Life Processes: The Machinery of Existence

This assessment covers the fundamental biological mechanisms that keep organisms alive. Below is a detailed syllabus review for your final revision before starting.

1. Introduction: What Defines "Alive"?

In biology, mere visible movement is not the sole criteria for life. Molecular movement is the true scientific definition. Metabolism, the sum of all chemical reactions (Anabolism and Catabolism), drives existence. The four pillars include Nutrition, Respiration, Transportation, and Excretion.

2. Nutrition: Acquisition of Energy

Autotrophic Nutrition: Green plants use photosynthesis to convert CO2 and H2O into glucose using sunlight and chlorophyll. The process involves photolysis of water and the reduction of CO2. Plants store energy as Starch, while animals store it as Glycogen.

Heterotrophic Nutrition: This includes Holozoic (Humans), Saprophytic (Fungi), and Parasitic (Tapeworms) modes. Human digestion begins in the buccal cavity where salivary amylase breaks starch into sugar. The stomach uses HCl and Pepsin for proteins, while the small intestine is the site for complete digestion via bile juice and pancreatic enzymes like Trypsin and Lipase.

3. Respiration: Energy Release

Respiration is the cellular breakdown of glucose. In the cytoplasm, glucose breaks into pyruvate. Aerobic respiration occurs in the mitochondria producing 38 ATP. Anaerobic respiration in yeast produces Ethanol and CO2, while in human muscles, it produces Lactic Acid, leading to cramps.

4. Transportation: Logistics of Life

The human circulatory system features a 4-chambered heart allowing double circulation. Oxygenated blood flows through the left side (Atrium/Ventricle), while deoxygenated flows through the right. Arteries carry blood away from the heart at high pressure. In plants, Xylem transports water via transpiration pull, and Phloem translocates food using ATP.

5. Excretion: Waste Management

The human excretory system consists of kidneys, ureters, bladder, and urethra. The Nephron is the functional unit performing filtration and selective reabsorption. Plants excrete waste via stomata, transpiration, or by storing it in resins, gums, or falling leaves.