Anatomy
1 questionsType of collagen found in space of Disse in liver is -
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 421: Type of collagen found in space of Disse in liver is -
- A. Collagen I & II
- B. Collagen III & IV (Correct Answer)
- C. Collagen II
- D. Collagen II & V
Explanation: ***Collagen III & IV*** - The **space of Disse** in the liver contains a delicate extracellular matrix predominantly composed of **collagen type III (reticular fibers)**, which provides structural support, and **collagen type IV**, a major component of basement membranes. - This specific collagen composition is crucial for regulating the exchange of solutes between **sinusoidal blood** and **hepatocytes**, as well as for the functional integrity of the liver [1]. *Collagen I & II* - **Collagen type I** is the most abundant collagen in the human body, found in connective tissues like **bone, skin, tendons, and ligaments**, but is not primary in the space of Disse. - **Collagen type II** is characteristic of **hyaline cartilage** and vitreous humor, and is not a significant component of the liver's extracellular matrix in the space of Disse. *Collagen II* - As mentioned, **collagen type II** is primarily found in **cartilage** and vitreous humor, which are distinct from the architectural requirements of the liver sinusoidal space. - Its presence in the space of Disse would not provide the necessary structural flexibility and support for the metabolic functions of the liver. *Collagen II & V* - While **collagen type V** is a minor fibrillar collagen that associates with collagen type I in many tissues, it is not a primary component of the space of Disse. - **Collagen type II** is, again, largely confined to cartilaginous structures, making this an unlikely combination for the liver microenvironment.
Biochemistry
4 questionsWhich of the following statements regarding collagen synthesis is incorrect?
Which is the first steroid intermediate formed in the conversion of cholesterol to steroid hormones?
Which of the following is NOT a characteristic of the genetic code?
Albumin is the primary transport protein in blood for which of the following substances?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 421: Which of the following statements regarding collagen synthesis is incorrect?
- A. Hydroxylation of lysine occurs in ER
- B. Synthesized in ribosomes as preprocollagen
- C. Triple helix assembly occurs in ER
- D. Hydroxylation of proline occurs in Golgi apparatus (Correct Answer)
Explanation: ***Hydroxylation of proline occurs in Golgi apparatus*** - This statement is incorrect because the **hydroxylation of proline** residues occurs in the **endoplasmic reticulum** (ER), not the Golgi apparatus. - This step is critical for forming stable **triple helix** structures of collagen and requires **vitamin C**. *Synthesized in ribosomes as preprocollagen* - This statement is correct. Collagen synthesis begins in the cytoplasm, where mRNA is translated by **ribosomes** into **preprocollagen**, which contains a signal peptide. - The signal peptide directs the nascent polypeptide chain into the lumen of the **endoplasmic reticulum**. *Hydroxylation of lysine occurs in ER* - This statement is correct. Following entry into the ER, specific **lysine** residues are hydroxylated by **lysyl hydroxylase** to form hydroxylysine. - This hydroxylation, along with that of proline, is crucial for **cross-linking** and stability of the collagen molecule. *Triple helix assembly occurs in ER* - This statement is correct. After hydroxylation and glycosylation of some residues, three procollagen alpha chains self-assemble to form a **triple helix** within the **endoplasmic reticulum**. - This assembly is stabilized by **disulfide bonds** at the C-terminal ends and molecular chaperones.
Question 422: Which is the first steroid intermediate formed in the conversion of cholesterol to steroid hormones?
- A. Glucocorticoid
- B. Mineralocorticoid
- C. Estradiol
- D. Pregnenolone (Correct Answer)
Explanation: ***Pregnenolone*** - **Pregnenolone** is the **first steroid intermediate** formed from **cholesterol** in steroidogenesis - The conversion occurs in mitochondria via the **cholesterol side-chain cleavage enzyme (P450scc/CYP11A1)** - This is the **rate-limiting step** in steroid hormone biosynthesis - From pregnenolone, all other steroid hormones are subsequently synthesized *Progesterone* - Progesterone is the **second intermediate**, formed from pregnenolone - It serves as a precursor for glucocorticoids, mineralocorticoids, and androgens - Not the first intermediate from cholesterol *Glucocorticoid* - Glucocorticoids (e.g., cortisol) are **end products**, not intermediates - Formed several steps downstream from cholesterol via pregnenolone and progesterone *Mineralocorticoid* - Mineralocorticoids (e.g., aldosterone) are **end products**, not intermediates - Synthesized from progesterone through multiple enzymatic steps *Estradiol* - Estradiol is a **late-stage product** synthesized from androgens - Requires aromatase enzyme for conversion from testosterone - Multiple steps removed from the initial cholesterol conversion
Question 423: Which of the following is NOT a characteristic of the genetic code?
- A. Overlapping (Correct Answer)
- B. Universal
- C. Degeneracy
- D. Nonambiguous
Explanation: ***Overlapping*** - The genetic code is generally **non-overlapping**, meaning each nucleotide is part of only one codon, and codons are read sequentially. - An overlapping code would mean that a single nucleotide could be part of multiple codons, which is not how protein synthesis typically occurs. *Nonambiguous* - This statement IS a characteristic; each codon specifies **only one amino acid**, meaning there is no ambiguity about which amino acid will be added. - While multiple codons can specify the same amino acid, a single codon never specifies more than one different amino acid. *Universal* - This statement IS a characteristic; the genetic code is largely **universal** across almost all organisms, from bacteria to humans. - The same codons typically specify the same amino acids in different species, which supports the idea of common ancestry. *Degeneracy* - This statement IS a characteristic; the genetic code is **degenerate**, meaning that most amino acids are specified by more than one codon. - This redundancy helps protect against the effects of single-nucleotide mutations.
Question 424: Albumin is the primary transport protein in blood for which of the following substances?
- A. Free fatty acids (FFA) (Correct Answer)
- B. Thyroxine
- C. Steroid
- D. Calcium
Explanation: ***Free fatty acids (FFA)*** - **Albumin is the PRIMARY and MAJOR transport protein for free fatty acids** in the bloodstream, with each albumin molecule having **6-7 high-affinity binding sites** for FFAs. - This binding is essential for transporting water-insoluble fatty acids from **adipose tissue** (during lipolysis) to peripheral tissues for **β-oxidation and energy production**. - In the context of lipid metabolism, albumin-FFA transport is the **most quantitatively significant** and physiologically important binding function. - **Clinical relevance:** Impaired albumin levels directly affect FFA transport capacity. *Thyroxine* - While albumin does bind thyroid hormones, **thyroxine-binding globulin (TBG)** is the **primary carrier** (~70% of T4), followed by transthyretin (~15%). - Albumin binds only ~10-15% of circulating T4 with **low affinity**, serving as a secondary reserve. - TBG has **much higher affinity** for thyroid hormones than albumin. *Steroid* - Steroids are primarily transported by **specific binding globulins**: **corticosteroid-binding globulin (CBG)** for cortisol and **sex hormone-binding globulin (SHBG)** for testosterone/estrogen. - While albumin binds ~10-20% of steroids, it is a **secondary carrier** with lower affinity than the specific globulins. *Calcium* - Although ~40-45% of plasma calcium is albumin-bound (important for calcium homeostasis), this is a **passive binding function** rather than active transport. - Albumin's role with calcium is primarily **buffering** rather than the dedicated transport function it provides for FFAs. - In the context of **lipid metabolism** and **transport proteins**, FFA binding is the hallmark function of albumin.
Internal Medicine
1 questionsWhich of the following is not an obstructive lung disease?
NEET-PG 2013 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 421: Which of the following is not an obstructive lung disease?
- A. Emphysema
- B. Interstitial fibrosis (Correct Answer)
- C. Asthma
- D. Bronchitis
Explanation: ***Interstitial fibrosis*** - **Interstitial fibrosis** is a **restrictive lung disease**, characterized by **reduced lung elasticity** and lung volumes, rather than airway obstruction [1]. - In this condition, the **lung tissue becomes scarred and stiff**, making it difficult to expand fully during inspiration [1]. *Emphysema* - **Emphysema** is a classic **obstructive lung disease** caused by the destruction of the **alveolar walls**, leading to enlarged air spaces and loss of elastic recoil [3]. - This destruction results in **airflow limitation**, particularly during exhalation, as airways collapse prematurely. *Asthma* - **Asthma** is an **obstructive lung disease** characterized by **reversible airway inflammation**, bronchoconstriction, and increased mucus production [2]. - These factors lead to **episodic airflow obstruction**, making it difficult to breathe, especially during exacerbations [2]. *Bronchitis* - **Bronchitis**, particularly **chronic bronchitis**, is an **obstructive lung disease** defined by chronic inflammation of the bronchi. - This inflammation causes **mucus hypersecretion** and narrowing of the airways, leading to persistent cough and airflow limitation.
Pathology
3 questionsWhich of the following conditions is least associated with tumor suppressor genes?
All are growth promoting oncogenes except ?
What is a hamartoma?
NEET-PG 2013 - Pathology NEET-PG Practice Questions and MCQs
Question 421: Which of the following conditions is least associated with tumor suppressor genes?
- A. Neurofibromatosis
- B. Retinoblastoma
- C. Acute Myeloid Leukemia (AML) (Correct Answer)
- D. Breast cancer
Explanation: ***Multiple endocrine neoplasia*** - This syndrome involves mutations in **proto-oncogenes** like RET rather than tumor suppressor genes. - The condition is mainly characterized by the presence of **multiple endocrine tumors** rather than a failure of tumor suppression. *Retinoblastoma* - Associated with mutations in the **RB1 tumor suppressor gene**, leading to uncontrolled cell proliferation [1] [2]. - Classic example of **loss of function** in a tumor suppressor gene resulting in cancer, specifically in early childhood [1] [2]. *Neurofibromatosis* - Caused by mutations in **NF1** or **NF2 genes**, both of which function as tumor suppressors. - Leads to benign tumors such as **neurofibromas** and other neurogenic tumors due to malfunction in tumor suppression. *Breast cancers* - Often related to mutations in tumor suppressor genes such as **BRCA1** and **BRCA2**, which increase cancer risk [2]. - Implicated in the hereditary form of breast and ovarian cancers due to their roles in DNA repair and cell cycle regulation [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 227-228. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 298-302.
Question 422: All are growth promoting oncogenes except ?
- A. FGF
- B. PDGF
- C. TGF-α
- D. TGF-β (Correct Answer)
Explanation: ***TGF-p*** - **TGF-p (Transforming Growth Factor beta)** is primarily known as a **growth inhibitory** factor rather than a promoting oncogene. - It plays a crucial role in **cell differentiation**, **apoptosis**, and inhibits cell proliferation, counteracting the effects of other oncogenes. *TGF-a* - **TGF-a (Transforming Growth Factor alpha)** is a **growth factor** that stimulates cell proliferation and is involved in various cancers [1][2]. - It binds to the **EGF receptor**, promoting growth and tumor development. *PDGF* - **PDGF (Platelet-Derived Growth Factor)** acts as a potent **mitogen** for connective tissue cells and is involved in wound healing and tumor growth [2][4]. - It plays a central role in promoting cell proliferation and migration, contributing to cancer progression [4]. *FGF* - **FGF (Fibroblast Growth Factor)** promotes mitosis and is crucial in **angiogenesis**, wound healing, and several developmental processes [2]. - Its overexpression is linked to various tumors, making it a significant oncogenic growth promoter [2][3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 30-31. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 292. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 292-293. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 31-32.
Question 423: What is a hamartoma?
- A. Malignant tumor
- B. Metastatic tissue
- C. Hemorrhage in vessel
- D. Developmental malformation (Correct Answer)
Explanation: ***Development malformation*** - A **hamartoma** is a type of **benign tumor** that consists of an overgrowth of mature cells, representing a **developmental malformation** [1]. - It is formed from tissues that are normally present in the affected organ but are disorganized, leading to a characteristic appearance. *Malignant tumor* - Hamartomas are classified as **benign tumors** [1], not malignant, as they do not invade surrounding tissues or metastasize. - Despite being a growth, they do not exhibit the aggressive characteristics of malignant tumors. *Hemorrhage in vessel* - Hemorrhage refers to bleeding within a vessel and is unrelated to the definition or nature of a **hamartoma**. - Hamartomas do not consist of blood or bleeding; instead, they involve disorganized tissue growth. *Metastatic tissue* - Metastatic tissue refers to cancerous cells that have spread from their original site, which contrasts with the **non-cancerous** nature of hamartomas [1]. - Hamartomas do not involve the spread of cancer cells, but rather a **local abnormality** in tissue arrangement. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 481-482.
Psychiatry
1 questionsWhat is the name of the syndrome associated with the deletion of chromosome 22?
NEET-PG 2013 - Psychiatry NEET-PG Practice Questions and MCQs
Question 421: What is the name of the syndrome associated with the deletion of chromosome 22?
- A. Down syndrome
- B. Di George syndrome (Correct Answer)
- C. Turner syndrome
- D. Klinefelter syndrome
- E. Prader-Willi syndrome
Explanation: ***Di George syndrome*** - Di George syndrome, also known as **22q11.2 deletion syndrome**, is caused by a deletion on the long arm of chromosome 22. - This syndrome is associated with varied clinical features, including **congenital heart defects**, **thymic hypoplasia** (leading to immune deficiencies), **hypocalcemia** due to parathyroid hypoplasia, and characteristic facial features. *Down syndrome* - Down syndrome is caused by a **trisomy of chromosome 21**, meaning there's an extra copy of chromosome 21. - It is characterized by intellectual disability, distinctive facial features, and developmental delays, and is not associated with chromosome 22 deletion. *Turner syndrome* - Turner syndrome is a chromosomal condition affecting females, characterized by the partial or complete absence of one of the **X chromosomes (45, X0)**. - It leads to short stature, ovarian dysfunction, and characteristic physical features, unrelated to chromosome 22. *Klinefelter syndrome* - Klinefelter syndrome is a chromosomal disorder in males resulting from an extra **X chromosome (47, XXY)**. - Individuals often experience hypogonadism, reduced fertility, and abnormal body proportions, which is distinct from a deletion on chromosome 22. *Prader-Willi syndrome* - Prader-Willi syndrome is caused by a **deletion of paternal chromosome 15q11-q13** or maternal uniparental disomy. - It presents with hypotonia, hyperphagia, obesity, intellectual disability, and hypogonadism, unrelated to chromosome 22 deletion.