Samacheer Kalvi 9th Science Nutrition and Health Exercise Solutions

Nutrition is the process by which organisms obtain and utilise food for growth, energy, repair, and maintenance of the body.

• Macronutrients: Nutrients required in large amounts. Examples: carbohydrates, proteins, fats.
• Micronutrients: Nutrients required in small amounts. Examples: vitamins and minerals (iron, iodine, calcium).

A balanced diet is one that provides all nutrients — carbohydrates, proteins, fats, vitamins, minerals, water, and dietary fibre — in the right proportion to maintain good health and prevent deficiency diseases.

Vitamin C (ascorbic acid) prevents scurvy. Sources: Citrus fruits (oranges, lemons), amla, guava, tomatoes, green leafy vegetables.

Goitre is the enlargement of the thyroid gland caused by iodine deficiency. It can be prevented by using iodised salt in cooking and eating iodine-rich foods (seafood, dairy products).

1. Autotrophic nutrition: Organisms make their own food using simple inorganic substances. Example: Green plants (photosynthesis). 2. Heterotrophic nutrition: Organisms depend on others for food. Examples: Humans (holozoic), fungi (saprophytic), tapeworm (parasitic).

Food preservation is the process of treating food to prevent spoilage by microorganisms (bacteria, fungi), insects, and environmental factors, thereby extending its shelf life.

Methods: 1. Drying (Dehydration): Removing water from food to prevent microbial growth. e.g., drying fruits, vegetables, fish. 2. Salting / Sugar: Adding salt or sugar draws out water from food and inhibits microbial growth. e.g., pickles, jams. 3. Pasteurisation: Heating food to a specific temperature and then rapidly cooling it. e.g., milk. 4. Refrigeration / Freezing: Low temperature slows down microbial growth. e.g., frozen vegetables, meat. 5. Canning: Food is sealed in airtight containers after sterilisation. e.g., canned fruits. 6. Chemical preservatives: Adding safe chemicals (benzoic acid, sulphur dioxide) to prevent spoilage. e.g., sauces, squashes.

1. Holozoic nutrition: Organisms ingest solid food and digest it internally.

• Example: Humans, amoeba, dogs.
• Subtypes: Herbivores (eat plants), Carnivores (eat animals), Omnivores (eat both).

2. Saprophytic nutrition: Organisms feed on dead and decaying organic matter.

• Example: Fungi (mushrooms, bread mould), bacteria.

3. Parasitic nutrition: Organisms (parasites) live on or inside another organism (host) and derive nutrition from it, harming the host.

• Example: Tapeworm (in intestine), Cuscuta (dodder plant), Malarial parasite (Plasmodium).

The human digestive system consists of the alimentary canal and digestive glands:

Alimentary canal: Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Rectum → Anus

1. Mouth: Teeth chew food; salivary glands secrete saliva (contains salivary amylase → digests starch to maltose). Tongue mixes food with saliva and helps in swallowing. 2. Oesophagus: Carries food from mouth to stomach by peristalsis. 3. Stomach: Gastric glands secrete gastric juice (HCl + pepsin). HCl kills germs and provides acidic medium; pepsin digests proteins to peptides. 4. Small intestine: Longest part (about 6 m). Liver secretes bile (emulsifies fat); pancreas secretes pancreatic juice (amylase, trypsin, lipase). Intestinal glands secrete intestinal juice. Complete digestion and absorption occur here through villi. 5. Large intestine: Absorbs water and minerals; forms faeces. 6. Rectum and Anus: Expel undigested waste (defecation).

Malnutrition is a condition caused by improper nutrition — either insufficient (undernutrition) or excessive (overnutrition) intake of nutrients.

Undernutrition (Deficiency):

• Causes: Lack of sufficient food, poor diet, poverty, digestive disorders.
• Effects: Stunted growth, weak immunity, deficiency diseases (kwashiorkor, marasmus, anaemia, goitre, rickets, scurvy, beriberi, night blindness).

Overnutrition (Excess):

• Causes: Excessive intake of calories, fats, and sugars; sedentary lifestyle.
• Effects: Obesity, diabetes, heart disease, hypertension, joint problems.

• Teeth chew and grind food into smaller pieces (mechanical digestion).
• Salivary glands secrete saliva containing salivary amylase.
• Salivary amylase converts starch into maltose (chemical digestion).
• Tongue mixes food with saliva, forms a bolus, and pushes it to the pharynx.

• Food moves from mouth to stomach by rhythmic muscular contractions called peristalsis.
• No digestion occurs here.

• Gastric glands secrete gastric juice containing:
• Hydrochloric acid (HCl): Kills germs, provides acidic medium (pH ~2), activates pepsin.
• Pepsin: Digests proteins into peptides.
• Mucus: Protects the stomach lining from acid.
• Food is churned and mixed with gastric juice to form a semi-solid paste called chyme.

• The longest part of the alimentary canal (~6 m).
• Bile (from liver): Emulsifies fats (breaks large fat globules into smaller ones).
• Pancreatic juice (from pancreas): Contains:
• Trypsin → digests proteins into peptides
• Amylase → digests starch into maltose
• Lipase → digests fats into fatty acids and glycerol
• Intestinal juice (from intestinal glands): Completes digestion of all nutrients.
• Absorption: Digested food is absorbed through villi (finger-like projections) into the blood.
• Glucose, amino acids → absorbed into blood capillaries
• Fatty acids and glycerol → absorbed into lacteals (lymph vessels)

• Absorbs water and minerals from undigested food.
• Remaining waste forms faeces, stored in the rectum and expelled through the anus.

General Prevention of Deficiency Diseases: 1. Eat a balanced diet containing all nutrients. 2. Use iodised salt to prevent goitre. 3. Include fresh fruits and vegetables for vitamins. 4. Get adequate sunlight for Vitamin D. 5. Drink safe, clean water and maintain hygiene. 6. Breastfeed infants for at least 6 months.

Food preservation is the process of treating and handling food to stop or slow down spoilage by microorganisms, enzymes, and environmental factors, thereby extending its shelf life.

Methods of Food Preservation:

1. Drying (Dehydration): Removing water from food to prevent microbial growth.

• Examples: Dried fruits (raisins, figs), dried fish, dried vegetables.
• Principle: Microorganisms need moisture to grow.

2. Salting / Sugaring: Adding salt or sugar draws out water from food and inhibits microbial growth.

• Salt: Pickles, cured meats, dried fish.
• Sugar: Jams, jellies, marmalades, squashes.

3. Pasteurisation: Heating food to a specific temperature (about 72°C for 15 seconds for milk) and then rapidly cooling it.

• Examples: Milk, fruit juices.
• Principle: Kills harmful bacteria without destroying nutrients.

4. Refrigeration and Freezing: Low temperature slows down or stops microbial growth and enzyme activity.

• Examples: Frozen vegetables, ice cream, chilled milk, meat.

5. Canning and Bottling: Food is sealed in airtight containers after sterilisation by heating.

• Examples: Canned fruits, canned beans, bottled jams.

6. Chemical Preservatives: Adding safe food-grade chemicals to prevent spoilage.

• Examples: Sodium benzoate in sauces, sulphur dioxide in dried fruits, acetic acid (vinegar) in pickles.

7. Fermentation: Microorganisms convert sugars into acids or alcohol, preserving food.

• Examples: Curd (yoghurt), dosa batter, cheese, wine.