IGCSE Biology 0610: Identifying Five Uses of Respiratory Energy

A hiker climbs a steep hill carrying a heavy backpack on a cold, windy day. For each description below, state the use of the energy released by respiration that is being shown.

(a) As she climbs, the muscle fibres in her legs shorten repeatedly, pulling on her leg bones and driving each step up the slope. [1]

(b) Partway up, she trips on a loose stone. Her leg muscles react and correct her balance within a fraction of a second, faster than she can consciously think, because electrical signals travel rapidly along her nerve cells. [1]

(c) Feeling a chill in the wind, her body starts to shiver, and heat released by her cells helps keep her core body temperature steady. [1]

(d) In her small intestine, glucose from her packed lunch is absorbed into her blood, moving from a region of lower concentration in the gut to a region of higher concentration in the blood. [1]

(e) Over the following days, her leg muscles repair and adapt to the climb as her cells join amino acids together to build new muscle proteins. [1]

Part (a): Repeated shortening of leg muscle fibres

Muscle fibres shortening repeatedly to pull on bones and drive movement is muscle contraction, one of the processes that needs a continuous supply of energy released by respiration.

Part (b): Rapid electrical signals correcting her balance

Correcting her balance faster than she can consciously think, driven by electrical signals travelling along nerve cells, is the transmission of nerve impulses. Sending these signals along nerve cells needs energy released by respiration.

Part (c): Shivering and staying warm in the wind

Heat released by her cells helping to keep her core body temperature steady, especially in cold, windy conditions, is an example of using energy released by respiration for keeping the body warm (maintaining a constant body temperature).

Part (d): Glucose moving into the blood against its concentration gradient

Glucose moving from a region of lower concentration in the gut to a region of higher concentration in the blood is moving against its concentration gradient. This cannot happen by diffusion alone, so it must be active transport, which needs energy released by respiration.

Part (e): Joining amino acids to build new muscle proteins

Joining amino acids together to build new muscle proteins as her muscles repair and adapt is protein synthesis, which needs energy released by respiration.

Final answers

(a) Muscle contraction
(b) Transmission of nerve impulses
(c) Keeping the body warm (maintaining a constant body temperature)
(d) Active transport
(e) Protein synthesis