Question

Consider a single murine hepatocyte at homeostasis with its surrounding environment, which includes other neighboring hepatocytes and extra-hepatic tissues. Due to changes in the organism’s activity, this hepatocyte receives signals that trigger the need to synthesize exactly 20 copies of a protein required for altered amino acid metabolism.

Use the following assumptions/constraints when determining your answers:

1. All of the necessary catalytic complexes have already been synthesized within the cell
2. Nucleotides used for transcription must be accounted for
3. A single transcript is sufficient for translation of all 20 polypeptides
4. The primary transcript contains 400 nucleotides that are not translated. This includes the stop codon and a single intron that must be removed by the spliceosome prior to translation
5. The poly-A tail contains an additional 210 nucleotides
6. Amino acids and tRNA’s are readily available, energy required for their synthesis/replacement does not need to be accounted for
7. Each of the 20 protein molecules to be synthesized are identical, and contains 613 amino acids
8. Once translated, no further processing of the 20 molecules occurs, they fold spontaneously and do not require other post-translational modifications
9. Do not account for waste products

Questions:

1. How many equivalents of ATP are required to synthesize these 20 protein molecules?

2. Under aerobic conditions, how many molecules of glucose must be consumed in order to generate the ATP necessary to complete synthesis of these 20 protein molecules?

3. Under anaerobic conditions, how many molecules of glucose will be needed?

4. In the absence of glucose and under aerobic conditions, how many molecules of a triacylglyceride containing three palmitic acid groups would be needed to supply sufficient ATP?

5. In the absence of glucose and under anaerobic conditions, how many molecules of a triacylglyceride containing three palmitic acid groups would be needed?

Answer 1