NEET-PG 2012 Practice Questions

Q: Enzymes of glycolysis are found in:

Cytosol. ***Cytosol*** - Glycolysis is a metabolic pathway that occurs in the **cytosol** of cells. - All the enzymes required for the conversion of glucose to pyruvate are freely dissolved in the **cytoplasm**. *Cell membrane* - The cell membrane is primarily involved in **regulating the passage of substances** into and out of the cell, as well as cell signaling. - Glycolytic enzymes are not associated with the cell membrane. *Mitochondria* - Mitochondria are the primary site of **oxidative phosphorylation** and the **citric acid cycle**, not glycolysis. - While pyruvate (the end product of glycolysis) moves into the mitochondria for further metabolism, the initial glycolytic steps do not occur there. *Ribosomes* - Ribosomes are responsible for **protein synthesis** (translation). - They do not contain enzymes for metabolic pathways like glycolysis.

Q: Which enzyme is primarily associated with the reduction of NADP+ to NADPH in the pentose phosphate pathway?

G6PD. ***G6PD*** - **Glucose-6-phosphate dehydrogenase (G6PD)** catalyzes the first committed step in the pentose phosphate pathway, converting **glucose-6-phosphate** to **6-phosphogluconolactone**. - This reaction involves the reduction of **NADP+ to NADPH**, making G6PD the primary enzyme for NADPH production in this pathway. *APDH* - **APDH (adenosine phosphosulfate reductase)** is involved in sulfur metabolism and has no direct role in the pentose phosphate pathway or NADPH production. - This enzyme primarily functions in prokaryotes for the **reduction of APS (adenosine 5'-phosphosulfate)**. *α-keto glutarate dehydrogenases* - **Alpha-ketoglutarate dehydrogenase** is a mitochondrial enzyme part of the **Krebs cycle**, converting **alpha-ketoglutarate to succinyl-CoA**. - This enzyme is crucial for ATP production and generates **NADH**, not NADPH, in its reaction. *None of the options* - This option is incorrect because **G6PD** is indeed the primary enzyme responsible for NADPH generation in the pentose phosphate pathway.

Q: Pantothenic acid is needed for donating the following moiety?

Acetyl group. ***Acetyl group*** - **Pantothenic acid** (vitamin B5) is a crucial component of **coenzyme A (CoA)**, which plays a central role in transferring **acetyl groups**. - This transfer is vital in numerous metabolic pathways, including the **Krebs cycle**, fatty acid synthesis, and fatty acid oxidation. *Carboxyl* - The transfer of **carboxyl groups** is typically mediated by a different coenzyme, **biotin** (vitamin B7), not pantothenic acid. - Biotin-dependent enzymes are involved in carboxylation reactions like those in gluconeogenesis and fatty acid synthesis. *Hydroxyl* - While hydroxyl groups are common in organic chemistry, pantothenic acid's primary role is not the donation of isolated **hydroxyl groups**. - Hydroxyl groups are often donated or accepted during redox reactions or hydrolysis, often by specific enzymes directly. *Amino* - The transfer of **amino groups** is primarily associated with **pyridoxal phosphate (PLP)**, the active form of vitamin B6. - PLP-dependent enzymes, such as **transaminases**, are critical for amino acid metabolism.

Q: Which condition is characterized by spongiform degeneration of the cerebral cortex?

Creutzfeldt-Jakob disease. ***Creutzfeldt-Jakob disease*** - This is a **prion disease** characterized by rapid cognitive decline, myoclonus, and distinctive EEG changes, with **spongiform degeneration of the cerebral cortex** as the hallmark neuropathological feature [1]. - The spongiform changes are due to intracellular vacuoles within neurons and astrocytes, giving the brain tissue a **spongy appearance** [2]. - CJD shows **widespread cortical involvement**, making it the classic answer for cortical spongiform degeneration [2]. *Subacute sclerosing panencephalitis* - This condition is a rare, **chronic, progressive encephalitis** caused by persistent measles virus infection. - It is characterized by widespread **demyelination, gliosis, and intranuclear inclusion bodies**, but not spongiform degeneration. *Fatal familial insomnia* - This is another **prion disease** that also exhibits spongiform degeneration, but the key difference is **anatomical distribution** [2]. - FFI primarily affects the **thalamus** (a subcortical structure) and causes severe insomnia, dysautonomia, and motor signs [2]. - While spongiform changes occur in FFI, they are most prominent in the **thalamus rather than the cerebral cortex**, making CJD the better answer for cortical spongiform degeneration [2]. *Cerebral toxoplasmosis* - This is an **opportunistic infection of the brain** caused by **_Toxoplasma gondii_**, primarily seen in immunocompromised individuals. - It typically results in the formation of **abscesses or ring-enhancing lesions**, rather than spongiform degeneration. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 712-713. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1284-1286.

Q: A mutation in the transthyretin (TTR) protein causes which of the following types of amyloidosis?

Familial amyloidotic polyneuropathy. ***Familial amyloidotic polyneuropathy*** - This condition is specifically caused by **mutations in the transthyretin (TTR) protein**, leading to amyloid deposition primarily in nerves [1]. - It presents with **peripheral neuropathy**, including sensory and autonomic symptoms, which align with TTR mutations [1]. *Familial Mediterranean fever* - This is an autoinflammatory disorder caused by mutations in the **MEFV gene**, unrelated to transthyretin. - It is characterized by recurrent **fever, abdominal pain**, and **serositis**, not amyloidosis caused by TTR. *Prion protein associated amyloidosis* - Relates to prion diseases like **Creutzfeldt-Jakob disease**, caused by abnormal **prion proteins** rather than TTR [1]. - Symptoms are usually **neurodegenerative** in nature, not linked to familial amyloidogenic processes. *Dialysis associated amyloidosis* - This form of amyloidosis is due to the accumulation of **beta-2 microglobulin**, not mutations in TTR [1]. - Commonly presents with **joint pain** and carpal tunnel syndrome associated with long-term dialysis [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 266.

Q: What color is emitted by FITC after absorbing blue light?

Yellow-green. ***Yellow-green*** - Fluorescein isothiocyanate (FITC) is a common fluorochrome used in **fluorescence microscopy** and flow cytometry. - Upon excitation by blue light (typically around 495 nm), FITC emits light in the **yellow-green spectrum**, specifically around 521 nm. - This is the **spectroscopically accurate** description of FITC's emission peak. *Orange-red* - **Orange-red emission** is characteristic of fluorochromes like **phycoerythrin (PE)** or **Texas Red**, not FITC. - These fluorochromes have different **excitation and emission maxima** compared to FITC. *Apple-green* - While FITC fluorescence is sometimes clinically described as **"apple-green"** (especially in immunofluorescence), this is a **subjective visual description** rather than a precise spectral term. - The more **spectroscopically accurate** description is **yellow-green**, which reflects FITC's specific emission peak at 521 nm. - "Apple-green" typically suggests a purer green without the yellow component. *Golden-brown* - **Golden-brown** is not a typical emission color for fluorochromes like FITC. - This color is generally associated with **pigments** or stained tissues (e.g., lipofuscin, hemosiderin), not fluorescent probes.

Q: What is the most common cause of nephritic syndrome in adults, excluding IgA nephropathy?

Membranoproliferative glomerulonephritis. ***None*** - Nephritic syndrome in adults is often caused by various conditions, but there is **no single most common cause** that universally applies. - The true prevalence can vary by population, but conditions like **IgA nephropathy** or **post-infectious glomerulonephritis** [1] are frequently encountered rather than one specific disease. *Membranoproliferative glomerulonephritis* - This condition can cause a **nephritic syndrome** [1], but it is not the most common cause in adults, often seen in association with **hepatitis C** or other infections. - In practice, **IgA nephropathy** or **post-streptococcal glomerulonephritis** [1] are more frequently recognized causes of nephritic syndrome in adults. *Membranous glomerulonephritis* - Primarily presents with **nephrotic syndrome** rather than nephritic features [1], making it less likely to be cited as a common cause of nephritic syndrome. - It is associated with **anti-phospholipase A2 receptor antibodies** but lacks the inflammatory features of nephritis [1]. *FSGN* - **Focal Segmental Glomerulosclerosis** is associated with nephrotic syndrome and doesn't typically lead to classic nephritic features, such as hematuria and hypertension [1]. - Its primary presentation is with **proteinuria** and possible renal failure but not with the typical characteristics of nephritic syndrome [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 915-919.

Q: What is the duration of the second heart sound (S2)?

0.08 sec. ***0.08 sec*** - The second heart sound (S2) is composed of two components: A2 (aortic valve closure) and P2 (pulmonic valve closure). The normal duration of S2, encompassing both components, is approximately **0.08 seconds**. - This short duration reflects the rapid closure of the aortic and pulmonic valves at the beginning of **diastole**. *0.15sec* - A duration of **0.15 seconds** for S2 is significantly longer than normal, which could indicate abnormal valve function or conditions causing delayed valve closure. - Such prolonged duration might be observed in conditions like **severe pulmonic stenosis** or **pulmonic hypertension**, which are not the typical duration of a healthy S2. *0.12 sec* - A duration of **0.12 seconds** is also longer than the typical normal range for S2. - While still shorter than 0.15 seconds, it could suggest subtle delays in valve closure or splitting that exceeds the usual physiological splitting. *0.1 sec* - A duration of **0.1 seconds** is slightly prolonged but generally falls within a range that might be considered borderline or indicative of minimal physiological variations. - However, in typical healthy individuals, the S2 duration is closer to 0.08 seconds, making 0.1 seconds less precise for the most common duration.

Q: Insensible water loss per day is ?

1000 ml. ***1000 ml*** - **Insensible water loss** occurs through the skin (evaporation) and respiratory tract (exhalation) without conscious perception. - The typical daily insensible water loss in an adult is approximately **800-1000 ml/day**. - **Breakdown**: Skin evaporation (~400-500 ml) + Respiratory tract (~300-400 ml) = **~900-1000 ml total**. - **1000 ml** is the standard value cited in major physiology textbooks (Guyton & Hall, Ganong) and is the most commonly accepted answer for NEET PG examinations. *100 ml* - This value is significantly **lower** than the actual insensible water loss, which occurs continuously throughout the day. - Such a low volume would imply negligible evaporation and respiratory loss, which is not physiologically accurate. *300 ml* - While greater than 100 ml, 300 ml is still **far below** the typical range for daily insensible water loss. - This amount represents only about one-third of the actual insensible losses from the skin and respiratory system combined. *700 ml* - Although this value is sometimes mentioned in literature, it is at the **lower end** of the physiological range. - The more widely accepted standard value for insensible water loss in a healthy adult under normal conditions is **900-1000 ml/day**. - 700 ml would underestimate the normal daily insensible losses.

Q: Ptyalin is secreted by?

Salivary gland. ***Salivary gland*** - **Ptyalin**, also known as **salivary amylase**, is an enzyme produced by the salivary glands. - Its primary role is to initiate the **digestion of carbohydrates** (starches) in the mouth. *Gastric gland* - Gastric glands primarily secrete **hydrochloric acid** and **pepsinogen**, involved in protein digestion. - They do not produce ptyalin or enzymes for carbohydrate digestion. *Duodenal gland* - Duodenal glands (Brunner's glands) secrete alkaline mucus to protect the duodenum from acidic chyme. - They are not involved in the production of carbohydrate-digesting enzymes like ptyalin. *Pancreatic gland* - The pancreas produces **pancreatic amylase**, which continues starch digestion in the small intestine. - While it secretes an amylase, it is distinct from salivary amylase (ptyalin) and released into the duodenum, not the mouth.

Question 1

Enzymes of glycolysis are found in:

Accepted Answer

Cytosol

Answer

Cell membrane

Answer

Mitochondria

Answer

Ribosomes

Question 2

Which enzyme is primarily associated with the reduction of NADP+ to NADPH in the pentose phosphate pathway?

Accepted Answer

G6PD

Answer

APDH

Answer

α-keto glutarate dehydrogenases

Answer

None of the options

Question 3

Pantothenic acid is needed for donating the following moiety?

Accepted Answer

Acetyl group

Answer

Carboxyl

Answer

Hydroxyl

Answer

Amino

Question 4

Which condition is characterized by spongiform degeneration of the cerebral cortex?

Accepted Answer

Creutzfeldt-Jakob disease

Answer

Subacute sclerosing panencephalitis

Answer

Fatal familial insomnia

Answer

Cerebral toxoplasmosis

Question 5

A mutation in the transthyretin (TTR) protein causes which of the following types of amyloidosis?

Accepted Answer

Familial amyloidotic polyneuropathy

Answer

Familial Mediterranean fever

Answer

Dialysis associated amyloidosis

Answer

Prion protein associated amyloidosis

Question 6

What color is emitted by FITC after absorbing blue light?

Accepted Answer

Yellow-green

Answer

Orange-red

Answer

Apple-green

Answer

Golden-brown

Question 7

What is the most common cause of nephritic syndrome in adults, excluding IgA nephropathy?

Accepted Answer

Membranoproliferative glomerulonephritis

Answer

FSGS

Answer

Membranous glomerulonephritis

Answer

Post-infectious glomerulonephritis

Question 8

What is the duration of the second heart sound (S2)?

Accepted Answer

0.08 sec

Answer

0.15 sec

Answer

0.1 sec

Answer

0.12 sec

Question 9

Insensible water loss per day is ?

Accepted Answer

1000 ml

Answer

100 ml

Answer

700 ml

Answer

300 ml

Question 10

Ptyalin is secreted by?

Accepted Answer

Salivary gland

Answer

Gastric gland

Answer

Duodenal gland

Answer

Pancreatic gland

NEET-PG 2012

Biochemistry

Pathology

Physiology