General Physiology Practice Questions

Q: Which ion is least common in End-of-Functional-Test (EOF)?

Potassium (K+). **Explanation:** The question refers to the composition of **Extracellular Fluid (ECF)**. In medical entrance exams, "EOF" is often a typographical variant or specific nomenclature used for ECF in certain contexts. The fundamental concept being tested is the distribution of electrolytes across the cell membrane. **1. Why Potassium (K+) is the Correct Answer:** Potassium is the **primary intracellular cation**. While it is highly concentrated inside the cell (~140 mEq/L), its concentration in the extracellular fluid is remarkably low, typically ranging between **3.5 to 5.0 mEq/L**. Among the options provided, Potassium has the lowest numerical concentration in the ECF, making it the "least common" ion in this compartment. **2. Analysis of Incorrect Options:** * **Sodium (Na+):** This is the **primary extracellular cation**. Its concentration in the ECF is high (~135–145 mEq/L), maintaining osmotic balance. * **Chloride (Cl-):** This is the **primary extracellular anion**. Its concentration is significant (~98–108 mEq/L) to balance the positive charge of Sodium. * **Bicarbonate (HCO3-):** While lower than Sodium or Chloride, its ECF concentration (~22–28 mEq/L) is still significantly higher than that of Potassium. **High-Yield Clinical Pearls for NEET-PG:** * **Gibbs-Donnan Effect:** Explains why plasma has slightly more proteins and different ion concentrations compared to interstitial fluid. * **Na+-K+ ATPase Pump:** The active transporter responsible for maintaining these steep concentration gradients (3 Na+ out, 2 K+ in). * **Hypokalemia/Hyperkalemia:** Because ECF potassium is so low, even small absolute changes (e.g., a 2 mEq/L shift) can lead to life-threatening cardiac arrhythmias. * **Magnesium:** The second most abundant intracellular cation (after Potassium).

Q: Cell volume and shape are maintained by which of the following?

Gibbs-Donnan effect. **Explanation:** The **Gibbs-Donnan effect** (or Donnan Equilibrium) describes the behavior of charged particles near a semi-permeable membrane when one of the ions is "non-diffusible" (e.g., intracellular proteins). Because these negatively charged proteins cannot leave the cell, they influence the distribution of diffusible ions (like $Na^+$, $K^+$, and $Cl^-$). This creates an osmotic gradient that draws water into the cell. To counteract this and maintain constant **cell volume and shape**, the cell utilizes the $Na^+\text{-}K^+$ ATPase pump to actively extrude sodium. Without the balance provided by the Gibbs-Donnan effect and active transport, cells would swell and rupture. **Analysis of Options:** * **A. Goldman effect:** This refers to the **Goldman-Hodgkin-Katz (GHK) equation**, which is used to calculate the resting membrane potential based on the permeability and concentration gradients of multiple ions. It relates to electrical excitability, not volume maintenance. * **C. Singer’s effect:** This is a distractor. S.J. Singer is famous for the **Singer-Nicolson Fluid Mosaic Model**, which describes the structure of the cell membrane (phospholipid bilayer with embedded proteins), but there is no specific "Singer’s effect" related to cell volume. **High-Yield Clinical Pearls for NEET-PG:** * **Gibbs-Donnan Equation:** At equilibrium, the product of diffusible ions on one side equals the product of diffusible ions on the other ($[K^+]_i \times [Cl^-]_i = [K^+]_o \times [Cl^-]_o$). * **Oncotic Pressure:** The Gibbs-Donnan effect is responsible for about 6-7 mmHg of the total plasma oncotic pressure due to the presence of albumin. * **Regulatory Volume Increase/Decrease (RVI/RVD):** While Gibbs-Donnan sets the baseline, acute volume changes are managed by $Na^+\text{-}H^+$ exchangers and $K^+\text{-}Cl^-$ cotransporters.

Q: What is the osmotic pressure of 1 mole of an ideal solute in relation to pure water?

22.4 atm. **Explanation:** The osmotic pressure of a solution is determined by the number of particles (solute) present in a given volume, a principle governed by **van't Hoff’s Law**. This law states that osmotic pressure ($\pi$) is analogous to the Ideal Gas Law ($PV = nRT$). **Why Option B is Correct:** According to the laws of thermodynamics and physical chemistry, **1 mole of an ideal, non-ionizable solute** dissolved in 1 liter of water at standard temperature and pressure (0°C or 273K) exerts an osmotic pressure of **22.4 atmospheres (atm)**. This value is a constant derived from the formula $\pi = iCRT$, where: * $i$ = Van't Hoff factor (1 for ideal solute) * $C$ = Concentration (1 mol/L) * $R$ = Gas constant (0.0821 L·atm/mol·K) * $T$ = Temperature (273 K) Calculation: $1 \times 1 \times 0.0821 \times 273 \approx 22.4 \text{ atm}$. **Why Incorrect Options are Wrong:** * **Options A, C, and D:** These values (6.5, 4, and 2 atm) do not correspond to the standard physical constant for a 1-molar solution. They are arbitrary numbers that do not satisfy the $PV=nRT$ derivation for a molar concentration at standard temperature. **High-Yield Clinical Pearls for NEET-PG:** * **Osmolarity vs. Osmolality:** In clinical medicine, we usually measure *osmolality* (mOsm/kg of water) because it is independent of temperature. * **Plasma Osmotic Pressure:** Normal plasma osmolality is ~285–295 mOsm/L. * **Oncotic Pressure:** Also known as colloid osmotic pressure, it is specifically exerted by proteins (mainly albumin) and is approximately **25–28 mmHg** (not atm), crucial for preventing edema. * **Conversion:** 1 mOsm/L of a solute exerts an osmotic pressure of approximately **19.3 mmHg**.

Q: True about moderate aerobic exercise?

Increased core temperature. **Explanation:** During moderate aerobic exercise, the body undergoes several physiological adaptations to meet increased metabolic demands. **Why Option D is Correct:** The primary byproduct of muscular contraction is **heat**. During exercise, metabolic rate increases significantly, leading to thermogenesis. While the body employs cooling mechanisms (like sweating and peripheral vasodilation), the rate of heat production initially exceeds the rate of dissipation, resulting in a **rise in core body temperature**. This is a hallmark of the physiological response to physical exertion. **Why Other Options are Incorrect:** * **Option A (Decrease in blood pH):** In **moderate** aerobic exercise, the body remains in a steady state where oxygen delivery meets demand. Significant lactic acid accumulation (which causes a drop in pH) typically occurs only during **strenuous/anaerobic** exercise after crossing the lactate threshold. * **Option B & C (Changes in PaO2 and PaCO2):** In a healthy individual performing moderate exercise, alveolar ventilation increases in precise proportion to the increase in oxygen consumption ($VO_2$) and carbon dioxide production ($VCO_2$). Therefore, arterial gas pressures (**PaO2 and PaCO2**) remain remarkably **constant**. A decrease in PaCO2 (hypocapnia) only occurs during heavy exercise due to compensatory hyperventilation triggered by lactic acidosis. **High-Yield Pearls for NEET-PG:** 1. **Arterial vs. Venous:** While arterial $PO_2$ and $PCO_2$ remain constant during moderate exercise, **venous** $PO_2$ decreases and **venous** $PCO_2$ increases. 2. **Hemoglobin Dissociation Curve:** Exercise shifts the curve to the **right** (due to increased $H^+$, $CO_2$, and temperature), facilitating oxygen unloading at the tissues. 3. **Ventilation:** The initial rise in ventilation at the start of exercise is **neurogenic** (proprioceptors and motor cortex), not chemical.

Q: High anion gap metabolic acidosis is seen in which of the following conditions?

Diabetes mellitus. **Explanation:** Metabolic acidosis is categorized based on the **Anion Gap (AG)**, calculated as $[Na^+] - ([Cl^-] + [HCO_3^-])$. A High Anion Gap Metabolic Acidosis (HAGMA) occurs when fixed acids (unmeasured anions) are added to the blood, consuming bicarbonate. **Why Diabetes Mellitus is Correct:** In uncontrolled Diabetes Mellitus (specifically Diabetic Ketoacidosis), a lack of insulin leads to the breakdown of fatty acids into **ketoacids** ($\beta$-hydroxybutyrate and acetoacetate). These ketoacids dissociate, releasing $H^+$ ions that neutralize $HCO_3^-$, while the remaining ketoacid anions increase the unmeasured anion pool, resulting in **HAGMA**. **Analysis of Incorrect Options:** * **Diarrhea:** Causes direct loss of bicarbonate from the lower GI tract. To maintain electroneutrality, the body retains chloride, leading to **Normal Anion Gap Metabolic Acidosis (NAGMA)** or hyperchloremic acidosis. * **Adrenal Insufficiency (Addison’s Disease):** Deficiency of aldosterone leads to decreased $H^+$ secretion in the distal tubule and hyperkalemia (which inhibits ammonia production). This results in **NAGMA**. * **Renal Tubular Acidosis (RTA):** Whether due to failure to reabsorb $HCO_3^-$ (Type 2) or failure to secrete $H^+$ (Type 1), RTA is a classic cause of **NAGMA**. **NEET-PG High-Yield Pearls:** * **Mnemonic for HAGMA:** **MUDPILES** (Methanol, Uremia, DKA, Paraldehyde/Propylene glycol, INH/Iron, Lactic acidosis, Ethylene glycol, Salicylates). * **Mnemonic for NAGMA:** **HARDUP** (Hyperalimentation, Acetazolamide, Renal tubular acidosis, Diarrhea, Ureteroenteric fistula, Pancreatic fistula). * **Goldman’s Formula:** Used to calculate the expected $pCO_2$ compensation in metabolic acidosis: $pCO_2 = 1.5 \times [HCO_3^-] + 8 \pm 2$.

Q: What is the function of the Golgi apparatus?

Maturation of protein. The Golgi apparatus functions as the "Post Office" or "Quality Control Center" of the cell. Its primary role is the post-translational modification, sorting, and packaging of proteins received from the Endoplasmic Reticulum (ER). ### **Explanation of Options** * **B. Maturation of protein (Correct):** After proteins are synthesized in the ribosomes, they are transported to the Golgi apparatus. Here, they undergo "maturation" through processes like **glycosylation** (adding sugar moieties), **sulfation**, and **phosphorylation**. This ensures the protein reaches its functional 3D conformation and is correctly tagged for its final destination (e.g., secretion, lysosomes, or plasma membrane). * **A. Synthesis of protein:** This is the function of **Ribosomes** (specifically those on the Rough ER). The Golgi modifies proteins but does not create the polypeptide chains. * **C. Degradation of protein:** This is primarily the function of **Lysosomes** (via acid hydrolases) and **Proteasomes** (via the ubiquitin-proteasome pathway). * **D. Sequencing of protein:** Protein sequencing (the order of amino acids) is determined by the **mRNA template** during translation at the ribosome level, based on the genetic code from DNA. ### **High-Yield Facts for NEET-PG** * **I-Cell Disease:** A clinical correlation where a deficiency in the enzyme *phosphotransferase* prevents the tagging of proteins with **Mannose-6-Phosphate** in the Golgi. This leads to proteins being secreted extracellularly rather than going to lysosomes. * **Polarity:** The Golgi has a **Cis-face** (entry point near the ER) and a **Trans-face** (exit point where vesicles bud off). * **Vesicle Transport:** **COPII** coats vesicles moving from ER to Golgi (Anterograde), while **COPI** coats vesicles moving from Golgi back to ER (Retrograde).

Question 1

Which ion is least common in End-of-Functional-Test (EOF)?

Accepted Answer

Potassium (K+)

Answer

Sodium (Na+)

Answer

Chloride (Cl-)

Answer

Bicarbonate (HCO3-)

Question 2

All are factors determining diffusion across a membrane except?

Accepted Answer

Particle size

Answer

Temperature

Answer

Membrane pore size

Answer

Concentration gradient

Question 3

Cell volume and shape are maintained by which of the following?

Accepted Answer

Gibbs-Donnan effect

Answer

Goldman effect

Answer

Singer's effect

Answer

None of the above

Question 4

What is the osmotic pressure of 1 mole of an ideal solute in relation to pure water?

Accepted Answer

22.4 atm

Answer

6.5 atm

Answer

4 atm

Answer

2 atm

Question 5

Which of the following will not cause a low lung diffusing capacity (DL)?

Accepted Answer

Increased diffusion distance

Answer

Decreased capillary blood volume

Answer

Decreased surface area

Answer

Decreased cardiac output

Question 6

Synaptic potentials can be recorded by which of the following methods?

Accepted Answer

Microelectrode

Answer

Patch clamp technique

Answer

Voltage clamp technique

Answer

Electroencephalography (EEG)

Question 7

True about moderate aerobic exercise?

Accepted Answer

Increased core temperature

Answer

Decrease in blood pH

Answer

Increase in PaO2

Answer

Decrease in PaCO2

Question 8

A man weighing 70 kg has a hematocrit of 45%. What is his approximate plasma volume?

Accepted Answer

3080 mL

Answer

2310 mL

Answer

2695 mL

Answer

2890 mL

Question 9

High anion gap metabolic acidosis is seen in which of the following conditions?

Accepted Answer

Diabetes mellitus

Answer

Diarrhea

Answer

Adrenal insufficiency

Answer

Renal tubular acidosis

Question 10

What is the function of the Golgi apparatus?

Accepted Answer

Maturation of protein

Answer

Synthesis of protein

Answer

Degradation of protein

Answer

Sequencing of protein

General Physiology — MCQs

General Physiology — MCQs

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