aggressive, and pleasure-seeking aspect of personality.
A. The superego drives the individual to accomplish moral aims, and in doing so, often counteracts the id.
The superego is the “moral” component of human personality. It typically drives individuals to avoid behaviors that are morally wrong while striving to fulfill realistic goals.
Where would glycoproteins be found in/around a cell?
Glycoproteins (or carbohydrates associated with proteins) either occur as secreted extracellular proteins or as an extracellular segment of integral membrane proteins.
They would not be found on the cytoplasmic face of the membrane.
Where would glycolipids be found in/around a cell?
Glycolipids are lipids with attached carbohydrate groups. They are found on the exoplasmic surface of all human cell membranes and extend from the phospholipid bilayer into the aqueous environment, where they act as recognition sites for chemicals and as cellular attachment sites.
They are not found on the cytoplasmic face of a bilayer.
Skeletal muscle is especially rich in phospholipids, of which 10-20% are arachidonic acid. Which of the following changes would lead to a decrease in the fluidity of the sarcolemma?
A. Increasing the temperature of the cellular environment
B. Replacing arachidonic acid with unsaturated phospholipids containing fewer than 20 carbons
C. Increasing the cholesterol content present in the membranes at low temperatures
D. Converting some of the arachidonic acid present into its all-trans unsaturated geometric isomer
D. Converting some of the arachidonic acid present into its all-transunsaturated geometric isomer
Remember that the sarcolemma is the skeletal muscle plasma membrane. Cis double bonds tend to introduce “kinks” in phospholipid chains, decreasing the packing efficiency and increasing the fluidity of a membrane when compared to trans-unsaturation. Note the many cis bonds present in arachidonic acid! Converting some of the arachidonic acid into its all-trans unsaturated geometric isomer would allow the hydrocarbon tails to pack more closely together, decreasing fluidity:
Cas9 is an endonuclease. An endonuclease acts to:
A. lyse the cell walls of pathogenic bacteria.
B. degrade the protein coats of invading viruses.
C. cleave nucleic acid from the ends of an RNA molecule.
D. cleave nucleic acid within a DNA molecule.
D. cleave nucleic acid within a DNA molecule.
An endonuclease cleaves within a nucleic acid molecule. It can be specific for either DNA or RNA (DNase or RNase, respectively). Note that with enzymes, the “-ase” ending signals that it is an enzyme, while the rest of the name signals what the enzyme acts on. Here, “endo-” means within and “nucl-”refers to nucleic acids. In particular, many endonucleases are known as restriction enzymes, which cleave nucleic acids at specific sites, as shown below:
Fertility researchers noticed that some metaphase II-arrested oocytes contain an abnormal chromosome number. Nondisjunction involving which of the following would be likely to create this abnormality?
I. Homologous chromosomes
II. Ova
III. Sister chromatids
A. I only
B. II only
C. I and III only
D. I, II, and III
A. I only
Nondisjunction occurs when homologous chromosomes or sister chromatids do not separate properly during meiosis or mitosis.
This lack of proper separation can happen during anaphase I, when a pair of homologous chromosomes fail to separate; alternatively, it can occur during anaphase II, when sister chromatids do not separate.
During oogenesis, a metaphase II-arrested oocyte would have already passed through meiosis I (including anaphase I). An abnormal chromosome number, known as aneuploidy, may have been caused by failure of homologous chromosomes to separate during meiosis I, as shown below:
siRNA binds to complementary base-pair sequences on the mRNA they target, thereby blocking translation. siRNA with the sequence 5’-CUAGGUCGAUCAAU-3’ was designed to target EOLA1 mRNA and was injected into human umbilical vein endothelial cells (HUVEC). For the siRNA to work, the EOLA1 gene must contain which antisense strand?
A. 5’-CUAGGUCGAUCAAU-3’
B. 5’-CTAGGTCGATCAAT-3’
C. 3’-CTAGGTCGATCAAT-5’
D. 3’-GATCCAGCTAGTTA-5’
B. 5’-CTAGGTCGATCAAT-3’
If the siRNA sequence is 5’-CUAGGUCGAUCAAU-3’, then it must bind the following complementary mRNA sequence: 3’-GAUCCAGCUAGUUA-5’. The mRNA strand represents the same sequence as the sense strand on the DNA, with the exception of the replacement of uracil (U) for thymine (T). DNA is complementary and anti-parallel; therefore, the antisense strand will be complementary to the mRNA sequence given above, which should yield 5’-CTAGGTCGATCAAT-3’.
In rare cases, a person can be more resistant to bacterial infection due to the presence of antibodies in the small intestine that neutralize LPS. If biomedical researchers hope to use this natural immunity to develop an Ig-based therapy, which antibodies from these people should the researchers screen for?
A. IgG antibodies
B. IgE antibodies
C. IgM antibodies
D. IgA antibodies
D. IgA antibodies
The question essentially asks which antibodies are involved in the immune response of the small intestine. IgA antibodies are present in mucosal areas such as the gut, respiratory tract, saliva, and urogenital tract.
The structures of the various types of immunoglobulins are shown below:
A geneticist is attempting to determine whether a recessive mutation is X-linked or autosomal. What information would be the most useful for her to gather?
A. Whether the mutation skips generations
B. The percentage of male offspring showing the effects of the mutation
C. The percentage of female offspring showing the effects of the mutation
D. Whether significantly more males than females show the effects of the mutation
D. Whether significantly more males than females show the effects of the mutation
In X-linked recessive mutations, many more males manifest the phenotype because males only have one X chromosome. Therefore, if males inherit a single mutated X chromosome, they will show the effects of the mutation, whereas females who inherit a single mutated X chromosome will not show the effects of the mutation due to the presence of a second, non-mutated X chromosome. This inheritance pattern is shown below:
CZ extract functions as which kind of inhibitor of α-glucosidase?
A. Mixed
B. Competitive
C. Noncompetitive
D. Uncompetitive
B. Competitive
Figure 1 shows that CZ extract leaves Vmax (the y-intercept on a Lineweaver-Burk graph) of α-glucosidase unchanged while increasing Km (as represented indirectly by the x-intercept, which is -1/Km on a Lineweaver-Burk graph). An unchanged Vmax and an increased Km are hallmarks of competitive inhibition.
Epinephrine acts to promote glycogenolysis. Which of the following molecules and pathways does epinephrine most likely upregulate? (shown in figure)
A. PP1, dephosphorylating glycogen phosphorylase and promoting G1P synthesis
B. PP1, phosphorylating glycogen phosphorylase and promoting G1P synthesis
C. cAMP, phosphorylating glycogen phosphorylase and promoting G1P synthesis
D. cAMP, dephosphorylating glycogen synthase and promoting glycogen synthesis
C. cAMP, phosphorylating glycogen phosphorylase and promoting G1P synthesis
This question is asking us to interpret Figure 2 and determine the likely action of epinephrine. Glycogenolysis is the breakdown of glycogen. The answer must talk about phosphorylating glycogen phosphorylase or phosphorylating glycogen synthase, rending the former active and the latter inactive. If epinephrine acted to upregulate PP1, then we would be moving toward glycogen production.
Using the figure, which of the following does insulin most likely upregulate in the liver?
A. cAMP
B. PP1
C. Protein kinase A
D. Phosphorylase kinase A
B. PP1
This question is asking us to combine our outside knowledge of what insulin does with the information in Figure 2. In the liver, insulin acts to increase glycogenesis in order to decrease blood glucose levels. This means that insulin will need to act to dephosphorylate both glycogen synthase and glycogen phosphorylase, rendering the former active and the latter inactive. Since PP1 accomplishes this, it is the correct option.
Which of the following hormones acts to decrease blood pressure?
A. Aldosterone
B. Atrial natriuretic peptide
C. Vasopressin
D. ACTH
B. Atrial natriuretic peptide
Atrial natriuretic peptide is released from the atria of the heart in response to high blood pressure. It has the exact opposite mode of action of aldosterone. The function, structure, stimulus, and effects of the hormones involved in fluid regulation are summarized below:
