General Physiology Practice Questions

Q: Activation of protein kinase C causes which of the following?

Phosphorylation of proteins. **Explanation:** The core function of **Protein Kinase C (PKC)** is the **phosphorylation of specific serine and threonine residues** on target proteins. In the Gq-protein signaling pathway, the activation of Phospholipase C (PLC) leads to the hydrolysis of PIP₂ into Inositol trisphosphate (IP₃) and Diacylglycerol (DAG). While IP₃ increases intracellular calcium, **DAG directly activates PKC**. Once activated, PKC acts as a kinase, transferring phosphate groups from ATP to proteins, thereby altering their enzymatic activity, structural conformation, or binding properties. **Analysis of Options:** * **Option A & C:** Adenylyl cyclase activation and increased cAMP levels are characteristic of the **Gs-protein pathway** (Protein Kinase A pathway). PKC is part of the Gq pathway and does not typically stimulate cAMP production; in some tissues, PKC may actually inhibit adenylyl cyclase. * **Option D:** While phosphorylation by PKC *can* eventually modulate ion channels, "increased conduction" is not a universal or primary effect. The most direct and defining biochemical action of any kinase is the covalent modification of proteins via phosphorylation. **High-Yield NEET-PG Pearls:** * **PKC Activators:** Diacylglycerol (DAG), Calcium ($Ca^{2+}$), and Phorbol esters (experimental tools). * **G-Protein Specificity:** Remember the mnemonic **"Qis (Kiss) and Qiq (Kick) till you siq (sick) SQS"**: * **Gq:** H1, α1, V1, M1, M3 (Activates PLC $\rightarrow$ PKC). * **Gs:** β1, β2, D1, H2, V2 (Activates Adenylyl Cyclase $\rightarrow$ PKA). * **Gi:** M2, α2, D2 (Inhibits Adenylyl Cyclase). * **Tumor Promotion:** Phorbol esters act as tumor promoters because they permanently activate PKC, leading to uncontrolled cell phosphorylation and proliferation.

Q: What is true about metastatic calcification?

Calcification starts in mitochondria. **Explanation:** Calcification is the abnormal deposition of calcium salts in tissues. It is broadly classified into two types: **Dystrophic** and **Metastatic**. **Why Option D is Correct:** In **Metastatic Calcification**, the process typically begins in the **mitochondria** of cells. This occurs because mitochondria are the primary sites of energy production and accumulate calcium ions during states of hypercalcemia. When the intracellular calcium concentration exceeds the mitochondrial capacity, precipitation occurs, leading to cell injury and widespread calcification. **Analysis of Incorrect Options:** * **Option A (Serum calcium level is normal):** This is incorrect. Metastatic calcification occurs in **normal tissues** due to **hypercalcemia** (elevated serum calcium). Normal serum calcium levels are characteristic of *Dystrophic* calcification. * **Option B (Occurs in dead or dying tissue):** This describes **Dystrophic calcification**, which occurs in necrotic, degenerated, or damaged tissues despite normal calcium metabolism. * **Option C (Occurs in damaged heart valves):** This is a classic example of **Dystrophic calcification** (e.g., calcific aortic stenosis). Metastatic calcification typically affects healthy tissues with an alkaline internal environment, such as the gastric mucosa, kidneys, and lungs. **High-Yield Clinical Pearls for NEET-PG:** * **Favored Sites:** Metastatic calcification favors organs that excrete acid (Lungs, Stomach, Kidneys) because the resulting **internal alkalinity** predisposes them to calcium salt precipitation. * **Common Causes:** Hyperparathyroidism (most common), Vitamin D toxicity, and bone resorption (multiple myeloma or bony metastasis). * **Dystrophic vs. Metastatic:** Remember, Dystrophic = **D**amaged tissue/Normal Ca²⁺; Metastatic = **M**etabolic derangement/High Ca²⁺.

Q: Which of the following is true about facilitated diffusion?

It requires a carrier protein.. ### Explanation **Facilitated diffusion** is a form of passive transport that allows large or polar molecules (like glucose and amino acids) to cross the cell membrane. Since these molecules are not lipid-soluble, they cannot pass through the phospholipid bilayer directly and require the assistance of specific **integral membrane proteins** known as **carrier proteins**. #### Why Option B is Correct: Facilitated diffusion relies on a **carrier-mediated mechanism**. The substance binds to a specific receptor site on the carrier protein, inducing a conformational change that moves the molecule to the other side of the membrane. This process is characterized by **specificity, competition, and saturation kinetics (Vmax)**. #### Why Other Options are Incorrect: * **Options A & C:** Facilitated diffusion is a **passive process**. It does not require metabolic energy (ATP) because the driving force is the intrinsic kinetic energy of the molecules moving down their gradient. * **Option D:** It occurs **along (down) the electrochemical or concentration gradient** (from high concentration to low concentration). Transport against a gradient is a hallmark of Active Transport. --- ### High-Yield NEET-PG Pearls: * **GLUT Transporters:** The most classic example of facilitated diffusion is the transport of glucose into cells via **GLUT-4** (insulin-dependent) and other GLUT isoforms. * **Saturation (Vmax):** Unlike simple diffusion, which increases linearly with concentration, facilitated diffusion reaches a "Transport Maximum" (Tm) when all carrier proteins are occupied. * **Stereospecificity:** These carriers are highly specific; for example, the carrier for glucose will transport **D-glucose** but not L-glucose. * **Ion Channels vs. Carriers:** While both are passive, ion channels are generally faster and do not undergo the significant conformational changes seen in carrier proteins.

Q: All of the following are examples of primary active transport, except:

Na+/ glucose symporter. ### Explanation **Concept Overview:** Transport across cell membranes is categorized based on energy requirements. **Primary Active Transport** directly utilizes energy from ATP hydrolysis to move solutes against their electrochemical gradient. **Secondary Active Transport** (like the Na+/glucose symporter) does not use ATP directly; instead, it hitches a ride on the energy stored in an electrochemical gradient (usually Na+) created by a primary active transporter. **Why Option C is Correct:** The **Na+/glucose symporter (SGLT)** is a classic example of **Secondary Active Transport**. It moves glucose against its concentration gradient by utilizing the downward sodium gradient established by the Na+/K+ ATPase. Since it does not hydrolyze ATP itself, it is not a primary active transporter. **Analysis of Incorrect Options:** * **Option A (Na+/K+ ATPase):** The most ubiquitous primary active transporter. It pumps 3 Na+ out and 2 K+ in per ATP hydrolyzed, maintaining resting membrane potential. * **Option B (H+/K+ ATPase):** Found in gastric parietal cells, this "proton pump" uses ATP to secrete H+ into the stomach lumen in exchange for K+. It is the target of Proton Pump Inhibitors (PPIs). * **Option D (SERCA):** The **S**arco/Endoplasmic **R**eticulum **C**a2+ **A**TPase is a primary active transporter that pumps calcium from the cytosol into the SR to allow for muscle relaxation. **High-Yield NEET-PG Pearls:** 1. **P-type ATPases:** Na+/K+ ATPase, H+/K+ ATPase, and SERCA are all "P-type" because they are phosphorylated during the transport cycle. 2. **SGLT Locations:** SGLT-1 is primarily in the small intestine, while SGLT-2 is in the proximal convoluted tubule (PCT) of the kidney (target of Gliflozins). 3. **Digitalis/Ouabain:** These drugs inhibit the Na+/K+ ATPase, leading to increased intracellular Na+, which indirectly slows the Na+/Ca2+ exchanger, increasing cardiac contractility.

Q: Who is considered the Father of Physiology?

Claude Bernard. **Explanation:** **Claude Bernard (Option B)** is widely recognized as the "Father of Physiology" due to his pioneering work in establishing the scientific method in medicine. His most significant contribution is the concept of **"Milieu Intérieur"** (internal environment), which posits that the stability of the internal environment is the condition for free and independent life. This concept laid the foundational groundwork for the later development of the theory of **Homeostasis** by Walter Cannon. Bernard was also the first to describe the glycogenic function of the liver and the role of pancreatic juice in digestion. **Analysis of Incorrect Options:** * **Herophilus of Chalcedon (Option A):** Known as the "Father of Anatomy." He was the first to perform systematic human dissections and distinguished between sensory and motor nerves. * **Louis Pasteur (Option C):** Known as the "Father of Microbiology." He developed the germ theory of disease, pasteurization, and vaccines for rabies and anthrax. * **Rudolf Virchow (Option D):** Known as the "Father of Modern Pathology." He is famous for the cell theory principle *"Omnis cellula e cellula"* (every cell originates from another cell). **High-Yield Facts for NEET-PG:** * **Walter Cannon:** Coined the term **"Homeostasis"** and described the "Fight or Flight" response. * **Guyton:** Often associated with modern medical physiology education, but Bernard holds the historical title. * **Milieu Intérieur:** Focuses on the ECF (Extracellular Fluid) acting as a protective buffer for cells against external changes.

Q: Which of the following is an effect of acetylcholine?

Contracts the lower esophageal sphincter (LES). **Explanation:** Acetylcholine (ACh) is the primary neurotransmitter of the parasympathetic nervous system. In the gastrointestinal tract, it generally acts to stimulate motility and secretions. **1. Why Option B is Correct:** The Lower Esophageal Sphincter (LES) is regulated by the autonomic nervous system. Acetylcholine acts on **M3 muscarinic receptors** located on the smooth muscle of the LES, causing **contraction**. This increases the resting tone of the sphincter, preventing gastroesophageal reflux. Conversely, relaxation of the LES is mediated by non-adrenergic, non-cholinergic (NANC) neurons releasing Nitric Oxide (NO) and Vasoactive Intestinal Peptide (VIP). **2. Why the Other Options are Incorrect:** * **Option A:** As stated above, ACh contracts the LES. Relaxation is primarily mediated by NO and VIP during the swallowing reflex. * **Option C:** In most vascular beds, ACh causes **vasodilation** (not constriction) by stimulating the release of Endothelium-Derived Relaxing Factor (EDRF/Nitric Oxide) from endothelial cells. * **Option D:** ACh acts on M3 receptors in the lungs to cause **bronchoconstriction** and increased mucus secretion. Bronchodilation is a sympathetic effect mediated by $\beta_2$ receptors. **Clinical Pearls for NEET-PG:** * **Achalasia Cardia:** Characterized by failure of the LES to relax due to loss of inhibitory (NO/VIP) neurons in the myenteric plexus. * **Atropine:** An anticholinergic drug that decreases LES pressure, potentially worsening GERD. * **SLUDGE Syndrome:** A mnemonic for cholinergic excess (Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis).

Question 1

Activation of protein kinase C causes which of the following?

Accepted Answer

Phosphorylation of proteins

Answer

Increase in adenylyl cyclase activity

Answer

Increased cyclic AMP (cAMP) levels

Answer

Increased ion channel conduction

Question 2

Which is the most potent oxygen free radical?

Accepted Answer

Hydroxyl radical

Answer

Hydrogen peroxide

Answer

Superoxide radical

Answer

Both Hydroxyl radical and Hydrogen peroxide

Question 3

What is true about metastatic calcification?

Accepted Answer

Calcification starts in mitochondria

Answer

Serum calcium level is normal

Answer

Occurs in dead or dying tissue

Answer

Occurs in damaged heart valves

Question 4

Action potential across the cell membrane is maintained by?

Accepted Answer

Na+ K+ pump

Answer

cAMP

Answer

Ca++

Answer

Phosphodiesterase

Question 5

Which of the following is true about facilitated diffusion?

Accepted Answer

It requires a carrier protein.

Answer

It is an active process.

Answer

It requires ATP.

Answer

It occurs against the concentration gradient.

Question 6

All of the following are examples of primary active transport, except:

Accepted Answer

Na+/ glucose symporter

Answer

The Na+/K+ ATPase in the red cell membrane

Answer

The H+/K+ ATPase in the parietal cell of stomach

Answer

SERCA in the skeletal muscle

Question 7

Acclimatization does NOT include which of the following?

Accepted Answer

Decreased concentration of 2,3-DPG in RBC

Answer

Hyperventilation

Answer

Increased erythropoiesis

Answer

Kidneys excrete more alkali

Question 8

Who is considered the Father of Physiology?

Accepted Answer

Claude Bernard

Answer

Herophilus of Chalcedon

Answer

Louis Pasteur

Answer

Robin Virchow

Question 9

What is the most serious complication of a prolonged sitting position?

Accepted Answer

Venous air embolism

Answer

Dysrhythmias

Answer

Hypotension

Answer

Nerve palsies

Question 10

Which of the following is an effect of acetylcholine?

Accepted Answer

Contracts the lower esophageal sphincter (LES)

Answer

Relaxes the lower esophageal sphincter (LES)

Answer

Constricts the blood vessels

Answer

Relaxes the bronchial muscles

General Physiology — MCQs

General Physiology — MCQs

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