Questions - Answers
Very short answer type questions (2 marks)
1. Medicines are either man made (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. Sulfonamide -----------------
c. Vitamin C -----------------
d. Growth hormone ------------------
A:
a. Penicillin - Natural
b. Sulfonamide - Synthetic
c. Vitamin C – Natural
d. Growth hormone - Natural
2. 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 -------------------
A:
a. Polysaccharide - Glycosidic bond
b. Protein - Peptide bond
c. Fat - Ester bond
d. Water - Hydrogen bond
3. Give one example for each of aminoacids, sugars, nucleotides and fatty acids.
A:
Amino acids - Glycine
Sugars - Fructose
Nucleotides - Adenylic acid
Fatty acids - Palmitic acid
4. Starch, Cellulose, Glycogen, Chitin are polysaccharides found among the following. Choose the one appropriate and write against each.
a. Cotton fibre ---------------
b. Exoskeleton of cockroach -------------
c. Liver ----------------
d. Peeled potato ------------------
A:
a. Cotton fibre - Cellulose
b. Exoskeleton of cockroach - Chitin
c. Liver - Glycogen
d. Peeled potato - Starch
Short answer type question (4 marks)
1. Schematically represent primary, secondary and tertiary structures of a hypothetical polymer using protein as an example.
A: The structure of proteins is determined by the number and sequence of aminoacids. Proteins show four levels of structures:
* Primary structure: A thread like linear chain of aminoacids.
* Secondary structure: The threads folded into other forms.
* Tertiary structure: Long protein chains folded into hollow woolen ball like structure.
* Quaternary structure: More than one polypeptide chains folded into spheres, cubes or
plates.
Long answer type questions (8 marks)
1. Nucleic acids exhibit secondary structure. Describe through Watson and Crick model.
A: Nucleic acids like DNA and RNA contain nucleotides. Each nucleotide in the nucleic acid contains 3 parts:
* Heterocyclic compound – nitrogen base
* Mono saccharide - ribose or deoxyribose sugar
* Phosphoric acid or phosphate
* A nucleic acid with deoxyribose sugar is called DNA or Deoxyribonucleic acid.
* According to Watson and Crick model of DNA, the B-DNA exists as a double helix.
* Two polynucleotide strands run anti parallel to each other in opposite direction.
* Sugar-phosphate-sugar forms the backbone.
* Nitrogen bases are present perpendicular to the backbone.
* Adenine pairs with Thymine by two hydrogen bonds.
* Guanine pairs with cytosine by three hydrogen bonds.
* Thus the DNA molecule appears like a helical stair case.
* At each step of ascent the strand turns 36º.
* One full turn of helical strand involves ten base pairs.
* The pitch is 34Aº and rise per base pair is 3.4Aº.
(Note: diagram carries marks)
