Ad Banner Placeholder

Cambridge IGCSE Biology · 0610

Chapter 6: Plant nutrition (Part 1)

Definition of photosynthesis

Photosynthesis
A metabolic reaction occurring in plants in which light energy is used to synthesise carbohydrates from raw materials (carbon dioxide and water).
Location
This process takes place in the chloroplasts of plant cells.
Chlorophyll
A green pigment found in chloroplasts that transfers light energy into chemical energy for the synthesis of carbohydrates.

Exam Traps

  • Do not name chlorophyll as the location of photosynthesis — it is a pigment within chloroplasts.
  • Avoid describing photosynthesis as breaking down glucose; that is respiration.

Equations for photosynthesis

Word equation
Carbon dioxide + water → glucose + oxygen (in the presence of light and chlorophyll).
Balanced chemical equation
6CO2 + 6H2O → C6H12O6 + 6O2
Word and balanced chemical equations for photosynthesis with light and chlorophyll shown above and below the arrow
Diagram 1: The photosynthesis equation. The word equation and balanced chemical equation are shown with “light” and “chlorophyll” written above and below the arrow.

Exam Traps

  • Do not reverse the equation or give the respiration equation instead.

Use and storage of carbohydrates

Carbohydrates produced during photosynthesis have five primary uses in the plant:

  1. Starch: Used as an energy store.
  2. Cellulose: Used to build cell walls.
  3. Glucose: Used in respiration to provide energy.
  4. Sucrose: Used for transport in the phloem.
  5. Nectar: Used to attract insects for pollination.

Exam Traps

  • Do not say starch is the direct product of the photosynthesis equation — that is glucose.
  • Avoid stating glucose is transported in the phloem; sucrose is the usual transport sugar.

0/15

Ad Banner Placeholder