Key Metabolic Terms Explained
(a) Substrate Level Phosphorylation
This is a metabolic process where a phosphate group is directly transferred from a phosphorylated intermediate to ADP, forming ATP. It occurs in glycolysis and the Krebs cycle, independent of the electron transport chain.
(b) Glycolysis
Glycolysis is the ten-step pathway by which glucose is broken down into two molecules of pyruvate, producing ATP and NADH. It takes place in the cytoplasm and is the first step in both aerobic and anaerobic respiration.
(c) Anaplerotic Reactions
These are chemical reactions that replenish intermediates of the TCA (Krebs) cycle that have been extracted for biosynthetic purposes. For example, pyruvate can be converted into oxaloacetate to replenish TCA intermediates.
(d) Chemotrophs
Chemotrophs are organisms that obtain energy through the oxidation of electron donors in their environments. These donors can be organic or inorganic molecules, and chemotrophs include many bacteria and archaea.
(e) Catabolism
Catabolism refers to the breakdown of complex molecules into simpler ones, releasing energy in the form of ATP. This energy is used by cells for maintenance, growth, and various biological functions.
These foundational terms are crucial for understanding how cells harness, transform, and utilize energy through various metabolic pathways.