Chapter 16: Excretory Products and their Elimination Application Questions | biology Class 11 CBSE

ByteNotes

Chapter 16: Excretory Products and their Elimination Application Questions | biology Class 11 CBSE | ByteNotes.in

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 1

Applied Concept

A patient's blood test shows a very low GFR. With reference to the JGA, explain the cascade of events that the body initiates to restore normal GFR.

A low GFR is detected by the JG (juxtaglomerular) cells located at the junction of the DCT and afferent arteriole, which form the JGA.
JG cells respond by releasing renin, which converts angiotensinogen in the blood to angiotensin I, and subsequently to angiotensin II.
Angiotensin II acts as a potent vasoconstrictor, increasing glomerular blood pressure to restore GFR; it also triggers aldosterone release from the adrenal cortex.
Aldosterone promotes Na+ and water reabsorption from the distal tubule, increasing blood volume and pressure, further supporting GFR restoration through the renin-angiotensin mechanism.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

A person living in a hot desert environment produces very little urine. With reference to ADH and the collecting duct, explain the physiological basis of this observation.

In a hot desert environment, the person loses significant body water through sweating, reducing blood and body fluid volume and increasing ionic concentration.
Osmoreceptors detect this change and stimulate the hypothalamus to release ADH (antidiuretic hormone/vasopressin) from the neurohypophysis.
ADH increases the permeability of the DCT and collecting duct to water, promoting maximal water reabsorption from the filtrate back into the blood.
The result is the production of a small volume of highly concentrated urine, conserving the body's water supply — a vital adaptation in water-scarce conditions.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 3

Applied Concept

A fish taken from a freshwater aquarium and placed in seawater begins to lose water and dehydrates. With reference to the type of nitrogenous waste it excretes, explain why it faces an additional challenge in the new environment.

Bony freshwater fishes are ammonotelic and excrete ammonia by diffusion through gill surfaces and body surfaces, which requires a large and continuous supply of water.
In seawater, the fish faces osmotic water loss (water moves out of the body to the hypertonic surroundings), severely limiting available water.
This reduction in water availability makes ammonia excretion far more difficult, as ammonia requires abundant water for dilution to prevent toxic accumulation.
Marine fish are therefore primarily ureotelic (excreting less-toxic urea requiring less water), illustrating the challenge of adapting ammonotelism to saline, water-scarce environments.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 4

Applied Concept

A doctor finds glucose in a patient's urine during a routine check-up. The patient does not have diabetes. What renal explanation could account for this finding?

In a healthy kidney, glucose in the glomerular filtrate is completely reabsorbed by the PCT through active transport, so no glucose should appear in normal urine.
If glucose appears in the urine (glycosuria) without diabetes mellitus, it may indicate damage or dysfunction of the PCT, impairing its ability to actively reabsorb filtered glucose.
This condition, called renal glycosuria, occurs when the renal threshold for glucose is exceeded or when PCT transport proteins are deficient or damaged.
Urine analysis revealing glycosuria thus serves as an important clinical diagnostic indicator of both metabolic and renal tubular disorders.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 5

Applied Concept

With reference to the counter current mechanism, explain why a person severely dehydrated can still produce urine, albeit in very small quantities.

Even in severe dehydration, the kidneys retain the medullary osmotic gradient (300 to 1200 mOsmol/L) established by the counter current mechanism of Henle's loop and vasa recta.
High ADH levels in dehydration maximize water reabsorption from the DCT and collecting duct, driven by the steep osmotic gradient of the medullary interstitium.
The collecting duct reabsorbs the maximum possible water, producing a very small volume of extremely concentrated urine rather than stopping urine production entirely.
This ensures that even while conserving nearly all available water, the body continues to eliminate urea and other toxic nitrogenous wastes, maintaining survival.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 6

Applied Concept

A patient with chronic kidney failure is advised to undergo hemodialysis twice a week. Explain the principle behind hemodialysis and why it cannot fully replace a natural kidney.

Hemodialysis works on the principle of diffusion across a semi-permeable membrane; blood drawn from the patient is passed through a dialysing unit containing a coiled cellophane tube surrounded by dialysing fluid identical to plasma but lacking nitrogenous wastes.
Urea and other nitrogenous wastes diffuse from blood across the porous cellophane membrane into the dialysing fluid down the concentration gradient, cleaning the blood.
Hemodialysis is limited because it only removes accumulated wastes; it cannot replicate the kidney's continuous, dynamic hormonal regulation of fluid balance, electrolytes, and acid-base status.
Kidney transplantation from a close relative (to minimize immune rejection) is the definitive treatment, as a transplanted kidney restores full physiological function that dialysis can only partially and intermittently replicate.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 7

Applied Concept

Birds and reptiles excrete uric acid as nitrogenous waste. With reference to the advantages of uric acid, explain how this helps birds survive long migratory flights.

Uric acid is the least toxic of the major nitrogenous wastes and is nearly insoluble; it can be excreted as a semi-solid paste or pellet with minimal water loss, unlike ammonia or urea.
During long migratory flights, birds are unable to drink water regularly and must minimize water expenditure; uricotelic excretion allows them to dispose of metabolic nitrogen waste without significant water loss.
The low water requirement for uric acid excretion also means that birds carry less water weight during flight, aiding efficiency and endurance.
Additionally, uric acid's low toxicity allows its temporary storage in the body without harm, providing metabolic flexibility during extended periods without excretion opportunities.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 8

Applied Concept

A student observes that earthworms come out of the soil after heavy rain. With reference to their excretory structures, explain what happens to nitrogenous waste excretion in waterlogged soil.

Earthworms use nephridia as their excretory structures, which help remove nitrogenous wastes and maintain fluid and ionic balance.
Nephridia function by releasing nitrogenous waste into the surrounding soil moisture; in normal moist soil, this process operates efficiently.
In heavily waterlogged soil, the concentration gradient for diffusion of wastes may be disrupted, and reduced oxygen availability (anaerobic conditions) can impair metabolic processes.
Earthworms surface during heavy rain primarily to avoid drowning and to re-establish efficient excretion in a less saturated environment, where their nephridia can function optimally.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 9

Applied Concept

A patient is prescribed a diuretic drug that inhibits ADH action. Predict the changes in urine volume and concentration, and the possible consequences for the patient.

ADH normally promotes water reabsorption from the DCT and collecting duct; if ADH action is inhibited, these segments become impermeable to water, and less water is reabsorbed.
As a result, large volumes of dilute urine would be produced — a condition called diuresis; the patient's urine output would increase significantly.
This increased water loss through urine could lead to dehydration, reduced blood volume, decreased blood pressure, and elevated plasma osmolarity.
The clinical use of diuretics is intentional for conditions like hypertension and edema (excess fluid retention), but excessive diuresis without monitoring can cause serious electrolyte imbalances and dehydration.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 10

Applied Concept

With reference to the structure of the Bowman's capsule and its cells, explain how the kidney ensures that blood proteins are not lost in urine during filtration.

Glomerular filtration involves blood passing through three layers: the endothelium of glomerular capillaries (with pores), the basement membrane, and the epithelium of Bowman's capsule.
The epithelial cells of Bowman's capsule, called podocytes, are arranged intricately to form minute spaces called filtration slits or slit pores.
These filtration slits are sized to allow water and small solutes through while physically excluding large molecules like plasma proteins (e.g., albumin) due to their large molecular size.
The basement membrane also acts as a molecular sieve and carries a negative charge that repels negatively charged proteins; this combined multi-layer barrier ensures the filtrate is essentially protein-free, preserving plasma colloid osmotic pressure.

ByteNotes

Premium Access

Unlock all Application Questions

You are viewing 10 free application questions from this chapter. Upgrade to Premium to unlock the remaining 12 questions.

Upgrade to Premium12 questions locked

Chapter sections

Chapter 16: Excretory Products and their Elimination | Application Questions

A patient's blood test shows a very low GFR. With reference to the JGA, explain the cascade of events that the body initiates to restore normal GFR.

A person living in a hot desert environment produces very little urine. With reference to ADH and the collecting duct, explain the physiological basis of this observation.

A fish taken from a freshwater aquarium and placed in seawater begins to lose water and dehydrates. With reference to the type of nitrogenous waste it excretes, explain why it faces an additional challenge in the new environment.

A doctor finds glucose in a patient's urine during a routine check-up. The patient does not have diabetes. What renal explanation could account for this finding?

With reference to the counter current mechanism, explain why a person severely dehydrated can still produce urine, albeit in very small quantities.

A patient with chronic kidney failure is advised to undergo hemodialysis twice a week. Explain the principle behind hemodialysis and why it cannot fully replace a natural kidney.

Birds and reptiles excrete uric acid as nitrogenous waste. With reference to the advantages of uric acid, explain how this helps birds survive long migratory flights.

A student observes that earthworms come out of the soil after heavy rain. With reference to their excretory structures, explain what happens to nitrogenous waste excretion in waterlogged soil.

A patient is prescribed a diuretic drug that inhibits ADH action. Predict the changes in urine volume and concentration, and the possible consequences for the patient.

With reference to the structure of the Bowman's capsule and its cells, explain how the kidney ensures that blood proteins are not lost in urine during filtration.

Unlock all Application Questions