Biological Organisation and Digestive System

Biological Organisation

• Biological organisation describes the hierarchical levels of structure in living things: cells → tissues → organs → organ systems → organisms.

Key Definitions

• Cell: The fundamental unit of life.
• Tissue: A group of similar cells performing a specific function.
• Organ: A structure composed of different tissues, working together for a specific function (e.g., heart, stomach).
• Organism: A complete living entity, made up of multiple organ systems, functioning as a whole.

Digestive System

• The digestive system, an organ system, breaks down food. Organs involved include the mouth, esophagus, stomach, small intestine, large intestine, liver, and pancreas.
• Digestion involves enzymes breaking down food into small, absorbable molecules.

Enzymes and Metabolism

• Metabolism: All chemical reactions within an organism.
• Enzymes: Biological catalysts that accelerate metabolic reactions without being consumed.
• Enzymes have a specific 3D structure, including an active site.
• Enzymes function best within specific temperature and pH ranges (optimum conditions).
• Denaturation: Enzymes lose their shape and function when exposed to extreme temperatures or pH changes.

Digestive Enzymes

• Amylase: Breaks down starch into sugars (produced in salivary glands, pancreas; active in mouth and small intestine).
• Proteases: Break down proteins into amino acids (produced in stomach, pancreas, small intestine; active in stomach and small intestine).
• Lipases: Break down lipids (fats) into glycerol and fatty acids (produced in pancreas; active in small intestine).
• These enzymes convert large, insoluble food molecules into small, soluble ones for absorption.

Products of Digestion

• The products of digestion (glucose, amino acids, fatty acids) are used to build new carbohydrates, lipids, and proteins for growth, repair, and energy storage.

Bile

• Bile: Made in the liver and stored in the gallbladder.
• Bile is alkaline and neutralizes stomach acid.
• Bile emulsifies fats, increasing the surface area for lipase action.

Factors Affecting Fat Breakdown

• Bile helps break larger fat globules into smaller droplets, increasing the surface area allowing lipase to act more effectively. Optimum temperature and slightly alkaline pH are also essential for maximum lipase activity.

Circulatory System

• The heart pumps blood through a double circulatory system:
  • Pulmonary circulation: Blood travels to the lungs to pick up oxygen and release carbon dioxide.
  • Systemic circulation: Oxygenated blood is pumped to the rest of the body.

Blood Vessels

• Arteries: Carry blood away from the heart (e.g., aorta, pulmonary artery); thick, elastic walls for withstanding high pressure.
• Veins: Carry blood to the heart (e.g., vena cava, pulmonary veins); thinner walls with valves to prevent backflow.
• Capillaries: Tiny vessels for gas and nutrient exchange; thin, single-cell walls for efficient diffusion.

Blood Components

• Red blood cells: Carry oxygen using hemoglobin; biconcave shape for large surface area.
• White blood cells: Fight infection; some engulf pathogens or produce antibodies.
• Platelets: Involved in blood clotting.
• Plasma: Carries nutrients, hormones, and waste products.

Explore the hierarchical structure of living organisms and understand the roles of various biological components, including cells, tissues, organs, and organ systems. Dive deep into the digestive system and learn about the key enzymes involved in metabolism. Assess your knowledge and familiarize yourself with essential definitions in biology.