Tag: biomolecules: chemical constituents of living cells
Questions Related to biomolecules: chemical constituents of living cells
Which is true about enzymes?
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All enzymes are not proteins
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All enzymes are vitamins
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All enzymes are proteins
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All proteins are enzymes
Enzymes are protein in nature. But some enzymes like ribozymes and ribonuclease are RNA based enzymes. It is also known as ribonucleic acid enzymes. These are RNA molecules which helps in the catalysis of a particular reaction. It was discovered in year 1982. The RNA can act as both genetic material and can act as a biocatalyst but different from protein-based enzymes. It acts as a part of ribosome which attaches to the amino acid during protein synthesis. Thomas R. Cech and Sidney Altman discovered catalytic properties of RNA. So, the correct answer is option A.
Enzymes functional in a cell are
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Inducible, constitutive and repressible
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Inducible and repressible
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Inducible only
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Repressible only
Enzymes are inducible in nature because as the substrate molecules attaches to the active site of the enzyme, it induces a conformational change on the active site to fit in properly.
Most of hydrolytic reactions are
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Exothermic
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Endothermic
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Irreversible
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Reversible
Hydrolytic reactions are the reactions which involves breaking of the bond by the addition of water. It can be reversed by the condensation reaction where the joining of two molecule leads to release of water by formation of bonds. Saccharification is the reaction where the complex sugar molecule is broken into its component sugar molecules by hydrolysis. It can be reversed by condensation reaction.
Enzyme generally have?
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Same pH and temperature optima
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Same pH but different temperature optima
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Different pH but same temperature optima
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All wrong
The optimum temp of enzymes is 20-35°C. They become inactivated at very low temperature and denatured (destroyed) at very high temp i.e. greater than 45°C. Low molecular weight enzymes are comparatively more heat stable. In archaebacterium Pyrococcus furiosus, the optimum temperature of hydrogenase is greater than 95°C. This heat-stable enzyme enables Pyrococcus to grow at 100°C. The optimum pH of most endoenzyme is pH 7.0 (neutral pH). However, digestive enzymes can function at different pH. For example, salivary amylase act best at pH 6.8, pepsin act best at pH2 etc. Any fluctuation in pH from the optimum causes ionization of R-groups of amino acids which decrease the enzyme activity.
Serine proteases are called so because they
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They require serine for their activity
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cleave after serine residues in the substate
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Are inhibited by the presence of free serine
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Have a serine residue at their active sire
Serine proteases are enzymes that cleave peptide bonds in proteins, in which serine serves as a nucleophilic amino acid at enzyme's active site. Serine proteases are responsible for coordinating various physiological functions including digestion, immune response, blood coagulation, and reproduction. Hence, serine proteases are called so because they require serine for their activity.
Specific enzymes are needed for the break-down of a particular substance.
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True
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False
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Either
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Neither
Mark the INCORRECT statement about the enzyme carboxypeptidase.
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Zinc is the co-factor for this proteolytic enzyme
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It is exopeptidase
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It cleaves the peptide bond at N-terminal end of the polypeptide chain
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It is an enzyme of pancreatic juice
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$\alpha$-amylase
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Glucokinase
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Lactate dehydrogenase
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All of the above
Which one of following vitamin is a precursor of FAD
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Niacin
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Riboflavin
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Thiamine
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Ubiquinor
FAD also is known as Flavin Adenine Dinucleotide. It is a redox-active co-enzyme associated with various proteins. Riboflavin is the precursor of FAD.
The active site of an enzyme is formed by
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Exposed sulphur bonds
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Side chains of the amino acids
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Amino groups of the amino acids
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Carboxyl group of the amino acids
The enzyme active site is composed of the amino acid residues. Side chains of the amino acids are seen in the active site region of the enzyme. The difference in the identity, charge, and spatial orientation of the functional groups located there results in the difference in enzyme specificity.