CBSE Class 10 Biology Life Processes MCQs Set 27

Answer: (a) Starch

Explanation:
1. Amylase breaks down starch into sugars like maltose.
2. Proteins need proteases and fats need lipases.

Teacher's Note:
1. Cane sugar (sucrose) is digested by sucrase.
2. Amylase is found in saliva and in pancreatic juice.

Answer: (a) Pancreas

Explanation:
1. Trypsin is a protein-digesting enzyme in pancreatic juice.
2. It acts in the small intestine.

Teacher's Note:
1. It is released in the inactive form trypsinogen.
2. The intestine activates it.

Answer: (a) Inactive due to HCl

Explanation:
1. The stomach is strongly acidic because of HCl.
2. Ptyalin works only in a nearly neutral medium and is inactivated in acid.

Teacher's Note:
1. Rennin and pepsin do not inactivate ptyalin.
2. Starch digestion resumes in the small intestine.

Answer: (a) Trypsin and pepsin

Explanation:
1. Proteolytic enzymes digest proteins.
2. Trypsin and pepsin are both proteases.

Teacher's Note:
1. Amylase acts on starch and lipase on fats.
2. Ptyalin is a kind of amylase.

Answer: (d) Intestine

Explanation:
1. Bile enters the duodenum, part of the small intestine.
2. There it emulsifies the fats.

Teacher's Note:
1. Bile is made in the liver but acts in the intestine.
2. The stomach contains little fat digestion.

Answer: (c) Small intestine

Explanation:
1. The small intestine receives bile, pancreatic juice and intestinal juice that complete the digestion of all three.
2. The large intestine mainly absorbs water.

Teacher's Note:
1. The final products are glucose, amino acids, fatty acids and glycerol.
2. These are then absorbed.

Answer: (a) Proteins, carbohydrates and fats

Explanation:
1. Pancreatic juice contains trypsin (proteins), amylase (carbohydrates) and lipase (fats).
2. It therefore acts on all three food groups.

Teacher's Note:
1. This makes the pancreas the most important digestive gland.
2. It also has sodium bicarbonate to neutralise acid.

Answer: (a) Blood capillaries of the villi

Explanation:
1. Amino acids and glucose pass into the blood capillaries of the villi.
2. Fatty acids and glycerol enter the lacteals.

Teacher's Note:
1. From the capillaries blood carries them to the liver.
2. Lacteals are lymph vessels.

Answer: (b) Bacteria present in their stomach help in digestion of cellulose

Explanation:
1. Symbiotic bacteria in the rumen or caecum secrete cellulase.
2. Animals themselves cannot make an enzyme to digest cellulose.

Teacher's Note:
1. Herbivores like cows have a long intestine as well.
2. Grinding teeth only break food physically.

Answer: (a) (i), (ii) and (v)

Explanation:
1. (i) is wrong: Hydra ingests food with its tentacles.
2. (ii) is wrong: bile is made in the liver and stored in the gall bladder.
3. (v) is wrong: the rumen, not the omasum, is the largest chamber.

Teacher's Note:
1. Statements (iii) and (iv) are correct.
2. Learn the four chambers of a ruminant stomach in order: rumen, reticulum, omasum, abomasum.

Answer: (c) Physico-chemical process

Explanation:
1. Respiration involves physical steps like breathing and diffusion of gases, and chemical steps in which food is oxidised in cells.
2. So it is a physico-chemical process.

Teacher's Note:
1. Gas exchange is the physical part.
2. Oxidation of glucose to release energy is the chemical part.

Answer: (d) Glucose in cytoplasm gives pyruvate, which in cytoplasm gives ethanol and CO₂

Explanation:
1. Glycolysis splits glucose into pyruvate in the cytoplasm.
2. In yeast, without oxygen, pyruvate is converted to ethanol and CO₂, also in the cytoplasm.

Teacher's Note:
1. Anaerobic respiration does not use mitochondria.
2. In muscle cells pyruvate becomes lactic acid instead.

Answer: (d) Conversion of pyruvate to lactic acid

Explanation:
1. During heavy exercise the oxygen supply is not enough.
2. Muscle cells then convert pyruvate into lactic acid, whose build-up causes cramps.

Teacher's Note:
1. Yeast makes ethanol, but animal muscle makes lactic acid.
2. Massage and rest help remove the lactic acid.

Answer: (d) All of these

Explanation:
1. Leaf Z photosynthesised in light, so its bubbles are oxygen.
2. Leaf X was in the dark, so it only respired and its bubbles are CO₂.
3. Petroleum jelly blocked the stomata of Y, so no gas could leave it.

Teacher's Note:
1. Gases leave a leaf through stomata.
2. Each statement explains one of the observations, so all are correct.

Answer: (d) Diffusion across membranes

Explanation:
1. In every animal gases cross a respiratory surface by diffusion.
2. Not all animals have breathing movements or use active transport.

Teacher's Note:
1. Hydra and earthworms exchange gases without special breathing movements.
2. Diffusion needs a moist, thin surface.

Answer: (d) They have to pump large volumes of water through their gills because of water's low oxygen content

Explanation:
1. Water contains much less dissolved oxygen than air.
2. So fish must pass large volumes of water over the gills to get enough oxygen.

Teacher's Note:
1. This is why the breathing rate of aquatic animals is faster.
2. Gills are always moist because they are in water.

Answer: (d) Epiglottis

Explanation:
1. The epiglottis is a flap that covers the glottis while swallowing.
2. This directs food into the food pipe.

Teacher's Note:
1. The glottis is the opening into the windpipe.
2. Food entering the windpipe causes choking.

Answer: (b) Glottis

Explanation:
1. The opening of the larynx into the pharynx is called the glottis.
2. It is guarded by the epiglottis.

Teacher's Note:
1. The gullet is the oesophagus.
2. The trachea runs from the larynx to the bronchi.

Answer: (a) Alveoli

Explanation:
1. Air passes through trachea, bronchi and bronchioles to the alveoli.
2. Gas exchange with blood happens in the alveoli.

Teacher's Note:
1. Alveoli have thin walls and a rich blood supply.
2. They give the lungs a very large surface area.

Answer: (b) Larynx

Explanation:
1. The larynx or voice box contains the vocal cords.
2. Air passing over them makes them vibrate to produce sound.

Teacher's Note:
1. The syrinx is the sound-producing organ of birds.
2. Larynx is at the top of the trachea.

Answer: (d) All of the above

Explanation:
1. The rib cage is formed by the ribs, the sternum and the vertebral column.
2. Together they enclose and protect the lungs.

Teacher's Note:
1. The ribs also help in breathing movements.
2. The diaphragm forms the floor of this cavity.

Answer: (d) Nostrils, pharynx, larynx, trachea, alveoli

Explanation:
1. Air enters through the nostrils into the nasal cavity, then passes into the pharynx.
2. It then goes to the larynx, trachea, bronchi, bronchioles and alveoli.

Teacher's Note:
1. The pharynx comes before the larynx.
2. Learn the sequence: nostrils, pharynx, larynx, trachea, bronchi, bronchioles, alveoli.

Answer: (a) Contract

Explanation:
1. The diaphragm contracts and flattens during inhalation.
2. This increases the space in the chest.

Teacher's Note:
1. During exhalation it relaxes and becomes dome-shaped.
2. It is a sheet of muscle that separates the thorax from the abdomen.

Answer: (a) Relaxation of the diaphragm and intercostal muscles

Explanation:
1. Normal expiration is passive.
2. Relaxation of the diaphragm and the intercostal muscles reduces the chest volume and pushes air out.

Teacher's Note:
1. Inspiration is the active step.
2. Forced expiration also uses abdominal muscles.