ERRATA SUPPLEMENT 2014

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1 ERRATA SUPPLEMENT OUT OF 684 ITEMS (664 QUESTIONS PLUS 20 PLATES) The ECG plates of Q 445 and 446 are interchanged by misprint

2 Q4 Which of the following is derived from fourth branchial arch? (A) Inter arytenoid (B) Lateral thyroarytenoid (C) Posterior arytenoid (D) Cricothyroid ANSWER: (D) Cricothyroid REF: Grays anatomy 40 th ed chapter 35 See APPENDIX-6 BRANCHIAL ARCHES Q105 Affinity for oxygen is decreased due to increase of? (A) CO 2 (B) Body temperature (C) ph (D) 2,3 DPG ANSWER: (C) ph REF: Harper 27 th ed chapter 6, Ganong s 22 nd ed ch: 35, Guyton 12th Edn Page: 499, 500, 501 Repeat biochemistry 2012 Session II OXYGEN DISSOCIATION CURVE: The quaternary structure of hemoglobin determines its affinity for O2. In deoxyhemoglobin, the globin units are tightly bound in a tense (T) configuration, which reduces the affinity of the molecule for O2. When O2 is first bound, the bonds holding the globin units are released, producing a relaxed (R) configuration, which exposes more O 2 binding sites. The net result is a 500-fold increase in O 2 affinity. In tissues, these reactions are reversed, resulting in O2 release. ODC curve has a characteristic sigmoid shape due to the T R interconversion. Combination of the first heme in the Hb molecule with O2 increases the affi nity of the second heme for O2, and oxygenation of the second increases the affinity of the third, and so on, so that the affinity of Hb for the fourth O 2 molecule is many times that for the first. Because the blood leaving the lungs and entering the systemic arteries usually has a Po2 of about 95 mm Hg, one can see from the dissociation curve that the usual oxygen saturation of systemic arterial blood averages 97 percent. Conversely, in normal venous blood returning from the peripheral tissues, the Po2 is about 40 mm Hg, and the saturation of hemoglobin averages 75 percent P 50 is the partial pressure of O2 that half-saturates a given hemoglobin. It expresses the relative affinities of different Hemoglobins for Oxygen. The P50 of normal adult haemoglobin is 26 mmhg and HbF is 20 mm Hg. It is the most sensitive point for detecting a shift of the curve. Specifying the P50 of a curve allows comparison with the

3 position of other curves under different conditions. All the factors which cause dissociation of oxygen from hemoglobin raise p50, which is indicated by a right ward shift in the oxygen dissociation curve. The higher the P50, the lower the affinity of hemoglobin for O2 SHIFT OF ODC Right shift (Mnemonic- CADET turns to Left shift, increase affinity, Decrease P50 Right), Decrease affinity, increase P50, 1. C- Increase CO 2 1. Decrease CO 2 2. A- Acid (Low ph), Chronic anemia (due 2. Alkalosis (High ph) to increased 2,3DGP) 3. Decreased 2,3 DGP 3. D- 4. Decreased body temperature Increased 2,3-diphosphoglycerate (2, 5. High Fetal hemoglobin 3DPG, AKA 2,3-bisphosphoglycerate) 6. Carboxyhemoglobin 4. E- Exercise 5. T- Increase in body temperature 7. Methemoglobinemia Utilization Coefficient The percentage of the blood that gives up its oxygen as it passes through the tissue capillaries is called the utilization coefficient. The normal value for this is about 25 percent, as is evident from the preceding discussion-that is, 25 percent of the oxygenated hemoglobin gives its oxygen to the tissues. During strenuous exercise, the utilization coefficient in the entire body can increase to 75 to 85 percent The Bohr Effect

4 A shift of the oxygen-hemoglobin dissociation curve to the right in response to increases in blood carbon dioxide and hydrogen ions has a significant effect by enhancing the release of oxygen from the blood in the tissues and enhancing oxygenation of the blood in the lungs. This is called the Bohr effect, which can be explained as follows: As the blood passes through the tissues, carbon dioxide diffuses from the tissue cells into the blood. This increases the blood Pco2, which in turn raises the blood H2CO3 (carbonic acid) and the hydrogen ion concentration. Haldane effect: Exactly the opposite effects occur in the lungs, where carbon dioxide diffuses from the blood into the alveoli. This reduces the blood Pco2 and decreases the hydrogen ion concentration, shifting the oxygen-hemoglobin dissociation curve to the left and upward. Therefore, the quantity of oxygen that binds with the hemoglobin at any given alveolar Po2 becomes considerably increased, thus allowing greater oxygen transport to the tissues Note: The ODC is not altered in acute anemia The HbF (fetal hemoglobin) curve is left-shifted (higher oxygen affinity) as compared to the HbA curve because of lower binding of 2,3 DPG by HbF. The curve has a sigmoid shape very similar to the normal ODC for adult haemoglobin but slightly left shifted. The P50 is lower at about 18 mmhg. (Values between 18 and 20mmHg are quoted in various sources.) The myoglobin curve is a rectangular hyperbola with a very low P50 (2.75 mmhg). It lies well to the left of the sigmoid-shaped haemoglobin curve. It has a much higher oxygen affinity. Carboxyhemoglobin: The left shift occurs because the binding of carbon monoxide causes a conformational change in the haemoglobin causing increased affinity for oxygen by the other subunits. ODC is extremely left-shifted and is a rectangular hyperbola. A frequent source of confusion in viva candidates is in distinguishing carboxyhaemoglobin from carbaminohaemoglobin. The first is Hb combined with CO and the second is Hb carrying CO2 Methhemoglobinemia: Methemoglobin is an altered state of hemoglobin in which the ferrous (Fe2+) irons of heme are oxidized to the ferric (Fe3+) state. The ferric hemes of methemoglobin are unable to bind oxygen. In addition, the oxygen affinity of any remaining ferrous hemes in the hemoglobin tetramer is increased. As a result, the oxygen dissociation curve is "left-shifted" Q106 Factor that will shift oxygen dissociation curve to left is? (A) Anemia (B) Methemoglobinemia (C) Increase H+ (D) Increase body temperature

5 ANSWER: (B) Methemoglobinemia REF: Ganong s 22 nd ed ch: 35, Guyton 12th Edn Page: 499, 500, 501 See previous question Q141 Phototropism means? (A) Growing towards the sunlight (B) Obtaining energy from sunlight (C) Reflecting energy from light source (D) None of above ANSWER: (A)Growing towards the sunlight REF: Lehninger's Principles of Biochemistry 4th Ed page 5 Photo Greek= Light Tropism (Greek, tropos= growth) is a biological phenomenon indicating growth o turning movement of a biological organism, usually a plant in response to an environmental stimuli (eg light; phototropism) Trophism (Greek, trophs= nourishment) We can classify organisms according to how they obtain the energy and carbon they need for synthesizing cellular material. There are two broad categories based on energy sources: 1. Phototrophs (Greek trophe-, nourishment ) trap and use sunlight. The phototrophs can be further divided into those that can obtain all needed carbon from CO2 (autotrophs)and those that require organic nutrients (heterotrophs). 2. Chemotrophs derive their energy from oxidation of a fuel. All chemotrophs require a source of organic nutrients; they cannot fix CO2 into organic compounds. No chemotroph can get its carbon atoms exclusively from CO2 (that is, no chemotrophs are autotrophs), but the chemotrophs may be further classified according to a different criterion: whether the fuels they oxidize are inorganic (lithotrophs) or organic (organotrophs). Q561. X-ray of choice for age detection in 6 months old child is? (A) Skull (B) Hand (C) Knee (D) Shoulder ANSWER: (D) Shoulder REF: Ghai 8 th ed page 6 EXPLANATION IS CORRECT

6 Q163 DNA of HBV is? (A) Single stranded (B) Double stranded (C) Partially single stranded (D) Partially double stranded ANSWER: (D) Partially double stranded REF: Jawetz 24 th ed chapter 35 See APPENDIX- 97 CLINICAL AND EPIDEMIOLOGIC FEATURES OF VIRAL HEPATITIS Genome of HBV: One molecule of circular partially double-stranded DNA with unequal strands. The negative DNA strand is full length (with 3200 nucleotides) and positive DNA strand is partially complete (with 1700 to 2800 nucleotides) Q300 Blue line on gums are seen in which poisoning? (A) Arsenic (B) Copper (C) Lead (D) Mercury ANSWER: (C)Lead > (D) Mercury REF: Forensic Medicine and Toxicology By R.N.Karmakar 3 rd ed page 97, A Manual of Toxicology By John Reese page 314 APPENDIX-42 for ANTIDOTES & TOXICOLOGY The blue or saturnine or Burtonian line at the edge of the gums, first pointed out by Dr. Burton, is nearly always observed in cases of chronic lead-poisoning due to formation of lead sulphide. It is most marked around upper incisors. Although this blue line is valuable indication of lead poisoning, it should be remembered that it occasionally occurs as the result of the introduction into the system of other metals, as mercury and silver. Q493 True about Chronic pancreatitis are all EXCEPT: (A) Damage to exocrine part with damage to endocrine part (B) Can leads to malignancy (C) Whipple s procedure can be done

7 (D) Gall bladder stone is the most common cause ANSWER: (D) Gall bladder stone is the most common cause REF: Schwartz 9th ed chapter 33, Sabiston 18 th ed chapter 55 EXPLANATION IS CORRECT PLATE X-12 PLATE X-12 KEY VARICOCELE Idiopathic/ Primary varicocele In 95 % of cases no cause is found. Incompetent or absent valves of testicular vein and internal spermatic vein Common on left side because left testicular vein has longer course and perpendicular entry into the left renal vein Secondary varicocele A pelvic or abdominal malignancy most commonly RCC Post nephrectomy due to removal of draining renal vein Obstruction of the inferior vena cava. Retroperitoneal mass; Sudden onset, older age Retroperitoneal fibrosis or adhesions One non-malignant cause of a secondary varicocele is the so-called "Nutcracker syndrome", a condition in which the

8 superior mesenteric artery compresses the left renal vein, causing increased pressures there to be transmitted retrograde into the left pampiniform plexus. Typically, varicoceles arise secondary to incompetent internal spermatic vein valves. However, the presence of unilateral right-sided varicocele raises the suspicion of poor drainage at the junction of the right testicular vein and right renal vein, which could be secondary to a large right-sided renal mass. In addition, the sudden onset of varicocele in an older man raises the suspicion of a retroperitoneal mass leading to inadequate drainage of the testicular veins. Varicocele is usually symptom less Annoying dragging discomfort that is worse if the testis is unsupported. Examination of a man with varicocele when he is upright reveals a mass of dilated, tortuous veins lying posterior to and above the testis. It may extend up to the external inguinal ring, and the Coughing/ Valsalva maneuver can increase the degree of dilation. Varicocele gives the feeling of bag of worms Decompress/reduces in supine position Characteristically, the varicocele does not decompress in the supine position in RCC Boe sign: after holding the varicocele between thumb and fingers, patient is asked to bow. Varicocele reduces in size due to reduced blood flow of testicular vein. Sperm concentration and motility is significantly decreased in 65% to 75% of subjects causing infertility Varicocele is the most common surgically correctable cause of male infertility Operation is not indicated for asymptomatic varicocele. The simplest procedure is laparoscopic ligation of the testicular vein above the inguinal ligament where the pampiniform plexus has coalesced into one or two vessels. However, when facilities are available, embolisation of the testicular vein under radiographic control is probably the treatment of choice. Because of the presence of plentiful collateral veins, recurrence is common after all types of varicocele surgery. In the Gat-Goren procedure, invented by an Israeli Gynecologist, essentially the same thing happens as with an embolization. The difference, however, is that instead of using metal coils or a balloon to stop the blood flow to the site of the varicocele, a liquid which selectively closes off the offending veins is injected. Varicocelectomy, the surgical correction of a varicocele, is performed on an outpatient basis. The three most common approaches are inguinal (groin), retroperitoneal (abdominal), and infrainguinal/subinguinal (below the groin). a) Palomo's operation: suprainguinal extraperitoneal/retroperitoneal ligation of testicular vein b) Inavissevich approach: inguinal approach, easier and safer c) Marc Goldstein approach: Subinguinal approach at superficial inguinal ring outside the external oblique aponeurosis without opening of external oblique aponeurosis d) Scrotal approach: done in grade 4 varicocele