SS1 Biology Lesson Note on Nutrition

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SUB TOPIC 3:  NUTRITION

Nutrition can be defined as the totality of the processes by which a living thing obtains, and uses food. We have two types of nutrition; plant and animal nutrition.

PLANT NUTRITION

In plant nutrition, we have photosynthesis and chemosynthesis. The later is a process through which non-green plants use either parasitic or saprophytic modes of nutrition to obtain their food. It can occur in colourless autotrophic bacteria.

Photosynthesis is the process by which green plants make use of raw materials such as carbon (iv) oxide and water to produce sugar and Oxygen in presence of sunlight or solar energy and chlorophyll.

EQUATION FOR PHOTOSYNTHESIS

6CO₂     +     6H₂O → C₆H₁₂O₆           +      6O₂ 

Light Reaction

• Light energy is captured by chlorophyll
• The energy splits water into hydrogen (H⁺) and hydroxyl (OH^–) ions. The process is called photolysis of water and it is the first step in photosynthesis.

4H₂O → 4H⁺ + 4(OH^–)   + ATP

• The hydroxyl part is reconverted to water and Oxygen is given off as a by-product.

4(OH) → 2H₂O + O₂ 

• The compound (NADH) coenzyme is reduced by hydrogen ion and ATP is formed.

With the energy provided by ATP, the reduced compound (NADH) brings about the assimilation of carbon (iv) oxide through a series of small steps, each controlled by a specific enzyme to form sugar or starch.

CO₂ + 2H_{2 →} CH₂O + H₂O O

The overall reaction is below:

CO₂ + 2H₂O →  CH₂O + H₂O + O₂ 

Significance of Photosynthesis

1. All living things are supported by the by-products of photosynthesis. For example, all animals and non-green plants obtain their energy from green plants.
2. It brings about the purification of the atmosphere by removing excess carbon (iv) oxide (carbon iv oxide)

Materials Necessary for Photosynthesis

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