Q1
What is mechanical digestion?
APhysical breakdown of food
BChemical breakdown by enzymes
CNo breakdown at all
DOnly absorption
ICSEClass 9 (ICSE)BiologyCh 11 · Topic 1
The Digestive System
The digestive system breaks down food into nutrients through mechanical and chemical processes, involving organs from mouth to intestines.
Core concept
Mechanical digestion (chewing, churning) physically breaks food into smaller pieces, while chemical digestion (enzymes) breaks down molecules.
How it works
Enzymes, like amylase (breaks down starch) and protease (breaks down proteins), speed up chemical digestion at specific points in the digestive tract.
Why it matters
The small intestine is where most nutrient absorption occurs, with finger-like projections called villi increasing surface area for absorption.
Key detail
Understanding the digestive system helps us appreciate how our body extracts nutrients from food for energy, growth, and repair.
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Quick notes
• Mechanical digestion physically breaks down food.
• Chemical digestion uses enzymes.
• Amylase breaks down starch.
• Protease breaks down proteins.
• The small intestine absorbs most nutrients.
• Villi are finger-like projections increasing surface area.
• This maximises nutrient absorption.
• The digestive system provides energy for growth and repair.