1. Which residues are present in histone proteins?
a) Lysine & proline
b) Glutamic acid & aspartic acid
c) Arginine & Histidine
d) Serine & Cysteine
Explanation: DNA is a negatively charged molecule that wounds around histone proteins. They are rich in both arginine and histidine residues (both are positively charged Amino acids) which helps the negatively charged DNA bind to it. This forms a strong ionic bond formation allowing the DNA to be tightly packed into chromosomes.
2. Which of the following groups of amino acids are least soluble in water?
a) Polar
b) Non-polar
c) Polar charged
d) Polar uncharged
Explanation: Non-polar amino acids have side chains that are essentially hydrocarbons(sulphur in case of methionine and cysteine). This causes the amino acid water interaction to be weak and thus are sparsely soluble in water. The amino acids included in this category are alanine, valine, leucine, isoleucine, tryptophan, phenylalanine and methionine. Phenylalanine is least soluble due to its bulky aromatic side chain.
3. What are molecular chaperones?
a) Enzymes
b) Cell mass
c) Tumor
d) Helper proteins
Explanation: Molecular chaperones are helper proteins that help unfolded or misfolded polypeptide chains to assume a certain folded state. The role of these proteins is to prevent the proteins from non-selectively interacting with other components in the cell.
4. Chaperones bind to which type of amino acid residues in the protein?
a) Charged
b) Uncharged
c) Hydrophobic
d) Hydrophilic
Explanation: Chaperons are helper proteins that binds to hydrophobic amino acid residues that are part of the core of the folded protein. In the denatured state the core amino acid residues are exposed which is identified. Once bound the polypeptide molecule is folded like a hairpin into its tertiary state.
5. Which of the following molecules bind to nascent polypeptides synthesized on the ribosomes?
a) Chaperonins
b) Hsp70
c) Hsp72
d) Hsp
Explanation: Hsp70 is a class of molecular chaperones that bind to nascent proteins being synthesized on ribosomes. Hsp70 chaperones prevent the newly synthesized proteins from binding to other proteins in the cytosol which could lead to misfolding or aggregation.
6. TriC is a _____________
a) hsp70
b) chaperonin
c) organelle
d) enzyme
Explanation: TriC is a chaperonin that helps stabilize long polypeptides. It contains chambers in which peptides can reside without any interference from the external environment.
7. Heat-shock response was first observed in which organism?
a) C. elegans
b) Drosophila
c) Arabidopsis
d) Bacteria
Explanation: Heat shock response on the form of production of heat shock proteins was first observed in Drosophila. In 1962, an Italian biologist was studying the development of Drosophila when it was observed that increasing the temperature, at which larvae grow new heat shock proteins appear on the chromosome.
8. Rubisco is a ________________
a) nucleic acid
b) protein
c) carbohydrate
d) fiber
Explanation: Rubisco is a protein found in chloroplasts of plant cells, it catalyzes the reaction in which carbon dioxide taken up from the atmosphere is covalently linked to organic molecules.
9. Tobacco Mosaic Virus consists of one long molecule of ______________
a) DNA
b) Carbohydrates
c) Glycerol
d) RNA
Explanation: In 1955 at the University of California, it was demonstrated that TMV particles consist of one long molecule of RNA which is 6600nucleotides long wound in a helical capsule made of 2130 identical protein subunits
10. TMV particles are not capable of self-assembly.
a) True
b) false
Explanation: In the first experiments conducted in 1955, the RNA and protein components of a TMV were separated and then mixed together. After a brief incubation period, the recovered mixture contained infective particles. This confirmed the self-assembly property in TMV.