Chung Cheng High School Science Notes 14.1

Study Notes

Why Do We Need Food?

Provides energy for muscle and organ function, replaces lost energy.
Supports growth and repair by synthesizing new protoplasm.
Maintains health through intake of vitamins and minerals.

Components of Food

Essential components include carbohydrates, proteins, fats, vitamins, minerals, dietary fiber, and water.

Importance of Digestion

Animals consume food for nutrients; they cannot produce their own.
Nutrients in food are initially large, complex, and insoluble molecules and must be broken down into small, soluble forms.
Digestion allows nutrients to be absorbed into cells for use in cellular respiration and energy production.

Digestion Process

Ingestion: Taking food into the mouth.
Digestion: Breaking down food into smaller, absorbable forms.
Absorption: Nutrients diffuse from the small intestine into the bloodstream.
Assimilation: Utilizing absorbed nutrients for energy.
Egestion: Eliminating indigestible matter via the anus.

Structure of the Human Digestive System

Comprised of the alimentary canal and associated organs: liver, gallbladder, esophagus, stomach, pancreas, large intestine, small intestine, rectum, and anus.
Alimentary canal order: mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.

Types of Carbohydrates

Polysaccharides: Starch (energy storage in plants) and cellulose (not digestible by humans).
Disaccharides: Maltose (from starch), sucrose (table sugar), and lactose (milk sugar).
Monosaccharides: Glucose (main energy source), fructose (fruit sugar), galactose.

Digestion Methodologies

Physical Digestion: Breakdown into smaller pieces without chemical change (e.g., chewing).
Chemical Digestion: Breakdown into simpler molecules, requiring enzymes.

Role of Enzymes

Enzymes are proteins that accelerate chemical reactions, essential for digestion.
Specific enzymes act on specific substrates (e.g., amylase for starch).
Enzymes operate optimally at specific pH and temperature ranges; extremes can denature them.

Major Digestive Enzymes

Proteases: Digest proteins into polypeptides.
Lipase: Breaks down fats into fatty acids and glycerol.
Carbohydrases: Digests carbohydrates.

Digestion Sequence in the Alimentary Canal

Mouth: Physical breakdown and mixing with saliva (starch to maltose).
Stomach: Churning action mixes food with gastric juices (proteins to polypeptides).
Small Intestine: Final digestion of carbohydrates, proteins, and fats with assistance from liver and pancreas.

Absorption and Egestion

Digestive end products absorbed in the small intestine include glucose, amino acids, fatty acids, and glycerol.
Remaining water absorbed in the large intestine; undigested material stored in the rectum is egested as feces.

End Products of Digestion

Glucose: Used for respiration.
Amino acids and fatty acids: Utilized for building body structures and functions.

Description

This quiz covers important concepts related to the human digestive system, including the reasons we need food for energy, growth, and health. It is aimed at students in class 2 Bn to help them understand the functions and components of the digestive system.