Uses of Energy from Respiration in Living Organisms
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key concept
Energy from respiration is used for: muscle contraction, active transport of ions and molecules, synthesis of large molecules from smaller ones (e.g. Proteins from amino acids), cell division, maintaining body temperature in mammals, and transmitting nerve impulses.
When asked why respiration is important, simply stating "organisms need energy" earns one mark at best. Name at least three specific uses and connect each to a process the organism carries out. The more concrete your examples, the more marks you score.
Muscle contraction and movement
Muscles require energy from respiration to contract. Every voluntary movement: walking, running, lifting: depends on muscle fibres using energy released from glucose. Even involuntary muscle contractions, such as the heart beating and peristalsis in the gut, require a continuous energy supply from respiration.
This is why muscle cells contain many mitochondria: they need to respire rapidly to meet high energy demands. During vigorous exercise, if aerobic respiration cannot supply enough energy, anaerobic respiration supplements it.
Active transport and synthesis
Active transport moves substances against their concentration gradient and requires energy from respiration. Examples include root hair cells absorbing mineral ions from soil and nerve cells pumping ions to restore resting potential after a nerve impulse.
Synthesis of large molecules requires energy to form chemical bonds. Plants build cellulose from glucose, proteins from amino acids, and starch from glucose for storage. Animals synthesise proteins for growth and repair, glycogen from glucose for storage in liver and muscle cells, and lipids for long-term energy storage and cell membrane construction.
Body temperature and other uses
Mammals and birds are endothermic: they maintain a constant body temperature partly using heat released as a by-product of respiration. In cold environments, metabolic rate increases (including shivering) to generate more heat. This is why these animals need a relatively large and continuous food intake.
Other energy uses include: cell division (mitosis and meiosis require energy to replicate DNA and separate chromosomes); nerve impulse transmission (energy restores the ion balance across nerve cell membranes after each impulse); and bioluminescence in certain organisms.
Try a focused question (3 marks)
State three uses of energy released by respiration in a named organism.
Show the answer and marking guidance
In humans: muscle contraction for movement.
Active transport of mineral ions into root hair cells in plants (or ions across nerve cell membranes in animals).
Synthesis of proteins from amino acids for growth and repair.
Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.
Common mix-ups to avoid
Check these points against your own answer before moving on.
Writing "organisms need energy to live" without naming specific uses.
Confusing energy release (respiration) with energy intake (eating).
Saying respiration produces energy rather than releases energy stored in glucose.
Forgetting that plants also respire and use energy for active transport and synthesis.