FL 3 B/B Review

ELISA

tests for presence of a protein product

foramen ovale

connects the two atria in the fetal heart

RT-PCR

uses reverse transcriptase and PCR to create and amplify a specific cDNA sequence, and then can be tested for; allows us to determine if transcription is occurring

transduction

when a lysogenic virus excises from the genome and takes a portion of the genome with it; any new hosts infected by that virus will be given the new genes, however this does not increase the size of the population

conjugation

In bacteria, the direct transfer of DNA between two cells that are temporarily joined.

As GC/AT ratio increases the Tm value

increases, because GC pairing involves 3 H bonds, so melting point decreases when less hydrogen bonding in structure

Which of the following processes do NOT occur at the placenta? 1. Diffusion of amino acids from fetal blood to maternal blood 2. Mixing of maternal and fetal blood and gas exchange 3. Exchange of CO2 and O2 between fetal and maternal blood

1 and 2 only. Item I does not occur: Amino acids are charged and cannot cross the placental and fetal capillary membranes. Item II does not occur: Fetal and maternal blood do not mix, so the only way substances can cross the placental barrier is if they are lipid soluble or if they are actively transported Item III is correct: CO2 and O2 are lipid soluble and easily cross the barrier

Muscle fibers are composed of small contractile units called sarcomeres. During contraction, which of the following occurs within a sarcomere? 1. Myosin filaments shorten. 2. Actin filaments shorten. 3. Overlap between actin and myosin filaments increases.

3 only. Items I and II are false: During contraction, neither myosin nor actin filaments get shorter. The overlap between them increases to make the sarcomere shorter (eliminate choices A, C and D). Item III is true: The overlap between the fibers increases as part of contraction.

DNA adds onto strands through the ____ end

5'

catabolic

A process in which large molecules are broken down

anabolic

A process in which large molecules are built from small molecules

zona pellucida

A thick, transpartent coating rich in glycoproteins that surrounds an oocyte.

In Graves disease, thyroid-stimulating immunoglobulins (TSI) contain an active site that can mimic the active site of TSH to stimulate thyroid hormone production. One would expect TSI to cause: A. an increase in thyroid gland size because of the trophic effect of TSH. B. a decrease in thyroid gland size because of competitive inhibition with TSH. C. no change in thyroid gland size because antibodies only recognize foreign particles. D. an immune response against TSH molecules.

A. an increase in thyroid gland size because of the trophic effect of TSH. As described in the passage, goiter is caused by overstimulation of the thyroid gland by TSH. If TSI mimics TSH, then it would produce the same response: enlargement of the thyroid gland (choice A is correct).

A mutation in the thyroid hormone receptor which blocks hormone binding would cause which of the following? A. Atrophy of the thyroid gland B. Elevated secretion of TRH C. Decreased T3 levels in plasma D. Atrophy of the anterior pituitary

B. Elevated secretion of TRH Thyroid hormone causes feedback inhibition of TRH and TSH secretion. Therefore, if thyroid hormone receptors were defective, it would prevent feedback inhibition and cause increases in levels of TRH

A semipermeable membrane separates an aqueous solution of 0.003 MNaCl from an aqueous solution of 0.0025 MBaF2. With this apparatus, one would observe that water crosses the membrane: A. from the BaF 2 solution to dilute the NaCl solution. B. from the NaCl solution to dilute the BaF 2 solution. C. from the BaF 2 solution to concentrate the NaCl solution. D. from the NaCl solution to concentrate the BaF 2 solution.

B. From the NaCl solution to dilute the BaF2 Osmotic pressure is a colligative property, which means it depends only on the concentration of solute particles, and not their identity. Therefore, a 0.003 M solution of NaCl will have an effective molality of 0.006 M (since NaCl is composed of two ions) and a 0.0025 M solution of BaF2 will have an effective molality of 0.0075 M (since BaF2 is composed of three ions). Osmotic pressure will drive movement of water from the lower concentration solution (NaCl) to the higher concentration solution (BaF2). Note that this movement of water acts to dilute the BaF2 solution.

Large waist circumference is an important factor in health because is it one symptom used to diagnose metabolic syndrome; others include elevated blood pressure, elevated fasting plasma glucose, and high serum triglycerides. Visceral fat is associated with increased plasma levels of tumor necrosis factor-alpha (TNFα) and altered levels of adiponectin, a 244-amino acid hormone secreted from adipose tissue. Adiponectin automatically self-associates into larger structures such as trimers, hexamers or dodecamers, and high-molecular weight forms are likely the most biologically active. Serum levels correlate inversely with body fat percentage in adults. Many catabolic processes are positively regulated by adiponectin. Adiponectin can bind one of three receptors (ADIPOR1, ADIPOR2 or CDH13) at a target cell and this causes activation of AMP-activated protein kinase (AMPK). Which of the following is most likely true? A. Adiponectin and ADIPOR1 cooperate to activate lipogenesis and modulate insulin secretion by pancreatic β-cells. B. High adiponectin levels activate AMPK, which stimulates hepatic fatty acid oxidation and ketogenesis. C. Adiponectin binding to CDH13 negatively regulates AMPK and this stimulates skeletal muscle fatty acid oxidation and muscle glucose uptake. D. ADIPOR2 stimulates AMPK activity, which promotes of cholesterol synthesis, lipogenesis, and triglyceride synthesis.

B. High adiponectin levels activate AMPK, which stimulates hepatic fatty acid oxidation and ketogenesis. The passage says that adiponectin up-regulates catabolic processes (such as fatty acid oxidation), which means it also likely downregulates anabolic processes (such as lipogenesis, cholesterol synthesis and triglyceride synthesis). This means answer choices A and D are incorrect (eliminate both). The question stem says that adiponectin binding to ADIPOR1, ADIPOR2 or CDH13 activates AMPK (eliminate choice C). By process of elimination, the correct answer is choice B.

Mucosal erosions, the hallmark of peptic ulcer disease (PUD), typically cause nausea, pain, and bleeding. Rarer causes of PUD are conditions that increase circulating levels of histamine or gastrin. Zollinger-Ellison syndrome (ZES), for example, is caused by a gastrin-secreting tumor in the stomach. Patients with ZES have very high levels of gastrin and often develop multiple ulcers. The majority of ZES patients also suffer from malabsorptive diarrhea as a result of acid-mediated precipitation of bile salts, inactivation of pancreatic enzymes, and destruction of intestinal mucosal surfaces. Which of the following contributes to the diarrhea experienced by ZES patients? A. Precipitation of bile salts hinders protein breakdown and amino acid absorption. B. Increased HCl in the stomach and small intestine breaks down lipases and amylases. C. Gastrin-releasing cells replace insulin-releasing cells. D. Vagotomy in these patients leads to increased water reabsorption by colonic mucosal cells.

B. Increased HCl in the stomach and small intestine breaks down lipases and amylases. The passage states that increased acid causes bile salt precipitation and degradation of pancreatic enzymes. Bile salt precipitation would hinder fat emulsification and digestion, not protein digestion (choice A is wrong). The pancreatic enzymes include lipases and amylases, which aid in the digestion of fats and carbohydrates, respectively. If the fats and carbohydrates are not digested, they will pass into the large intestine where their presence would act osmotically to prevent the reabsorption of water. When water is not reabsorbed from the large intestine, diarrhea is the result (choice B is correct).

Fetal circulation differs from adult circulation in many ways. One of the main differences is that in the former: A. fetal hemoglobin has lower O2 affinity than does maternal hemoglobin. B. a pathway exists for blood to circumvent the lungs. C. blood flows through the systemic vascular system only. D. the ductus arteriosus carries oxygenated blood, while in the adult it carries deoxygenated blood.

B. a pathway exists for blood to circumvent the lungs. The passage states that fetal hemoglobin has a higher affinity for oxygen (choice A is wrong) and that there is some blood flow through the pulmonary circuit (choice C is wrong). The ductus arteriosus does carry oxygenated blood in the fetus but closes shortly after birth so that this vessel is not present in adults (choice D is wrong). The purpose of the ductus arteriosus is to help shunt blood past the inactive fetal lungs (choice B is correct).

In transposition of the great arteries, a congenital birth defect, the aorta of the newborn is connected to the right ventricle and the pulmonary artery is attached to the left ventricle. This would result after birth in circulation of: A. oxygenated blood through the systemic vasculature and deoxygenated blood through the pulmonary vasculature. B. deoxygenated blood through the systemic vasculature and oxygenated blood through the pulmonary vasculature C. oxygenated blood through both the systemic and pulmonary vasculature. D. deoxygenated blood through both the systemic and pulmonary vasculature.

B. deoxygenated blood through the systemic vasculature and oxygenated blood through the pulmonary vasculature In the normal circulation, the right ventricle pumps blood through the pulmonary artery to the lungs. Blood returns from the lungs to the left atrium and is pumped by the left ventricle through the aorta to the rest of the body. If blood from the left ventricle passes to the pulmonary artery instead of the aorta and is then returned to the left atrium, oxygenated blood will loop around through the pulmonary system without passing to the rest of the body. At the same time, the deoxygenated blood from the systemic circulation will pass to the right atrium, then back out to the systemic circulation through the aorta rather than the pulmonary artery, causing deoxygenated blood to loop through this system (choice B is correct and choice A is wrong). Choices C and D are wrong since they have all blood either oxygenated or deoxygenated.

Decreased secretion of aldosterone has all of the following effects EXCEPT: A. increased loss of Na + in urine. B. decrease in extracellular fluid volume. C. increase in arterial pressure. D. increase in urine volume.

C. increase in arterial pressure Aldosterone causes increased sodium reabsorption, and because of the rise in systemic Na+, there will be decreased water loss, increased extracellular fluid volume and increased blood pressure. Decreased secretion of aldosterone would cause the opposite: increased loss of sodium (choice A is true and eliminated), a decrease in the extracellular fluid volume (choice B is true and eliminated), and an increase in urine volume (choice D is true and eliminated). It will not cause an increase in blood pressure, however, since more urine is formed and extracellular fluid volume lost (choice C is false and thus the correct answer choice).

Most biological unsaturated fatty acids are cis and contain non-conjugated double bonds. Because of this, additional steps are required in β-oxidation. These most likely include: A. Changing a single double bond to trans via a reductase enzyme in the mitochondrial matrix. B. Combining two double bonds via a reductase enzyme (which uses NAD+ as a reducing agent), then changing the resultant trans double bond to cis via an isomerase enzyme. C. Moving a single double bond down the fatty acid chain via a translocase enzyme in the mitochondrial matrix. D. Combining two double bonds via a reductase enzyme (which uses NADPH as a reducing agent), then changing the resultant cis double bond to trans via an isomerase enzyme.

D. Combining two double bonds via a reductase enzyme (which uses NADPH as a reducing agent), then changing the resultant cis double bond to trans via an isomerase enzyme. Monounsaturated fatty acids require an isomerase enzyme to move the double bond during β -oxidation (eliminate choice A). Polyunsaturated fatty acids require both an isomerase and a reductase enzyme to complete β -oxidation; this also requires the reducing agent NADPH (choice D is correct). Note that NAD+ is an oxidizing agent (not a reducing agent) because it oxidizes another molecule, and is thus reduced itself (eliminate choice B). β -oxidation does not require a translocase enzyme (eliminate choice C).

An ectopic TSH-secreting tumor is suspected in a hyperthyroidic (high thyroid-hormone concentration) patient with goiter. Administration of a high dose of thyroid hormone confirms this, due to the fact that: A. [TSH] in the plasma decreases dramatically. B. [TRH] in the pituitary circulation increases. C. [TRH] in the pituitary circulation remains constant. D. [TSH] in the systemic circulation remains high.

D. [TSH] in the systemic circulation remains high. In a normal individual, high levels of thyroid hormone would suppress the release of TRH by the hypothalamus and TSH by the anterior pituitary. Injection of even more thyroid hormone should suppress the release of TRH and TSH even further. If this does not occur, and TRH and/or TSH levels remain high, it is likely that something outside the normal axis is involved. The passage states that ectopic tumors do not respond to normal feedback inhibition pathways; so, if an ectopic TSH-secreting tumor were present, the injection of thyroid hormone would not reduce the level of TSH in the system (choice D is correct and choice A is wrong).

corona radiata

Outer layer of cells surrounding the oocyte. These cells are secreted by follicle cells.

melting temperature DNA

Temperature at which dna has reached half total maximum denaturation (random coil or single stranded state)

What forms the BBB?

Tight junctions between endothelial cells that form the capillary walls

ductus arteriosus

a blood vessel in a fetus that bypasses pulmonary circulation by connecting the pulmonary artery directly to the ascending aorta

Hemoglobin binds oxygen __________, and so has a _________ binding curve

cooperatively; sigmoidal

dictyate

resting state of oogensis; oocytes in a girl remain in dictyate (period of arrest) until onset of menstrual cycle