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Biochemistry Mcqs

Q:

Which of the following is true about phosphodiester linkage?

A) 3’-phosphate group of one nucleotide unit is joined to the 5’-hydroxyl group of the next nucleotide B) 3’-phosphate group of one nucleotide unit is joined to the 3’-hydroxyl group of the next nucleotide
C) 5’-phosphate group of one nucleotide unit is joined to the 3’-hydroxyl group of the next nucleotide D) 5’-phosphate group of one nucleotide unit is joined to the 5’-hydroxyl group of the next nucleotide
 
Answer & Explanation Answer: C) 5’-phosphate group of one nucleotide unit is joined to the 3’-hydroxyl group of the next nucleotide

Explanation: A 5’-phosphate group of one nucleotide unit is joined to the 3’-hydroxyl group of the next nucleotide.

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316
Q:

What is the reaction in DNA replication catalyzed by DNA ligase?

A) Addition of new nucleotides to the leading strand B) Addition of new nucleotide to the lagging strand
C) Formation of a phosphodiester bond between the 3’-OH of one Okazaki fragment and the 5’-phosphate of the next on the lagging strand D) Base pairing of the template and the newly formed DNA strand
 
Answer & Explanation Answer: C) Formation of a phosphodiester bond between the 3’-OH of one Okazaki fragment and the 5’-phosphate of the next on the lagging strand

Explanation: DNA ligase catalyzes the formation of a phosphodiester bond between 3’-OH of one Okazaki fragment and 5’-phosphate of the next.

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304
Q:

The buffer capacity is equal to __________

A) ?n / ?pH B) pH / ?n
C) ± 1pKa D) ± 2pKa
 
Answer & Explanation Answer: A) ?n / ?pH

Explanation: Buffer capacity = number of moles of acid or base added to 1 liter of buffer/change in pH.

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257
Q:

Which of the following is not the classified form of conjugated proteins?

A) Lipoproteins B) Glycoproteins
C) Metalloproteins D) Complete proteins
 
Answer & Explanation Answer: D) Complete proteins

Explanation: On the basis of the chemical nature of their prosthetic groups conjugated proteins are classified into lipoproteins, glycoproteins and metalloproteins.

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247
Q:

Which of the following mechanisms will remove uracil and incorporate the correct base?

A) Nucleotide excision repair B) Direct repair
C) Base excision repair D) Mismatch repair
 
Answer & Explanation Answer: C) Base excision repair

Explanation: Small, non-helix-distorting base lesions are removed from the genome through base excision repair.

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244
Q:

Southern blotting technique is used in ____________

A) Monoclonal antibody production B) In vitro culture
C) Genetic finger printing D) Polymerase chain reaction
 
Answer & Explanation Answer: C) Genetic finger printing

Explanation: Applications of southern blotting:
In RFLP, forensics, diagnosis of HIV, etc.

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239
Q:

Whenever the cell’s ATP supply is depleted, which of the following enzyme’s activity is increased?

A) Pyruvate kinase B) Phosphofructokinase-1
C) Hexokinase D) Glucokinase
 
Answer & Explanation Answer: B) Phosphofructokinase-1

Explanation: Phosphofructokinase-1 is a regulatory enzyme that plays a key role in glycolysis control. When the cell’s ATP supply is reduced, its activity increases.

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234
Q:

Which of the following is false about purine and pyrimidine bases?

A) They are hydrophobic and relatively insoluble in water at the near-neutral pH of the cell B) At acidic or alkaline pH the bases become charged and their solubility in water increases
C) Purines have two rings in their structure, but pyrimidine bases have only one ring D) At acidic or alkaline pH the bases become charged and their solubility in water decreases
 
Answer & Explanation Answer: D) At acidic or alkaline pH the bases become charged and their solubility in water decreases

Explanation: At acidic or alkaline pH the bases become charged and their solubility in water increases.

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