Question

how to choose and solve these 4 multiple choices about biochem? THANKS

The coding sequence on an mRNA contains 137 codons including start and stop codons. How many nucleotides are required to produce this mRNA? How many residues are encoded by this mRNA?

A. 405, 135

B. 408, 136

C. 408, 137

D. 411, 136

E. 411, 137

What is the smallest number of GTP consumed in the synthesis of a 100-residue protein?

A. 100

B. 101

C. 198

D. 199

E. 200

Which of the following statements about heme structure is correct?

A. Heme consists of four porphyrin rings.

B. The central iron is in the plane of porphyrin plane in deoxyhemoglobin.

C. The axial coordination positions of heme are occupied by two imidazole rings.

D. The distal histidine is protonated while interacting with the oxygen bound at the heme.

E. Carbon monoxide has a stronger affinity than oxygen to heme.

Which of the following statements is NOT an explanation for how oxygen is released from oxy-haemoglobin.

A. Carbon dioxide has a stronger affinity than oxygen to heme, and displaces oxygen in tissues.

B. Formation of carbonic acid lowers the oxygen affinity of haemoglobin in tissues.

C. The structure of deoxyhemoglobin is stabilized by the interaction with BPG.

D. Salt bridges are formed with N-terminal carbamates in deoxyhemoglobin.

E. Salt bridges are formed between acidic and basic side chains of His146 and Asp94, respectively in deoxyhemoglobin .

Answer 1

c) 408,137

Protein coding sequences are DNA sequences that are transcribed into mRNA and in which the corresponding mRNA molecules are translated into a polypeptide chain. Every three nucleotides, termed a codon, in a protein coding sequence encodes 1 amino acid in the polypeptide chain.

c) 198

an energy-rich nucleotide analogous to ATP that is composed of guanine, ribose, and three phosphate groups and is necessary for peptide-bond formation during protein synthesis. — called also guanosine triphosphate.

3) answer

C. The axial coordination positions of heme are occupied by two imidazole rings.

D. The distal histidine is protonated while interacting with the oxygen bound at the heme.

4) answer

D. Salt bridges are formed with N-terminal carbamates in deoxyhemoglobin.

E. Salt bridges are formed between acidic and basic side chains of His146 and Asp94, respectively in deoxyhemoglobin .