Question

Identify the 3 energy substrates and explain (in detail) how each are utilized by the cells to produce ATP. Include as much detail as possible.

Answer 1

Once ATP stores are depleted, PC, muscle glycogen and muscle triglycerides are all used to resynthesise ATP.

Creatine phosphate : The ATP-PC system uses a stored molecule in the muscle called creatine phosphate (CP) to resynthesise ATP. It is the breakdown of this molecule that releases the energy needed to rejoin the ADP and free phosphate to form ATP.  The breaking of the PC bond releases 43.3 kJ (10.3 kcal) per mole, which is considerably more than that seen in the breakdown of the high-energy bonds in ATP, indicating that there is more than enough energy to reconstitute ATP. Unfortunately, the energy available from the store of PC is also limited and is enough for only about another 5 to 8 seconds of maximal effort.This system is anaerobic as it works without oxygen, and does not produce any waste products. This system provides us with immediate energy but it is very limited and can only last up to about 10-12 seconds. It is therefore used for activities that involve short bursts of energy for example 100m sprint, long jump, high jump etc.

.Glycogen, Glycolysis is the first of the main metabolic pathways of cellular respiration to produce energy in the form of ATP, The glycolysis process is a multi-step metabolic pathway, In the first and third steps of the pathway, ATP energizes the molecules. Thus, two ATP molecules must be expended in the process. Further along in the process, the six-carbon glucose molecule converts into intermediary compounds and is then split into two three-carbon compounds. The latter undergo additional conversions and eventually form pyruvic acid at the conclusion of the process. The first phase of glycolysis requires energy, while the second phase completes the conversion to pyruvate and produces ATP and NADH for the cell to use for energy. Overall, the process of glycolysis produces a net gain of two pyruvate molecules, two ATP molecules, and two NADH molecules for the cell to use for energy.

Fat or triglycerides : To obtain energy from fat, triglycerides must first be broken down by hydrolysis into their two principal components, fatty acids and glycerol. The breakdown of fat occurs in cytoplasm and the process is known as beta oxidation. In the first step faatty acid is converted into fatty acyl CoA molecules this fatty acyl CoA combines with carnitine to create a fatty acyl carnitine molecule, inside the mitochondrial matrix the fatty acyl carnitine molecule is converted back into fatty acyl CoA and then into acetyl CoA, this molecule than enters the kerbs cycle to produce ATP