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AoS 1: How cellular processes work - Photosynthesis

Full Day
Book Program
Year Levels
Unit 3 — How do cells maintain life?


All organisms require energy to perform cellular processes. Although different organisms obtain energy in different ways, they often use it in similar ways. Plants use the pigment chlorophyll to absorb light energy in chloroplasts in their leaves and transform it into useable chemical energy via the process of photosynthesis. Photosynthesis is an endergonic reaction, meaning it requires an input of energy to occur. The energy for photosynthesis is obtained from light.

While it appears a simple process, it is actually quite complex and involves several steps. Two types of reactions occur in photosynthesis: light dependent (photochemical) and light independent (biochemical) reactions.

Light dependent reactions are known as photochemical reactions because they require light to occur. Light independent reactions are known as biochemical reactions because they occur independently of light conditions.

Photochemical reactions oxidise water (split the hydrogen and oxygen atoms), release the oxygen as a bi-product, produce ATP (adenosine triphosphate) and reduce NADP (add hydrogen to it) to become NADPH (nicotinamide adenine dinucleotide phosphate-oxidase). The ATP and NADPH are then used in biochemical reactions which reduce CO2 to carbohydrates in the form of sugar.

Biochemical reactions of photosynthesis occur either in the light or in the dark, provided that ATP, NADPH and CO2 are all present. NADPH is a membrane bound enzyme complex which is formed from NADP in the last step of the electron chain in the light dependent reactions of photosynthesis.

Prior Knowledge

A knowledge of the processes of photosynthesis and respiration is preferred.

Learning Intentions

In this program student’s will:

  • Consider photosynthetic rate under different light intensities
  • Consider photosynthetic rate under different student determined variables
  • Explain gas exchange from leaves under varying conditions using photosynthesis and respiration theory


  • Measure the rate of photosynthesis occurring in chloroplasts in light compared with dark
  • Design and conduct an experiment testing photosynthetic rate after altering another variable i.e. light intensity or chloroplast concentration
  • Measure gas exchange from leaves under different variables.

VCE links

  • Outcome 1 SAC - Explain the dynamic nature of the cell in terms of key cellular processes including regulation, photosynthesis and cellular respiration, and analyse factors that affect the rate of biochemical reactions.