Short Answer Type Questions-II

Q. 1. What are the various types of nitrogen bases found in DNA ? Name the type of
bond seen between (i) two nitrogen bases of DNA (ii) phosphate and hydroxyl group of
sugar of DNA. [KVS Silchar 2017]
Ans. Types of nitrogenous bases found in DNA are:
(a) Adenine : Abbreviated 'A', has a 2-ring structure, so that it is a purine.
(b) Thymine: Abbreviated T, is a pyrimidine, which. means it has a 1-ring structure. It's only
present in DNA, where it pairs with adenine.
(c) Guanine: Abbreviated 'G', is part of both DNA, where it bonds with cytosine.
(d) Cytosine : abbreviated C, is part of DNA and bonds with guanine. It has one ring, so it's
a pyrimidine.
(i) Hydrogen bond
(ii) Phosphodiester bond
Q. 2. Give the structural formula of (i) adenine (ii) adenosine (iii) adenylic acid.
[KVS Agra 2017]
Ans.

Q. 3. Describe the primary, secondary and tertiary structure of a protein ? [KVS Agra
2016]
Ans. (i) Primary Structure : The linear sequence of amino acids units in a polypeptide chain
is called the primary structure of protein molecule.
Ribonuclease an enzyme, is a protein with primary structure only.
(ii) Secondary Structure : The polypetides chain that forms a 3-dimensional structure, is
called as secondary structure. It possess three forms :
(a) α helix: The coils of helix are held together by hydrogen bonds between amino acids.
(b) β helix : More than one chain lie side by side joined together by hydrogen bonds between
the carboxyl group of amino acids.
(c) Collagen proteins: It is a right handed super helix formed by the twisting of three helices
of polypeptide chains interwined with each other.
(iii) Tertiary Structure : The tertiary structure of protein brings distant amino acid side, chains
nearer to form active sites of enzyme proteins. The tertiary structure is maintained by weak
bonds, such as hydrogen, ionic and hydrophilic hydrophobic bonds, formed between one part
of a polypeptide and another The biological activity of a protein molecule depends largely on
the specific tertiary structure Tertiary structure is found in globular proteins.
Q. 4. RNA and DNA are the basic genetic material of living beings. Write three points of
difference between them. [KVS Guwahati 2016]
Ans. Difference between DNA and RNA is :

S.No. DNA RNA

(i) It usually occurs inside the nucleus Very little RNA occurs inside the nucleus.
and some cell organelles. Most of it is found in the cytoplasm.
(ii) DNA is the genetic material RNA is not the genetic material except in
certain viruses.
(iii) It is double stranded except some RNA is single stranded with exception of
viruses. some viruses.
(iv) It contains deoxyribose sugar. It contains ribose sugar.
(v) Nitrogen base thymine occurs in DNA Thymine is replaced by uracil. The other
along with three others-adenine, three are similar.
cytosine and guanine
(Any three)
Q. 5. Distinguish between Biomicromolecules and Biomacromolecules.
Ans.
S.No. Biomicromolecules Biomacromolecules
(i) Small in size. Large in size.
(ii) Low molecular weight. High molecular weight.
(iii) Possess simple structure. Possess complex structure.
(iv) Found as molecular solution in intracel- Found as colloidal solution in intra-
lular fluid. cellular fluid.
(v) Building blocks (monomers) of mac- Constituted by polymerization of
romolecules. macromolecules.
(vi) E.g., inorganic water compounds E.g., only organic compounds (poly-
(mineral salts, gases), organic saccharides, proteins and nucleic acids).
compounds (sugars, lipids, nucleotides).
Q.6. What is the difference between nucleotide and nucleoside ? Give one example of
each.
Ans.

S.No. Nucleotide Nucleoside

(i) Nucleotide is made up of base, sugar and Nitrogenous base and sugar form a
phosphoric acid. nucleoside.
(ii) Nucleotide of RNA is called ribonucleo- Nucleoside with - ribose sugar is
tide and nucleotide having deoxyribo- called riboside or ribonucleoside.
nucleotide is called deoxyribonucleotide. Nucleoside with deoxyribose sugar is
called deoxyribonucleoside.
(iii) Example : Adenylic acid, guanylic acid, Example: Adenosine, guanosine,
cytidylic acid, thymidylic acid, uridylic cytidine, thymidine and uridine.
acid, AMP.

Q. 7. What are nucleotides ? Describe their structure. [KVS Guwahati 2016]

Ans. Nucleotides are the building blocks of nucleic acids. They are composed of three subunit
molecules:
(i) Nitrogenous bases : Cytosine (C). Thymine (T), Adenine (A), Guanine (G).
(ii) Five carbon sugar.
(iii) Phosphate group.
The phosphate group and 5-carbon sugar compose the backbone of the double helix, while
the nitrogenous bases are located in the middle and are bonded to each other.
Q. 8. What is meant by tertiary structure of protein? Why a tertiary structure is essential
for a protein? [KVS Mumbai 2016]
Ans. The complex three dimensional shape formed by the coiling and folding of helical
polypeptide chain is known as tertiary structure of proteins. Such structure are held together
by weak bonds formed between various parts of polypeptide chain. The biological activity of a
protein molecule depends largely upon the specific tertiary structure.
Q. 9. List out six major proteins and their functions.
Ans. Collagen - Intercellular ground substance
Trypsin - Enzyme
Antibody - Fights infectious agents
Receptor - Sensory perception
GLUT-4 - Enable glucose transport into cells.
Insulin – Hormone
Q.10. List any five functions of nucleic acids.
Ans. (i) DNA is a genetic material which carries all the hereditary information.
(ii) DNA also transfer genetic information from one generation to other.
(iii) RNAs are involved in the expression of genetic code of DNA by forming specific protein.
(iv) Some RNAs act as enzyme.
(v) RNA helps in protein synthesis. (Any three)
Q. 11. What are fatty acids ? Compare saturated and unsaturated fatty acids.
Ans. Fatty acids : Fatty acids are organic acids with a long hydrocarbon chain ending in
carboxyl group (-СООН).
Characteristics of fatty acids are:
(i) Has a long chain of carbon atoms.
(ii) Is insoluble in water.
(iii) Is soluble in organic solvents.
(iv) Must leave an oily spot on a piece of paper.
(i) Saturated fatty acids : They do not have any double bond in between carbon atoms of
molecular chain. Examples are:

Palmitic acid - CH3 (CH2)14СООН

Stearic acid – CH3 (CH2)16СООН
(ii) Unsaturated fatty acids: They have one or more double bonds in between carbon atoms
of molecular chain. Unsaturated fatty acids have lower melting points as compared to
saturated fatty acids. Examples are:
Oleic acid – CH3 (CH2)7CH = CH(CH2)7 COOH
Linoleic acid – CH3 (CH2)4CH = (CHCH2)2 (CH2)6 COOH
Q. 12. Differentiate between anabolic and catabolic pathways. How are the pathways
regulated ?
Ans.

S. No. Anabolic pathways Catabolic pathways

(i) Anabolic pathway is called anabolism. Catabolic pathways is known as
catabolism.
(ii) It consumes energy to make complex It liberates energy by breaking
molecules like glucose. chemical bond. Glucose is broken
down to release energy.

(iii) Example: Photosynthesis. Example: Cellular respiration.

Regulation of Pathways: (i) Biochemical pathways are tightly regulated by cells regulatory
systems.
(ii) It depends on the allosteric site on the enzyme that catalyses the first reaction in the
pathway.
(iii) The product of one reaction may serve as substrate for next reaction.
(iv) The method of regulating mechanism is feedback mechanism.
Q.13. How are amino acids bonded together ? Describe how these bonds are formed.
Ans. Two amino acids are joined through amino group of one and carboxylic group of the
other forming peptide group by loss of water molecule.

Q.14. What are mucopolysaccharides?

Ans. (i) Mucopolysaccharides are the slimy substances or mucilages which possess acidic or
aminated polysaccharides formed from galactose, mannose, sugar derivatives and uronic
acids.
(ii) They are found inside the plant cell walls, outside the cells or bodies of bacteria, blue-
green algae, cementing layer between cells, inside body fluids, connective tissues and
cartilages.
Q. 15. In nutshell explain the various types of nucleic acids.
Ans. Various types of nuclei acids are:
S.No Name Type of molecule Location/site Function (s)
(i) Deoxyribonucleic Shape: double In nucleus, mito- Acts as store of coded
acid (DNA). helix; with many chondria and instructions; for
thousands of sub- chloroplasts. synthesis of proteins
units. needed by cells.
 (ii) Messenger Single-stranded; In nucleus, cyto- Made on DNA
ribonucleic acid polymer, with plasm, and ribo- template; carry coded
(mRNA). hundred of sub- somes. instruction for protein
units. synthesis.
(iii) Ribosomal Single-stranded Only occurs in Makes part of
ribonucleic acid (ss), polymer of ribosomes. ribosome
(rRNA). less than one structure; helps in
hundred sub-units. locating mRNA.
(iv) Transfer Single-stranded Occurs in cyto- Acts as amino acid
ribonucleic (ss), polymer of plasm. carriers; takes specific
acid (tRNA). less than one amino acid
hundred sub-units. from cytoplasm to
mRNA
template on the
ribosomes.

Q. 16. Define primary and secondary metabolites. [KVS 2012-13]

Ans. (1) Primary metabolities : Metabolites which are found in animal tissues. They play
specific role in normal physiological process. e.g., carbohydrates, protein, fats.
(ii) Secondary metabolites : These are metabolites found in plant, fungal and microbial
cells as a by product of main metabolic reactions. e.g. Alkaloids, rubber, terpenoides,
essential oils, etc.
Q. 17. (i) On what basis are enzymes classified ?
(ii) List any four classes of enzymes and mention their functions ? [KVS Mumbai 2016]
Ans. Enzymes are classified according to their function and type of reaction in which they are
taking part. Four main classes of enzymes are :
(i) Oxidoreductases : These enzymes catalyze oxidation and reduction reactions, usually
involving the transfer of hydrogen from one molecule to another.
S reduced + S’ oxidized ------S oxidized + S’ reduced
(ii) Transferases : These enzymes transfer a chemical group from one substrate to another
but never hydrogen e.g. phosphotransferase catalyzes the transfer of a phosphate group from
one molecule to another.
(iii) Hydrolases : These enzymes carry out hydrolysis reactions i.e., breakdown of large
molecules by addition of water e.g. lipases breakdown lipids into fatty acids and glycerol.
(iv) Ligase or synthetase : These enzymes form bonds to join two molecules together, using
energy supplied from the breakdown of ATP e.g. DNA ligase is used to repair breaks in DNA
molecules.
Q. 18. State the effect of chemicals on enzyme action with suitable example. [KVS Agra
2016]
Ans. The enzymes are proteins having high molecular weight. Enzymes are highly specific in
their action. Enzymes action can be inhibited by certain chemicals. It is called enzyme
inhibition, e.g. noncompetitive inhibition.
Non-competitive inhibition : Some chemicals act like poison and destroy the enzyme
structure. Non-competitive inhibitors do not resemble the substrate in structure. They inhibit
the enzyme action by binding to the enzyme at the place other than the active site, e.g.
cyanide inhibits the mitochondrial enzyme cytochrome oxidase which is necessary for
respiration.
Q. 19. Enzymes are classified into different groups based on the reaction they catalyse.
Write the name and function of each of these groups of enzymes. [KVS Silchar 2017]

OR
In how many categories are enzymes classified? [NCT-2007]
Ans. The modern system of enzyme classification was introduced by International Union of
Biochemistry. It grouped enzymes into the following six categories :
(i) Oxidoreductases : They take part in oxidation and reduction reactions or transfer of
electrons.
(ii) Transferases : They transfer group from one molecule to another e.g., glutamate pyruvate
transaminase.
(iii) Hydrolases : They break up large molecules into smaller ones with the help of hydrogen
and hydroxyl groups of water molecules. The phenomenon is called hydrolysis.
(iv) Lyases : The enzyme cause cleavage, removal of groups without hydrolysis, addition of
groups to double bonds or reverse. e.g. aldolase.
(v) Isomerase : The enzyme causes rearrangment of molecular structure to effect isomeric
changes. These are of three types-isomerases, epimerases, mutase.
(vi) Ligases : The enzyme catalyse bonding of two chemicals with the help of energy
obtained from ATP. Е.g. pyruvate carboxylase.
Q. 20. What are the characteristics of enzymes?
Ans. Enzymes-characteristics:
(i) Approximately all the enzymes are proteinaceous in nature. An enzyme/protein has a
primary structure (amino acid sequence of protein). Enzyme like protein has secondary and
the tertiary structure.
(ii) The backbone of protein chain folds upon itself, chain criss-crosses itself and so several
crevices or pockets are made out. One pocket is known as ‘active site'. So the enzymes,
through their active site, catalyse reactions at a high rate.
(iii) The enzymes get denatured at a high temperatures (above 40°C). The enzymes isolated
from organisms who live under extremely high temperatures e.g., hot vents and sulphur
springs, are stable and retain their catalytic power at high temperatures (upto 80°-90°C).
(Any three)
Q. 21. What is activation energy?
Ans. Activation energy: It is the energy required to initiate a chemical or biochemical
reaction. Activation energy overcomes the energy barrier of the reactants which occurs
amongst the reactants due to (i) presence of electrons over their surface, (ii) absence of
precise and forceful collisions, essential for bringing the reactive sites of the chemical
together.

Fig. Activation energy requirement of non catalysed and enzyme catalysed chemical reaction
Q. 22. What is enzymatic competitive inhibition? Give one example. [KVS 2012-
13]
Ans. Enzymatic Competitive Inhibition:
(i) Chemicals that prevent the enzyme to function, are known as inhibitors.
(ii) Enzymatic competitive inhibition is done by the substance which closely resembles the
substrate in its molecular structure.
(iii) Enzyme + Inhibitor = Enzyme-inhibitor complex.
(iv) The activity of the enzyme is limited by competitive inhibitor and no product is formed.
Example: Malonate inhibits the action of succinic dehydrogenase because it shows close
resemblance with the succinate substrate.
Q. 23. Describe the steps of catalytic cycle of an enzyme action. [NCT-2011]
OR
Enlist four steps involved in catalytic action of an enzyme. [INCT-2009]
Ans. Steps of catalytic cycle of an enzyme action are:
(i) The substrate binds to the active site of the enzyme.
(ii) This binding of the substrate induces the enzymes to alter its shape and fit more closely
around the substrate.
(iii) The active site of the enzyme, now is in close proximity of the substrate breaks the
chemical bonds of the substrate and an enzyme-product complex is formed.
(iv) The enzyme releases the products of the reaction and the free enzyme is ready to take up
another molecule of the substrate.
Q. 24. What is the effect of increase in substrate concentration on the rate of enzymatic
reaction ? [KVS 2012-13]
Ans. Increase in substrate concentration increases the rate of reaction. The enhanced rate is
due to two factors :
(i) Occupation of one and more active sites by the substrate molecules.
(ii) Higher number of collisions between substrate molecules. The rise in velocity is quite high
in the beginning but it decreases progressively with the increase in substrate concentration.