What is Nutrition?
Nutrition is the process by which living organisms obtain and use food for energy, growth, repair, and maintenance.
- Provides energy for all activities
- Supplies building materials for growth and repair
- Regulates and maintains body functions
Modes of Nutrition
Autotrophs synthesize food from inorganic substances using light or chemical energy (e.g., green plants).
Heterotrophs obtain ready-made organic food by ingesting or absorbing other organisms (e.g., animals, fungi).
Autotrophs vs. Heterotrophs
Energy Acquisition Strategies
| Category | Energy Source | Raw Material Source | Example |
|---|---|---|---|
| Autotroph | Sunlight | CO₂ and H₂O | Rose plant |
| Heterotroph | Food eaten | Pre-formed organic molecules | Human |
Photosynthesis: Step-by-Step
Sunlight + chlorophyll → Light reaction (produces ATP, NADPH) → Dark reaction in stroma (forms glucose)
Overall Equation
6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Diagram: labeled chloroplast diagram with thylakoids, stroma, arrows for light and dark reactions
Label the Chloroplast
Drag the tags onto the thylakoid, grana, and stroma regions of the chloroplast diagram.
Test for Starch in Leaves
Activity Steps
- Dip a fresh leaf in boiling water for 1 min.
- Heat the leaf in alcohol until it loses all green colour.
- Rinse, place on a white tile, and add a few drops of iodine solution.
Observation
Areas turning blue-black contain starch, proving photosynthesis; sections that stay brown show no starch formed.
Human Digestive System Overview
Food pathway: Mouth → Esophagus → Stomach → Small Intestine → Large Intestine.
- Salivary glands
- Liver
- Pancreas
Arrange the Digestive Journey
Drag & Drop Activity
Drag each organ into the correct order of passage: Mouth, Stomach, Small Intestine, Large Intestine, Anus.
What is Respiration?
Respiration is a cellular chemical process that releases usable energy from food, usually in the presence of oxygen.
Breathing vs Cellular Respiration
Breathing is the mechanical movement of air into and out of lungs; cellular respiration is the biochemical breakdown of glucose within cells to yield energy.
Aerobic vs. Anaerobic Respiration
Key Differences
| Feature | Aerobic | Anaerobic |
|---|---|---|
| Oxygen presence | Required | Not required |
| ATP yield | 38 ATP | 2 ATP |
| End products | CO₂ + H₂O | Lactic acid / Ethanol + CO₂ |
Human Respiratory System
Air flow: Nostrils → Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
Alveoli spread out to about 70 m²—roughly half a badminton court—for efficient gas exchange.
Quick Quiz: Where Does It Happen?
Where does gas exchange take place?
A) Trachea B) Alveoli C) Bronchi
Stages of Cellular Respiration
- 1. Glycolysis – occurs in the cytoplasm; splits glucose into pyruvate, netting 2 ATP.
- 2. Krebs Cycle – takes place in the mitochondrial matrix; releases CO₂, forms NADH/FADH₂ and 2 ATP.
- 3. Electron Transport Chain – located on the inner mitochondrial membrane; uses NADH/FADH₂ to generate the majority of ATP and produce water.
Muscle Fatigue Explained
Riya sprints 200 m; moments later her thigh muscles burn and feel heavy.
With oxygen scarce, her muscles shift to anaerobic respiration, converting glucose to lactic acid and causing the burn.
Why Do Athletes Breathe Faster?
Rapid breathing quickly repays oxygen debt and expels excess CO₂ to stabilize the blood.
During a marathon’s last kilometres, an athlete’s breathing rate can triple to generate enough ATP for muscles.
Nutrition & Respiration: Concept Map
Energy Conversion Flowchart
Start with Food Digestion Nutrients Cellular Respiration ATP + CO₂ Photosynthesis (plants) back to Food (cycle)
Key Takeaways
Summary
- Nutrition supplies matter and energy for organisms.
- Photosynthesis is the autotrophic nutrition pathway.
- Digestion breaks food into absorbable molecules.
- Respiration converts glucose to ATP; aerobic yields more ATP than anaerobic.