MEDICAL BIOLOGY, ANATOMY, HUMAN PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedonyuk 2010

BIOLOGY

CHAPTER 1. BIOLOGICAL FOUNDATIONS OF HUMAN VITAL ACTIVITY

1.1. GENERAL CHARACTERISTICS OF LIFE

Basic Properties of Life

Life exists in the form of open systems capable of self-renewal, self-reproduction, and self-regulation. These fundamental properties of life are sustained by three flows: matter, energy, and information. Life is characterized by a set of properties, the primary ones being METABOLISM and Energy transformation, The ability to counteract increasing Entropy, irritability, heredity and Variability, reproduction, GROWTH AND DEVELOPMENT, as well as discreteness and integrity. Non-living objects may exhibit one or several of these properties, but they never display all of them simultaneously.

Metabolism and energy transformation. Metabolism is the sum of chemical processes that sustain the vital activity of organisms. It consists of Catabolism and anabolism—two opposite yet closely interrelated processes that Complement each other. Catabolism (dissimilation) is The breakdown of complex organic molecules into simpler end products, releasing the energy necessary for vital activity. A portion of the released energy is used to synthesize ATP. Anabolism (assimilation) is the synthesis of complex organic substances specific to a given species from simpler precursors, a process requiring energy in the form of ATP. Metabolism is directly linked to energy exchange. A distinction is made between exergonic (energy-releasing) and endergonic (energy-consuming) reactions.

Depending on their mode of Nutrition, organisms are classified as autotrophic or heterotrophic. Autotrophic organisms synthesize organic substances from atmospheric carbon dioxide and Water using solar energy (Photosynthesis) or the energy of Chemical Reactions (Chemosynthesis). Photosynthetic organisms include green plants, while chemosynthetic ones include certain Bacteria (such as sulfur bacteria). Heterotrophic organisms feed on ready-made organic substances synthesized by autotrophs. A continuous exchange of matter and energy with the environment is the primary hallmark of life; when this exchange ceases, life ends as well. Environmental exchange determines the steady thermodynamic state of a biological System and Its ability to resist the increase of entropy.

Ability to counteract increasing entropy. All biological systems are open thermodynamic systems governed by the Laws of Thermodynamics. The First Law is the law of conservation of energy, which states that energy cannot be created or destroyed, only transformed from one form to another and redistributed. The Second Law states that a system and its environment, if left to themselves, tend toward maximum disorder. Entropy is the measure of a system's disorder, and it can either increase or decrease. All living systems break down (entropy increases) unless energy is expended to maintain their order. A defining feature of biological systems is their ability to accumulate Free energy—ultimately derived from the sun—and counteract spontaneous entropy growth. Unlike non-living systems, living systems never reach an energy equilibrium; instead, they maintain a steady state (Temperature, pH, ion concentration).

Heredity is the property of organisms to transmit their traits and developmental characteristics to offspring, ensuring material and functional continuity between generations.

Variability is the property of organisms to acquire new traits or lose previous ones during development. Variability also refers to the differences between individuals of the same species. While opposite to heredity, variability is closely intertwined with it.

Irritability is the ability of organisms to selectively respond to Changes in the internal and external environment with excitability. Movement is one of the manifestations of irritability.

Reproduction is the ability of living organisms to produce offspring of their own kind, thereby ensuring the continuity of life on Earth. Any species consists of individuals, each of which will sooner or later cease to exist, but through reproduction, the life of the species goes on.

Growth. Growth is characterized by an increase in the Organism's size and the mass of the protoplasmic organic matter, which is measured by The amount of nitrogen or protein.

Development is The process of formation of an organism and its Organs. A distinction is made between individual development (ontogeny) and historical development (phylogeny), which are closely interrelated.

Discreteness and integrity. Discreteness (from Latin discretus — separate, discontinuous) refers to the discontinuous nature of biological Organization. Every living system is simultaneously discrete and integrated. Discreteness is manifested, for instance, in the fact that the organic world consists of distinct units—organisms; each organism consists of organs, each organ of Tissues, each tissue of Cells, and so on. At the same time, the organic world is integrated, as the existence of some organisms depends on others. Similarly, all parts of an organism are interconnected and function as a single whole. Discreteness is closely linked to the various Levels of biological organization.