Title Ex-2 Qs+Ans+sol.(Biomolecules).pdf ✅

30 BIOMOLECULES EXERCISE – 2: Previous Year Competition Questions 1. Which of the following are not secondary metabolites in plants? (NEET 2021) (a) Vinblastin, curcumin (b) Rubber, gums (c) Morphine, codeine (d) Amino acids, glucose Ans. (d) Sol. Secondary metabolites are organic compounds produced by various organisms such as fungal, microbial, and plant cells. They do not play an important role in normal physiological processes but do have ecological importance. The following table shows the various categories of secondary metabolites. Pigments Carotenoids, Anthocyanins, etc. Alkaloids Morphine, Codeine, etc. Terpenoides Monoterpences, Diterpences etc. Essential oils Lemon grass oil, etc. Toxins Abrin, Ricin Lectins Concanavalin A Drugs Vinblastin, curcumin, etc. Polymeric substances Rubber, gums, cellulose From the above table, it is clear that option (d) i.e., amino acids and glucose do not belong to the secondary metabolite category while others are secondary metabolites. 2. Identify the incorrect pair. (NEET 2021) (a) Lectins- Concanavalin A (b) Drugs- Ricin (c) Alkaloids- Codeine (d) Toxin- Abrin Ans. (b) Sol. There are many different categories of secondary metabolites produced by various organisms. Out of the four pairs given above, the (b) option is incorrect because ricin belongs to the toxin category, not to drugs. Hence, the (b) option is incorrectly paired. 3. Following are the statements with reference to ‘lipids’. (NEET 2021) (a) Lipids having only single bonds are called unsaturated fatty acids. (b) Lecithin is a phospholipid. (c) Trihydroxy propane is glycerol. (d) Palmitic acid has 20 carbon atoms including carboxyl carbon. (e) Arachidonic acid has 16 carbon atoms. Choose the correct answer from the given options below. (a) (b) and (c) only (b) (b) and (e) only (c) (a) and (b) only (d) (c) and (d) only Ans. (a) Sol. -Lipids are water-insoluble fatty acids. Fatty acids are composed of carboxyl group attached to the R group where R group can be methyl (-CH3), ethyl (- C2H5), etc. Palmitic acid has 16 carbons atoms whereas arachidonic acid has 20 carbon atoms including carboxyl carbon. Hence, the (d) and (e) statements are wrong. -Depending upon the type of bonds, lipids can be saturated (with single bonds) and unsaturated (with double bonds). Hence, the (a) statement is also incorrect. - Some lipids also contain phosphorus and phosphorylated group. For example- Lecithin is a phospholipid, present in the cell membrane. Hence, the (b) statement is correct. - The simplest lipid is glycerol which is trihydroxy propane. Hence, the (c) statement is correct. Therefore, option (a) is correct. 4. Match list-I with list-II. (NEET 2021) List-I List-II (a) Protein (i) C=C bonds (b) Unsaturated fatty acids (ii) Phosphodiester bonds (c) Nucleic acids (iii) Glycosidic bonds (d) Polysaccharides (iv) Peptide bonds (a) (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii) (b) (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
BIOMOLECULES 31 (c) (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii) (d) (a)-(i), (b)-(iv), (c)-(iii), (d)-(ii) Ans. (c) Sol. -Proteins are composed of a linear chain of amino acids which are linked by peptide bonds. The peptide bond is formed when the carboxyl group of one amino acid reacts with the amino group of another amino acid with loss of water (dehydration). -Polysaccharides are composed of sugar/monosaccharides molecules that are joined to each other via glycosidic bonds. This bond is formed by the condensation of two carbon atoms of monosaccharide units with a loss of water. - Fatty acids can be of two types depending upon the types of the bond present- Saturated fatty acids (with single bonds) and unsaturated fatty acids (with double bonds). -Nucleic acids are composed of nucleotides which are joined by phosphodiester bonds where a 3’-carbon of one sugar of a nucleotide to 5’-carbon of sugar of the next nucleotide by a phosphate group. The bond formed between phosphate and hydroxyl group is an ester bond. As there is one ester bond formed on either side, it is known as a phosphodiester bond. Hence, option (c) is correct. 5. Identify the basic amino acid from the following. (NEET 2020) (a) Lysine (b) Valine (c) Tyrosine (d) Glutamic acid Ans. (a) Sol. Based on the number of amino and carboxyl groups, the amino acids are categorized into three classes Acidic amino acid- Glutamic acid Basic amino acid- Lysine Neutral amino acid- Valine, tyrosine Out of the four amino acids given above, lysine is a basic amino acid. Hence, (a) option is correct. 6. Which one of the following is the most abundant protein in the animals? (NEET 2020) (a) Lectin (b) Insulin (c) Hemoglobin (d) Collagen Ans. (d) Sol. Proteins are composed of amino acids. They perform a wide variety of functions such as replication, defense, dietary activities, etc. Collagen is the main structural component of the extracellular matrix (ECM). It is the most abundant protein present in the animal world. Hence, the (d) option is correct. Whereas lectins are carbohydrate-binding proteins that bind to specific sugars. Insulin is a peptide hormone secreted by beta cells of the pancreas. Its main function is to control the metabolism of carbohydrates, fats, and proteins. Hemoglobin is an iron-containing metalloprotein present in the red blood cells of vertebrates. Adult hemoglobin is made up of 4 subunits. i.e., 2 α and 2- β subunits. 7. Identify the substances having glycosidic bonds and peptide bonds, respectively in their structure. (NEET 2020) (a) Cellulose, lecithin (b) Inulin, insulin (c) Chitin, cholesterol (d) Glycerol, trypsin Ans. (b) Sol. -A glycosidic bond is formed by condensation of one carbon atom of one monosaccharide with another carbon atom of the next monosaccharides with loss of water. These bonds are present in polysaccharides. Out of the options given above, only cellulose and inulin are polysaccharides. -A peptide bond is formed when the carboxyl group of one amino acid reacts with an amino group of the next amino acid with loss of water. These bonds are present in proteins. Out of the four options given above, trypsin and insulin are proteins. Hence, the (b) option is correct. -Whereas glycerol, lecithin, and cholesterol belong to the lipid category. 8. Secondary metabolites such as nicotine, strychnine, and caffeine are produced by plants for their (NEET 2020) (a) Defense action (b) Effect on reproduction (c) Nutritive value (d) Growth response Ans. (a) Sol. Different varieties of secondary metabolites are produced by plants. One of them is alkaloid compounds which mainly play an important role in defense action against herbivores. For example- Nicotine is produced by the tobacco plant, strychnine is produced by Strychnos nux-vomica, and caffeine is produced by coffee plants. 9. Which one of the following statements is correct? (NEET 2020) (a) Adenine pairs with thymine through three H- bonds. (b) Adenine does not pair with thymine
32 BIOMOLECULES (c) Adenine pairs with thymine through two H-bonds. (d) Adenine pairs with thymine through one H-bonds. Ans. (c) Sol. DNA is composed of two polynucleotide chains that have antiparallel polarity. The backbone of polynucleotide chains is formed by the sugar- phosphate-sugar chain and nitrogenous bases project inside. The nitrogenous bases present in two strands are paired by hydrogen bonds (shown in the figure). Adenine pairs with thymine through two hydrogen bonds (arrowed in the image) whereas guanine pairs with cytosine through three hydrogen bonds. Hence, the (c) option is correct. 10. Match the following. (NEET 2020) (a) Inhibitor of catalytic activity (i) Ricin (b) Possess peptide bonds (ii) Malonate (c) Cell wall material in fungi (iii) Chitin (d) Secondary metabolite (iv) Collagen Choose the correct option from the following. (a) (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii) (b) (a)-(ii), (b)-(iii), (c)-(i), (d)-(iv) (c) (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i) (d) (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii) Ans. (c) Sol. Secondary metabolites are those organic compounds that do not play an important role in the normal physiological processes. An example of a secondary metabolite is ricin (toxin). -Amino acids are joined with each other via peptide bonds to form protein. An example of protein is collagen. -The cell wall of fungi is made up of complex polysaccharides known as chitin. -Inhibitor is a substance which when binds to an enzyme, shuts off enzyme activity. This process is known as inhibition. When the inhibitor closely resembles the substrate and inhibits the activity of enzymes is known as competitive inhibition. An example of competitive inhibition is malonate. Malonate inhibits the activity of the succinate dehydrogenase enzyme and closely resembles its substrate succinate. -Hence, the correct option is (c). 11. Concanavalin A is (NEET 2019) (a) An alkaloid (b) An essential oil (c) A lectin (d) A pigment Ans. (c) Sol. A variety of secondary metabolites are produced by the plant, microbial and fungal cells. Concanavalin A is a lectin (carbohydrate-binding protein). Hence, the (c) option is correct. 12. Purines found both in DNA and RNA in (NEET 2019) (a) Adenine and thymine (b) Adenine and guanine (c) Guanine and cytosine (d) Cytosine and thymine Ans. (b) Sol. Nucleotides are composed of three components- A nitrogenous base, a pentose sugar, and phosphate. nitrogenous bases are of two types- Purines (Adenine, guanine) and pyrimidines (Cytosine, thymine, and uracil). Purines are present in RNA and DNA. However, in the case of pyrimidines, cytosine is present in both RNA and DNA. Uracil is RNA exclusive while thymine is DNA exclusive. Hence, the (b) option is correct. 13. Consider the following statements. (NEET 2019) 1. Coenzyme or metal ion that is tightly bound to enzyme protein is called a prosthetic group. 2. A complete catalytic active enzyme with its bound prosthetic group is called apoenzyme. Select the correct option. (a) Both 1 and 2 are true (b) 1 is true but 2 is false (c) Both 1 and 2 are false (d) 1 is false but 2 is true Ans. (b) Sol. A conjugate enzyme is composed of 2 parts- protein component (Apoenzyme) and non-protein part (co- factor). A cofactor is a non-protein component that binds with the protein component and makes the enzyme catalytically active. So, statement 2 is incorrect because a complete catalytic active enzyme with its bound prosthetic group is called holoenzyme, not apoenzyme. Apoenzyme + Cofactor = Holoenzyme Co-factors are of three types- Co-enzyme, prosthetic group, and metal ions. Prosthetic groups are organic compounds that bind tightly to the apoenzyme. For example- Haem is a prosthetic group of peroxidase and catalase enzymes. Hence, statement 1 is correct.
BIOMOLECULES 33 Whereas other co-factors loosely bind to an apoenzyme. 14. The two functional groups characteristic of sugars are (NEET 2018) (a) Carbonyl and phosphate (b) Carbonyl and methyl (c) Hydroxyl and methyl (d) Carbonyl and hydroxyl Ans. (d) Sol. Sugars are also called carbohydrates. Carbohydrates can be defined as aldehyde or ketone compounds which are polyhydroxy (OH group-containing) and compounds which under hydrolysis will give us the former. Hence, the important functional groups are carbonyl and hydroxyl. 15. Which one of the following statements is correct with reference to enzymes? (NEET 2017) (a) Apoenzyme = Holoenzyme + Coenzyme (b) Holoenzyme = Apoenzyme - Coenzyme (c) Coenzyme = Apoenzyme + Holoenzyme (d) Holoenzyme = Apoenzyme + Co-factor Ans. (d) Sol. A holoenzyme is complete and catalytically active. Holoenzyme (complete enzyme structure) has two components: apoenzyme (protein portion) and co- factor (non-protein portion activating the enzyme). Co-factors can be inorganic (metal ions) or organic. Organic cofactors are of two types: Prosthetic group (if it is tightly bound) and coenzyme (if loosely attached). 16. Which of the following are not polymeric? (NEET 2017) (a) Nucleic acids (b) Proteins (c) Polysaccharides (d) Lipids Ans. (d) Sol. By definition, a polymer has monomeric units which bind to each other by a particular bond. In proteins, for example, the attachment of amino acids is via peptide bonds. Lipids however are esters of glycerol and fatty acid chains and are fat-soluble. Lipid can be a big molecule but since it does not have any monomers, it cannot be classified as to form polymers. 17. A typical fat molecule is made up of (NEET 2016) (a) Three glycerol molecules and one fatty acid molecule (b) One glycerol and three fatty acid molecules (c) One glycerol and one fatty acid molecule (d) Three glycerol and three fatty acid molecules Ans. (b) Sol. A typical lipid or fat molecule has one glycerol and three fatty acid molecules. It is the general structure to understand any lipid structure. 18. Which one of the following statements is wrong? (NEET 2016) (a) Sucrose is a disaccharide (b) Cellulose is a polysaccharide (c) Uracil is a pyrimidine (d) Glycine is a sulfur-containing amino acid Ans. (d) Sol. Glycine is the simplest amino acid. The general structure of an amino acid has a carbon molecule to which a carboxyl, amino, a hydrogen and a substituent group attach. In the case of glycine, the substituent group is hydrogen and so, not a sulfur- containing amino acid. 19. A non-proteinaceous enzyme is (NEET 2016) (a) Lysozyme (b) Ribozyme (c) Ligase (d) Deoxyribonuclease Ans. (b) Sol. Most enzymes are proteins. A non-proteinaceous enzyme is a ribozyme, which is RNA chain that catalyzes just like its protein counterparts do. It is found in the ribosomes where amino acids are joined. 20. Which of the following biomolecules is common to the respiration-mediated breakdown of fats, carbohydrates, and proteins? (NEET 2016) (a) Glucose-6-phosphate (b) Fructose 1, 6-bisposphate (c) Pyruvic acid (d) Acetyl CoA Ans. (d) Sol. Respiration is amphibolic in nature (meaning it is both catabolic and anabolic), where carbohydrates form pyruvic acid (via glycolysis), even proteins form pyruvic acid (via transamination). It then enters the mitochondria where it is broken down into acetyl CoA. Fats oxidize to form acetyl Co-A. Hence, the common biomolecule among these is acetyl CoA. 21. Which of the following is the least likely to be involved in stabilizing the three-dimensional folding of most proteins? (NEET 2016) (a) Hydrogen bonds (b) Electrostatic interaction (c) Hydrophobic interaction (d) Ester bonds Ans. (d) Sol. Ester bonds are least likely involved in stabilizing the three-dimensional folding of most proteins as this bond is found in lipids, where the fatty acid chains are attached to the glycerol molecule by the ester bonds.