NCERT Exemplar MCQs

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(c) All living organisms and non-living matter in our biosphere are made of similar elements and compounds. Several pieces of research performed on plants, animals, and microbes confirmed that a relative abundance of organic compounds i,e., carbon, hydrogen, and oxygen in living organisms than in the earth’s crust (non-living matter).
Whereas, the percent composition of other inorganic molecules like calcium and gold is more in the earth’s crust as compared to living matter.
Representation of inorganic constituents of lining tissues.

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(a) Silicon is not found freely in nature, but it does occur as oxides and silicates, whereas magnesium, iron, and sodium are present in living organisms as ions. Silicon is essential to plant life but is often found in minute quantities in the human body and its function is still unknown.

Magnesium is an abundant element. It is essential for a number of enzymes and their action, particularly those utilising ATP.

Iron is an important constituent of haemoglobin and plays a vital role by taking part in \(\mathrm{O}_{2}\) transport, and electron transport chain.

Sodium plays a vital role in animals by regulating nerve impulse transmission and altering the membrane permeability. It also has an indispensable role in osmoregulation.

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(d) Glycine is the simplest amino acid with an amino group and a carboxyl group. Whereas formic acid is the simplest carboxylic acid, glycerol is a fatty acid and glycolic acid is carboxylic acid substituted with hydroxyl group.

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(d) A zwitterion is a neutral molecule having both the cationic and anionic charges on the same molecule. Amino acids are the best-known examples of zwitterion.

In an acidic solution,’ the amino group accepts a hydrogen ion to become positively charged. Whereas, in an alkaline solution, the carboxyl group donates a hydrogen ion to become negatively charged. The \(\mathrm{pH}\) at which the amino acid is electrically neutral is called isoelectric \(\mathrm{pH}\).

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(a) Fructose is a ketohexose. Its carbon is attached to a hydrogen atom by a single bond and to an oxygen atom by a double bond.

Erythrose is a tetrose carbohydrate \(\left(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{4}\right)\). Its a part of tetrose family and possesses one aldehyde group.

Ribulose is a ketopentose, containing five carbon atoms and includes ‘ketone’ as a functional group.

Ribose is a pentose which is a major component of DNA and RNA.

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(d) Each nucleoside is made up of cyclic nitrogenous base, purine or pyrimidine, and a pentose sugar. On phosphorylation, it forms a nucleotide i.e., a molecule with nitrogenous base pentose sugar and three phosphate groups.

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(a) On homogenising any tissue in an acid, the acid-soluble pool represents cytoplasm. Homogenisation is a process whereby a biological sample is brought to a state such that all fractions of the sample are equal in composition.

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(b) There is an abundance of water in living matter. It is the only polar molecule in living organisms, that can diffuse through a cell membrane without active transport. It is vital for a number of metabolic reactions and is one of the raw materials for photosynthesis.

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(a) Proteins are heteropolymers made of about 20 different kinds of monomers, i.e., amino acids. Each of these amino acids is made up of carbon, amino group, carboxyl group, hydrogen, and an R-functional group. This variable R-group is what that makes each monomer different from one another.

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(d) Proteins can sometimes function as hormones, i.e., peptide hormones such as insulin, growth hormone, etc. Other compounds such as antibiotics, florigen, and melanin are non-proteineceous in nature.

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(a) Glycogen is the storage polysaccharide present in animals. Glycogen consist of glucose molecule linked together with \(\alpha(1 \rightarrow 4)/latex] linkages with [latex]\alpha(1 \rightarrow 6)\) branch points occurring every 8-12 residues.

Galactose, on the other hand, is a monosaccharide, and combines with glucose through a condensation reaction, resulting in the formation of the disaccharide, lactose.
Ribose is a pentose monosaccharide that has all hydroxyl groups on the same side in fisher projection. It forms a part of the backbone in RNA and DNA. Amino acids are the monomers of proteins.

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(a) Glycogen is the multibranched polysaccharide of glucose units popularly known as animal starch, as it is chemically similar to starch. It has 30,000 glucose residues and a molecular weight of about \(4.8\) million. Glucose residues in glycogen are arranged in highly branched bush-like chains.

There are two main linkage patterns, observed in glycogen, i.e., \(\alpha\) 1-4 linkage in the straight part and \(\alpha 1-6\) linkage in the area of branching. The distance between two branching points is 10-14 glucose residues. Glycogen has as many non-reducing ends as branches plus one.

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(a) The primary structure of a protein refers to a linear sequence of amino acids in a polypeptide chain, held together by peptide bonds. These are two ends of a polypeptide chain, the carboxyl terminus (C-terminus) and the amino terminus (N-terminus) based on the nature of the free group on each extremity.