Problem 168 - Objective Biology for NEET

Question

Assertion: Renal tubules use to maintain ionic balance and \(\mathrm{pH}\) of body fluids. Reason: \(\mathrm{H}^{+}, \mathrm{K}^{+}\) and \(\mathrm{NH}_{3}\) could be secreted into filtrate by renal tubules.

Step-by-Step Solution

Answer

The provided assertion is correct. Renal tubules do help maintain ionic balance and pH of body fluids. They do this by secreting ions such as \( H^{+} \), \( K^{+} \) and \( NH_{3} \) into the filtrate.

Step 1: Understand the Role of Renal Tubules

Renal tubules, a part of the nephron in kidneys, have a crucial function in the urinary system. They help filter blood, remove waste products, and maintain the electrolyte balance and pH levels in the body fluids.

Step 2: Understand the Secretion of Ions into Filtrate

Renal tubules perform the task of secreting ions such as \( H^{+} \) (Hydrogen ions) and \( K^{+} \) (Potassium ions) into the filtrate. The hydrogen ions help to maintain pH balance, whereas the potassium ions help maintain the ionic balance.

Step 3: Understand the Role of Ammonia (\( NH_{3} \))

Ammonia (\( NH_{3} \)) is also secreted into the filtrate by renal tubules. This secretion aids in the maintenance of acid-base balance, as ammonia combines with hydrogen ions to form ammonium (\( NH_{4}^{+} \)), helping to eliminate excess hydrogen ions from the body, hence regulating the pH.

Key Concepts

Ionic Balance

In the human body, **ionic balance** is critical for maintaining healthy cellular function.
The renal tubules of the nephron play a key role in this balance by regulating levels of ions like sodium ( abla^{+} abla abla Na abla^{+} abla abla abla ), potassium ( abla^{+} abla abla K^{+} abla abla abla abla ), and chloride ( abla^{+} abla abla Cl^{-} abla abla abla abla ). These ions must be precisely controlled to ensure *osmotic balance* and proper *nerve and muscle function*.
**Key Functions of Ionic Balance:**

• Regulation of blood pressure
• Maintaining nerve impulses and muscle contractions
• Balancing fluid distribution across cells

The kidneys adjust the ionic composition of urine through processes such as reabsorption and secretion in the renal tubules. This selective handling of ions is essential for homeostasis, ensuring that neuron activity and muscle contractions proceed smoothly.

pH Balance

Maintaining a stable internal environment is vital for good health, and **pH balance** is a core component of this. The kidneys, by the action of the renal tubules, contribute significantly to this balance.
They do so by managing the concentration of hydrogen ions ( abla^{+} abla abla H abla^{+} abla abla abla ), which directly influences the pH level of blood.
**Mechanisms to Regulate pH:**

• Secretion of hydrogen ions into the urine, reducing acidity in blood
• Reabsorption of bicarbonate ( abla^{+} abla abla HCO_3^{-} abla abla abla abla ), neutralizing blood acidity

Through these processes, the kidneys can effectively maintain blood pH within the tightly controlled range of 7.35 to 7.45, an essential condition for enzyme function and metabolic reactions.

Secretion of Ions

The **secretion of ions** is a vital function of the renal tubules, ensuring the balance of electrolytes and acid-base homeostasis. The nephron's ability to secrete ions such as hydrogen ( abla^{+} abla abla H^{+} abla abla abla abla ) and potassium ( abla^{+} abla abla K^{+} abla abla abla abla ) is pivotal to its operation.
**Steps in Ion Secretion:**

• Transport of ions from blood to renal tubule cells
• Movement of ions into the filtrate within the tubules
• Regulation based on the body’s ionic and pH state

This mechanism prepares waste for excretion while fine-tuning the body's ion concentration.

Ammonia Secretion

**Ammonia secretion** is a critical mechanism for excreting excess nitrogen and maintaining acid-base balance. The renal tubules convert glutamine, an amino acid, into ammonia ( abla^{+} abla abla NH_{3} abla abla abla abla ), which freely diffuses into the renal tubular fluid.
**Role of Ammonia in pH Regulation:**

• Ammonia combines with hydrogen ions to create ammonium ( abla^{+} abla abla NH_{4}^{+} abla abla abla abla )
• This process assists in trapping hydrogen ions, thereby reducing acidity

By binding with hydrogen ions, ammonia helps excrete what's necessary and stabilize pH levels, ensuring metabolic processes function correctly.

Nephron Function

The **nephron function** is the cornerstone of kidney operation, each human kidney contains roughly a million nephrons. Their role spans beyond just filtering blood.
They ensure **filtrate processing** to form urine correctly.
**Key Functions of the Nephron:**

• Filtering waste products from the blood
• Reabsorbing vital nutrients, ions, and water
• Secreting unwanted substances into the filtrate

Through these processes, nephrons maintain overall ionic balance, ensure optimal blood pH, and remove waste products, pushing homeostasis forward with each heartbeat.