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Q12(d):
Fill in the gaps :
(d) A healthy adult human excretes (on an average) _______ gm of urea/day.
Solution :
Step 1: Identifying the Metabolic Context
In human physiology, the liver is the primary site of urea synthesis through the Ornithine Cycle (also known as the Urea Cycle). Ammonia ($NH_3$), which is highly toxic, is converted into urea ($NH_2CONH_2$) to facilitate safe excretion via the kidneys. The quantity of urea excreted is intrinsically linked to the dietary intake of proteins and the metabolic rate of the individual. [Per Guyton and Hall, Textbook of Medical Physiology]
Step 2: Quantitative Analysis of Urea Excretion
A healthy adult human on a standard diet typically catabolizes proteins, resulting in the production of nitrogenous waste. Clinical physiological data indicates that the daily excretion of urea in urine is significantly dependent on protein consumption. Standard biological benchmarks establish the following parameters:
| Metric | Value |
|---|---|
| Average Protein Intake | $70 - 100$ grams/day |
| Average Urea Excretion | $25 - 30$ grams/day |
Step 3: Justification and Calculation
The calculation is based on the stoichiometry of nitrogen metabolism. The excretion of approximately $25$ to $30$ grams of urea per day serves to maintain nitrogen balance, ensuring that the blood urea nitrogen (BUN) levels remain within the normal range of $7 - 20$ $mg/dL$. Deviation from this range indicates potential renal impairment or metabolic abnormalities. [Reference: NCERT Biology Class 11, Chapter 19: Excretory Products and Their Elimination]
Visual Representation of Urea Molecule
Final Solution: A healthy adult human excretes (on an average) 25-30 gm of urea/day.
More Questions from Class 11 Biology Excretory Products and Elimination EXERCISES
- Q1: Define Glomerular Filtration Rate (GFR)
- Q2: Explain the autoregulatory mechanism of GFR.
- Q3(a): Indicate whether the following statements are true or false : (a) Micturition is carried out by a reflex.
- Q3(b): Indicate whether the following statements are true or false : (b) ADH helps in water elimination, making the urine hypotonic.
- Q3(c): Indicate whether the following statements are true or false : (c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule.
- Q3(d): Indicate whether the following statements are true or false : (d) Henle’s loop plays an important role in concentrating the urine.
- Q3(e): Indicate whether the following statements are true or false : (e) Glucose is actively reabsorbed in the proximal convoluted tubule.
- Q4: Give a brief account of the counter current mechanism.
- Q5: Describe the role of liver, lungs and skin in excretion.
- Q6: Explain micturition.
- Q7: Match the items of column I with those of column II : Column I Column II (a) Ammonotelism (i) Birds (b) Bowman’s capsule (ii) Water reabsorption (c) Micturition (iii) Bony fish (d) Uricotelism (iv) Urinary bladder (e) ADH (v) Renal tubule
- Q8: What is meant by the term osmoregulation?
- Q9: Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic, why ?
- Q10: What is the significance of juxta glomerular apparatus (JGA) in kidney function?
- Q11(a): Name the following: (a) A chordate animal having flame cells as excretory structures
- Q11(b): Name the following: (b) Cortical portions projecting between the medullary pyramids in the human kidney
- Q11(c): Name the following: (c) A loop of capillary running parallel to the Henle’s loop.
- Q12(a): Fill in the gaps : (a) Ascending limb of Henle’s loop is _______ to water whereas the descending limb is _______ to it.
- Q12(b): Fill in the gaps : (b) Reabsorption of water from distal parts of the tubules is facilitated by hormone _______.
- Q12(c): Fill in the gaps : (c) Dialysis fluid contain all the constituents as in plasma except _______.
CBSE Solutions for Class 11 Biology Excretory Products and Elimination
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Plant Kingdom
- Animal Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Cell – The Unit of Life
- Biomolecules
- Cell Cycle and Division
- Transport in Plants
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Plant Growth and Development
- Digestion and Absorption
- Breathing and Exchange of Gases
- Body Fluids and Circulation
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
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