CBSE Class 10 Science Advanced Biology Nutrition MCQs Set 01

Answer: (c) Glucose formed during photosynthesis get stored as starch.

Explanation:
1. The glucose made in a leaf is quickly used up or changed into other substances.
2. The extra glucose is joined together and stored as starch, which collects in the leaf and is easy to detect with iodine (blue-black colour).
3. So we test for starch, because glucose formed during photosynthesis gets stored as starch.

Teacher's Note:
1. Iodine solution is the standard test for starch, not for glucose.
2. Remember that the leaf stores its extra food as starch, while plants store sugar as sucrose only in some organs such as sugarcane stems.

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

Explanation:
1. (i) The pointer lands on one of the two bean-shaped guard cells, so it is correct.
2. (ii) The label says 'thin wall', but the line ends on the wall next to the pore. That wall is the thick inner wall of the guard cell, so it is wrong.
3. (iii) points to the outer wall of the guard cell, which is thin, so (iii) is correct, but it is not paired in any option.
4. (iv) 'Nucleus' points to a small granule (a chloroplast) and not to the large dark nucleus, so it is wrong. (v) points to the epidermal cell beside the guard cells, so it is correct.
5. The correctly labelled parts among the options are (i) and (v), so the answer is (a).

Teacher's Note:
1. In a stomatal diagram, the wall facing the pore is thick and the wall facing the epidermal cells is thin.
2. Look carefully at where the label line ends, not only at the label text.

Answer: (b) photoautotrophs

Explanation:
1. Green plants contain chlorophyll and make their food from CO₂ and water using sunlight.
2. An organism that uses light energy to make its own food is a photoautotroph.
3. So plants are photoautotrophs.

Teacher's Note:
1. Photo means light and auto means self.
2. Chemoautotrophs use energy from chemical reactions, as in nitrifying and sulphur bacteria.

Answer: (a) Detritivores

Explanation:
1. Detritus means dead and decaying organic remains.
2. Organisms that feed on such material, for example earthworms, are detritivores.
3. Frugivores eat fruits, so the answer is detritivores.

Teacher's Note:
1. Match the feeding terms: herbivore (plants), carnivore (flesh), frugivore (fruits), detritivore (dead remains), sanguivore (blood).
2. The spelling 'Fruigivores' in the option is a misprint of frugivores.

Answer: (b) Holozoic

Explanation:
1. Amoeba engulfs solid food particles with its pseudopodia, digests them inside a food vacuole and throws out the waste.
2. Taking in and digesting solid food is called holozoic nutrition.
3. So amoeba shows holozoic nutrition.

Teacher's Note:
1. Holo means whole and zoic means animal-like: whole food is taken in.
2. Fungi and bacteria that feed on dead matter are saprotrophs.

Answer: (d) CO₂ and water

Explanation:
1. The equation of photosynthesis is 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O.
2. The substances used up (the raw materials) are carbon dioxide and water.
3. Sunlight is the energy source and chlorophyll is the pigment; oxygen is a product. So the answer is CO₂ and water.

Teacher's Note:
1. Separate raw materials (CO₂, water) from requirements (light, chlorophyll) and products (glucose, oxygen).
2. Oxygen is released, never used, in photosynthesis.

Answer: (d) algae present in ocean and fresh water sources

Explanation:
1. Water bodies cover most of the earth, and the tiny algae living in them are present in huge numbers.
2. Together, the algae of oceans and fresh water carry out about 80% of the photosynthesis on earth.
3. The answer is algae present in ocean and fresh water sources.

Teacher's Note:
1. Land plants account for only about one-fifth of the total.
2. The printed key is followed here; the figure of 80% is for algae of all water bodies together.

Answer: (b) Photolysis of water

Explanation:
1. The dark reaction, including carboxylation, needs enzymes such as RuBisCO.
2. The light reaction as a whole needs the enzyme-based machinery of the thylakoids, but the splitting of water by light (photolysis) is brought about directly by light energy with only Mn²⁺ and Cl⁻ ions.
3. Per the book, photolysis of water needs ions but no enzyme, so the answer is photolysis of water.

Teacher's Note:
1. Photolysis means breaking by light.
2. The dark reaction and carboxylation are the enzyme-controlled steps.

Answer: (b) they reflect green light

Explanation:
1. Chlorophyll absorbs mainly blue and red light.
2. Green light is reflected, and that reflected light reaches our eyes, so leaves look green.
3. The answer is they reflect green light.

Teacher's Note:
1. The colour we see in an object is the colour it reflects.
2. This is also why photosynthesis is least in green light.

Answer: (c) Nicotinamide adenine dinucleotide phosphate

Explanation:
1. NADP stands for Nicotinamide Adenine Dinucleotide Phosphate.
2. Option (a) leaves out 'adenine' and option (b) says 'nicotine' instead of 'nicotinamide'.
3. So the answer is (c).

Teacher's Note:
1. Read each word of the long name: N-icotinamide A-denine D-inucleotide P-hosphate.
2. NADPH₂ carries hydrogen to the dark reaction.

Answer: (b) 390 – 780 nm

Explanation:
1. Plants use the visible part of the spectrum.
2. The visible region lies between about 390 nm (violet) and 780 nm (red).
3. So the answer is 390 – 780 nm.

Teacher's Note:
1. Below 390 nm is ultraviolet and above 780 nm is infrared.
2. The text also quotes 400–700 nm as the usable range.

Answer: (c) During morning and evening hours

Explanation:
1. At the compensation point the CO₂ used in photosynthesis equals the CO₂ released in respiration.
2. This happens when light is weak, which is in the early morning and in the evening.
3. So the answer is during morning and evening hours.

Teacher's Note:
1. At midday photosynthesis is faster than respiration; in darkness only respiration occurs.
2. No net gas exchange occurs at the compensation point.

Answer: (b) Blue and red light

Explanation:
1. The absorption of chlorophyll is highest in the blue-violet and red regions.
2. Green light is reflected, so it is not absorbed much.
3. So chlorophyll absorbs mostly blue and red light.

Teacher's Note:
1. The two peaks of chlorophyll absorption are in blue and in red.
2. Maximum photosynthesis occurs in red light.

Answer: (a) Stroma

Explanation:
1. CO₂ fixation is part of the dark reaction (Calvin–Benson cycle).
2. The dark reaction takes place in the stroma of the chloroplast.
3. So the answer is stroma.

Teacher's Note:
1. Light reaction: grana. Dark reaction: stroma.
2. The stroma holds the enzymes of the dark reaction.

Answer: (d) Chloroplast

Explanation:
1. Stroma is the colourless, protein-rich fluid in which the grana lie embedded.
2. It is found inside the chloroplast.
3. So the answer is chloroplast.

Teacher's Note:
1. Do not confuse stroma (chloroplast) with the matrix of mitochondria.
2. Grana plus stroma make up the inside of a chloroplast.

Answer: (b) taller than those grow in light

Explanation:
1. A seedling in the dark has no light to bend towards and stretches rapidly in search of light.
2. It becomes tall, thin, pale yellow and weak. This is called etiolation.
3. So such seedlings are taller than those grown in light.

Teacher's Note:
1. Etiolated seedlings lack chlorophyll and cannot photosynthesise.
2. They survive only on the food stored in the seed.

Answer: (d) 20

Explanation:
1. Humans have two sets of teeth: 20 milk teeth and 32 permanent teeth.
2. All 20 milk teeth (8 incisors, 4 canines, 8 molars) are shed and replaced; the 12 permanent molars come only once.
3. So the number of teeth that grow twice is 20.

Teacher's Note:
1. Milk teeth: 20. Permanent teeth: 32. Difference: 12 teeth that never have a milk version.
2. Dental formula for milk teeth: i 2/2, c 1/1, m 2/2.

Answer: (b) Liver

Explanation:
1. Bile is made by the cells of the liver.
2. It is stored and concentrated in the gall bladder, and sent to the duodenum when needed.
3. So bile is produced by the liver.

Teacher's Note:
1. Remember: produced in the liver, stored in the gall bladder.
2. Bile has no enzymes.

Answer: (c) pepsin, trypsin and peptidase

Explanation:
1. Protein digestion starts in the stomach with pepsin.
2. In the duodenum trypsin of the pancreatic juice continues it, and in the small intestine the peptidases of the intestinal juice finish it.
3. The sequence is pepsin, trypsin, peptidase.

Teacher's Note:
1. Follow the food: stomach, then duodenum, then ileum.
2. Ptyalin acts on starch, so it can never be in a protein sequence.

Answer: (a) amoeba is unicellular

Explanation:
1. Amoeba consists of a single cell.
2. The food is digested inside this cell, in the food vacuole, so digestion is intracellular.
3. The reason is that amoeba is unicellular.

Teacher's Note:
1. Intracellular means inside a cell.
2. In humans digestion is extracellular, in the cavity of the alimentary canal.

Answer: (c) Mouth → Pharynx → Oesophagus → Stomach

Explanation:
1. Food enters the mouth, passes through the pharynx (throat), and goes down the oesophagus into the stomach.
2. In option (a) the pharynx comes after the stomach and in (b) the stomach comes after the small intestine; in (d) the oesophagus comes before the mouth.
3. The correct path is Mouth → Pharynx → Oesophagus → Stomach.

Teacher's Note:
1. Learn the order of the canal from top to bottom: mouth, pharynx, oesophagus, stomach, small intestine, large intestine, anus.
2. Check each arrow in the options one by one.

Answer: (a) incisors

Explanation:
1. Incisors are the sharp, chisel-shaped front teeth used to cut food.
2. Canines tear food, while premolars and molars grind it.
3. The answer is incisors.

Teacher's Note:
1. Cut: incisors. Tear: canines. Grind: premolars and molars.
2. Elephant tusks are modified incisors.

Answer: (c) to provide increased surface area for absorption of digested food

Explanation:
1. Villi are finger-like projections on the inner wall of the small intestine.
2. They greatly increase the surface area, so more digested food can be absorbed quickly.
3. Their most important function is to increase the surface area for absorption.

Teacher's Note:
1. Capillaries and lacteals lie inside villi, but that is a result of the design, not the main purpose.
2. Surface area is the key idea for absorption.

Answer: (a) Bile

Explanation:
1. Pancreatic juice has amylase, trypsin and lipase; intestinal juice has several enzymes; saliva has salivary amylase.
2. Bile contains bile salts and pigments but no enzymes.
3. The answer is bile.

Teacher's Note:
1. Bile helps digestion by emulsifying fats, not by chemical action.
2. It also makes the food alkaline.

Answer: (b) mechanical digestion

Explanation:
1. Chewing breaks food into smaller pieces with the teeth, but does not change its chemical nature.
2. Breaking food physically is mechanical (physical) digestion.
3. So chewing is mechanical digestion.

Teacher's Note:
1. Chewing is voluntary; peristalsis is involuntary.
2. Chemical digestion is done by enzymes.

Answer: (b) small intestine

Explanation:
1. Microvilli are tiny projections on the free surface of the cells lining the villi of the small intestine.
2. They increase the area for absorption even more.
3. So they are present in the small intestine.

Teacher's Note:
1. Villi are visible to a hand lens; microvilli need a microscope.
2. Both are found in the small intestine.

Answer: (b) protein in acid medium in stomach

Explanation:
1. Pepsin works in the stomach, where HCl makes the medium acidic.
2. Trypsin works in the duodenum, where bile and pancreatic juice make the medium alkaline.
3. So pepsin digests protein in acid medium in stomach.

Teacher's Note:
1. Remember: pepsin, stomach, acid; trypsin, duodenum, alkaline.
2. The pH of the stomach is about 1.5 to 3.

Answer: (d) bigger pieces of food are broken down into smaller pieces and saliva is properly mixed with it

Explanation:
1. Chewing breaks food into small pieces, which gives enzymes a larger surface to act on.
2. It also mixes saliva with the food, so that salivary amylase can start digesting starch.
3. Option (d) states both reasons, so the answer is (d).

Teacher's Note:
1. When two options are partly right, choose the one that is complete.
2. Both reasons, smaller pieces and mixing with saliva, matter.

Answer: (b) peristalsis

Explanation:
1. The muscular walls of the canal contract and relax in a wave, which pushes the food forward.
2. This wave-like movement is called peristalsis.
3. The answer is peristalsis.

Teacher's Note:
1. Peritoneum is a membrane; cyclosis is movement of cytoplasm.
2. Peristalsis is involuntary.

Answer: (c) cytoplasm

Explanation:
1. The enzymes break the food in the food vacuole into soluble substances.
2. The soluble food then diffuses from the vacuole into the surrounding cytoplasm.
3. So absorption occurs in the cytoplasm.

Teacher's Note:
1. The contractile vacuole removes excess water, not food.
2. The vacuole then shrinks and disappears.

Answer: (c) Annelida

Explanation:
1. The book says that flatworms had only a mouth, and that a coiled, well-developed alimentary canal appeared in Annelida and continued up to mammals.
2. So it first developed in Annelida.

Teacher's Note:
1. Earthworm is an annelid and has a complete digestive tract.
2. Protozoans and sponges have no alimentary canal.

Answer: (d) buccal cavity

Explanation:
1. Saliva contains salivary amylase (ptyalin).
2. It begins to change starch into maltose while the food is in the mouth.
3. So digestion of starch starts in the buccal cavity.

Teacher's Note:
1. Protein digestion starts in the stomach; fat digestion in the small intestine.
2. Starch is the only food whose digestion begins in the mouth.