CBSE Class 10 Biology Life Processes MCQs Set 30

Answer: (c) Urea

Explanation:
1. Mammals convert toxic ammonia into urea in the liver.
2. Urea is removed by the kidneys.

Teacher's Note:
1. Mammals are ureotelic.
2. Glucose is a useful nutrient, so it is reabsorbed.

Answer: (d) Urea, uric acid, glucose and water

Explanation:
1. Filtration in the glomerulus lets through small molecules: water, glucose, amino acids, salts, urea and uric acid.
2. Ammonia is not a normal component of the human filtrate.

Teacher's Note:
1. Large proteins and blood cells stay in the blood.
2. Most glucose and water is reabsorbed later.

Answer: (b) Urethra

Explanation:
1. The bladder stores urine, which leaves the body through the urethra.
2. The ureters bring urine into the bladder.

Teacher's Note:
1. Micturition is the release of urine.
2. The urethra is longer in males than in females.

Answer: (b) Ammonia and carbon dioxide

Explanation:
1. In the ornithine cycle the liver combines two molecules of ammonia with one molecule of CO₂ to make urea.
2. It is less toxic than ammonia.

Teacher's Note:
1. The cycle is also called the urea cycle.
2. It needs ATP.

Answer: (a) Plasma

Explanation:
1. Urea is a small soluble molecule dissolved in the blood plasma.
2. It is carried from the liver to the kidneys.

Teacher's Note:
1. Plasma is the liquid part of blood.
2. Blood cells carry gases and fight infection.

Answer: (b) Medulla

Explanation:
1. The loop of Henle dips down into the medulla of the kidney.
2. It helps to concentrate urine.

Teacher's Note:
1. The Bowman's capsule and glomerulus are in the cortex.
2. The pelvis collects urine.

Answer: (b) Cortex

Explanation:
1. Each renal corpuscle consists of the glomerulus and Bowman's capsule, located in the kidney cortex.
2. The loops of Henle and collecting ducts are in the medulla.

Teacher's Note:
1. Do not confuse this with Malpighian tubules of insects.
2. The cortex gives the kidney a granular appearance.

Answer: (a) Glomerulus

Explanation:
1. The uriniferous tubule is the tube which starts from the Bowman's capsule.
2. The glomerulus is a tuft of capillaries and not a part of the tubule.

Teacher's Note:
1. Tubule = PCT, loop of Henle, DCT.
2. The glomerulus is in the cup of Bowman's capsule.

Answer: (c) With the left kidney at a higher level than the right

Explanation:
1. The right kidney is pushed slightly down by the liver.
2. So the left kidney lies a little higher than the right.

Teacher's Note:
1. Both kidneys are in the abdomen near the back.
2. They are bean-shaped.

Answer: (a) 5, 1, 2, 4, 3

Explanation:
1. The loop of Henle concentrates urine (5).
2. The renal artery carries blood to the kidney (1).
3. The PCT is the main site of reabsorption (2).
4. The glomerulus filters blood (4) and the DCT secretes (3).

Teacher's Note:
1. Reabsorption is greatest in the PCT.
2. The DCT also helps tune the salt level.

Answer: (a) Filtration of blood

Explanation:
1. Blood pressure in the glomerulus forces water and small solutes out into the Bowman's capsule.
2. This is ultrafiltration.

Teacher's Note:
1. Reabsorption takes place in the tubule.
2. The loop of Henle helps in concentrating urine.

Answer: (a) Blood plasma minus blood proteins

Explanation:
1. The filtrate is plasma without the large protein molecules and blood cells.
2. It also has glucose, salts, amino acids and urea.

Teacher's Note:
1. This fluid is called the glomerular filtrate.
2. About 180 litres of filtrate are made in a day.

Answer: (c) Loop of Henle

Explanation:
1. The loop of Henle, with the collecting duct, creates a salt gradient in the medulla.
2. This allows mammals to form urine more concentrated than blood.

Teacher's Note:
1. Birds also have some short loops.
2. Only mammals can produce highly concentrated urine in this way.

Answer: (c) Proximal convoluted tubule

Explanation:
1. The cells of the PCT have microvilli forming a brush border.
2. This increases the surface area for reabsorption.

Teacher's Note:
1. It resembles the villi of the intestine.
2. The PCT reabsorbs glucose, amino acids and much water.

Answer: (c) Proximal convoluted tubule

Explanation:
1. Most glucose, amino acids, salts and water are reabsorbed in the PCT.
2. Its brush border helps this absorption.

Teacher's Note:
1. The collecting duct adjusts the final water amount.
2. Reabsorption saves useful materials.

Answer: (a) Ultrafiltration

Explanation:
1. Urine formation begins with ultrafiltration in the glomerulus.
2. It is followed by reabsorption and tubular secretion.

Teacher's Note:
1. The filtration is due to pressure.
2. Water reabsorption occurs by osmosis later.

Answer: (c) Passing out of urine

Explanation:
1. Micturition is the process of discharging urine from the bladder.
2. It is controlled by the nervous system.

Teacher's Note:
1. Removal of faeces is called defaecation.
2. Urine stored in the bladder is released through the urethra.

Answer: (d) Synthesis of urea

Explanation:
1. Kidneys remove wastes, balance water and salts and regulate pH.
2. Urea is made in the liver, not the kidney.

Teacher's Note:
1. The kidney only filters urea out of the blood.
2. The kidney also secretes the hormone erythropoietin.

Answer: (b) Urochrome

Explanation:
1. Urochrome is a pigment formed from the breakdown of haemoglobin.
2. It gives urine its yellow colour.

Teacher's Note:
1. Dilute urine looks pale and concentrated urine looks darker.
2. Melanin is the skin pigment.

Answer: (a) Homeostasis

Explanation:
1. Homeostasis is the maintenance of a stable internal environment.
2. Excretion and osmoregulation help it.

Teacher's Note:
1. Haemostasis means stopping blood loss.
2. Haemopoiesis is the formation of blood cells.

Answer: (a) Collecting tubule of the kidney

Explanation:
1. ADH increases water reabsorption in the collecting tubule (and distal tubule).
2. This makes the urine concentrated.

Teacher's Note:
1. ADH is released by the posterior pituitary.
2. Lack of ADH causes diabetes insipidus.

Answer: (c) Transpiration

Explanation:
1. Plants lose excess water as vapour through stomata in transpiration.
2. Photosynthesis and respiration are not means of excreting water.

Teacher's Note:
1. Guttation is loss of water in liquid form.
2. Transpiration also cools the plant.

Answer: (d) Both CO₂ and water

Explanation:
1. Respiration of glucose gives CO₂ and water along with energy.
2. Oxygen is used, not produced.

Teacher's Note:
1. Plants also excrete waste as gums, resins and latex.
2. Some wastes are stored in old xylem or shed leaves.