Option (d) is correct. Malonate is the competitive inhibitor of catalytic activity of succinic dehydrogenase. Collagen is proteinaceous in nature and possesses peptide bonds. Chitin is a homopolymer present in the cell wall of fungi and exoskeleton of arthropods. Abrin and ricin are toxins, secondary metabolites.

Option (b) is correct as lysine is a basic amino acid because its side chain contains nitrogen and resembles ammonia, which is a base. Valine is a neutral amino acid, glutamic acid is an acidic amino acid, while tyrosine is an aromatic amino acid.

Inulin is a fructan (polysaccharide of fructose). Adjacent fructose units are linked through glycosidic bond. Insulin is a protein composed of 51 amino acids. Adjacent amino acids are attached through peptide bond.

Collagen is the most abundant protein in animal world and RuBisCO is the most abundant protein in the whole of the biosphere because it is present in every plant that undergoes photosynthesis and molecular synthesis through the Calvin cycle.

Floridean starch has structure similar to amylopectin and glycogen as both are made from α-D glucose monomers. The key difference between amylopectin and glycogen is, amylopectin is a soluble form of starch, while glycogen is an insoluble form of starch.

‘Ramachandran plot’ is used to confirm the structure of proteins. Ramachandran plot is a plot of the angles-phi (ϕ) and psi (ψ) of amino acids found in a peptide chain. This plot was developed by G N Ramachandran, an Indian Scientist in 1963.

Option (a) is correct match which is as follows: Chemically, aquaporins are major intrinsic proteins that form pores in the membranes of cell. Asparagine is beta-amide derivative of aspartic acid. Abscisic acid is an apo-carotenoid. Chitin is a heteropolysaccharide consisting of two types of monosaccharide monomers.

Chilled ethanol is used to precipitate DNA out of a mixture of biomolecules. Low temperature protects the DNA by slowing down the activity of enzymes that could break it apart and ethanol helps in the quick precipitation of DNA.

Proteins are polypeptides, they are linear chain of amino acids linked by peptide bond. Unsaturated fatty acids are carbon chains containing one or more double bonds with terminal carboxylic acid. The two sugar molecules of nucleic acids are linked together via phosphodiester bond. Polysaccharides are long chain of sugar molecules joined with a covalent bond, i.e., glycosidic linkage.

Sugars are chemically carbohydrates. They are polyhydroxy aldoses, ketoses and their condensation products. Aldoses bear a terminal aldehyde or —CHO group while ketoses have an internal ketone or —CO group. Thus, they possess two functional groups, i.e., carbonyl and hydroxyl.

Option (d) is correct. Malonate is the competitive inhibitor of catalytic activity of succinic dehydrogenase. Collagen is proteinaceous in nature and possesses peptide bonds. Chitin is a homopolymer present in the cell wall of fungi and exoskeleton of arthropods. Abrin and ricin are toxins, secondary metabolites.

Among the following, epinephrine is an amino acid derived hormone. It is a catecholamine which is produced in the chromaffin cells of adrenal medulla from amino acids tyrosine. On the other hand, estradiol and estriol are steroid hormones involved in the regulation of estrous and menstrual cycles. Ecdysone is also a steroid hormone that controls moulting in insects.

The graph shows the exothermic reaction A in the presence of enzyme as it lowers down the activation energy substantially. The B graph shows this reaction in the absence of enzyme when activation energy is quite high. Thus, option (b) is correct.

Ribozyme is a form of ribosomal RNA (23 SrRNA) which acts as a catalyst in splicing of RNA during protein synthesis. It is the only non-protein enzyme known so far, rest all the enzymes are proteinaceous.

A typical fat molecule is triglyceride formed by esterification of one glycerol and three fatty acid molecules. The three fatty acids can be of same type or different depending on the type of the fat molecules.

Ester bonds are the least likely to be involved in stabilising the 3D folding of most proteins. A long protein chain gets folded upon itself like a hollow woolen ball, giving rise to a tertiary structure (3D) structure. This structure is stabilised by several types of bonds, i.e., hydrogen bonds, ionic bonds, Vanderwaal’s interactions, covalent bonds and hydrophobic bonds. Ester bond is formed between sugar and phosphate in a nucleotide and is not involved in stability of a polypeptide chain.

Glycine is the simplest amino acid in which functional group ‘R’ is replaced by hydrogen atom (H).

Essential chemical components of many coenzymes are vitamins, e.g., coenzyme Nicotinamide Adenine Dinucleotide (NAD) and NADP contain the vitamin niacin. Proteins, nucleic acids and carbohydrates are not enzymatic biomolecules.

The substrate binds to the enzyme at its active site forming an enzyme-substrate complex. This complex formation is a transient and unstable phenomenon. Very soon, the product is released from the active site. All other intermediate structural states are unstable. Stability is related to energy status of the molecule or the structure.

A fat is formed of two kinds of smaller molecules, i.e., glycerol and fatty acids. In making a fat, free fatty acid molecules join to glycerol by an ester linkage. A fatty acid has a long carbon skeleton, usually 16 or 18 carbon atoms in length. If there are no double bonds between carbon atoms composing the chain, then as many hydrogen atoms as possible are bonded to the carbon skeleton. This is called saturated fatty acid. Unsaturated fatty acid has one or more double bonds. Phosphoglycerides are esters of two fatty acids, phosphoric acid and a trifunctional alcohol glycerol. The fatty acids are attached to the glycerol at the 1 and 2 position on glycerol through ester bonds.

Macromolecule chitin is a complex polysaccharide containing amino sugars and chemically modified sugars (e.g., glucosamine, N-acetyl galactosamine, etc). Polysaccharides are long carbohydrate molecules of monosaccharide units joined together by glycosidic bonds. They have a general formula Cx(H2O)y. Chitin is the main component of the cell wall of fungi, the exoskeletons of arthropods, insects and radulae of molluscs, etc.

Prosthetic groups are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme. For example, in peroxidase and catalase, which catalyse the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme.

Statement A is true but B is false. Correct information about statement B is as follows: A complete catalytic, active enzyme with its bound prosthetic group is called holoenzyme. An apoenzyme is an inactive enzyme which gets activated by the binding of an organic or inorganic cofactor.

Statins are commercial blood cholesterol lowering agents as they competitively inhibit the enzymes involved in cholesterol synthesis. They are obtained from a yeast, Monascus purpureus.

Among the given options except lipids all are polymers. These are formed by the polymerisation of monomers. The basic unit of lipid are fatty acids and glycerol molecules that do not form repetitive chains. Instead they form triglycerides from three fatty acids and one glycerol molecules.

Primary metabolites are compounds that are directly involved in the growth and development of a plant like amino acids and sugars (glucose). Primary metabolites prominently function in growth, development and reproduction of cell. Secondary metabolites are compounds produced in other metabolic pathways that, although important, are not essential for the functioning of the plant.

Phosphodiester bond is responsible for linking nucleotides in nucleic acid (DNA and RNA).

The chitinous exoskeleton of arthropods is formed by the polymerisation of N-acetyl glucosamine, which is a derivative of glucose. It is also a characteristic component of the cell wall of fungi, the radulae of molluscs and the beaks and internal shells of cephalopods, including squid and octopuses.

Option (b) is incorrect with respect to enzyme action because addition of a lot of succinate reverses the inhibition of succinic dehydrogenase by malonate. Inhibition of succinic dehydrogenase by malonate is an example of competitive inhibition. Competitive inhibition occurs when enzyme and inhibitor both have more or less similar structure and are present in higher concentration. Thus, both enzyme and inhibitor compete for the active site of enzyme resulting in the decrease of enzymatic activity.

Sucrose is a disaccharide of glucose and fructose. It is a non-reducing sugar as it does not contain any free anomeric carbon atom. Maltose is a disaccharide of 2 glucose units. Its first glucose residue cannot undergo oxidation, whereas the second residue can undergo oxidation because it has a reactive free anomeric carbon atom. Hence, it is a reducing sugar. Lactose and ribose-5-phosphate are also reducing in nature due to the presence of a free ketonic or aldehyde group.

Nucleoside is made up of ribose sugar and nitrogenous base only. Uracil forms nucleoside with only ribose sugar. So, the option with category nucleoside component uracil is correct.

Structure D represents basic amino acid lysine whereas structure A represents glutamic acid (acidic amino acid) and structure B represents alcoholic amino acid serine.

Collagen is the most abundant protein (structural protein) in the animal world while Ribulose Bisphosphate Carboxylase Oxygenase (RuBisCO) is the most abundant protein in the whole of the plant world.

X-axis represents temperature and Y-axis represents enzyme activity. All enzymes act at an optimum temperature, above and below this temperature, the enzyme activity declines.

Lecithin is a phospholipid composed of choline and inositol. It is found in all living cells as a major component of cell membrane.

There are total five nitrogenous bases found in nucleic acids. Out of these adenine, guanine (purines) and cytosine, thymine (pyrimidines) are present in DNA, while RNA contains uracil in place of thymine (both pyrimidines) along with rest 3 similar to DNA.

The wrongly matched pair is ‘b’ because alcohol (ethyl alcohol) can be produced by fermentation of any carbohydrate containing a fermentable sugar. The development of synthetic alcohol follows following reaction.

Succinic dehydrogenase oxidises succinate to fumarate. Malonate, an analogue of succinate, is a strong competitive inhibitor of succinate dehydrogenase and therefore blocks the activity of citric acid cycle in eukaryotes. In Krebs’ cycle the reversible hydration of fumarate to malate is catalysed by fumarase enzyme.

Modern detergents contain enzyme preparation of alkaliphiles. Detergents represent the largest industrial application of enzymes amounting to 25–30% of total sales of enzyme. The enzymes used in detergents must be cost effective, safe to use and perform the task in the presence of anionic and non-ionic detergents, soaps, oxidants, etc. at pH between 8–10.5. Chief enzymes used are proteases, α-amylase, and sometimes cellulase.

In DNA molecule the adjacent deoxyribonucleotides are joined in a chain by phosphodiester bridges or bonds, which link the 5′ carbon of deoxyribose of one mononucleotide unit with 3′ carbon of deoxyribose of next mononucleotide unit. According to Watson and Crick, DNA molecule consists of two such polynucleotide chains wrapped helically around each other, with the sugar phosphate chain on the outside and purine and pyrimidine on the inside of helix. The two strands run antiparallel, i.e., one strand has phosphodiester linkage in 3′→5′ direction while other strand has phosphodiester linkage in 5′→3′ direction.

DNA and RNA, the principal genetic materials of living organisms, are chemically called nucleic acids. These are polymers of nucleotides. Each nucleotide is composed of phosphoric acid, pentose sugar and nitrogenous base. The nitrogenous bases are of two types, i.e., purine and pyrimidines. Purines are heterocyclic and two rings, e.g., adenine, guanine. Pyrimidines are single ring compound, e.g., thymine, cytosine, uracil.

In 1953 James Watson and Francis Crick suggested that in a DNA molecule there are two polynucleotide chains arranged antiparallel or in opposite directions.

The lipids of cell membrane are of three types namely phospholipids, glycolipids and sterols. The sterol found in the membrane may be cholesterol (animals), phytosterol (plants) or ergosterol (microorganisms). Cell membrane is made up of lipid + protein (60%) and carbohydrates (2-10%). Proline is an amino acid.

About 98% of the mass of every living organism including bacterium and human beings is composed of just six elements, i.e. Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O), Phosphorus (P) and Sulphur (S). Chargaff (1950) suggested that despite wide compositional variations exhibited by different types of DNA the total amount of purines equaled the total amount of pyrimidines (A + G = T + C).

Barley seeds are rich in carbohydrate (starch). The starch is hydrolysed by α-amylase to monosaccharide units at the time of germination of seeds.

Coenzyme is an organic non-protein molecule that associates with an enzyme molecule in catalysing biochemical reactions. It usually participates in the substrate-enzyme interaction by donating or accepting certain chemical groups. Holoenzyme is a complex comprising of enzyme molecule and its cofactor. The enzyme is catalytically active in this state. Apoenzyme is an inactive enzyme that must associate with a specific cofactor molecule in order to function. Isoenzyme or isozyme is one of the several forms of an enzyme that catalyse the same reaction but differ from each other in properties such as substrate affinity and maximum rates of enzyme-substrate reaction.

B-DNA is helical structure with 20Å diameter and the distance between the two base pairs is 3.4Å and there are 10 base pairs in each turn or pitch (one round). Hence, one turn of the helix is approximately 34Å or 3.4 nm (10Å = 1.0 nm). Z-DNA (in comparison to B-DNA) is left handed double helical structure in which double helix winds to left in zig-zag pattern (instead of right, like B-DNA).

Nucleotides are the building blocks of nucleic acids (DNA and RNA). A single nucleotide is composed of a phosphate molecule, a five carbon sugar (either ribose or deoxyribose) and a purine (adenine or guanine) or a pyrimidine (thymine or cytosine or uracil) nitrogenous base.

Km, Michaelis-Menten constant, is defined as substrate concentration at which reaction velocity of enzyme-catalysed reaction is half of maximum velocity (i.e. Km = ½ Vmax). Km can vary greatly from enzyme to enzyme and even for different substrates of the same enzyme.

Enzymes, vitamins and hormones help in regulation of metabolism. Enzyme is a proteinaceous catalyst produced by a cell and responsible for the high rate and specificity of one or more biochemical reactions. Vitamin is an organic substance generally synthesised by plants (except vitamin D). Hormones are chemical messengers which bring about specific physiological responses.

A competitive inhibitor competes with substrate molecule for occupying the active site of an enzyme. These inhibitors have structural resemblance with substrate molecules due to which they easily bind with active site of an enzyme and form an enzyme-inhibitor complex. E + I (enzyme + inhibitor) → EI complex.

DNase (deoxyribonuclease) or simply nuclease is an enzyme which breaks down DNA by hydrolysis of the phosphodiester bonds of its sugar-phosphate backbone. Depending on the position of hydrolysing phosphodiester bonds, nucleases are of two types: (i) Endonucleases (ii) Exonucleases. Endonucleases hydrolyse internal phosphodiester bonds in a polynucleotide chain (i.e. DNA), while exonucleases hydrolyse terminal phosphodiester bonds in a polynucleotide chain (i.e. DNA).

Proteins are polymers of amino acids in which amino acids are joined by peptide bonds. Glycine is the simplest amino acid.

Cytochrome is the respiratory pigment. It is composed of protein, iron and porphyrin ring. Functions as an enzyme in the respiratory chain. Metal atom in porphyrin ring changes its valency for molecule to function. Cytochromes are located in inner mitochondrial membranes and thylakoids of chloroplasts.

Cholesterol forms a major component of animal cell membrane liposomes (artificially created spheres surrounded by a phospholipid bilayer like a membrane) which are used for transformation (transgenics).

Bloor (1943) first time used the term ‘lipid’. These are the compounds of C, H, O but the ratio of H and O is more than 2 : 1 that is the ratio of oxygen is lesser as compared to carbohydrates. Lipids are insoluble in water but soluble in non-polar solvents such as benzene, chloroform, etc. Common lipid occurring in a cell is phospholipid. It contains a hydrophilic (polar) head and a hydrophobic (non-polar) tail.

Collagen is a major fibrous protein of connective tissue, occurring as white fibres produced by fibroblast.

Glucose, fructose, mannose, galactose are hexose monosaccharides. The monosaccharides have free aldehyde or ketone group which can reduce Cu²⁺ to Cu. Therefore, these are called reducing sugars.

Cellulose is fibrous polysaccharide that forms the structural component of plant cell wall, some primitive fungi and tunic of ascidians. Cellulose is the most abundant organic substance on earth. It can be digested by only a few microbes present in the gut of ruminants and white ants.

Erucic acid occurs as glycerides in vegetable oils. It is a monounsaturated omega-9 fatty acid. It is found in rapeseed, mustard seed and wallflower seed.

In feedback inhibition, the product of an enzyme-catalysed reaction accumulates and acts as inhibitor of the reaction. Example: Glucose + ATP → (Hexokinase) Glucose-6-phosphate + ADP (end product inhibits the enzyme).

Enzymes enhance the rate of a reaction by lowering the activation energy (the energy required for substances to react and get converted into product) without altering the overall energy change of the reaction.

For human beings, eight amino acids are essential. These are leucine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

A nucleotide contains (a) a 5-C sugar (b) a phosphate molecule (c) a nitrogenous base. ATP is also a nucleotide. It also has a 5-C sugar (ribose), 3 phosphate molecules and a nitrogenous base (adenine).

Glycoproteins (mucoproteins) are conjugated protein having a simple or complex sugar (galactose) residue at their N-terminal end. Glycoprotein is found in egg white, mucin, antibody IgG, cell membrane, saliva, synovial fluid, heparin. Lipoproteins contain lipids and nucleoproteins contain nucleic acid as the prosthetic group.

For human beings, eight amino acids are essential: Leucine, Isoleucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan and Valine. So, these are known as essential amino acids and cannot be synthesised in animal body.

In the beginning of S-phase, DNA replication occurs. DNA replication can occur in diffuse/less tightly coiled euchromatin. So active DNA stains light in colour when stained with acetocarmin and feulgen reagent in comparison to heterochromatin.

Cellulose (CHO)₆₁₀₅n is the most abundant organic polymer. It is a polysaccharide and consists of long unbranched chains of glucose residues linked by β, 1-4 glycosidic bonds. In plants, cellulose is formed from sugar. It serves as building material in the formation of cell wall.

Lactose (CHO)₁₂₂₂₁₁ is a disaccharide found in mammalian milk. It comprises of galactose and glucose units which are linked together by β, 1-4 glycosidic bonds. It is a reducing sugar.

Holoenzyme consists of a proteinaceous part called apoenzyme and a non-proteinaceous part called cofactor. Cofactor is necessary for the activity of holoenzyme. Cofactors may be inorganic (metal activators) or organic (coenzymes and prosthetic groups) and can be separated by dialysis.

DNA consists of deoxyribose sugar, phosphate molecules and nitrogenous bases—adenine, guanine, cytosine and thymine, whereas RNA consists of ribose sugar, phosphate molecules and nitrogenous bases—adenine, guanine, cytosine and uracil. Thus, estimating the incorporation of radiolabelled thymine can measure DNA synthesis and radiolabelled uracil can measure RNA synthesis.

All three protein enzymes amylase, rennin and trypsin act respectively on the substrates starch, lactose and protein. Amylase acts at an optimum pH—6.8-7, rennin at pH-2 and trypsin at an optimum pH—8.5.

Purines are 9-membered double ring nitrogen bases which possess nitrogen at 1, 3, 7 and 9 positions, e.g., adenine (A), guanine (G). These purines are present in both DNA and RNA.

Proteins are the most diverse among organic compounds. Among the biomolecules, proteins constitute 9-12%, fat 1-3%, carbohydrates 1-2%, minerals 1-3%, nucleic acids 2% and water 60-75%.

Starch and glycogen are storage polysaccharide and cellulose is a structural polysaccharide. Starch has straight chain of 1,4 α-D pyranose glucose units and side chains or amylopectin part of 2-200 thousand glucose units that are attached to straight chains by 1,6 α-D glycosidic bonds. Glycogen is long chain branched polymer of 5-300 thousand glucose units, straight chain linked by α-D 1-4 glycosidic bonds and side chains through α-D1→6 glycosidic bonds. Cellulose, a fibrous polysaccharide has a linear chain of 6-10 thousand 1→4 linked β-pyranose glucose chain.

The bonds that exist between the phosphate group of one nucleotide and hydroxyl group of sugar (ribose or deoxyribose) of the adjacent nucleotide is known as phosphodiester bond.

Pyrenoids consist of dense proteinaceous area surrounded by starchy sheath. These are unique to chloroplast of algae and are associated in polymerising sugars into reserve polymers (starch).

Enzymes act by reducing the activation energy required. The binding energy of the enzyme-substrate complex helps lower the activation energy.

Length of one helix or the pitch per turn of helix is 34Å in B-DNA, 25Å in A-DNA and 46Å in Z-model of DNA. In Z-DNA sugar moieties are seen in opposite direction. So the 3-5 diester bond forms zig-zag structure in Z-DNA.

Ribonucleic Acid (RNA) is a single chain polyribonucleotide which functions as carrier of coded genetic information from DNA to cytoplasm, and takes part in protein and enzyme synthesis. RNA is more common and abundant than DNA. There are six types of RNAs—ribosomal (most abundant), transfer RNA (15% of total RNA), messenger RNA (2–5%), small sized nuclear RNA, small cytoplasmic RNA, and genetic RNA (in viruses called riboviruses).

Nitrogen bases are of two types—purines and pyrimidines. Purines are 9-membered double ring nitrogen bases which possess nitrogen at 1, 3, 7 and 9 positions, e.g., adenine (A), guanine (G). Pyrimidines are 6-membered nitrogen bases that contain nitrogen at 1 and 3 positions, e.g., cytosine (C), thymine (T), uracil (U).

Amino acids are smallest structural units of proteins. Plants and some microorganisms can synthesise these amino acids from inorganic nitrogen/α-keto acids by reductive amination and transamination. Amino acids besides bearing a carboxyl group, possess an amino group attached to α-carbon, hence, called as α-amino acids.

In humans, about two-third of body is formed of water. About 65-70% of human body is water, of these about 55% (20-22 L) is confined to cells as intracellular water.

A glycogen molecule is a long highly branched chain of about 30,000 to 100,000 α-D glucose units joined by glycosidic bonds. It is storage form of glucose, popularly called animal starch. It provides energy to animals, fungi and bacteria.

Isoenzymes (analogous enzymes) are multiple molecular forms of the same enzyme with same substrate activity found in the same organism. Different genes produce different Km constants and operate at different pH. Examples: LDH has 5 isoenzymes in man, α-amylase in wheat has 16 isoenzymes.

Uracil forms nucleoside with only ribose sugar while thymine forms the same with only deoxyribose sugar. Other nitrogen bases (adenine, guanine, cytosine) produce nucleosides with both sugars.

Nucleic acids are repeating units of nucleotides, DNA is formed of the repeating units of deoxyribonucleotides and RNA is a mixed polymer chain of ribonucleotides.

Nucleic acids (DNA and RNA) are linear mixed polymers of nucleotides, also called polynucleotides. Nucleic acids were first discovered by Miescher (1868–69) as nuclein and named nucleic acid by Altmann (1889). They are formed of C, H, O, N and P comprising nitrogenous heterocyclic bases viz. purines or pyrimidines, pentose sugar and phosphoric acid.

Coenzymes/cofactors are organic substances (often vitamins) loosely attached to apoenzymes. A holoenzyme is a conjugated enzyme. Example: Potassium (K⁺) is an essential element, loosely held to the apoenzyme part of pyruvate kinase, acting as an inorganic cofactor (metal activator).

DeoxyriboNucleic Acid (DNA) is helically coiled macromolecule, made up of two antiparallel polydeoxyribonucleotide chains held together by hydrogen bonds. The chains are interlocked and are coiled around a common axis. DNA has a diameter of 20Å. One turn of spiral has a distance of 34Å containing 10 nucleotides in each turn.

Ribonucleic Acid (RNA) contains pyrimidine bases—cytosine and uracil and purine bases—adenine and guanine. Thymine is the pyrimidine base present only in DNA and uracil is present only in RNA, though other nitrogenous bases remain the same in both DNA and RNA.