Nutrition in Humans: Enzymes & Digestive System

Study Notes

Food provides energy essential for daily activities, cellular processes like respiration, and muscular contraction.
Nutrients in food are critical for body growth and repair of worn-out parts.

Carbohydrates: Primary energy source; found in rice, noodles, and potatoes.
Proteins: Necessary for growth and repair; serve as chemical messengers; sourced from fish, meat, eggs, beans, and dairy products.
Fats: Provide energy and insulation; includes butter, oil, and nuts.
Vitamins and Minerals: Required in small amounts for maintaining health; sourced from fruits, vegetables, and dairy products.

Starch (Iodine Test): Add 2-3 drops of iodine solution to sample. Color change to dark blue indicates presence; yellow indicates absence.
Reducing Sugars (Benedict’s Test): Mix 2.0 cm³ of sample with 2.0 cm³ Benedict’s solution, heat in water bath. Color changes (green to brick-red) indicate presence; blue indicates absence.
Proteins (Biuret Test): Add 5% sodium hydroxide to the sample, followed by copper(II) sulfate. Color change to purple indicates presence.

Digestion involves breaking down large food molecules into smaller components for absorption and use by the body.

Large molecules such as starch, proteins, and fats are synthesized from smaller basic units: glucose, amino acids, and glycerol/fatty acids, respectively.

Enzymes function based on the 'lock and key' hypothesis, where specific substrates fit into specific active sites of enzymes.
Enzyme-substrate complex formation leads to substrate conversion into products with high specificity.

Mouth: Ingestion and initial digestion; salivary glands secrete amylase.
Oesophagus: Transports food to the stomach via peristalsis.
Stomach: Food digestion continues; acidic environment activates pepsin for protein digestion.
Small Intestine: Major digestion and absorption occur; enzymes like lipase, maltase, and protease act here.
Pancreas: Produces digestive enzymes; secretes bicarbonate to neutralize stomach acid.
Gall Bladder: Stores bile, aiding fat digestion.
Liver: Processes nutrients and detoxifies substances.
Large Intestine: Absorption of water; compacts waste.
Rectum and Anus: Egestion of feces.

Rhythmic, wave-like contractions of smooth muscles mix and propel contents throughout the alimentary canal.

Villi are finger-like projections in the small intestine that increase surface area for absorption.
Capillaries transport nutrients, while lacteals absorb fatty acids and glycerol.