Consider a single murine T lymphocyte circulating through the bloodstream and at
ID: 78629 • 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 53 copies of a protein required for mediating an inflammatory response. Below are the five questions that you will be required to address on the next page:
1. How many equivalents of ATP are required to synthesize these 53 protein molecules?
2. Under aerobic conditions, how many molecules of glucose must be consumed to generate the ATP necessary to complete synthesis of these 53 protein molecules?
3. Under anaerobic conditions, how many molecules of glucose will be needed to generate the ATP necessary to complete synthesis of these 53 protein molecules?
4. In the absence of glucose and under aerobic conditions, how many molecules of a triacylglyceridecontaining 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 triacylglyceridecontaining three stearic acid groups would be needed?
Use the following assumptions/constraints when determining your answers:
All 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 53 polypeptides.
The primary transcript contains 204 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 123 nucleotides.
Amino acids and uncharged tRNA’s are readily available; energy required for their synthesis/replacement does NOT need to be accounted for.
Each of the 53 protein molecules to be synthesized are identical, and contain 623 amino acids.
Once translated, no further processing of the 53 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.
Explanation / Answer
Answer:
A molecule of GTP has an amount of energy built into its triphosphate group which is equivalent to the amount of energy built into the triphosphate group of a molecule of ATP. Those molecules have an equivalent amount of energy.
1. Each protein contains 623 amino acids.
623 molecules of ATP are converted into AMP + 1246 Pi to activate the 623 amino acids, which is equivalent to 1246 molecules of ATP.
One molecule of GTP is required for initiation, and 1244 molecules of GTP are needed to form 622 peptide bonds.
So, for each protein, ATP equivalent required = 1246 + 1245 = 2491
Poly(A) polymerase is highly specific for ATP and will use this ATP to build a poly(A) tail on nearly any RNA strand.
The poly-A tail contains an additional 123 nucleotides = 123 ATP
For each protein, number of ATP equivalent required = 2491 + 123 = 2614
Total ATP equivalent for 53 proteins = 2614 x 53 = 138542
2. 38 ATP molecules can be made per oxidised glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system).
38 ATP = 1 molecule of glucose
138542 ATP = 1/38x138542 = 3645.84 = 3646 glucose molecules (approx.)
So, 3646 glucose molecules are required during aerobic respiration for generating 138542 ATP molecules.
3. Considering that 1 molecule of glucose gives only 2 molecules of ATP because only glycolysis is generating the energy currency:
2 ATP = 1 molecule of glucose
138542 ATP = 1/2x138542 = 69271 glucose molecules (approx.)
4. 1 mol of Tristearin produces 3 moles of Stearic acid which is a saturated fatty acid .
Number of ATP produced from 1 molecule of tristearin = 461 ATP
So, number of tristearin required to supply sufficient ATP = 1/461x138542 = 300.52 = 301 (approx.)
(Since there are multiple subparts, the first 4 subparts have been answered according to the rules of Chegg)