NEET-PG 2018

353 Questions — Page 35 of 36

Anatomy

3 questions

Q341

Identify the function of the muscles marked in red:

Q342

Which is correct about structures marked as "X" found in smooth muscle?

Q343

Which of the following has maximum smooth muscle as compared to wall thickness?

NEET-PG 2018 - Anatomy NEET-PG Practice Questions and MCQs

Question 341: Identify the function of the muscles marked in red:

A. Flexion at MCP joint (Correct Answer)
B. Flexion at IP joint
C. Extension at MCP joint
D. Abduction at MCP joint

Explanation: ***Flexion at MCP joint*** - The muscles shown in red are the **lumbricals**, which primarily function to **flex the metacarpophalangeal (MCP) joints** and **extend the interphalangeal (IP) joints**. - This is their most fundamental action when identifying lumbrical function, as they originate from **flexor digitorum profundus tendons** and insert into the **extensor expansion**, providing precise **MCP joint flexion**. - This unique action creates the **"lumbrical grip"** essential for precision handling. *Flexion at IP joint* - Lumbricals actually **extend the interphalangeal (IP) joints**, not flex them, making this option anatomically incorrect. - **Flexion at IP joints** is performed by the **flexor digitorum superficialis** (PIP joints) and **flexor digitorum profundus** (DIP joints). - The lumbrical insertion into the **extensor hood** produces IP extension, the opposite of this option. *Extension at MCP joint* - **Extension at the MCP joints** is primarily performed by the **extensor digitorum** and other **extrinsic extensor muscles**. - Lumbricals produce the opposite action, **flexing the MCP joints** rather than extending them. *Abduction at MCP joint* - **Abduction at the MCP joints** is primarily performed by the **dorsal interossei muscles** using the **DAB** (Dorsal ABduct) mnemonic. - Lumbricals do not contribute to **finger abduction** but rather focus on **MCP flexion, IP extension**, and **fine motor control**.

Question 342: Which is correct about structures marked as "X" found in smooth muscle?

A. A band
B. Dense bodies (Correct Answer)
C. Calmodulin
D. H band

Explanation: ***Dense bodies*** - The structures marked "X" are **dense bodies**, which are analogous to **Z-discs** in skeletal muscle, serving as attachment points for **actin filaments**. - They are crucial for transmitting the contractile force generated by the **actin-myosin bundles** to the cell membrane, leading to the characteristic corkscrew-like contraction of smooth muscle cells. *A band* - The **A band** is a region found in **striated muscle** (skeletal and cardiac muscle) where thick and thin filaments overlap, corresponding to the length of the myosin filaments. - Smooth muscle lacks the organized sarcomeric structure, and thus, **A bands** are not present. *Calmodulin* - **Calmodulin** is a calcium-binding protein that plays a key role in smooth muscle contraction by activating **myosin light chain kinase (MLCK)**. - However, it is a soluble protein involved in signaling, not a structural component like the dense bodies shown in the image. *H band* - The **H band** is located within the **A band** of a **sarcomere** in striated muscle, representing the central region where only thick (myosin) filaments are present. - Similar to the **A band**, the **H band** is a feature of striated muscle and is not found in the unstriated smooth muscle cells.

Question 343: Which of the following has maximum smooth muscle as compared to wall thickness?

A. A (Correct Answer)
B. B
C. C
D. D

Explanation: ***A*** - Structure A represents a **terminal bronchiole**, which has the **maximum proportion of smooth muscle relative to wall thickness** among all respiratory structures. - Terminal bronchioles lack cartilage and respiratory epithelium (no alveoli), making smooth muscle the dominant structural component of their walls, comprising a high percentage of the total wall thickness. - This abundant smooth muscle allows for precise control of **bronchoconstriction** and **bronchodilation**, which is crucial for regulating air distribution to the respiratory zones. *B* - Structure B appears to be a **respiratory bronchiole** or an **alveolar duct**, which is more distal than terminal bronchioles and has less smooth muscle relative to its wall thickness. - As airways progress distally from terminal bronchioles toward the alveoli, smooth muscle gradually decreases as the primary function shifts from conduction and airflow regulation to gas exchange. - Respiratory bronchioles have alveoli budding from their walls, which reduces the proportion of smooth muscle in the overall wall structure. *C* - Structure C points to an **alveolar sac**, which is composed primarily of **alveoli** clustered together. Alveolar walls are extremely thin to facilitate efficient gas exchange and contain very little to no smooth muscle. - The function of alveoli is gas exchange, not airflow regulation, hence they lack the contractile elements like smooth muscle that are abundant in conducting airways. *D* - Structure D points to an **individual alveolus**, which is the primary site of gas exchange. Alveolar walls are extremely thin and consist of type I pneumocytes (for gas exchange), type II pneumocytes (surfactant production), and alveolar macrophages. - **Alveoli** lack smooth muscle entirely, as their structure is optimized for diffusion and not for active constriction or dilation.

Biochemistry

4 questions

Q341

Which protein plays a role in the process shown below? (Recent NEET Pattern 2018)

Q342

Colipase is an enzyme found in secretions from which of the following? (Recent NEET Pattern 2018)

Q343

What is correct about the vitamin shown below?

Q344

The image shows the world's fastest athlete. Which of the following is used by his muscles for meeting energy demands to create world records in seconds?

NEET-PG 2018 - Biochemistry NEET-PG Practice Questions and MCQs

Question 341: Which protein plays a role in the process shown below? (Recent NEET Pattern 2018)

A. Clathrin (Correct Answer)
B. Ubiquitin
C. Pallidin
D. Actin

Explanation: ***Clathrin*** - **Clathrin** is the primary protein involved in forming coated pits and vesicles during receptor-mediated endocytosis, which is the process shown in the image. - It forms a characteristic **triskelion structure** (three-legged complex) that assembles into a polyhedral lattice around the budding vesicle. - This protein coat provides the mechanical force needed to bend the membrane and form vesicles for internalizing substances. - Clathrin-mediated endocytosis is the **most well-characterized pathway** for receptor-mediated uptake of molecules. *Pallidin* - Pallidin is a component of the **BLOC-1 complex** (Biogenesis of Lysosome-related Organelles Complex-1). - It is involved in the biogenesis and trafficking of lysosome-related organelles, not in the primary vesicle formation during endocytosis. - Mutations in pallidin cause Hermansky-Pudlak syndrome type 9. *Ubiquitin* - Ubiquitin is a small regulatory protein that marks other proteins for degradation via the **proteasome** or targets them for endocytosis. - While ubiquitination can signal for receptor internalization, ubiquitin itself does not form vesicle coats or directly participate in vesicle budding. *Actin* - Actin is a cytoskeletal protein that plays a supporting role in endocytosis, particularly in membrane invagination and vesicle scission. - It provides mechanical support and force for vesicle movement but is **not the primary coat protein** forming the vesicle structure during initial budding.

Question 342: Colipase is an enzyme found in secretions from which of the following? (Recent NEET Pattern 2018)

A. Salivary glands
B. Gallbladder
C. Pancreas (Correct Answer)
D. Small intestine
E. Liver

Explanation: ***Pancreas*** - The pancreas is the primary source of **colipase** secretion in the digestive system. - Colipase is an essential co-factor for **pancreatic lipase**, helping it to anchor to the surface of **lipid droplets** and digest triglycerides in the presence of bile salts. - Colipase is secreted by pancreatic acinar cells along with other pancreatic enzymes into the duodenum. *Salivary glands* - The salivary glands (parotid, submandibular, sublingual) produce saliva containing enzymes like **amylase** and **lingual lipase**. - These glands do not secrete colipase, which is involved in fat digestion in the small intestine, not in the mouth. *Gallbladder* - The gallbladder stores and releases **bile**, which aids in fat emulsification. - Bile does not contain colipase; colipase is produced by the pancreas and works synergistically with bile salts during fat digestion. *Small intestine* - The small intestine is where most nutrient absorption occurs and produces some enzymes (e.g., brush border enzymes like maltase, lactase). - The small intestine does not synthesize colipase; it receives colipase from pancreatic secretions via the pancreatic duct. *Liver* - The liver produces bile, which is stored in the gallbladder and released into the duodenum to emulsify fats. - The liver does not produce colipase; this enzyme is specifically secreted by pancreatic acinar cells.

Question 343: What is correct about the vitamin shown below?

A. γ-carboxylation of glycine residues to clotting factor 2,7, 9 and 10
B. γ-carboxylation of glutathione residues to clotting factor 2,7, 9 and 10
C. γ-carboxylation of aspartic acid residues to clotting factor 2,7, 9 and 10
D. γ-carboxylation of glutamic acid residues to clotting factor 2,7, 9 and 10 (Correct Answer)

Explanation: ***γ-carboxylation of glutamic acid residues to clotting factor 2,7, 9 and 10*** - The image depicts **gamma-glutamyl carboxylase** catalyzing the carboxylation of a glutamic acid residue to form gamma-carboxyglutamate. - This vitamin K-dependent modification is essential for the activation of **clotting factors II, VII, IX, and X**, which are proteins involved in blood coagulation. *γ-carboxylation of glycine residues to clotting factor 2,7, 9 and 10* - **Glycine** residues do not undergo gamma-carboxylation in the context of vitamin K-dependent protein modification. - The specific amino acid residue involved in this carboxylation is **glutamic acid**, not glycine. *γ-carboxylation of glutathione residues to clotting factor 2,7, 9 and 10* - **Glutathione** is a tripeptide (glutamate-cysteine-glycine) and is not a residue within a larger clotting factor protein that undergoes gamma-carboxylation. - Gamma-carboxylation is specific to **glutamic acid residues** within particular proteins, not glutathione. *γ-carboxylation of aspartic acid residues to clotting factor 2,7,9 and 10* - While **aspartic acid** is an acidic amino acid, it is not the specific residue that undergoes vitamin K-dependent gamma-carboxylation. - The reaction specifically targets the **gamma-carbon of glutamic acid residues**.

Question 344: The image shows the world's fastest athlete. Which of the following is used by his muscles for meeting energy demands to create world records in seconds?

A. Phosphofructokinase
B. Glucose 1-phosphate
C. Creatine phosphokinase
D. Phosphocreatine (Correct Answer)

Explanation: ***Phosphocreatine*** - **Phosphocreatine** is a high-energy phosphate compound stored in muscle cells, providing the most rapid source of ATP regeneration for short, intense bursts of activity lasting seconds. - During explosive activities like sprinting (0-10 seconds), the enzyme **creatine kinase** rapidly transfers a phosphate group from phosphocreatine to ADP, re-synthesizing ATP almost instantaneously. - This **phosphagen system** (ATP-PC system) is the primary energy source for world-record sprints, allowing for maximal power output before glycolysis can ramp up. *Phosphofructokinase* - **Phosphofructokinase (PFK)** is a key regulatory enzyme in glycolysis, not an energy substrate itself. - While glycolysis provides ATP for sustained high-intensity exercise (10 seconds to 2 minutes), it is significantly slower than the phosphocreatine system. - PFK catalyzes the rate-limiting step of glycolysis but does not directly provide the immediate energy for explosive movements in seconds. *Glucose 1-phosphate* - **Glucose 1-phosphate** is an intermediate in glycogenolysis (glycogen breakdown) and glycogen synthesis. - It must be converted to glucose 6-phosphate and then proceed through glycolysis to generate ATP, which takes longer than direct phosphocreatine utilization. - This pathway supports energy production but is not the immediate source for explosive power in seconds. *Creatine phosphokinase* - **Creatine phosphokinase (CPK)** or **creatine kinase (CK)** is the enzyme that catalyzes the transfer of phosphate from phosphocreatine to ADP. - While essential for the process, it is the enzyme facilitator, not the energy substrate itself. - The question asks what is "used" for energy, which refers to the substrate (phosphocreatine), not the enzyme.

Community Medicine

1 questions

Q341

The program shown in the image is used for monitoring:

Physiology

2 questions

Q341

Which ion plays a role in the process shown below? (Recent NEET Pattern 2018)

Q342

Which of the following is not a component of the process shown in the image?

NEET-PG 2018 - Physiology NEET-PG Practice Questions and MCQs

Question 341: Which ion plays a role in the process shown below? (Recent NEET Pattern 2018)

A. Potassium
B. Sodium
C. Magnesium
D. Calcium (Correct Answer)

Explanation: ***Calcium*** - **Calcium ions (Ca2+)** are the primary trigger for **exocytosis**, binding to **synaptotagmin** proteins on synaptic vesicles to initiate membrane fusion. - Ca2+ influx activates the **SNARE complex** formation, allowing vesicles to fuse with the plasma membrane and release neurotransmitters or other cellular contents. *Potassium* - **Potassium ions (K+)** are primarily responsible for maintaining the **resting membrane potential** and **repolarization** during action potentials. - While essential for neuronal function, K+ does not directly trigger **vesicle fusion** or exocytosis processes. *Sodium* - **Sodium ions (Na+)** are crucial for **action potential depolarization** and maintaining **electrochemical gradients** across cell membranes. - Na+ influx initiates nerve impulses but does not serve as the direct trigger for **vesicle release** during exocytosis. *Magnesium* - **Magnesium ions (Mg2+)** function as essential **cofactors** for numerous enzymes and play roles in **ATP metabolism** and **protein synthesis**. - Although Mg2+ can modulate some cellular processes, it is not the primary ion responsible for triggering **exocytotic release**.

Question 342: Which of the following is not a component of the process shown in the image?

A. Dynein
B. Kinesin
C. Myosin
D. Actin (Correct Answer)

Explanation: ***Actin*** - The image depicts **microtubule-based transport** involving motor proteins (dynein and kinesin) moving cargo along microtubules. - **Actin filaments** are a completely separate cytoskeletal system and are NOT components of the microtubule-based process shown. - This is the most fundamental distinction - actin vs. microtubule cytoskeletal systems. *Dynein* - **Dynein** is clearly shown in the image, transporting **retrograde cargo** toward the minus end of the microtubule. - It is a key motor protein for minus-end directed movement along microtubules. *Kinesin* - **Kinesin** is depicted in the image, transporting **anterograde cargo** toward the plus end of the microtubule. - It is the primary motor protein for plus-end directed movement along microtubules. *Myosin* - While **myosin** typically works with actin filaments rather than microtubules, it belongs to the same functional category as dynein and kinesin (motor proteins). - Some myosin isoforms can even associate with microtubule-based processes in specific contexts. - **Actin** is the better answer as it represents a completely different cytoskeletal system, whereas myosin is still a motor protein like the others listed.