Biomolecules Class 11 Biology Exam Questions

Exam Questions Class 11

Please refer to Biomolecules Class 11 Biology Exam Questions provided below. These questions and answers for Class 11 Biology have been designed based on the past trend of questions and important topics in your class 11 Biology books. You should go through all Class 11 Biology Important Questions provided by our teachers which will help you to get more marks in upcoming exams.

Class 11 Biology Exam Questions Biomolecules

Class 11 Biology students should read and understand the important questions and answers provided below for Biomolecules which will help them to understand all important and difficult topics.

Very Short Answer Type Questions:

Question. How are prosthetic groups different from co-factors?
Ans. Prosthetic groups are organic compounds that are tightly bound to the apoenzyme, (an enzyme without cofaetor) by covalent or non-covalent forces, e.g., in peroxidase and catalase, which catalyse the breakdown of hydrogen peroxide to water and oxygen, haeme is the prosthetic group and it is a part of the active site of the enzyme.
Co-factor is small, heat stable and non-protein part of conjugate enzyme. It may be inorganic or organic in nature.
Co-factors when loosely bound to a enzyme is called coenzyme and when tightly bound to apoenzyme is called prosthetic group.

Question. Glycine and alanine are different with respect to one substituent on the α-carbon. What are the other common substituent groups?
Ans. In both the amino acids the common substituent groups are NH2 COOH and H.

Biomolecules Class 11 Biology Exam Questions

Question. Medicines are either man made (i.e., synthetic) or obtained from living organisms like plants, bacteria, animals, etc., and hence, the latter are called natural products. Sometimes, natural products are chemically altered by man to reduce toxicity or side effects. Write against each of the following whether they were initially obtained as a natural product or as a synthetic chemical.
(a) Penicillin (b) Sulphonamide (c) Vitamin-C (d) Growth hormone
Ans. (a) Penicillin is a group of antibiotics derived from fungi Penicillium and was initially used as a natural product.
(b) Sulphonamide is a synthetic chemical. It is an antimirobial agent is the basis of several groups of drugs.
(c) Vitamin-C or L-ascorbic acid or ascorbate is a natural product and an essential nutrient for humans. It is present in citrus fruits.
(d) Growth hormone (GH or HGH) also known as somatotropin or somatropin is a peptide hormone occuring naturally in the body. It stimulates growth.

Question. Write the name of any one amino acid, sugar, nucleotide and fatty acid.
Ans. (a) Amino acid — Leucine (b) Sugar — Lactose
(c) Nucleotide — Adenosine triphosphate (d) Fatty acid — Palmitic acid

Question. Select an appropriate chemical bond among ester bond, glycosidic bond, peptide bond and hydrogen bond and write against each of the following.
(a) Polysaccharide (b) Protein (c) Fat (d) Water
Ans. (a) Polysaccharide is linked by glycosidic bond. Glycosidic bond is a type of covalent bond joining simple or units carbohydrate molecules together to form a long chain polysaccharide.

Biomolecules Class 11 Biology Exam Questions

(b) Protein are linked by peptide bonds. Peptide bond is a covalent chemical bond formed between two amino acids when the carboxyl group of one reacts with the amino group of other causing release of water molecule. Hence, called as dehydration synthesis reaction (condensation reaction).
Peptide bonds between a chain of amino acids results in the formation of protein.

Biomolecules Class 11 Biology Exam Questions

(c) Ester bonds are formed by the reaction between carboxyl group of fatty acid and hydroxyl group of triglycerols to form fat. Water is eliminated during this reaction.

Biomolecules Class 11 Biology Exam Questions

(d) Hydrogen bond is electrovalent interaction between polar molecules in which hydrogen is bound to a highly electronegative atom, such as N, O, S, F, etc. Water is the best known example

Biomolecules Class 11 Biology Exam Questions

Question. Starch, cellulose, glycogen, chitin are polysaccharides found among the following. Choose the one appropriate and write against each.
Cotton fibre ………………
Exoskeleton of cockroach ………………
Liver ………………
Peeled potato ………………
Ans. (a) Cotton fibre — Cellulose (b) Exoskeleton of cockroach — Chitin
(c) Liver — Glycogen (d) Peeled potato — Starch
Cellulose is a long chain of linked glucose molecules and is the main component of plant cell walls. Cotton is the purest natural form of cellulose. the cellulose content of cotton fibre is 90%.
Chitin is a long chain polymer that forms the hard part of the outer integument or exoskeleton of crustaceans and insects such as cockroach. It is also the main component of the cell walls of fungi.
Glycogen is a multibranched polysaccharide of glucose acting as a form of stored energy in the liver of animals.It is also found in some stored fungi.
Starch is a carbohydrate consisting of along chain of glucose units joined by glycosidic bonds. This polysaccharide is produced mostly by green plants for energy storage, e.g., peeled potato.

Question. Reaction given below is catalysed by oxidoreductase between two substrates A and A’, complete the reaction.
A reduced + A’ oxidised →
Ans. Oxidoreductase is an enzyme that catalyses oxidation and reductions reactions. This enzyme is associated in catalysing the transfer of e− from one molecule (the reductant),
also called as electron donor, to another molecule (the oxidant), also called as electron acceptor.
The complete reaction is

Biomolecules Class 11 Biology Exam Questions

Short Answer Type Questions:

Question. Schematically represent primary, secondary and tertiary structures of a hypothetical polymer say for example a protein.
Ans. Proteins are the large-sized, heteropolymeric macromolecules having one or more polypeptides (chains of amino acid).
Primary Structure The primary structure of a protein is the linear sequence of amino acid structural units and partially comprises its overall biomolecular structures. The amino acids are linked together in a sequence by peptide bonds.
In the primary structure of protein initiate from an amino-terminal (N) to the carboxyl terminal (C) end,

Biomolecules Class 11 Biology Exam Questions

Secondary Structure It is a three dimensional form of local segments of bipolymers such as proteins. Secondary structure of proteins is defined by hydrogen bonds between backbone amino and carboxyl groups. Mainly secondary structure in proteins possess two forms, i.e., a-helix and b-pleated sheet.
α-helix
is a polypeptide chain spirally coiled to form a right handed helix. This helix may be coiled regularly at places and at some places randomly coiled. The helix is stabilised by many hydrogen bonds which are formed between —CO of one amino acid and —NH group of next fourth amino acid.
β-pleated
sheets two or more polypeptide chains are joined together by intermolecular hydrogen bonds to produce a sheet like structure instead of fibre as in a-helix. The polypeptide strands in a sheet may run parallel in same direction, e.g., keratin or in opposite direction called antiparallel β-sheet, e.g., fibroin.

Biomolecules Class 11 Biology Exam Questions

Tertiary structure involves interactions that are caused by the bending and folding of α-helix or b-sheets leading to the formation of rods, spheres of fibres. Such interactions are typically conferred by H-bonds, ionic bonds, covalent bonds, van der Waat’s interactions and hydrophobic interactions or disulphide linkages. It gives the protein a three dimensional conformation.

Biomolecules Class 11 Biology Exam Questions

Question. Enzymes are proteins. Proteins are long chains of amino acids linked to each other by peptide bonds. Amino acids have many functional groups in their structure.
These functional groups are many of them at least, ionisable. As they are weak acids and bases in chemical nature, this ionisation is influenced by pH of the solution. For many enzymes, activity is influenced by surrounding pH. This is depicted in the curve below, explain briefly.

Biomolecules Class 11 Biology Exam Questions

Ans. Enzymes, generally function in a narrow range of pH. Most of the enzyme shows their highest activity at a particular pH called optimum pH, and it declines below and above this value.
Extremely high or low pH values generally results in complete loss of activity for most enzyms. The graph above represents the maximum enzyme activity at the optimum pH.

Question. Nucleic acids exhibit secondary structure, justify with example.
Ans.
Nucleic acids are polymeric macromolecules or large biological molecules, essential for all known forms of life. The secondary structrure of a nucleic acid molecule refers to the base pairing interactions within a single molecule or set of interacting molecules.
DNA and RNA represent two main nucleic acids, however their secondary structures differ e.g., the secondary structure of DNA comprises of two complementary strands of polydeoxyribonucleotide, spirally coiled on a common axis forming a helical structure.
This double helical structure of DNA is stabilised by phosphodiester bonds (between 5′ of sugar of one nucleotide and 3 of sugar of another nucleotide), hydrogen bonds (between bases, i.e., hydrogen of one base and nitrogen of oxygen of other base) and ionic interactioins.

Question. Is rubber a primary metabolite or a secondary metabolite? Write four sentences about rubber.
Ans. Rubber (cis 1, 4-polyisopyrene) is a secondary metabolite. Secondary metabolites are chemicals produced by plants for which no role has been found yet in growth, photosynthess, reproduction or other primary functions.
(i) Rubber is extracted from Havea brasiliensis (rubber tree).
(ii) It is a byproduct of the lactiferous tissue of the vessels that are in the form of latex.
(iii) It is the largest of the terpenoids because it contains over 400 isoprene units.
(iv) It is elastic, water proof and a good electrical conductor.

Question. Comment on the statement ‘living state is a non-equilibrium steady state to be able to perform work’.
Ans. Living organism are not in equilibrium because system at equilibrium cannot perform work. The living organisms exist in a steady state characterised by concentration of each of the biomolecules.
These biomolecules are in a metabolic flux. Any chemical or physical process moves simultaneously to equilibrium. As living organisms work continuously, they cannot afford to reach equilibrium. Hence, the living state is in a non-equilibrium steady-state to be able to perform work. This is achieved by energy input provided lay metobolism.

Long Answer Type Questions:

Question. Nucleic acids exhibit secondary structure. Describe through Watson-Crick model.
Ans. Nucleic acids are long chain macromolecules which are formed by end to end polymerisation of large number of repeated units called nucleotides. Nucleic acids show a wide range of secondary structures. A secondary structure is the set of interactions between bases and sugar phosphate backbone and is responsible for the shape that nucleic acid.

Biomolecules Class 11 Biology Exam Questions

James Watson and Francis Crick proposed a secondary structure of DNA molecules based on the crystallographic studies.
(i) DNA or deoxyribonucleic acid is a helically twisted double-chain polydeoxyribonucleotide macromolecule.
(ii) The two strands of DNA run anti-parallely to each other called as DNA duplex.
(iii) The spiral twisting of DNA has two types of alternate grooves, i.e., major and minor.
(iv) One turn of 360° of the spiral has about 10 nucleotides on each strand of DNA, occupying a distance of about 3.4 nm.
(v) The nucleotides within each strand are held together by the phosphodiester bonds between the 5′ carbon of one nucleotide and the 3′ carbon of the adjacent nucleotide.
These strong covalent bonds holds the sugar/phosphate backbone together.
(vi) The two strands of DNA are held together by weak hydrogen bonds between the nitrogenous bases. These hydrogen bonds are base specific. That is adenine forms 2 hydrogen bonds with thymine CA=T and cytosine forms 3 hydrogen bonds with guanine (C = G).
(vii) As specific and different nitrogen bases occur on two DNA chains, they are said to be complementary, i.e., purine lies opposite to pyrimidine. This purine-pyrimidine pairing
also contributes to the thickness of strand, i.e., 2nm, and makes the two chains complementary.

Biomolecules Class 11 Biology Exam Questions

Question. Describe various forms of lipid with a few examples.
Ans. Lipids are the esters of higher fatty acid with alcohol, such as glycerol, etc.
These can be classified as
1. Simple Lipids are esters of fatty acids with alcohol. These may be
(i) Fats These are esters of higher fatty acids with glycerol (triglycerides).
(ii) Waxes These are esters of higher fatty acids with alcohol other than glycerol.
2. Compound or conjugated lipids, are those compounds which contain simple lipids and prosthetic (other additional) group. They include
(i) Glycerophospholipids, also known as phospholipids in which one of the fatty acid is replaced by phosphoric acid which is linked to nitrogenous groups like choline, ethanolamine, serine etc, e.g., Lecithin and cephalin, etc.
(ii) Sphingo lipids, are lipides having phosphoric acid with amine alcohol 4-sphinganine or sphingosine instead of glycerol in addition to fatty acid and choline.
(iii) Glycolipids, i.e., those which contain spinganine with a fatty acid and a monosaccharide sugar, e.g., cerebrosides and gangliosides.
3. Steroids are compounds with different chemical nature but similar physical properties.
Their structure is based upon a 4 ring cyclopentenoperhydro phenanthrene, e.g., cholesterol.
4. Prostoglandins are derivatives of arachidonic acid and contain 20 C-atoms. These are biologically active lipids.

Biomolecules Class 11 Biology Exam Questions

Question. Formation of Enzyme substrate complex (ES) is the first step in the catalysed reactions. Describe the other steps till the formation of product.
Ans. Each enzyme molecule has an active site for specific binding of substrate molecules .The enzyme work by altering the activation energy of the reaction.
The catalytic site of an enzyme can be described as follows
(i) The substrate process to the active site of the enzyme, fitting into it.
(ii) Binding of the substrate induces the enzymes to alter its shape leading to formation of the Enzyme Substrate (ES) complex.
(iii) The active site of the enzyme, now is in close proximity with the substrate and break its chemical bonds and a new enzyme product complex is formed.
(iv) The enzyme releases the products of the reaction and the free enzyme is ready to bind to another molecule of substrate and run through the catalytic cycle once again.

Biomolecules Class 11 Biology Exam Questions

Question. What is the difference between a nucleotide and nucleoside? Give two examples of each with their structure.
Ans. Difference between a nucleotide and nucleoside is as follows

Biomolecules Class 11 Biology Exam Questions

Question. What are different classes of enzymes? Explain any two with the type of reactions they catalyse.
Ans. Enzymes are divided into six classes each with 4-13 sub-classes and named accordingly by a four-digit number.
(i) Oxidoreductases/dehydrogenases These enzymes take part in oxidation and reduction or transfer of e.
S (reduced) + S’ (oxidised) → S (oxidised) + S’ (reduced)
(ii) Transferaes These enzymes transfer a functional group from one molecule to another (other than hydrogen). The chemical group transfer does not occur in free state.

Biomolecules Class 11 Biology Exam Questions

(iii) Hydrolases These enzymes catalyse the hydrolysis of bonds like ester, ether, peptide, glycosidic C-C, C-halide, P-N etc.

Biomolecules Class 11 Biology Exam Questions

(iv) Lyases These enzymes causes cleavage, removal of groups without hydrolysis and addition of groups to double bonds or removal of groups producing double bond.

Biomolecules Class 11 Biology Exam Questions

(v) Isomerases These enzymes cause rearrangement of molecular structure to effect isomeric changes. They are of three types, i.e., isomerases, epimerases and mutases.

Biomolecules Class 11 Biology Exam Questions
Biomolecules Class 11 Biology Exam Questions

(vi) Ligases are enzymes catalysing bonding of two chemicals with the help of energy obtained from ATP resulting formation of bonds such as C —O, C —S, C —N and P—O e.g., pyruvate carboxyl use

Biomolecules Class 11 Biology Exam Questions