Pearson Edexcel · GCSE · Biology
Course version: 1BI0 · Version from Sept 2016
Describe photosynthesis in plants and algae as an endothermic reaction…
Full specification wording
Topic 6 – Plant structures and their functions: 6.2 Describe photosynthesis in plants and algae as an endothermic reaction that uses light energy to react carbon dioxide and water to produce glucose and oxygen
Photosynthesis happens in plants and algae.
Checked against the Pearson Edexcel 1BI0 specification (opens in a new tab) on .
- Point 2 of 15
Study notes
From the checked teaching notes for this specification point.
The idea
Photosynthesis happens in plants and algae. It is endothermic, meaning it takes in energy from the surroundings, here light energy absorbed by chlorophyll. That light energy drives a reaction in which carbon dioxide and water are the reactants, and glucose and oxygen are the products. The balanced summary equation is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. The glucose stores chemical energy and is used for respiration or built into biomass such as starch and cellulose; the oxygen is released. A reliable method is to label each part: reactants on the left, products on the right, and note that energy is absorbed, not released. Algae carry out the same reaction, often underwater, which is why ponds can become oxygenated in daylight.
What earns the marks
- Photosynthesis occurs in plants and algae.
- Carbon dioxide and water are the reactants.
- Glucose and oxygen are the products.
- The summary equation is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, showing light energy is used.
Common mistakes and how to put them right
Calling photosynthesis exothermic: correct this by stating it is endothermic and absorbs light energy.
Reversing reactants and products.
Put it right by placing carbon dioxide and water on the left and glucose and oxygen on the right.
Omitting algae: correct this by noting algae also photosynthesise, not only land plants.
Exam tips
- Always state that light energy is absorbed, to justify the term endothermic.
- Write the balanced equation with correct formulae and subscripts.
- Name both reactants and both products when describing the reaction.
Try the lesson
The start of the Topic 6 – Plant structures and their functions: 6.2 Describe photosynthesis in plants and algae as an endothermic reaction that uses light energy to react carbon dioxide and water to produce glucose and oxygen lesson, made from checked teaching notes for this specification point.
Have a go first
Which two raw materials does a green plant take in to make glucose during photosynthesis?
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