Urine Formation in the Nephron Practice Questions
20 free Urine Formation in the Nephron practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following is the first step in urine formation?
- A Tubular reabsorption
- B Concentration in the collecting duct
- C Tubular secretion
- D Filtration at the glomerulus
Correct answer: Filtration at the glomerulus
Urine formation begins with filtration at the glomerulus, where blood is filtered under pressure. About 125 mL of filtrate is produced per minute, totalling roughly 180 litres per day.
The glomerular filtration rate (GFR) in a healthy individual is approximately:
- A 125 mL/minute
- B 180 mL/minute
- C 125 mL/day
- D 500 mL/minute
Correct answer: 125 mL/minute
The GFR is the amount of filtrate formed by the kidneys per minute. In a healthy individual, it is approximately 125 mL/min, which totals about 180 liters per day.
Glomerular filtration is considered a process of 'ultrafiltration' because:
- A It requires high energy (ATP) to filter solutes
- B Plasma proteins are retained; all small solutes pass freely
- C Only waste products such as urea and creatinine are filtered out
- D It occurs exclusively in juxtamedullary nephrons of the medulla
Correct answer: Plasma proteins are retained; all small solutes pass freely
The filtration membrane has extremely fine pores (filtration slits) through which water, ions, glucose, urea, and other small solutes pass freely, while large plasma proteins are retained. The resulting filtrate is essentially protein-free plasma.
Which specialized cells of Bowman's capsule are arranged in an intricate manner to leave some minute spaces called filtration slits?
- A Endothelial cells
- B Glomerular podocytes
- C Mesangial cells
- D Tubular epithelial cells
Correct answer: Glomerular podocytes
Podocytes are the specialised visceral epithelial cells of Bowman's capsule. Their interdigitating foot-like processes (pedicels) create the slit pores through which plasma is filtered into the nephron lumen.
The GFR is regulated by a built-in mechanism involving the Juxtaglomerular Apparatus (JGA). JGA is formed by cellular modifications in which two structures?
- A PCT and Afferent arteriole
- B DCT and Afferent arteriole
- C Loop of Henle and Efferent arteriole
- D Collecting duct and Glomerulus
Correct answer: DCT and Afferent arteriole
The JGA is a sensitive region formed by the contact between the distal convoluted tubule (DCT) and the afferent arteriole. A fall in GFR activates the JG cells to release renin.
What percentage of the filtrate is reabsorbed by the renal tubules in a healthy human?
- A 50%
- B 75%
- C 99%
- D 10%
Correct answer: 99%
While 180 liters of filtrate are produced daily, only about 1.5 liters of urine are excreted. This indicates that nearly 99 percent of the filtrate is reabsorbed by the renal tubules.
Which of the following substances are reabsorbed from the filtrate by active transport?
- A Nitrogenous wastes like urea and creatinine
- B Water and lipid-soluble substances
- C Glucose and amino acids
- D Chloride ions and bicarbonate
Correct answer: Glucose and amino acids
Substances like glucose, amino acids, and Na+ are reabsorbed actively to ensure maximum recovery of nutrients. Nitrogenous wastes, on the other hand, are reabsorbed by passive transport.
In which part of the nephron does maximum reabsorption (70-80%) of electrolytes and water occur?
- A Proximal Convoluted Tubule (PCT)
- B Loop of Henle (descending limb)
- C Distal Convoluted Tubule (DCT)
- D Collecting duct (medullary portion)
Correct answer: Proximal Convoluted Tubule (PCT)
The PCT is lined with simple cuboidal brush border epithelium which increases the surface area for reabsorption. Nearly all essential nutrients and 70-80 percent of electrolytes and water are reabsorbed here.
Tubular secretion helps in the maintenance of ionic and acid-base balance of body fluids by secreting which ions into the filtrate?
- A Na+ and Cl-
- B H+, K+ and ammonia
- C Glucose and amino acids
- D Ca2+ and Mg2+
Correct answer: H+, K+ and ammonia
During urine formation, tubular cells secrete substances like H+, K+, and ammonia into the filtrate. This is a crucial step in maintaining the pH and ionic balance of the blood.
Which segment of the nephron is specialized for the 'minimum' reabsorption and plays a significant role in maintaining high osmolarity of medullary interstitial fluid?
- A Proximal convoluted tubule
- B Henle's loop
- C Distal convoluted tubule
- D Bowman's capsule
Correct answer: Henle's loop
The Henle's loop has minimum reabsorption in its ascending limb. Its primary function is to maintain the high osmolarity of the medullary interstitium, which is essential for water conservation.
The descending limb of the loop of Henle is:
- A Impermeable to water but freely permeable to electrolytes
- B Permeable to water but almost impermeable to electrolytes
- C Impermeable to both water and electrolytes completely
- D Freely permeable to both water and electrolytes
Correct answer: Permeable to water but almost impermeable to electrolytes
The descending limb allows water to pass out into the medullary fluid due to high osmotic pressure. Because it is impermeable to salts, the filtrate becomes concentrated as it moves down.
In the ascending limb of the loop of Henle, the filtrate becomes progressively:
- A Concentrated
- B Diluted
- C Isotonic
- D Acidic
Correct answer: Diluted
The ascending limb is impermeable to water but allows the transport of electrolytes actively or passively. As electrolytes leave the limb and enter the medullary fluid, the filtrate becomes diluted.
Conditional reabsorption of Na+ and water takes place in which part of the nephron?
- A PCT
- B Descending limb of Henle's loop
- C Distal Convoluted Tubule (DCT)
- D Ascending limb of Henle's loop
Correct answer: Distal Convoluted Tubule (DCT)
Reabsorption in the DCT is 'conditional' because it depends on hormonal regulation (like ADH and Aldosterone) to meet the body's specific needs for salt and water balance.
Which of the following is NOT secreted into the filtrate in the PCT?
- A Hydrogen ions
- B Ammonia
- C Potassium ions
- D Glucose (a reabsorbed nutrient)
Correct answer: Glucose (a reabsorbed nutrient)
Glucose is a valuable nutrient that is entirely reabsorbed in the PCT under normal conditions. H+, K+, and ammonia are secreted into the PCT to maintain pH balance.
Large amounts of water could be reabsorbed from this region to produce concentrated urine:
- A PCT
- B Ascending limb
- C Collecting duct
- D Bowman's capsule
Correct answer: Collecting duct
The collecting duct extends from the cortex to the inner parts of the medulla. It allows for the passage of large amounts of water, concentrating the urine based on the body's hydration state.
Reabsorption of water in the renal tubules occurs via:
- A Active transport against a concentration gradient
- B Osmosis following the osmotic gradient
- C Facilitated diffusion via carrier proteins
- D Phagocytosis by tubular cells
Correct answer: Osmosis following the osmotic gradient
Water reabsorption is a passive process that occurs via osmosis. It follows the osmotic gradient created by the active reabsorption of electrolytes like sodium.
The net filtration pressure (NFP) that causes ultrafiltration in the glomerulus is primarily determined by:
- A Glomerular capillary blood pressure
- B Atmospheric pressure acting on the kidney
- C Hydrostatic pressure within the renal vein
- D Intra-abdominal pressure from surrounding organs
Correct answer: Glomerular capillary blood pressure
Glomerular filtration is driven by the glomerular capillary blood pressure. This pressure is opposed by the colloidal osmotic pressure of plasma proteins and the hydrostatic pressure of the filtrate in the capsule.
Small amounts of urea are allowed to enter the thin segment of the ascending limb of Henle's loop to:
- A Excrete urea from the body at a faster rate
- B Increase the pH and alkalinity of urine
- C Maintain the osmolarity of the medullary interstitium
- D Prevent precipitation of calcium and kidney stone formation
Correct answer: Maintain the osmolarity of the medullary interstitium
A small amount of urea diffuses from the collecting duct into the medullary interstitium and then into the ascending limb. This cycling helps maintain the high osmotic gradient in the medulla.
If the brush border of the PCT is removed, what will be the effect on urine formation?
- A Complete cessation of urine formation in the kidney
- B More dilute urine with nutrients like glucose
- C More concentrated urine due to increased water reabsorption
- D Urine will contain large plasma proteins and albumin
Correct answer: More dilute urine with nutrients like glucose
The microvilli of the brush border provide the surface area for reabsorption. Without it, reabsorption of water and vital solutes like glucose would fail, leading to nutrient loss and high urine volume.
Which part of the nephron allows for the selective secretion of hydrogen and potassium ions and NH3 to maintain pH and sodium-potassium balance in blood?
- A Malpighian corpuscle
- B Henle's loop
- C Distal Convoluted Tubule (DCT)
- D Efferent arteriole
Correct answer: Distal Convoluted Tubule (DCT)
The Distal Convoluted Tubule (DCT) is capable of selective secretion of H+ and K+ ions and NH3. This maintains the ionic balance and pH of the blood before the filtrate enters the collecting duct.