b sc (zoology hon's) examination 2013 lzc-201: cell biology and

B Sc (Zoology Hon’s) Examination 2013 LZC-201: Cell biology and Biochemistry

SECTION A

1. Multiple choice type questions (Tick √ the appropriate answer) 10 x 1 = 10

i) Trilamilar structure was given by (b) Danielli & Devson

ii) Transport of protein is done by (a) Golgi body iii) The structural basis for pairing of homologus chromosome during prophase I (b)synaptonemal complex

iv) Desmosomes are concerned witH (d) cell adherence

v) Which of the following is basic amino acid c) lysine

vi) The correct representation of Michaelis – Menten kinetics is

a) V0 = Vmax x [S]

Vmax + [S]

vii) End product of glycolysis is (c) 2 molecules of pyruvic acid

viii) Oxidative phosphorylation means (c) ATP production in respiration

ix) How many base pairs are present in each turn of double helix of B DNA (a) 10 x) Which of the following base pairs is characteristics of tRNA

(a) Inositol (b) methyl cytosine

(c) 5-hydroxy tryptophan (d) all a,b & c

Section B

Q2. Descriptive type question (any four) 4x5=20

1). Comment on the following 5x1=5

a) Chromomere and centromere Chromomere- beads like structure formed due to accumulation of chromatin material and are visible

along the entire length of chromonemata. These tightly folded regions represent genes

Centromere –This region of the chromosome becomes attached to the mitotic spindle called as primary constriction


b) Cell theory by M J Schielden 1838 T Schwann1839 It states that

1. All organisms are made up of cells. The cell is a unit of structure and function

2. Each cell behaves independently and also functions as the integral part of the complete organism.

3. The cells are formed by the process similar to the crystal formation (pre existing cells)

c) Cytoskeleton

Made up of two types of protein

1. microtubules 2. microfilaments

(detail structure about the longitudinal bundles, flagellar function and role in intracellular transport.

d) Euchromatin and heterochromatin

Heterochromatin– The region of chromosome contains inert or late replicating genes. It show

Chromomere, chromocentre and knob. It contains highly repetitive DNA sequences. Euchromatin- Lightly stained region region relative decondensed and distributed throughout the

nucleus. During interphase of the cell cycle gene in this region are transcribed and the DNA is replicated

in preparation for the cell division

e) Golgi complex


ii) State and explain about cell transformation with reference to the cancerous cell? Describe briefly

about the types of the cancer and effected cell and tissue.

The process of cell – changes in which a cell loses its activity to control its rate of division and thus

become a tumour cell is call ed cell transformation. The growth resulting from the division of such

cells are called neoplastic growth or tumours which them becomes cancerous. (more explanation regarding abnormalities of genetical and hereditary)

TYPES OF CANCER

CARCINOMAS SARCOMAS LYMPHOMAS LEUKEMIAS

90% of human cancer 4% of human cancers 4% of human cancers 4% of human cancers

Arise from epidermal

cell

Solid tumour of

connective tissue

Excessive production

of lymphocytes

Neoblastic growth of

wbc

Ectoderm and

endodermal cells effect

Mesodermal cells are

effected

Hodkin’s Disease Mixed malignant

tumours

Examples- cervical,

breast, skin

Muscles, bone,

cartilage, fat and

fibrous tissue

lymph nodes, spleen Ectodermal and

mesodermal in origin

iii) Define enzyme. Discuss in details about different levels of regulation of enzyme

activity.

The term enzyme was coined by F Wilhelm Kuhne 1878 and designated as “ Biologically

active “ molecule. They alter the rate of chemical reaction without participating.

1. Explaination by Allosteric activity

2. Regualtion by phosphorylation for glucose metabolism


). Provide classification of lipids. Describe structure and function phospholipids and

cholesterol.


v). What is translation? Explain the mechanism of translation by providing stepwise

figures.

Synthesis of protein from a segment of DNA through RNA is Protein synthesis . It consists of three

stages .

1.initiation-the assembly of a ribosome on an mRNA molecule.

2.elongation-repeated cycles of amino acid addition.

3.termination-the release of the new protein chain.

1INITIATION Methionine is the first amino acids incorporated into a protein chain in both

prokaryotes (modified to N-formylmethionine) and eukaryotes.

Initiator tRNAs are special tRNAs recognizing the AUG (GUG) start codons in

prokaryotes and eukaryotes.

Initiator tRNAs differ from the one that inserts internal Met residues.

IF1 and IF3 bind to a free 30S subunits

IF2 complexed with GTP then bind to the small

subunits, forming a complex at RBS

The initiator tRNA can then bind to the complex at

the P site paired with AUG codon.

The 50S subunits can now bind. GTP is then

hydrolyzed and IFs are released to give the 70S

initiation complex

The assembled ribosome has two tRNA-binding sites,

which are called A- and P-site, for aminoacyl and

peptidyl sites respectively.

Only fMet-tRNAfMet

can be used for initiation by 30S

subunits; all other aminoacyl-tRNAs are used for

elongation by 70S ribosomes.


A-site

P site

E Site


vi). Describe about the reactions with the chemical formula involving α amino group.


vii) Describe the following (2.5+2.5=5)

a) polytene chromosome There are two special types of chromosome ( Lampbrussh chromosome

and Polytene chromosme

Polytene chromosomes:-

-formed in specialised cells viz, salivary gland cell of Chironomus larva, salivary glands of larva of D.

melanogaster and other members of the order Diptera

-formed when cells undergo repeated DNA replication without cell division

-many homologous chromatids remain synapsed together

-enables high levels of gene expression

-possess characteristic dark (euchromatin) and light (heterochromatin) banding patterns

-contain regions of swelling (called chromosomal puffs) that are associated with RNA transcription and

protein synthesis

- ‘puffing’ involves accumulation of proteins, synthesis of mRNA and storage of newly formed mRNA

- The largest puffs seen on the polytene chromosomes of Diptera are called Balbiani rings after E.G.

Balbiani (1881) who first described polytene chromosomes

b) Post transcriptional modifications

1. Splicing

2. Capping of 7mG(7 methyl guanosine) at 5’ end

3. Poly adenylation at 3’end

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b sc (zoology hon's) examination 2013 lzc-201: cell biology and

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