This definitions covers Key Definitions within Photosynthesis for GCSE Biology. Topic 1: Photosynthesis It is section 7 of 13 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 7 of 13
Practice
15 questions
Recall
20 flashcards
Key Definitions
Photosynthesis: A chemical process in which plants, algae, and some bacteria use light energy to convert carbon dioxide and water into glucose and oxygen. It is the means by which virtually all energy enters food chains.
Chlorophyll: The green pigment found in chloroplasts that absorbs light energy (mainly red and blue wavelengths) to power photosynthesis. It reflects green light, which is why plants appear green.
Chloroplast: A membrane-bound organelle found in plant cells and algae that is the site of photosynthesis. It contains chlorophyll and the enzymes needed to convert CO2 into glucose.
Limiting factor: The variable that is present in the lowest amount relative to what the process needs, and therefore controls the maximum rate of that process. For photosynthesis, the three main limiting factors are light intensity, CO2 concentration, and temperature.
Endothermic reaction: A chemical reaction that absorbs energy from the surroundings. Photosynthesis is endothermic because it takes in light energy and stores it as chemical energy in glucose molecules.
Glucose: A simple sugar with the formula C6H12O6, produced during photosynthesis. It is the primary energy source for cellular respiration and is also used to build starch, cellulose, lipids, and proteins in plants.
Starch: An insoluble storage carbohydrate made from many glucose molecules joined together. Plants convert excess glucose to starch for long-term energy storage (e.g., in roots, seeds, and leaves).
Rate of photosynthesis: How quickly photosynthesis is occurring, measured by the volume of oxygen produced per unit time (e.g., bubbles per minute from an aquatic plant) or by the decrease in CO2 concentration.