Organizational Hierarchy in Biology

Organisational Hierarchy in Biology

• Living organisms are organized in a hierarchical structure: cells → tissues → organs → organ systems → organisms.

Definitions

• Cell: The fundamental unit of life.
• Tissue: A group of similar cells performing a specific function.
• Organ: A structure of different tissues working together for a specific role (e.g., heart, stomach).
• Organism: A complete living individual composed of organ systems interacting.

The Digestive System

• The digestive system is an example of an organ system, with multiple organs working together to break down food and absorb nutrients.
• Organs involved include the mouth, esophagus, stomach, small intestine, large intestine, liver, and pancreas.
• This system processes food into absorbable smaller molecules.

Enzymes and Metabolism

• Metabolism: All chemical reactions within the body, including those for digestion and energy production.
• Enzymes: Biological catalysts that speed up metabolic reactions without being consumed themselves.
• Enzymes are proteins with a specific structure including an active site.

Enzyme Function and Conditions

• Enzymes function by decreasing activation energy, enabling chemical reactions to proceed faster.
• Enzymes work best at specific temperatures and pH levels which are enzyme-specific.
• Denaturation: Enzymes lose their shape and function when exposed to extreme temperatures or pH values.

Digestive Enzymes

• Amylase: Breaks down starch into sugars; produced in salivary glands and pancreas, acts in mouth and small intestine.
• Proteases: Break down proteins into amino acids; produced in stomach, pancreas, and small intestine.
• Lipases: Break down lipids into glycerol and fatty acids; produced in the pancreas, acting in the small intestine.

Absorption and Use of Digestive Products

• Enzymes break down food into small, soluble molecules (e.g., glucose, amino acids).
• These molecules are absorbed into the bloodstream and used to create new carbohydrates, lipids, and proteins for growth, repair, energy storage.

Bile

• Bile is produced in the liver, stored in the gallbladder.
• Bile is alkaline in nature.
• Bile neutralizes stomach acid and emulsifies fats thus facilitating digestion.

Factors Affecting Fat Breakdown

• Fat breakdown (by lipase) is enhanced by bile (emulsification), optimum temperature (body temperature), and slightly alkaline pH in the small intestine.

The Circulatory System

• The heart pumps blood in a double circulatory system:
  • Pulmonary circulation: Blood circulates to the lungs to exchange gases.
  • Systemic circulation: Oxygen-rich blood is circulated throughout the body.

Blood Vessels

• Arteries: Carry blood away from the heart (thick walls to withstand high pressure).
• Veins: Carry blood towards the heart (thinner walls with valves to prevent backflow).
• Capillaries: Tiny vessels for gas and nutrient exchange (thin walls for efficient exchange).

Blood Components

• Red blood cells: Carry oxygen using hemoglobin; flattened biconcave shape for large surface area.
• White blood cells: Fight infections.
• Platelets: Aid in blood clotting.
• Plasma: Carries nutrients, hormones, and waste products.