Photosynthesis is one of the most important biological processes that support life on Earth. It is the process by which green plants manufacture their own food using sunlight. This topic is very important in the Ghana Teacher Licensure Examination because it links plant biology, nutrition, ecology, and energy flow in nature. Teachers are expected not only to define photosynthesis but also to explain the process, conditions, and its importance to both plants and animals.

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Module 15.1: Definition of Photosynthesis (Word and Symbol)

Meaning of Photosynthesis

Photosynthesis is the process by which green plants use sunlight energy to combine carbon dioxide and water to produce food (glucose), releasing oxygen as a by-product. This process takes place mainly in the leaves of green plants.

The word photosynthesis comes from two Greek words:

• Photo meaning light

• Synthesis meaning to put together

Therefore, photosynthesis means “putting together with light.”

Word Equation of Photosynthesis

Carbon dioxide + Water → Glucose + Oxygen (in the presence of sunlight and chlorophyll)

This word equation shows that plants need carbon dioxide and water to produce glucose and oxygen.

Chemical (Symbol) Equation of Photosynthesis

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

This chemical equation explains the same process in symbolic form. It shows that six molecules of carbon dioxide combine with six molecules of water to form one molecule of glucose and six molecules of oxygen.

Explanation of the Equation

• Carbon dioxide enters the plant through tiny openings in the leaves called stomata.

• Water is absorbed from the soil through the roots and transported to the leaves.

• Sunlight provides the energy needed for the reaction.

• Chlorophyll traps the light energy.

• Glucose produced is used by the plant for energy and growth.

• Oxygen is released into the air as a waste product.

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Module 15.2: Factors Necessary for Photosynthesis

Photosynthesis can only take place when certain conditions or factors are present. These factors are very important because the absence of any one of them will slow down or stop the process.

1. Sunlight

Sunlight is the main source of energy for photosynthesis. Without light, plants cannot make food. Light provides the energy needed to break down water molecules and drive the chemical reactions involved in photosynthesis.

2. Chlorophyll

Chlorophyll is the green pigment found in the leaves of plants. It absorbs sunlight energy. Plants that do not have chlorophyll cannot carry out photosynthesis.

3. Water

Water is absorbed from the soil by the roots and transported to the leaves through the xylem tissues. Water is essential because it supplies hydrogen needed to form glucose.

4. Carbon Dioxide

Carbon dioxide is taken from the air through the stomata in the leaves. It provides carbon, which is used to form glucose.

5. Suitable Temperature

Photosynthesis works best at moderate temperatures. Very high or very low temperatures can slow down the process because enzymes involved in photosynthesis work best within a specific temperature range.

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Module 15.3: Importance of Photosynthesis

Photosynthesis is extremely important to life on Earth. Its importance can be explained under the following headings:

1. Source of Food

Photosynthesis is the primary source of food for all living organisms. Plants produce food for themselves, and animals depend on plants directly or indirectly for food.

2. Production of Oxygen

Oxygen released during photosynthesis is used by humans and animals for respiration. Without photosynthesis, there would be very little oxygen in the atmosphere.

3. Energy Supply

Photosynthesis converts light energy into chemical energy stored in food. This energy flows through the food chain to other organisms.

4. Maintains Balance of Gases

Photosynthesis helps to maintain the balance between oxygen and carbon dioxide in the atmosphere.

5. Supports Ecosystems

All ecosystems depend on photosynthesis because it provides energy at the base of the food chain.

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UNIT 16: FOOD AND NUTRITION

Introduction

Food and nutrition are essential topics in Integrated Science because they relate directly to human health and survival. Teachers must understand the different types of food, the effects of poor nutrition, and the importance of a balanced diet.

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Module 16.1: Food Types

Meaning of Food

Food is any substance that is eaten or drunk to provide nutrients needed for energy, growth, repair, and good health.

Types of Food (Classes of Food)

1. Carbohydrates

Carbohydrates provide energy for the body. Examples include rice, maize, cassava, yam, bread, and sugar.

2. Proteins

Proteins are needed for growth and repair of body tissues. Examples include meat, fish, eggs, beans, groundnuts, and milk.

3. Fats and Oils

Fats and oils provide energy and help keep the body warm. Examples include palm oil, groundnut oil, butter, and avocado.

4. Vitamins

Vitamins protect the body from diseases and help regulate body processes. Examples include fruits and vegetables such as oranges, mangoes, carrots, and kontomire.

5. Minerals

Minerals help build strong bones and teeth and regulate body functions. Examples include calcium, iron, and iodine.

6. Water

Water helps digestion, transportation of nutrients, and temperature regulation in the body.

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Module 16.2: Malnutrition

Meaning of Malnutrition

Malnutrition is a condition that occurs when the body does not receive the right amount of nutrients needed for healthy growth and development.

Types of Malnutrition

1. Undernutrition

This occurs when the body does not get enough food or nutrients.

Examples include:

• Kwashiorkor (lack of protein)

• Marasmus (lack of energy and protein)

2. Overnutrition

This occurs when a person eats too much food, especially fatty and sugary foods.

Effects of Malnutrition

• Poor growth

• Weak immune system

• Frequent illness

• Poor academic performance

• Obesity and heart diseases (overnutrition)

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Module 16.3: Balanced Diet

Meaning of a Balanced Diet

A balanced diet is a diet that contains all the classes of food in the correct proportions to maintain good health.

Components of a Balanced Diet

• Carbohydrates for energy

• Proteins for growth and repair

• Fats and oils for energy and warmth

• Vitamins and minerals for protection

• Water for body functions

Importance of a Balanced Diet

• Promotes good health

• Supports growth and development

• Prevents malnutrition and diseases

• Improves learning and productivity

Examples of Balanced Meals in Ghana

• Banku with okro soup and fish

• Rice with stew, vegetables, and meat

• Tuo zaafi with green leafy soup

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