Consider a single murine T lymphocyte circulating through the bloodstream and at
ID: 995117 • Letter: C
Question
Consider a single murine T lymphocyte circulating through the bloodstream and at homeostasis with its surrounding environment. Due to exposure of the organism to an external pathogen that infiltrates the blood, this lymphocyte receives signals that trigger the need to synthesize exactly 15 copies of a protein required for mediating an inflammatory response. In answering the following five questions use the following assumptions/constraints: All of the necessary catalytic complexes have already been synthesized within the cell Nucleotides used for transcription must be accounted for A single transcript is sufficient for translation of all 15 polypeptides. The primary transcript contains 300 nucleotides that are not translated. This includes the stop codon and a single intron that must be removed by the spliceosome prior to translation. The poly-A tail contains an additional 150 nucleotides Amino acids and tRNA’s are readily available, energy required for their synthesis/replacement does not need to be accounted for: Each of the fifteen protein molecules to be synthesized are identical, and contains 498 amino acids. Once translated, no further processing of the 15 molecules occurs, they fold spontaneously and do not require other post-translational modifications. The malate-aspartate shuttle is not functional in T-cells. Do not account for waste products.
1) How many equivalents of ATP are required to synthesize these fifteen 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 15 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 stearic 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 stearic acid groups would be needed?
Explanation / Answer
We have 498 amino acids. Activation and incorporation of single amino acid in peptide chain requires 2 ATP (or four high energy bonds).
ATP required for one polypeptide chain is 498*2 = 996 ATP
ATP for 15 protein molecules = 996*15 = 14940 ATP.
2) Under aerobic conditions
One glucose molecule produces 38(36) ATP under aerobic condition.
Number of glucose molecules required = 14940/38 = 393 glucose molecules.
3) Under anaerobic condition
Only 2 ATP are produced. Therefore, we require 14940/2 = 7470 Glucose molecules.
4) We get 147 ATP from stearic acid. (You can subtract 1 = 146)
We have triglyceride with 3 stearic acids.
Therefore, we get 147*3= 441 ATP
Triglycerides required = 14940/441 = 33.87 = 34 molecules.
5) Anaerobic workout will not burn any fat. So, no ATP as no oxidation.