Class 12 Chemistry Chapter 14 Biomolecules MCQs | Class 12 Chemistry Chapter 14 Biomolecules Objective Type Questions and Answers

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Questions
1 Platelet aggregation:
A is initiated at the site of an injury by conversion of fibrinogen to fibrin
B is inhibited in uninjured blood vessels by the secretion of prostacyclin by intact vascular endothelium
C causes morphological changes and a release of the vasodilator serotonine
D is inhibited by the release of ADP and thromboxane A2

Answer:is inhibited by the release of ADP and thromboxane A2
2 The cones of the retina:
A are responsible for colour vision
B are much more numerous than rods
C have red, blue and green light- sensitive pigments that differ because of small difference in the retinal prosthetic group
D do not use transducin in signal transduction

Answer: are responsible for colour vision
3 The nerve impulse that initiates muscular contraction
A begins with the binding of acetyl choline to receptors in the sarcoplasmic reticulum
B causes both the plasma membrane and the transverse tubules to undergo hyperpolariation
C causes opening of calcium channels which lead to an increase in calcium contreation within the sarcomere
D prevents sodium entering the sarcomere

Answer: causes opening of calcium channels which lead to an increase in calcium contreation within the sarcomere
4 When a muscle contracts, the
A Transverse tubules shorten, the myofibrils and sarcoplasmic reticulum close together
B Thin filaments and thick filaments of the sarcomere shorten
C Light chains dissociate from the heavy chains of myosin
D H bands and I bands of the sarcomere shorten because the thin filaments and thick filaments side past each other

Answer:H bands and I bands of the sarcomere shorten because the thin filaments and thick filaments side past each other
5 Lysis of a fibrin clot:
A is an equibrium wwith formation of the clot
B begins when plasmin binds to the clot
C requires the hydrolysis of plasminogen into heavy and light chains
D requires conversion of plasminogen by tissue plasminogen activator

Answer: requires conversion of plasminogen by tissue plasminogen activator
6 ATP concentration is maintained relatively constant during muscle contraction by
A increasing the metabolic activity
B the action of adenylate kinase
C theaction of creatne phosphokinase
D all of the above

Answer: all of the above
7 4-hydroxy proline is present in
A Collagen
B Plant cell wall
C Keratin
D Both plant cell wall and collagen

Answer: Both plant cell wall and collagen
8 Peptide bonds between amino acids are highly stable and have a half-life of seven years in intracellular condition. This is due to
A High activation energy required for hydrolysis
B Low activation energy required for hydrolysis
C Peptide bond is a covalent bond
D Peptide bond is rigid and planar

Answer:High activation energy required for hydrolysis
9 Tri-peptide consists
A 3 amino acids and 3 peptide bonds
B 2 amino acids and 3 peptide bonds
C 3 amino acids and 2 peptide bonds
D 3 amino acids and 4 peptide bonds

Answer:3 amino acids and 2 peptide bonds
10 All the following statements are true except
A Ornithine and citrulline are uncommon aminoacids
B Ornithine is an intermediates in Urea cycle
C Ormithine and citrulline are uncommon amino acids present in many proteins
D Both ornithine and citrulline are intermediates in urea cycle

Answer: Ormithine and citrulline are uncommon amino acids present in many proteins
11 The characteristic strong absorbance of 280nm of proteins is due to
A All amino acids can absorb at 280nm
B Only Tryptophan and tyrosine can absorb at 280 nm
C Tryptophan is responsible for the absorbance
D Tryptophan, tyrosine and phenylalanine can absorb at 280 nm

Answer: Tryptophan, tyrosine and phenylalanine can absorb at 280 nm
12 The formation of cystine occurs at
A ER
B Golgi
C Cytosol
D Mitochondria

Answer: ER
13 Which of the following interaction contributes most in protein folding

protein folding

A Covalent bond
B Ionic bond
C Hydrophobic interaction
D Vander walls interaction

Answer:Hydrophobic interaction
14 Which of the following aminoacid has pKa near neutrality
A Tryptophan
B Arginine
C Histidine
D Asparagine

Answer: Histidine
15 Desmosine is an unusual amino acid found in
A Myosin
B Troponin
C Actin
D Elastin

Answer: Elastin
16 How many small peptides are formed upon cleavage by trypsin if a protein has 5 lysine residues
A 4
B 5
C 6
D 7

Answer:6
17 EF-1α and EF-Tu are
A Analogs
B Homologs
C Paralogs
D Syllogs

Answer:Homologs
18 All the statements regarding peptide bond are true except
A Peptide bond is a co-valent bond
B Peptide bond is rigid and planar
C Peptide bond has partial double bond character
D Peptide bond is formed by non-condensation reaction

Answer:Peptide bond is formed by non-condensation reaction
19 Αlpha-helix has
A 3.6 residues/turn and is a right handed helix
B 3.8 residues/turn and is a right handed helix
C 3.6 residues/turn and is a left handed helix
D 3.8 residues/turn and is a left handed helix

Answer: 3.6 residues/turn and is a right handed helix
20 Which of the following amino acids are rarely present in alpha helix
A Glycine and proline
B Proline and tryptophan
C Tryptophan and glycine
D Proline only

Answer: Glycine and proline

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