What are the energy carriers involved in metabolism?

The primary energy carriers involved in metabolism are adenosine triphosphate (ATP), nicotinamide adenine dinucleotide (NADH), and flavin adenine dinucleotide (FADH2).

Adenosine triphosphate (ATP) is the main energy currency of the cell. It is a high-energy molecule that stores the energy we need to do just about everything. ATP is produced during the process of cellular respiration, particularly in the Krebs cycle and oxidative phosphorylation. When energy is needed by the cell, it is supplied by hydrolysing ATP into adenosine diphosphate (ADP) and an inorganic phosphate (Pi). This reaction releases energy that can be used for various cellular processes.

Nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH2) are two other important energy carriers in metabolism. They are both involved in the process of cellular respiration, acting as electron carriers in the electron transport chain. NADH and FADH2 are produced during the Krebs cycle, where they accept electrons from other molecules. These electrons are then transferred to the electron transport chain, where they are used to power the synthesis of ATP.

NADH and FADH2 are considered 'reduced' when they gain electrons (along with protons) and 'oxidised' when they lose electrons. The process of transferring electrons from NADH and FADH2 to the electron transport chain is a key part of oxidative phosphorylation, which generates the majority of ATP during cellular respiration.

In addition to ATP, NADH, and FADH2, there are other molecules that play a role in energy transfer during metabolism. These include coenzyme A (CoA), which carries acetyl groups, and guanosine triphosphate (GTP), which is similar to ATP and can be used to power cellular processes. However, ATP, NADH, and FADH2 are the primary energy carriers that you need to be familiar with for your IB Biology course.