Practice free Biomolecules (Zoology) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
The amino acid or acids which does or do not have Sulphur?
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12.2.2 Role of Macro and Micronutrients
Mineral Nutrition
Many enzymes of photosynthesis, respiration and nitrogen metabolism are activated by
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12.2.2 Role of Macro and Micronutrients
Mineral Nutrition
The native charge on DNA molecules is
DNA is acidic in nature
One turn of the helix in a B-form DNA is approximately [2006]
(b) B-DNA is helical structure with 20Å and the distance between the two base pairs is 3.4Å and there are 10 base pairs in each turn or pitch (one round). Hence, one turn of the helix is approximately 34Å or 3.4 nm (10Å = 1.0 nm). Z-DNA (in comparison to B-DNA) is left handed double helical structure in which double helix winds to left in zig-zag pattern (instead of right, like B-DNA).
Which of the following statements regarding enzyme inhibition is correct? [2005]
(b) A competitive inhibitor competes with substrate molecule for occupying the active site of an enzyme. These inhibitors have structural resemblance with substrate molecules due to which they easily get active site of an enzyme and form an enzyme-inhibitor complex.
E + I EI complex
(enzyme) (inhibitor)
If DNA percentage of thymine is 20. What is the percentage of guanine? [2002]
(c) Total DNA (100)= A + T + C + G
A = 20% (given)
A = T (base pairing rule)
100 = 20+ 20 + C + G
C + G = 100-40 = 60
C = G = 30
Which is wrong about nucleic acids? [1993]
(c) Length of one helix or the pitch per turn of helix is 34 Å in B-DNA, 25 Å in A-DNA and 46 Å in Z-model of DNA. In Z-DNA sugar molecules are seen in opposite direction. So the 3-5 diester bond forms zig-zag structure in Z-DNA.
In the DNA molecule [2008]
(d) In DNA molecule the adjacent deoxyribonucleotides are joined in a chain by phosphodiester bridges or bonds, which link the 5' carbon of deoxyribose of one mononucleotide unit with 3' carbon of deoxyribose of next mononucleotide unit.
According to Watson and Crick DNA molecule consists of two such polynucleotide chains wrapped helically around each other, with the sugar phosphate chain on the outside and purine and pyrimidine on the inside of helix.
The two strands run antiparallely, i.e. one strand has phosphodiester linkage in 3'5' direction while other strand has phosphodiester linkage in 5'3' direction.
Chargaff (1950) suggested that despite wide compositional variations exhibited by different types of DNA the total amount of purines equalled the total amount of pyrimidines (A+G = T+C).
The major portion of the dry weight of plants comprises of [2003]
(b) The major portion of the dry weight plants comprises carbon, nitrogen, oxygen, hydrogen.
Select the option which is not correct with respect to enzyme action. [2014]
(b) is incorrect with respect to enzyme action because addition of a lot of succinate reverse the inhibition of succinic dehydrogenase by malonate. If substrate succinate concentration is increased, it will remove malonate from its active site and thus succinate reverses the inhibition of dehydrogenase.
Inhibition of succinic dehydrogenase by malonate is an example of competitive inhibition.Competitive inhibition occurs when enzyme and inhibitor both have more or less similar structure and are present in higher concentration. Thus, both enzyme and inhibitor for compete for the active site of enzyme resulting in the decrease of the enzymatic activity.
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