Metabolism, Cellular Respiration, and Photosynthesis

Metabolism, Cellular Respiration, And Photosynthesis

Explain how ATP is used to power cellular reactions?

Cells require ATP as a source of free energy. ATP is capable of supplying energy for both heterotrophic and photosynthetic cells. It acts as a donor of high-energy phosphate to form high-energy. ATP is continuously consumed and regenerated from processes that need and give high-energy phosphates. Heterotrophic cells, through an exergonic process, get the chemical form of free energy through the catabolism of nutrient molecules and in turn it uses that energy to make ATP from ADP and Pi. ATP then donates some of its chemical energy to endergonic processes in the cell like the metabolic intermediates synthesis, macromolecules synthesis from smaller precursors, transport of substances across membranes against concentration gradients and mechanical motion.

Explain how ATP is generated during cellular respiration through the electron transport chain and chemiosmosis. How do glycolysis and the citric acid cycle figure into the process?

Food stuffs like fat, carbohydrate and protein are digested and absorbed to form fatty acids + glycerol, glucose, and amino acids respectively. Glucose undergoes glycolysis producing pyruvate. This is then degraded to the acetyl group of Acetyl-CoA which enters the citric acid cycle producing reducing equivalents (2H) which are then collected by the respiratory chain for oxication and coupled generation of ATP. ATP generated from anaerobic condition of glycolysis is only 2 compared to glycolysis under aerobic conditions with an ATP yield of 36 to 38.

The chemiosmotic theory on the other hand postulates that: the energy from oxidation of components in the respiratory chain generates hydrogen ions that are ejected to the outside of a coupling membrane in the mitochondrion. It means that there is an electrochemical potential difference that resulted from the asymmetric distribution of the hydrogen ions and this difference is also used to drive the mechanism responsible for the production of ATP.

Explain the process of ATP generation during noncyclic photophosphorylation?

In the noncyclic photophosphorylation, photons are absorbed by pigment molecules in the antenna complexes of Photosystem II. Excited electrons are captured by primary electron acceptor of the Photosystem II electron transport chain. This system also splits molecules of water into 1/2 O2, 2H+ and 2 electrons. This process is termed noncyclic because the electrons that pass through here do not return to the original photosystem. Photolysis, an ultraviolet light-mediated nonenzymatic reaction, generates H+ ions replacing those lost in the photosystems. This is explained through the chemiosmosis theory which states that as electrons are transported to the electron transport chain some energy is released which are used to pump protons across the thyalakoid membrane from the stroma of the chloroplast. This produces a proton gradient or what is called, proton motive force. This same force is used to generate ATP from ADP and Pi.

What are the roles of NADH and NADPH in cellular respiration and photosynthesis?