Final answer:
E) energy-investment and conservation Glycolysis begins with glucose and ends with pyruvate. It consists of two distinct phases: the trapping of glucose for splitting and the extraction of energy from the resulting molecules.
Step-by-step explanation:
Glycolysis begins with the six-carbon ring-shaped structure of a single glucose molecule and ends with two molecules of a three-carbon sugar called pyruvate. Glycolysis consists of two distinct phases. The first part of the glycolysis pathway traps the glucose molecule in the cell and uses energy to modify it so that the six-carbon sugar molecule can be split evenly into the two three-carbon molecules. The second part of glycolysis extracts energy from the molecules and stores it in the form of ATP and NADH-remember: this is the reduced form of NAD.
Glycolysis begins with an energy-investment stage. This involves the phosphorylation of glucose, which is followed by a series of reactions that lead to the cleavage of the six-carbon glucose molecule into two three-carbon molecules of pyruvate. During the initial phase of glycolysis, two ATP molecules are used to activate glucose and facilitate its subsequent breakdown; this process is hence energy consuming. The invested energy is then repaid in the second phase of glycolysis where a net gain of two ATP molecules and the production of NADH is achieved, demonstrating energy conservation.