Cell Biology

Cell Biology
ATP is the short form for Adenosine Triphosphate. It is the rich biochemical molecule that provides energy that enables all activities of the body to be carried out. The whole process that makes ATP produce the energy is complex to some extent. In a lay man’s language, ATP is an adenine nucleotide joined to three phosphates. Great amounts of energy are contained in the bond of the second and third phosphates (Hartwell et al 47). When it breaks energy is released. This energy can be produced by Cellular Respiration which occurs in three stages of metabolism, namely glycolysis, citric acid cycle and electron transport.
Glycolysis involves splitting glucose into two molecules. Enzymes break glucose into two molecules of pyruvate which is also called pyruvic acid. During this breaking down, two molecules of ATP are also produced. The final product of pyruvate can be used in anaerobic respiration if oxygen is absent or in aerobic respiration if it is present. Citric acid cycle finishes breakdown of carbon dioxide resulting in little volumes of ATP in addition to giving out of electrons. It achieves this by getting acetyl CoA, which is gotten from glucose, arrests its bond energy in the nature of ATP molecules together with NADH and FADH2. In electron transport, energy so far produced in the form of ADP and inorganic phosphate is converted to ATP by the chain transport of the electrons from the medium towards the inner membrane in the mitochondrion.
Oxygen plays a big role in this stage and without it, chain transport cannot take place.

The number of ATP molecules produced by Cellular respiration is 36 ATP for every glucose molecule although this number is not strictly the same for every organism. The definite quantity of ATP ranges from 32 to 38 ATPs for every glucose molecule. This is because the number produced depends on the variables of multifaceted enzymes in the cells DNA codes (Hartwell et al. 48). In fermentation, only two molecules of ATP are produced for every molecule of glucose used. Also, Oxygen is not used as opposed to the later. That is why in fermentation less energy is given out.
Glycolysis occurs in a series of steps, in the organelles of a cell. It first occurs in the cytoplasm. Then the subsequent steps take place in the mitochondrion. However, fermentation happens in the cytoplasm only. Usually, with prokaryotic cells, every form of metabolism occurs in the cytoplasm including fermentation whereas in eukaryotic ones only fermentation occurs in the cytoplasm. All other respiration forms occur in the mitochondria (Hartwell et al. 48). The citric acid cycle occurs in the mitochondria just like the changing of pyruvate to acetyl CoA.
Every enzyme in the cycle is soluble except succinate dehydrogenase implanted in the inner membrane of the mitochondrion. The eight steps of the cycle are a sequence of the redox, hydration and dehydration reactions that would only take place in the mitochondrion. Electron transport also takes place in the mitochondrion.

Work Cited
Hartwell, Leland H., et al. “From molecular to modular cell biology.” Nature 402 (1999): C47-
C52.