CBSE Class 10 Science Advanced Biology Nutrition MCQs Set 02

Answer: (b) ileum

Explanation:
1. In the duodenum bile and pancreatic juice act on the food.
2. In the ileum intestinal juice (succus entericus) is secreted and the digestion is completed.
3. So the answer is ileum.

Teacher's Note:
1. The large intestine only absorbs water.
2. Absorption is also mainly in the small intestine.

Answer: (a) salivary glands

Explanation:
1. Ptyalin is another name for salivary amylase.
2. It is secreted by the three pairs of salivary glands.
3. The answer is salivary glands.

Teacher's Note:
1. The mouth is the place of action, not the secreting organ.
2. Ptyalin converts starch into maltose.

Answer: (c) glucose and amino acids respectively

Explanation:
1. Carbohydrates are broken down finally to glucose.
2. Proteins are broken down finally to amino acids.
3. So the pair is glucose and amino acids.

Teacher's Note:
1. Fats give fatty acids and glycerol.
2. Keep the order of the words in the option in mind.

Answer: (d) Inorganic chemicals mainly

Explanation:
1. Chemosynthetic bacteria (nitrifying, iron, sulphur bacteria) do not use light.
2. They get energy by oxidising inorganic substances such as ammonia, iron or sulphur compounds, and use it to make food.
3. So the answer is inorganic chemicals.

Teacher's Note:
1. Chemoautotrophs use chemical energy; photoautotrophs use light.
2. Organic substances are the food of heterotrophs.

Answer: (d) Both (a) and (b)

Explanation:
1. The diagram shows a solid food particle being taken in and enclosed in a food vacuole. Taking in solid food is phagocytosis.
2. It also shows the residue of undigested food being thrown out of the cell, which is exocytosis.
3. Pinocytosis (cell drinking of liquid) is not shown, so the answer is both (a) and (b).

Teacher's Note:
1. Endocytosis brings material in (phagocytosis for solids, pinocytosis for liquids); exocytosis sends it out.
2. The printed option (d) read 'All of these'; it has been changed because pinocytosis is not shown in the diagram.

Answer: (b) Ultra violet and infra red

Explanation:
1. Arranged by wavelength the spectrum runs: X-ray, ultraviolet, visible, infrared, microwave.
2. So visible light lies between ultraviolet and infrared.
3. The answer is ultraviolet and infrared.

Teacher's Note:
1. Visible light is a narrow band (390 to 780 nm).
2. Violet is next to UV and red is next to IR.

Answer: (b) Chyme

Explanation:
1. Food chewed and mixed with saliva is a bolus.
2. After churning in the stomach it becomes a thick, acidic, semi-liquid mass called chyme, which passes into the duodenum.
3. The answer is chyme.

Teacher's Note:
1. Bolus: in the mouth. Chyme: from the stomach. Chyle: the milky fluid in lacteals.
2. Chyme is acidic.

Answer: (c) alimentary canal

Explanation:
1. Peristalsis is a wave of contraction in the muscular wall of a tube.
2. Food is pushed along the oesophagus, stomach and intestines by it.
3. So it occurs in the alimentary canal (the liver and hypothalamus have no such movement).

Teacher's Note:
1. The question was edited: the ureter also shows peristalsis, but only to move urine, so the words 'that pushes food forward' were added.
2. Peristalsis is involuntary.

Answer: (b) herbivorous

Explanation:
1. The appendix is a small, useless remnant of the caecum.
2. In herbivores the caecum is large and helps to digest cellulose.
3. So the ancestors of humans were herbivorous.

Teacher's Note:
1. A vestigial organ is a reduced organ that was useful in ancestors.
2. Cows and rabbits have a large caecum.

Answer: (c) Bile

Explanation:
1. Pancreatic juice, saliva and intestinal juice all contain enzymes, and enzymes are proteins.
2. Bile has no enzymes and contains bile salts and pigments.
3. So bile lacks proteins.

Teacher's Note:
1. Enzymes are proteins.
2. Saliva also has a small amount of mucus protein.

Answer: (b) Glycogen

Explanation:
1. Extra glucose from the blood is joined into the branched carbohydrate glycogen in the liver (and muscles).
2. It is changed back to glucose when the body needs energy.
3. So the answer is glycogen.

Teacher's Note:
1. Plants store starch; animals store glycogen.
2. Conversion of glucose to glycogen is glycogenesis.

Answer: (a) Pepsin, lipase and rennin

Explanation:
1. Gastric juice contains pepsin (digests proteins), rennin (curdles milk in infants) and a little gastric lipase, besides HCl and mucus.
2. Trypsin belongs to pancreatic juice, so the options with trypsin are wrong.
3. The answer is pepsin, lipase and rennin.

Teacher's Note:
1. Reject every option with trypsin to save time.
2. Gastric juice also contains HCl and mucus.

Answer: (c) Liver has regenerative capacity and will grow after partial hepatectomy

Explanation:
1. The liver is essential, so (b) is wrong, and the kidneys cannot take over its functions, so (d) is wrong.
2. The special property of the liver is that it can grow back to its original size after a part is removed (hepatectomy).
3. The answer is (c).

Teacher's Note:
1. Regeneration is the key idea.
2. This is why a part of the liver can be donated.

Answer: (b) Nitrogen

Explanation:
1. Insectivorous plants such as pitcher plant and Drosera grow in soils poor in nitrogen.
2. Insect bodies are rich in proteins, so digesting them supplies nitrogen.
3. The nutrient is nitrogen.

Teacher's Note:
1. Other plants take nitrogen as nitrates from the soil.
2. These plants still make food by photosynthesis; the insects only add nitrogen.

Answer: (c) conversion of pepsinogen to pepsin

Explanation:
1. The stomach releases pepsin in an inactive form, pepsinogen.
2. HCl activates it into pepsin and also gives the acid medium in which pepsin works.
3. The main function is the conversion of pepsinogen to pepsin.

Teacher's Note:
1. HCl also kills bacteria that enter with food.
2. Emulsification of fat is done by bile.

Answer: (c) Lipid

Explanation:
1. Lipase breaks down fats (lipids) into fatty acids and glycerol.
2. The substance on which an enzyme acts is its substrate, so the substrate of lipase is a lipid.

Teacher's Note:
1. Name tip: lipase acts on lipids, amylase on starch, protease on proteins.
2. Fats must first be emulsified by bile.

Answer: (b) intestinal juice

Explanation:
1. The glands in the wall of the small intestine secrete intestinal juice.
2. Its other name is succus entericus.
3. The answer is intestinal juice.

Teacher's Note:
1. Gastric juice comes from the stomach; bile from the liver.
2. It completes digestion in the ileum.

Answer: (a) Carbohydrates, fats, proteins

Explanation:
1. The body first uses its stored carbohydrate (glycogen) for energy.
2. When it is exhausted, stored fat is used, and proteins are used last because they are needed for body structure.
3. The sequence is carbohydrates, fats, proteins.

Teacher's Note:
1. Proteins are body-building material, so they are spared as long as possible.
2. Glycogen stores last for only about a day.

Answer: (a) Lymph capillaries within villi

Explanation:
1. Digested fats are absorbed through the lacteals, which are lymph capillaries in the villi.
2. Glucose and amino acids go into the blood capillaries.
3. So the answer is lymph capillaries within villi.

Teacher's Note:
1. Lacteal means milky: the lymph there looks milky after a fatty meal.
2. Fat is carried by lymph first and reaches the blood later.

Answer: (d) Milk, changing casein into calcium paracaseinate at 1–3 pH.

Explanation:
1. Rennin is a gastric enzyme found in infants. It curdles milk.
2. It converts the milk protein casein into calcium paracaseinate (curd) in the acidic medium of the stomach, at pH 1 to 3.
3. So the answer is (d).

Teacher's Note:
1. The pH 7.2 to 8.2 of option (b) is alkaline, so it cannot belong to the stomach.
2. The curdling keeps milk in the stomach longer for digestion.

Answer: (c) It increases surface area for absorption of food

Explanation:
1. The small intestine is about 6.5 m long and is also folded into villi.
2. A long tube with villi gives a large surface for absorbing digested food.
3. So the intestine is long to increase the surface area for absorption.

Teacher's Note:
1. Storage of food is done by the stomach, not the intestine.
2. Herbivores have an even longer small intestine.

Answer: (d) Sugar candy

Explanation:
1. Vegetables contain cellulose and starch, meat and egg contain proteins and fats; these need several steps.
2. Sugar candy is already a simple sugar and needs only one enzyme step (sucrose to glucose and fructose) before absorption.
3. So the food digested first is the sugar candy.

Teacher's Note:
1. The simpler the food molecule, the faster it is digested.
2. Proteins start digestion only in the stomach, fats only in the small intestine.

Answer: (d) conversion of glucose to glycogen

Explanation:
1. The word glycogenesis means 'formation of glycogen'.
2. It is the change of glucose into glycogen for storage.
3. The answer is conversion of glucose to glycogen.

Teacher's Note:
1. Breakdown of glycogen is glycogenolysis; breakdown of glucose to pyruvate is glycolysis.
2. Genesis means formation.

Answer: (c) Chymotrypsin

Explanation:
1. Rennin (an enzyme of the stomach of babies) is absent in adults, and 'renin' is a kidney hormone.
2. In adults the milk protein casein is digested by protein-splitting enzymes of the pancreatic juice. Of the two given, the printed key names chymotrypsin.
3. The answer is chymotrypsin.

Teacher's Note:
1. Rennin and renin are different: rennin is a digestive enzyme, renin is related to the kidney.
2. Trypsin also acts on proteins; the book's key chooses chymotrypsin.

Answer: (c) 3

Explanation:
1. The stomach produces HCl, so its contents are acidic with a pH of about 1.5 to 3.
2. This acid kills most bacteria that enter with the food.
3. So the pH is 3 (acidic).

Teacher's Note:
1. pH below 7 is acidic; above 7 is alkaline.
2. Of the options only 3 is acidic.

Answer: (c) Maltose - Pepsin

Explanation:
1. Trypsin digests proteins, lipase digests fats and amylase digests starch, so (a), (b) and (d) are correct.
2. Maltose is digested by maltase, not by pepsin, which acts on proteins.
3. The incorrect pair is maltose - pepsin.

Teacher's Note:
1. Maltose is acted upon by maltase.
2. Check each pair against its enzyme name.

Answer: (b) A = r, B = p, C = s, D = q

Explanation:
1. Crypts of Lieberkuhn are glands in the wall of the intestine: A = r.
2. The pancreas lies in the loop of the duodenum: B = p.
3. The adrenal glands sit on top of the kidneys: C = s. Gastric glands are in the stomach: D = q.
4. This combination is option (b).

Teacher's Note:
1. Match the easy ones first (gastric gland with stomach) and eliminate options.
2. Adrenal means beside the kidney (renal).

Answer: (c) pyridoxine

Explanation:
1. Vitamin B₁ is thiamine, B₅ is pantothenic acid and vitamin A is retinol.
2. Vitamin B₆ is pyridoxine.

Teacher's Note:
1. Learn B₁ thiamine, B₂ riboflavin, B₃ niacin, B₅ pantothenic acid, B₆ pyridoxine, B₁₂ cobalamin.
2. Retinol is vitamin A.

Answer: (a) Helping growth of gut microbes that break down cellulose

Explanation:
1. Ruminants such as cows have microbes in the rumen that digest cellulose.
2. The microbes need nitrogen to build their proteins, and urea supplies it.
3. So urea works by helping the growth of gut microbes that break down cellulose.

Teacher's Note:
1. Ruminants cannot make cellulase themselves; their gut microbes do it.
2. The rumen is the first chamber of the four-chambered stomach.

Answer: (d) Liver

Explanation:
1. Bile is made by the liver cells, stored in the gall bladder and released into the duodenum.
2. The answer is liver.

Teacher's Note:
1. Bile has no enzymes.
2. It is alkaline and emulsifies fats.

Answer: (a) Sodium bicarbonate

Explanation:
1. Excess acid in the stomach is neutralised by a mild base (an antacid).
2. Sodium bicarbonate (baking soda) is a mild base and is the common antacid. Sodium carbonate is too strongly basic, and the ammonium salts are not used.
3. The answer is sodium bicarbonate.

Teacher's Note:
1. Antacids also include milk of magnesia and aluminium hydroxide.
2. Neutralisation: acid + base gives salt and water.

Answer: (d) All of the above

Explanation:
1. Autotrophic nutrition (photosynthesis) needs carbon dioxide and water as raw materials, chlorophyll as the pigment and sunlight as the energy source.
2. All three are necessary, so the answer is all of the above.

Teacher's Note:
1. When all individual options are true, 'all of the above' is the answer.
2. Chemoautotrophs are an exception that need no light.