FMGE 2023 Practice Questions

Q: Which enzymes use molecular oxygen as a hydrogen acceptor to produce water?

Cytochrome c oxidase. ***Cytochrome c oxidase*** - This enzyme (Complex IV of the ETC) is responsible for the final step of cellular respiration, where it accepts electrons from **Cytochrome c**. - It catalyzes the four-electron reduction of molecular oxygen (**O₂**) to two molecules of **water** (**H₂O**), utilizing O₂ as the terminal hydrogen/electron acceptor. *Catalase* - Catalase breaks down **hydrogen peroxide** (**H₂O₂**) into water and molecular oxygen, acting as a peroxidase and protecting cells from reactive oxygen species. - It facilitates the breakdown of an existing toxic product and does not use O₂ as a hydrogen acceptor in a reduction reaction. *Superoxide dismutase* - This enzyme converts the hazardous **superoxide radical** (**O₂⁻**) into molecular oxygen and hydrogen peroxide. - It is critical for antioxidant defense but is involved in dismutation reactions, not in using O₂ as the final acceptor to form water. *Pyruvate dehydrogenase* - The pyruvate dehydrogenase complex links glycolysis to the Krebs cycle by converting **pyruvate** to **acetyl-CoA** (oxidative decarboxylation). - Its electron acceptors are **NAD⁺** and **lipoic acid** (which accept hydrogens/electrons to form NADH and reduced lipoic acid), not molecular oxygen.

Q: A 34-year-old male whose staple diet primarily consisted of only maize presents with diarrhea, dementia, and photosensitive dermatitis in sun-exposed areas. Which vitamin is most likely deficient in this patient?

Niacin. **Correct: Niacin** - The constellation of **dementia**, **diarrhea**, and **photosensitive dermatitis** (the 3 Ds) is the hallmark presentation of **Pellagra**. - A diet reliant on **maize** (corn) is a classic cause of Pellagra because maize is deficient in **tryptophan**, a vital precursor to Niacin (Vitamin B3). - Pellagra can progress to a fourth D (**Death**) if untreated. *Incorrect: Vitamin B6* - Deficiency typically manifests as **peripheral neuropathy**, **seborrheic dermatitis** (non-photosensitive), and microcytic anemia (**sideroblastic anemia**). - It is not associated with the severe chronic diarrhea or the characteristic sun-exposed rash seen in Pellagra. *Incorrect: Ascorbic acid* - Deficiency causes **Scurvy**, characterized by **bleeding gums**, **perifollicular hemorrhages** (petechiae), and **impaired wound healing**. - Neurological symptoms typical of dementia and pronounced gastrointestinal symptoms are not primary features of Scurvy. *Incorrect: Biotin* - Biotin (Vitamin B7) deficiency is rare, usually presenting with **alopecia**, non-specific dermatitis, and sometimes hypotonia or developmental delay. - It is differentiated by the absence of characteristic photosensitive rash and the severe central nervous system symptoms (dementia) that define this case.

Q: A female patient complains of swelling and pain in her great toe. Her uric acid level is found to be high. A drug that reduces uric acid levels is prescribed. Which of the following enzymes should the drug inhibit?

Xanthine oxidase. ***Xanthine oxidase*** - **Xanthine oxidase** catalyzes the conversion of hypoxanthine to xanthine and xanthine to uric acid in the purine degradation pathway - **Xanthine oxidase inhibitors** (allopurinol, febuxostat) are the mainstay drugs for chronic management of hyperuricemia and gout - By inhibiting this enzyme, these drugs reduce uric acid production, lowering serum uric acid levels and preventing crystal deposition in joints - The clinical presentation of **podagra** (acute pain and swelling of the great toe) with elevated uric acid is classic for **acute gouty arthritis** *Lysyl oxidase* - Involved in cross-linking collagen and elastin in connective tissue formation - Not related to purine metabolism or uric acid synthesis - Inhibition would affect collagen strength, not uric acid levels *Homogentisate oxidase* - Enzyme in the tyrosine degradation pathway - Deficiency causes alkaptonuria (accumulation of homogentisic acid) - Not involved in purine metabolism *Urease* - Bacterial enzyme that hydrolyzes urea to ammonia and carbon dioxide - Found in bacteria like *Helicobacter pylori* and *Proteus* species - Not involved in human uric acid synthesis or metabolism

Q: A 35-year-old woman presented to the clinic with the symptoms of hearing loss and pulsatile tinnitus. Further examination reveals conductive hearing loss with the Rinne test negative. A reddish mass is seen behind the tympanic membrane. What is the most likely diagnosis for this patient?

Glomus tumour. ***Glomus tumour (Correct Answer)*** - **Pulsatile tinnitus** combined with **conductive hearing loss** and a **reddish retrotympanic mass** forms the classic diagnostic triad for glomus tympanicum (a paraganglioma arising from glomus bodies). - The **reddish vascular mass** behind the tympanic membrane is pathognomonic, sometimes called the **'rising sun sign'** or demonstrating **Brown's sign** (blanching with pneumatic otoscopy). - This slow-growing, highly vascular tumor characteristically presents with these features in middle-aged adults. *Acute otitis media (Incorrect)* - This acute bacterial infection presents with rapid onset of **otalgia** (ear pain), **fever**, and a bulging, intensely red tympanic membrane. - While it causes temporary conductive hearing loss due to **purulent fluid** accumulation, it lacks the chronic presentation and **pulsatile tinnitus** characteristic of vascular masses. - The clinical course is acute (days), not chronic like glomus tumors. *Chronic otitis media (Incorrect)* - Defined by chronic inflammation typically resulting in **tympanic membrane perforation**, recurrent **otorrhea** (ear discharge), and possible **cholesteatoma** formation. - While it causes conductive hearing loss, it does **not** produce **pulsatile tinnitus** or a **reddish, vascular retrotympanic mass**. - The tympanic membrane shows perforation or scarring, not an intact membrane with a vascular mass behind it. *Serous otitis media (Incorrect)* - Also known as **otitis media with effusion**, involves sterile, non-purulent fluid in the middle ear from **eustachian tube dysfunction**. - The tympanic membrane appears dull, retracted, or shows **air-fluid levels** and bubbles, but does not show a vascular mass. - This condition does **not** cause **pulsatile tinnitus** and the fluid is serous, not vascular tissue.

Q: A male patient complained of imbalance, numbness of the foot, and muscle weakness. On history taking, he revealed that he has been taking multivitamin tablets more than the prescribed dose for 1 year. Which of the following is the most likely cause of the associated symptoms seen in this patient?

Vitamin B6 toxicity. ***Vitamin B6 toxicity*** - Chronic ingestion of high-dose **pyridoxine** (Vitamin B6) is a well-known cause of **sensory polyneuropathy**, which manifests as numbness (paresthesia) and gait imbalance (**ataxia**). - The toxicity primarily targets the sensory neurons of the **dorsal root ganglia**, leading to the observed sensory and motor deficits (muscle weakness). *Vitamin D toxicity* - This condition primarily causes **hypercalcemia**, leading to symptoms such as nausea, vomiting, confusion, and generalized weakness, often affecting renal function. - It is not typically associated with a chronic, distal, sensory-dominant **peripheral neuropathy** causing numbness and foot imbalance. *Vitamin C toxicity* - Vitamin C (ascorbic acid) is generally safe; high doses typically result in mild symptoms like gastrointestinal distress and an increased risk of developing **calcium oxalate kidney stones**. - It does **not** cause neurotoxic effects such as peripheral neuropathy or chronic ataxia. *Vitamin A toxicity* - Chronic hypervitaminosis A involves symptoms such as **hepatotoxicity**, dry skin/cheilitis, **bone and joint pain**, and pseudo-tumor cerebri (increased intracranial pressure). - While neurological symptoms like headache may occur due to increased pressure, clear-cut **sensory polyneuropathy and ataxia** are not characteristic features.

Q: A patient with a history of hypertension is given the drug 'X'. Identify 'X'?

Aliskiren. ***Aliskiren*** - Aliskiren is a **direct renin inhibitor**. The diagram shows that drug 'X' directly inhibits the release or action of **renin** from the kidneys. - By inhibiting renin, it blocks the first and rate-limiting step of the **Renin-Angiotensin-Aldosterone System (RAAS)**, preventing the conversion of **angiotensinogen** to **angiotensin I**. *Captopril* - Captopril is an **Angiotensin-Converting Enzyme (ACE) inhibitor**. It acts later in the pathway to block the conversion of **angiotensin I** to **angiotensin II**. - This mechanism is different from drug 'X', which acts on **renin** at the beginning of the cascade. *Spironolactone* - Spironolactone is an **aldosterone antagonist** and a potassium-sparing diuretic. It acts at the end of the RAAS pathway. - It works by blocking **aldosterone receptors** in the distal tubules of the kidney, preventing sodium and water reabsorption, which is downstream from the action of renin. *Losartan* - Losartan is an **Angiotensin II Receptor Blocker (ARB)**. It prevents **angiotensin II** from binding to its receptors on blood vessels and the adrenal glands. - This action occurs much later in the pathway compared to the direct inhibition of **renin** shown by drug 'X'.

Q: Which statement best describes the relationship between drug potency and efficacy in dose-response curves?

Drug B is the most efficacious. ***Drug B is the most efficacious*** - **Efficacy** refers to the **maximum effect (Emax)** a drug can produce, represented by the plateau height of the dose-response curve on the y-axis - **Drug B's curve reaches the highest point**, indicating it produces the greatest maximal blocking effect (~100 units) - **This makes Drug B the most efficacious drug** among the three, as it can produce the largest therapeutic response regardless of how much drug is given - Efficacy order: Drug B > Drug C > Drug D *Drug C is the most potent* - **Potency** refers to the amount of drug needed to produce a given effect, measured by **EC50** (the concentration producing 50% of maximal effect) - **The lower the EC50, the more potent the drug** (curve shifted to the left) - **Drug B has the lowest EC50** (its curve is furthest to the left), making it the most potent drug, not Drug C - Drug C requires a higher concentration than Drug B to achieve 50% effect, so it is less potent - Potency order: Drug B > Drug C > Drug D *Drug C is as efficacious as drug D* - **Drug C has higher efficacy than Drug D** because its curve reaches a higher plateau on the y-axis - Drug C achieves a maximal blocking effect of approximately 100 units, while Drug D reaches only approximately 75 units - **Different efficacy values** mean they are not equally efficacious - A drug's efficacy is independent of the dose required and depends only on the maximum achievable effect *Drug D is more potent than drug C* - **Drug C is actually more potent than Drug D**, not the reverse - Drug C's dose-response curve is **shifted to the left** of Drug D's curve, indicating a lower EC50 - This means **Drug C requires a lower concentration** to achieve 50% of its maximal effect compared to Drug D - The leftward shift indicates greater potency for Drug C

Q: Which drug elicits the following response on blood pressure and heart rate, as shown in the image?

Norepinephrine. ***Norepinephrine*** - Norepinephrine is a potent agonist at **α1** and **β1** receptors with minimal **β2** activity. The strong **α1** stimulation causes intense vasoconstriction, leading to a marked increase in systolic, diastolic, and mean arterial pressure, as seen in the graph. - Although norepinephrine directly stimulates the heart via **β1** receptors, the significant rise in blood pressure activates the **baroreceptor reflex**. This reflex increases vagal tone, which overrides the direct chronotropic effect and results in a net decrease in heart rate (reflex bradycardia). *Isoproterenol* - Isoproterenol is a non-selective **β-agonist** (**β1** and **β2**) and lacks **α-agonist** effects. It would cause a significant increase in heart rate (**β1** effect). - Its potent **β2** receptor stimulation leads to vasodilation and a *decrease* in diastolic and mean arterial pressure, which is the opposite of the response shown. *Epinephrine* - Epinephrine stimulates **α1**, **β1**, and **β2** receptors. At typical doses, the direct **β1** effect increases the heart rate, and the **β2** effect partially counteracts **α1**-mediated vasoconstriction, leading to a smaller rise in diastolic pressure. - The pronounced reflex bradycardia and significant increase in both systolic and diastolic pressure are more characteristic of norepinephrine's lack of **β2** agonism. *Dopamine* - Dopamine's effects are dose-dependent. At pressor doses (high doses) that stimulate **α1** receptors to increase blood pressure, there is also significant **β1** receptor stimulation. - The concurrent **β1** stimulation typically causes tachycardia or prevents significant reflex bradycardia, which is inconsistent with the graph showing a decreased heart rate.

Q: Which of the following drugs increases uric acid in urine?

Probenecid. ***Probenecid***- This drug is a **uricosuric agent** that works by inhibiting the reabsorption of urate at the **proximal convoluted tubule** of the kidney.- By blocking reabsorption, **probenecid** promotes the excretion of uric acid into the urine, thereby reducing serum uric acid levels.*Colchicine*- *Colchicine* is primarily used for the management of **acute gout flares** and works by inhibiting neutrophil migration and subsequent inflammatory responses.- It does **not** significantly alter the renal handling of uric acid; therefore, it does not increase uric acid excretion in the urine.*Febuxostat*- *Febuxostat* is a **non-purine selective inhibitor of xanthine oxidase**, an enzyme required for uric acid synthesis.- Its mechanism is to **decrease the production** of uric acid by the body, thus lowering serum levels, rather than promoting its excretion in the urine.*Allopurinol*- *Allopurinol* is a **purine analog and a xanthine oxidase inhibitor** used for the prophylactic management of chronic gout.- Like Febuxostat, it acts to **decrease the synthesis** (production) of uric acid, contrasting with uricosuric agents which increase excretion.

Q: Which of the following is the recommended treatment for the ureteric stone shown in the image?

Ureteroscopy. ***Ureteroscopy*** - This procedure involves passing a small, flexible scope through the urethra and bladder into the ureter to directly visualize and treat the stone. - It is a highly effective and preferred treatment for stones located in the **mid and distal ureter**, allowing for either retrieval with a basket or fragmentation with a laser. *Percutaneous nephrolithotomy* - This is an invasive procedure where an instrument is passed directly into the kidney through a small incision in the back. - It is primarily indicated for the removal of **large renal stones** (typically >2 cm) or staghorn calculi located within the kidney, not for ureteric stones. *ESWL* - Extracorporeal Shock Wave Lithotripsy (ESWL) uses focused **shock waves** from outside the body to break the stone into smaller fragments that can be passed in the urine. - While an option for some ureteric and kidney stones, its success rate is lower for stones in the **lower ureter** and for harder stones, making ureteroscopy often more effective. *Wait and watch* - This approach, often combined with **Medical Expulsive Therapy** (e.g., alpha-blockers), is reserved for small, uncomplicated stones (typically **<5 mm**) that are likely to pass spontaneously. - It is not recommended for larger stones, stones causing significant obstruction or severe symptoms, or those that fail to pass after a trial period.

Question 1

Which enzymes use molecular oxygen as a hydrogen acceptor to produce water?

Accepted Answer

Cytochrome c oxidase

Answer

Catalase

Answer

Superoxide dismutase

Answer

Pyruvate dehydrogenase

Question 2

A 34-year-old male whose staple diet primarily consisted of only maize presents with diarrhea, dementia, and photosensitive dermatitis in sun-exposed areas. Which vitamin is most likely deficient in this patient?

Accepted Answer

Niacin

Answer

Vitamin B6

Answer

Ascorbic acid

Answer

Biotin

Question 3

A female patient complains of swelling and pain in her great toe. Her uric acid level is found to be high. A drug that reduces uric acid levels is prescribed. Which of the following enzymes should the drug inhibit?

Accepted Answer

Xanthine oxidase

Answer

Lysyl oxidase

Answer

Homogentisate oxidase

Answer

Urease

Question 4

A 35-year-old woman presented to the clinic with the symptoms of hearing loss and pulsatile tinnitus. Further examination reveals conductive hearing loss with the Rinne test negative. A reddish mass is seen behind the tympanic membrane. What is the most likely diagnosis for this patient?

Accepted Answer

Glomus tumour

Answer

Chronic otitis media

Answer

Serous otitis media

Answer

Acute otitis media

Question 5

A male patient complained of imbalance, numbness of the foot, and muscle weakness. On history taking, he revealed that he has been taking multivitamin tablets more than the prescribed dose for 1 year. Which of the following is the most likely cause of the associated symptoms seen in this patient?

Accepted Answer

Vitamin B6 toxicity

Answer

Vitamin D toxicity

Answer

Vitamin C toxicity

Answer

Vitamin A toxicity

Question 6

A patient with a history of hypertension is given the drug 'X'. Identify 'X'?

Accepted Answer

Aliskiren

Answer

Losartan

Answer

Spironolactone

Answer

Captopril

Question 7

Which statement best describes the relationship between drug potency and efficacy in dose-response curves?

Accepted Answer

Drug B is the most efficacious

Answer

Drug C is as efficacious as drug D

Answer

Drug D is more potent than drug C

Answer

Drug C is the most potent

Question 8

Which drug elicits the following response on blood pressure and heart rate, as shown in the image?

Accepted Answer

Norepinephrine

Answer

Epinephrine

Answer

Dopamine

Answer

Isoproterenol

Question 9

Which of the following drugs increases uric acid in urine?

Accepted Answer

Probenecid

Answer

Allopurinol

Answer

Colchicine

Answer

Febuxostat

Question 10

Which of the following is the recommended treatment for the ureteric stone shown in the image?

Accepted Answer

Ureteroscopy

Answer

Percutaneous nephrolithotomy

Answer

ESWL

Answer

Wait and watch

FMGE 2023

Biochemistry

ENT

General Medicine

Pharmacology

Surgery