NEET-PG 2015 Practice Questions

Q: In the malate shuttle, how many ATPs are produced from one NADH?

2.5 ATP. ***2.5 ATP*** - In the **malate-aspartate shuttle**, mitochondrial **NADH** is regenerated from cytosolic NADH, and then enters the electron transport chain at **Complex I**. - **Complex I** entry means that NADH contributes to the pumping of enough protons to generate approximately **2.5 ATP** through oxidative phosphorylation. *1 ATP* - **1 ATP** is not the direct equivalent produced from the reoxidation of one NADH via the malate shuttle into the electron transport chain. - This value is typically associated with the direct hydrolysis of **ATP** or the energy equivalent of **GTP** produced in the citric acid cycle. *3 ATP* - Historically, **3 ATP** was the accepted stoichiometry for one NADH, but more accurate measurements of proton pumping and ATP synthase activity have revised this. - The value of 3 ATP per NADH does not reflect the most current understanding of mitochondrial bioenergetics. *2 ATP* - **2 ATP** is the approximate yield for **FADH2** entering the electron transport chain at **Complex II**, bypassing Complex I, and thus pumping fewer protons. - This value is not applicable to NADH transferred via the malate-aspartate shuttle, as NADH enters at Complex I.

Q: What type of receptor is the insulin receptor?

Tyrosine kinase. ***Tyrosine kinase*** - The insulin receptor is a **receptor tyrosine kinase (RTK)**, meaning it has intrinsic tyrosine kinase activity that phosphorylates specific tyrosine residues on itself and other intracellular proteins upon insulin binding. - This phosphorylation initiates a **signaling cascade** involving molecules like IRS proteins, PI3K/Akt, and MAPK pathways, leading to glucose uptake and metabolic regulation. *Guanylyl cyclase* - Guanylyl cyclase receptors, such as the **atrial natriuretic peptide receptor**, catalyze the conversion of GTP to **cGMP**, which acts as a second messenger. - This mechanism is distinct from the insulin receptor's direct protein phosphorylation. *Adenylyl cyclase* - Adenylyl cyclase is typically activated by **G-protein coupled receptors (GPCRs)**, leading to the conversion of ATP to **cAMP**, another second messenger. - The insulin receptor does not couple to G proteins or directly activate adenylyl cyclase. *IP3-DAG* - The **inositol triphosphate (IP3)** and **diacylglycerol (DAG)** pathway is primarily activated by certain **GPCRs** and involves the hydrolysis of PIP2 by phospholipase C, leading to calcium release and protein kinase C activation. - This pathway is not the primary signaling mechanism initiated by the insulin receptor.

Q: Carcinoma originating from glands is called?

Adenocarcinoma. ***Adenocarcinoma*** - Carcinoma that arises from **glandular epithelium** is specifically classified as adenocarcinoma [1]. - It often presents in organs like the **breast**, **prostate**, and **gastrointestinal tract** [4,5]. *Fibrosarcoma* - This is a **malignant tumor** derived from **fibrous connective tissue**, not glands. - Typically occurs in **soft tissues**, and is distinct from epithelial tumors like adenocarcinoma. *Squamous cell carcinoma* - Originates from **squamous epithelial cells** and primarily affects areas such as the **skin** and **mucous membranes** [2]. - It is not associated with glandular structures, differing markedly from adenocarcinoma. *Basal cell carcinoma* - Arises from **basal cells** in the **epidermis** (skin), not from glandular tissue. - It is the most common type of skin cancer and is largely not relevant to glandular origin. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 335-336. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 336-337. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 777-778. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 348-349.

Q: Which of the following is a type of small vessel vasculitis?

Granulomatosis with polyangiitis (GPA). ***Granulomatosis with polyangiitis (GPA)*** - GPA is a prototypic **ANCA-associated small vessel vasculitis** characterized by necrotizing granulomas and vasculitis [1], [2]. - It commonly involves the **upper and lower respiratory tracts** and the **kidneys** with necrotizing granulomatous inflammation [1], [2]. - Classified as small vessel vasculitis according to the **Chapel Hill Consensus Conference** classification. *Classical PAN* - This refers to **Polyarteritis Nodosa (PAN)**, which is a **medium-sized vessel vasculitis**. - PAN is characterized by multifocal inflammatory and necrotizing lesions of medium-sized muscular arteries, **not small vessels**. *Giant cell arteritis* - **Giant cell arteritis (GCA)** is a **large vessel vasculitis** that primarily affects the aorta and its major branches, particularly the temporal artery [3]. - Symptoms include headache, jaw claudication, and visual disturbances, reflecting the involvement of larger blood vessels [3]. *None of the options* - This option is incorrect because Granulomatosis with polyangiitis (GPA) is a clear example of a small vessel vasculitis. - There is a correct answer among the provided choices. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 519-520. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 536-537. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 515-516.

Q: Subepithelial deposits in the kidney are primarily associated with which condition?

Post-Streptococcal Glomerulonephritis (PSGN). ***PSGN*** - Post-streptococcal glomerulonephritis (PSGN) is characterized by **subepithelial immune complex deposits** [1], typically after a streptococcal infection [1]. - It is associated with **hematuria**, **edema**, and elevated **anti-streptolysin O (ASO)** titers. *GPS* - Minimal change disease (often referred to as idiopathic nephrotic syndrome) does not primarily feature **subepithelial deposits** but rather **effacement of podocyte foot processes**. - Clinical presentation includes **nephrotic syndrome** symptoms, not glomerulonephritis like PSGN. *MPGN-1* - Membranoproliferative glomerulonephritis type 1 includes **subendothelial deposits** rather than subepithelial deposits associated with PSGN. - Symptoms often include **nephritic syndrome** and is commonly linked with conditions like **HCV infection**. *All* - While several conditions can show **deposits in kidney**, not all are characterized by **subepithelial deposits**, hence this option is inaccurate. - Each type of glomerular disease has specific types of deposits (immune complex vs. complement) associated with their pathophysiology. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 914-916.

Q: Which protein primarily contributes to oncotic pressure in the blood?

Albumin. ***Albumin*** - **Albumin** is the most abundant plasma protein and its small size and high concentration make it the primary determinant of **oncotic pressure** in the blood. - Its presence in the capillaries draws water from the **interstitial space** back into the blood vessels, maintaining **fluid balance** and blood volume. *Fibrinogen* - **Fibrinogen** is a crucial protein involved in **blood clotting**, where it is converted into **fibrin** to form a clot. - While a plasma protein, its contribution to **oncotic pressure** is minor compared to albumin, as it's less abundant and larger in size. *Globulins* - **Globulins** are a diverse group of proteins involved in immune function (**immunoglobulins**), transport (e.g., **alpha** and **beta globulins**), and clotting. - While they contribute to total plasma protein concentration, their collective impact on **oncotic pressure** is secondary to that of albumin due to lower concentrations and varied molecular weights. *Transferrin* - **Transferrin** is a specific **beta-globulin** that plays a vital role in **iron transport** in the blood. - Its primary function is not related to **oncotic pressure**, and its concentration is significantly lower than albumin.

Q: Mechanism of secretion of ammonia in distal tubule is?

Passive diffusion. ***Passive diffusion*** - Ammonia (NH3) is a **lipid-soluble molecule** that can readily cross cell membranes, including those of the distal tubule and collecting duct, down its **concentration gradient**. - This process is crucial for regulating **acid-base balance**, as NH3 traps H+ ions to form NH4+, which is then excreted. *Primary active transport* - This mechanism involves the direct use of **ATP hydrolysis** to move ions against their concentration gradient, which is not the primary way ammonia is secreted in the distal tubule. - While NH4+ can be secreted via active transport in some segments (e.g., substituting for K+ on the Na-K-2Cl cotransporter in the thick ascending limb), free ammonia diffusion is distinct. *Symport* - **Symport** involves the co-transport of two or more different molecules or ions in the same direction across a cell membrane, powered by an electrochemical gradient. - This mechanism is not typically involved in the secretion of uncharged, lipid-soluble ammonia. *Antiport* - **Antiport** is a type of coupled transport where two different ions or molecules move in opposite directions across a membrane. - While antiport systems are essential for various renal functions (e.g., Na+/H+ exchanger), they are not the primary mechanism for the secretion of free ammonia in the distal tubule.

Q: Lower esophageal sphincter pressure is increased by all of the following substances, EXCEPT:

Secretin. ***Secretin*** - **Secretin** is a gastrointestinal hormone that *decreases* lower esophageal sphincter (LES) pressure - This hormone is released from S cells in the duodenum in response to acidic chyme - Its primary role is to stimulate the pancreas to release **bicarbonate-rich fluid** to neutralize acidic chyme entering the duodenum - By decreasing LES pressure, it facilitates the passage of gastric contents into the duodenum during digestion *Gastrin* - **Gastrin** is a hormone that *increases* lower esophageal sphincter (LES) pressure - This helps prevent gastroesophageal reflux when the stomach is distended - It also stimulates the secretion of **gastric acid** by parietal cells in the stomach - Released from G cells in the gastric antrum in response to protein ingestion *Motilin* - **Motilin** is a peptide hormone that *increases* lower esophageal sphincter (LES) pressure - It initiates the **migrating motor complex (MMC)** during the interdigestive period - Stimulates gastric and intestinal motility - Released from M cells in the duodenum and jejunum *Substance P* - **Substance P** is a neuropeptide that *increases* lower esophageal sphincter (LES) pressure - Functions as both a neurotransmitter and neuromodulator in the enteric nervous system - Plays a role in **smooth muscle contraction** and gastrointestinal motility - Also involved in pain transmission and inflammatory responses

Question 1

In the malate shuttle, how many ATPs are produced from one NADH?

Accepted Answer

2.5 ATP

Answer

1 ATP

Answer

3 ATP

Answer

2 ATP

Question 2

What type of receptor is the insulin receptor?

Accepted Answer

Tyrosine kinase

Answer

Guanylyl cyclase

Answer

Adenylyl cyclase

Answer

IP3-DAG

Question 3

What is defined as a negative autopsy?

Accepted Answer

No cause of death is found after both gross and histopathological examination.

Answer

Cause is apparent on gross examination but not on histopathological examination.

Answer

Gross findings are minimal.

Answer

Cause is apparent on gross examination but not found due to constraints on the part of the doctor.

Question 4

Carcinoma originating from glands is called?

Accepted Answer

Adenocarcinoma

Answer

Basal cell carcinoma

Answer

Squamous cell carcinoma

Answer

Fibrosarcoma

Question 5

Which of the following is a type of small vessel vasculitis?

Accepted Answer

Granulomatosis with polyangiitis (GPA)

Answer

Classical PAN

Answer

Giant cell arteritis

Answer

None of the options

Question 6

Subepithelial deposits in the kidney are primarily associated with which condition?

Accepted Answer

Post-Streptococcal Glomerulonephritis (PSGN)

Answer

None of these conditions are associated with subepithelial deposits.

Answer

Membranoproliferative Glomerulonephritis (MPGN) Type I

Answer

Goodpasture's Syndrome (GPS)

Question 7

Which protein primarily contributes to oncotic pressure in the blood?

Accepted Answer

Albumin

Answer

Globulins

Answer

Fibrinogen

Answer

Transferrin

Question 8

Mechanism of secretion of ammonia in distal tubule is?

Accepted Answer

Passive diffusion

Answer

Primary active transport

Answer

Symport

Answer

Antiport

Question 9

Lower esophageal sphincter pressure is increased by all of the following substances, EXCEPT:

Accepted Answer

Secretin

Answer

Motilin

Answer

Gastrin

Answer

Substance P

Question 10

What is the PRIMARY mechanism by which the Na+-Ca2+ exchanger functions in cardiac muscle cells?

Accepted Answer

Na+-Ca2+ exchanger acts to remove Ca2+ from heart muscle cells

Answer

Na+-Ca2+ exchanger requires ATP directly

Answer

The Na+-Ca2+ exchanger operates in reverse mode during normal cardiac contraction

Answer

The Na+-Ca2+ exchanger primarily moves Ca2+ into cardiac muscle cells during systole

NEET-PG 2015

Biochemistry

Forensic Medicine

Pathology

Physiology