Life Processes notes on Photosynthesis and the Human Digestive System, conceptual

Photosynthesis

Definition

• Photosynthesis is the process by which green plants make their own food using sunlight, carbon dioxide, and water.

Where It Happens

• Occurs in the leaves of plants, mainly in cells containing chlorophyll (green pigment).

Importance

• Produces food (glucose) for plants.

• Releases oxygen, which is essential for life on Earth.

• Forms the basis of the food chain.

Raw Materials Required

• Sunlight – source of energy

• Carbon dioxide – from the air

• Water – absorbed from the soil

Factors Affecting Photosynthesis

• Light intensity – more light increases the rate up to a point

• Availability of CO₂ – essential for glucose production

• Water supply – shortage can reduce photosynthesis

• Chlorophyll presence – without it, plants cannot perform photosynthesis

Products

• Glucose – stored as energy in plants

• Oxygen – released into the atmosphere

Significance

• Provides food and energy to all living organisms.

• Maintains oxygen and carbon dioxide balance in the environment.

2. Human Digestive System

Definition

• The human digestive system is responsible for breaking down food into simpler substances that can be absorbed and used by the body.

Main Organs and Their Functions

1. Mouth –

   • Food is chewed and mixed with saliva.

   • Saliva contains enzymes that start breaking down starch.

2. Esophagus –

   • A tube that connects the mouth to the stomach.

   • Moves food by a process called peristalsis (wave-like muscular movements).

3. Stomach –

   • Secretes acid and enzymes that digest proteins.

   • Food is converted into a semi-liquid called chyme.

4. Small Intestine –

   • Major site of digestion and absorption.

   • Receives bile from the liver (to digest fats) and enzymes from the pancreas.

   • Nutrients pass into the bloodstream from here.

5. Large Intestine –

   • Absorbs water and salts.

   • Forms feces, which are excreted through the rectum 

6. Liver –

   • Produces bile, which helps in fat digestion.

   • Stores vitamins and detoxifies harmful substances.

7. Pancreas –

   • Produces digestive enzymes and hormones like insulin.

Digestive Process (Conceptual)

• Food is mechanically broken in the mouth.

• Enzymes chemically break down carbohydrates, proteins, and fats.

• Nutrients are absorbed mainly in the small intestine.

• Undigested material is excreted.

Importance of Digestion

• Provides energy for the body.

• Supplies nutrients for growth, repair, and maintenance.

• Helps in eliminating waste products.

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