IB Sports, exercise and health science A.2.3 Energy Systems Key Definitions

A high-energy molecule that stores and provides energy for cellular processes, including muscle contraction and metabolism.

Adenosine triphosphate (ATP) is the primary chemical energy currency of the cell. Hydrolysis of ATP releases the energy used for muscle contraction, ion transport, and most other energy-requiring processes.

A type of exercise that improves the body's ability to sustain prolonged physical activity by enhancing cardiovascular and muscular efficiency.

The metabolic process that builds complex molecules from simpler ones, using energy (e.g., muscle protein synthesis).

The process of releasing energy from fatty acids inside the mitochondria. Fatty acid chains are gradually broken down into acetyl CoA molecules, each cycle shortening the chain by two carbons and yielding energy.

The primary form of carbon dioxide transport in the blood, formed when CO₂ combines with water.

The volume of blood the heart pumps per minute.

The metabolic process that breaks down complex molecules to release energy (e.g., breaking down glucose to produce ATP).

The controlled release of energy in the form of ATP from organic molecules inside cells. It takes place mainly in the mitochondria for aerobic respiration and in the cytosol for anaerobic glycolysis.

The process in which lactate is transported to the liver and converted back into glucose via gluconeogenesis.

A molecule stored in muscles that rapidly regenerates ATP from ADP during short, high-intensity activities.

The highest power output an individual can sustain over time without a rapid rise in blood lactate levels, closely related to endurance capacity.

A series of protein complexes in the mitochondria that transfer electrons to produce ATP during aerobic metabolism.

The energy continuum refers to the dynamic interaction of the three energy systems (phosphagen, glycolytic, and oxidative systems) during physical activity.

Energy systems are biochemical pathways that the body uses to produce adenosine triphosphate (ATP), the primary source of energy for all cellular activities, including muscle contractions during physical activity.

Excess post-exercise oxygen consumption (EPOC) refers to the continued elevation of oxygen consumption after exercise has ended.

The production of glucose from non-carbohydrate sources, such as proteins and fats.

The stored form of glucose found in the liver and muscles, which can be broken down into glucose for ATP production during exercise.

The process of converting glucose into glycogen for storage, mainly in the liver and muscles.

The process of breaking down glycogen into glucose to be released into the blood for energy use.

A process that breaks down glucose or glycogen into pyruvate without the use of oxygen, producing ATP and lactic acid as a byproduct.

Glycolysis is the process by which glucose is broken down to produce energy.

An iron-rich pigment in red blood cells that binds oxygen in the lungs and transports it to the body's tissues, then helps return carbon dioxide to the lungs.

Heart rate is the number of times the heart beats per minute (bpm). It reflects how fast the heart pumps blood to meet metabolic demands.