Nutrition

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Nutrition — Key Facts

• Nutrition is the process by which organisms obtain and utilize food for growth, energy, and maintenance
• Autotrophic nutrition: Organisms make their own food (e.g., green plants — photosynthesis)
• Heterotrophic nutrition: Organisms cannot make their own food; obtain food from other organisms
• Key types: Holozoidic (solid food), Holophytic (liquid food), Parasitic (absorb from host)

High-yield points:

• Photosynthesis word equation: Carbon dioxide + Water → Glucose + Oxygen (in presence of light and chlorophyll)
• Mineral nutrition: Macronutrients (N, P, K, Ca, Mg, S) and Micronutrients (Fe, Mn, Zn, Cu, B, Mo, Cl, Ni)
• Deficiency diseases in plants: Nitrogen — chlorosis; Phosphorus — purple leaves; Potassium — scorch; Magnesium — interveinal chlorosis

⚡ Exam tip: Memorise the word equation for photosynthesis and the functions of major mineral nutrients. NABTEB often asks about deficiency symptoms.

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Nutrition — Study Guide

1. Modes of Nutrition in Plants

• Photosynthesis: Occurs in chloroplasts; requires sunlight, chlorophyll, CO₂, and H₂O
• Chemosynthesis: Food production using chemical energy (certain bacteria)
• Saprophytic nutrition: Dead/decaying matter breakdown (e.g., fungi)
• Parasitic nutrition: Obtaining food from living host (e.g., mistletoe, dodder)

2. Mineral Nutrition in Plants Essential elements and their roles:

Element	Function	Deficiency Symptom
Nitrogen (N)	Leaf growth, chlorophyll	Yellowing (chlorosis) of older leaves
Phosphorus (P)	Root development, energy	Purple/discoloured leaves
Potassium (K)	Water regulation, enzyme activation	Leaf scorch, weak stems
Magnesium (Mg)	Chlorophyll component	Interveinal chlorosis
Calcium (Ca)	Cell wall formation	Distorted new leaves
Iron (Fe)	Chlorophyll synthesis	Young leaves turn yellow

3. Nutrition in Animals

• Holozoic: Ingestion → Digestion → Absorption → Assimilation → Egestion (e.g., humans, amoeba)
• Herbivores: Plant-eaters (cellulose-digesting bacteria in rumen)
• Carnivores: Flesh-eaters (sharp teeth, short intestine)
• Omnivores: Both plant and animal matter (e.g., humans)
• Parasites: Feed on host’s digested food (e.g., tapeworm, roundworm)

Standard questions:

• Draw and label the human digestive system
• Explain the process of photosynthesis
• Differentiate autotrophic and heterotrophic nutrition

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Nutrition — Comprehensive Notes

A. Photosynthesis: Detailed Process

Light Reactions (Grana/Thylakoid):

• Chlorophyll absorbs light energy
• Water is split (photolysis): 2H₂O → 4H⁺ + 4e⁻ + O₂
• ATP is produced via photophosphorylation
• NADPH is produced

Dark Reactions (Stroma):

• CO₂ is fixed via the Calvin Cycle
• 6CO₂ + 12NADPH + 18ATP → C₆H₁₂O₆ + 12NADP⁺ + 18ADP + 18Pi
• G3P (glyceraldehyde-3-phosphate) is the first stable product

Factors affecting photosynthesis:

1. Light intensity — increases rate up to a point (light saturation point)
2. CO₂ concentration — optimum ~0.03–0.04%
3. Temperature — optimum 25–35°C for most C₃ plants
4. Water — deficiency reduces photosynthesis
5. Chlorophyll — amount and health of chlorophyll

B. Animal Nutrition — Human Digestive System

Ingestion: Mouth — chewing, saliva (amylase begins starch digestion)

Digestion:

Region	Enzyme	Substrate	Product
Mouth	Salivary amylase	Starch	Maltose
Stomach	Pepsin + HCl	Proteins	Peptones
Duodenum	Pancreatic amylase	Starch	Maltose
Duodenum	Trypsin	Proteins	Peptides
Small intestine	Maltase, sucrase, lactase	Disaccharides	Monosaccharides

Absorption: Occurs mainly in the ileum via:

• Active transport (glucose, amino acids)
• Diffusion (water, small lipids)
• Osmosis (water)

Egestion: Unabsorbed waste passed through colon → rectum → anus

C. Nutritional Disorders

• Kwashiorkor: Protein deficiency — oedema, fatty liver, skin lesions
• Marasmus: Protein-calorie deficiency — wasting, no oedema
• Obesity: Excess calorie intake → BMI > 30
• Beriberi: Vitamin B1 (Thiamine) deficiency — nerve damage, heart failure
• Scurvy: Vitamin C deficiency — bleeding gums, poor wound healing
• Rickets: Vitamin D/Calcium deficiency — soft bones in children

Practice:

• Solve NABTEB past questions on nutrition
• Draw and label cross-section of a leaf showing photosynthesis sites
• Explain how mineral deficiencies affect plant growth

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