Gas Exchange: Night vs Day (Edexcel IGCSE Biology (Modular)) : Revision Note

Lára Marie McIvor

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Gas Exchange: Night vs Day

  • Plants can only photosynthesise when they have access to light, however, cells respire all the time

  • This means that gas exchange in plants varies throughout a 24 hour period

  • During the daytime plants both respire and photosynthesise

    • The rate of photosynthesis tends to be higher than the rate of respiration (unless there is a low light intensity)

    • Therefore there is a net diffusion of carbon dioxide into the plant and a net diffusion of oxygen out of the plant during the day

  • During the nighttime, plants only respire

    • This means that there is a net movement of oxygen into the plant and a net diffusion of carbon dioxide out of the plant during the nighttime

  • At low light intensities, the rate of photosynthesis is equal to the rate of respiration

    • This means that there is no net movement of oxygen or carbon dioxide in either direction

Photosynthesis and respiration in plants, IGCSE & GCSE Biology revision notes

Plants photosynthesise and respire during the day but only respire at night time

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Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Biology, Psychology & Sociology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

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