Biology Questions and Answers

Answer: C

The incorrect statement is that citrus fruits are a rich source of vitamin E.

Citrus fruits such as oranges and lemons are rich in vitamin C. Pulses are a rich source of protein, potato is rich in starch and whole grains are rich in fibre, so those statements are correct.

That makes the vitamin E statement the only wrong one.

Vitamin E is found in nuts, seeds and vegetable oils, while citrus fruits such as oranges and lemons are the standard source of vitamin C. Pulses give protein, potatoes give starch and wholegrains give fibre. The only incorrect line is therefore the one about citrus fruits and vitamin E.

Answer: C

The enzyme family is Cytochrome P450.

Cytochrome P450 enzymes, found mainly in the liver, oxidise many drugs and toxins so that they can be removed from the body.

Cytochrome F, D and b are components of electron-transport chains in photosynthesis or respiration, not the main drug-metabolising enzymes.

These enzymes, a large family of haem proteins, are found mostly in the liver and are named after their absorption peak at 450 nm. They help to metabolise a wide range of drugs and toxins. The other cytochromes named work in electron transport in cells and do not do this job.

Answer: C

The incorrect combination is Pectin - Fungus.

The cell wall of fungi is made mostly of chitin and glucans. Pectin is a part of the plant cell wall. Peptidoglycan in bacteria, chitin in the exoskeleton of insects and cellulose in plants are correct.

So only the pectin and fungus pair is wrong.

Peptidoglycan forms the cell wall of bacteria, chitin is in the exoskeleton of insects and also in the cell wall of fungi, and cellulose forms the plant cell wall. Pectin is a plant polysaccharide. So the pair that gives pectin for fungus is incorrect, because the fungal wall is made of chitin.

Answer: C

The organism is Saccharomyces cerevisiae.

This yeast ferments sugars in grape juice to alcohol and carbon dioxide, so it is used in making wine, beer and bread.

Lactobacillus makes curd, archaebacteria live in extreme habitats and Aspergillus is a mould used for enzymes and citric acid.

The yeast converts the sugar in fruit juices into ethanol and carbon dioxide without oxygen, a process called fermentation. This is used for wine, beer and bread. Lactobacillus works on milk to produce lactic acid, and Aspergillus is a fungus that makes enzymes and organic acids.

Answer: A

The cell is the Amoeba.

An amoeba moves and takes in food by extending temporary arm-like projections of its cytoplasm called pseudopodia.

Volvox moves with flagella, Spirogyra is a filamentous alga without such projections and yeast does not form pseudopodia.

Pseudopodia, meaning false feet, are temporary extensions of the cell used to move and to engulf food particles by phagocytosis. The amoeba is the standard example. Volvox swims with flagella, Spirogyra is a green alga that forms filaments, and yeast reproduces by budding.

Answer: A

Omega-3 fatty acids are good because they can control elevated triglyceride levels.

Omega-3 fatty acids lower the level of triglycerides in the blood and are linked to a lower risk of heart disease. They also tend to reduce, not raise, inflammation.

So the options that say they raise triglycerides, lower immune response or quickly activate inflammation are wrong.

These fats are found in oily fish, flaxseed and walnuts. They lower triglycerides, help to keep the heartbeat regular and have an anti-inflammatory effect. So the statements saying that they raise triglycerides, reduce immunity or activate inflammation go against what is known about them.

Answer: C

Hydrogen peroxide is decomposed into water and oxygen by the enzyme catalase. Lyases and isomerases are classes of enzymes that cleave bonds without hydrolysis and rearrange atoms within a molecule, and neither is the class that acts on hydrogen peroxide. 'Oxidoreductases' is the broad class to which catalase itself belongs, but the question names the enzyme that does the job, and the keyed answer is catalase. The reaction it speeds up is \[ 2\mathrm{H_2O_2} \to 2\mathrm{H_2O} + \mathrm{O_2} \] and catalase is found in nearly all organisms that live in oxygen.

Answer: D

The correct matching is A-2, B-3, C-1, D-4.

• Peristalsis is the rhythmic contraction of the muscles of the alimentary canal that pushes food along it.
• Gastric glands lie in the inner lining of the stomach and secrete hydrochloric acid, pepsin and mucus.
• Amylase, which begins the digestion of starch, is present in saliva.
• Bile juice is produced by the liver and stored in the gall bladder.

Amylase with saliva and bile with the liver are the two pairs that eliminate the other options.

Answer: B

A tadpole becomes a frog by metamorphosis.

Metamorphosis is a marked change of form during development after hatching. The aquatic tadpole, with gills and a tail, grows legs, develops lungs and absorbs its tail to become an adult frog, a process controlled by the thyroid hormone thyroxine.

Fertilisation is the fusion of egg and sperm, which happens before the tadpole exists. Budding is a form of asexual reproduction seen in yeast and Hydra. 'Embedding' is not a stage of frog development.

Answer: A

The correct match is a-iii, b-i, c-iv, d-ii.

• Absorption of digested food: the small intestine, whose villi give a large surface.
• Killing of bacteria: the stomach, where hydrochloric acid destroys most microbes in food.
• Chewing of food: the buccal cavity (mouth), with the teeth and tongue.
• Formation of faeces: the large intestine, which absorbs water and forms the waste into faeces.

Options C and D also start with (iii) but give the stomach's role to the large intestine or the mouth.