Living Things

Photosynthesis and Respiration

How do plants get their energy?

Animals need energy to grow and reproduce.  They get this energy from the plants and animals they eat.  Plants also need energy to grow and reproduce, however plants don’t eat, so they need to get their energy another way.

What is photosynthesis?

Photosynthesis is how plants get the energy they need to grow and reproduce.  They use the light from the sun, together with carbon dioxide and water to produce sugar (glucose).

Photosynthesis can be described using the following word equation:

carbon dioxide + water + sunlight ---> glucose + oxygen

Photosynthesis can also be written as a chemical equation.  The chemical equation is what chemists and other scientists use:

6 CO2 + 6 H2O + sunlight  ---> C6H12O6 + 6 O2

The carbon dioxide needed for photosynthesis to occur comes from the air around the plant.  The water enters the plant through its root system.

Leaves are the primary site of photosynthesis in plants.

 

Figure 1:  The Cells of a Leaf
(Image source: http://en.wikipedia.org/wiki/Image:Leaf_1_web.jpg)

 

What is respiration?

Photosynthesis produces glucose which is a type of sugar; however this sugar can’t be used by the plants until it is converted into energy.  Respiration is the process where plants convert glucose into energy that they can use to grow and reproduce.

Respiration can be described using the following word equation:

glucose + oxygen---> carbon dioxide + water + energy 

Respiration can also be written as a chemical equation.  The chemical equation is what chemists and other scientists use:

C6H12O6 + 6 O2  ---> 6 CO2 + 6 H2O + energy

 


Australian Curriculum links

Year 8

Science Understanding  - Earth and space sciences

(ACSSU225) Chemical change involves substances reacting to form new substances