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

BIOLOGY

CHAPTER 1. BIOLOGICAL BASES OF HUMAN VITAL ACTIVITY

1.3. MOLECULAR-GENETIC AND CELLULAR LEVELS OF LIFE ORGANIZATION

1.3.2. Structural, chemical, and functional organization of eukaryotic cells

The Cell as an open system. Organization OF THE flow of matter, energy, and information in the cell

The cell is an open biological system capable of self-renewal, self-reproduction, and self-regulation. These Fundamental properties of Living organisms are maintained by the flow of matter, energy, and information.

Flow of matter. The flow of matter comprises the Metabolic pathways of breakdown and synthesis of CARBOHYDRATES, Proteins, Lipids, and other substances. It begins with the intake of proteins, fats, carbohydrates, Vitamins, minerals, and Water into The Human Body as part of food. These are used as an energy source and building blocks for synthesizing the body's own components. High-molecular-weight Organic compounds (proteins, carbohydrates, lipids) are initially broken down into simple compounds (Amino Acids, Monosaccharides, Fatty acids, glycerol), which are absorbed by the epithelium of the gastric and intestinal mucosa. Via Blood AND Lymph, these substances enter the Cells, where intracellular METABOLISM takes place, forming the metabolic pool. Intracellular metabolism includes the following stages: 1) The breakdown of amino acids, monosaccharides, fatty acids, and glycerol with the release of energy and its accumulation in ATP molecules, and 2) the synthesis of proteins, Polysaccharides, lipids, and Nucleic Acids specific to the Organism. These processes require energy in the form of ATP. The End products of Metabolism are excreted from the body (carbon dioxide, water, ammonia, urea, etc.).

Flow of energy. It is represented by intracellular energy supply mechanisms—Fermentation, photo- or Chemosynthesis, and Respiration. The Central Role in the Bioenergetics of animal cells belongs to respiratory metabolism. It includes reactions of organic matter breakdown (monosaccharides, fatty acids, amino acids) and the utilization of the released energy for ATP synthesis. ATP and Other Compounds rich in energy suitable for subsequent use in the cell's vital activity are called high-energy (macroergic) compounds. They supply energy for all cellular processes.

Flow of information. It proceeds from DNA to protein. Information in DNA and protein molecules is encoded. The code symbols of DNA are NUCLEOTIDES, and those of proteins are amino acids. The sequence of amino acids in a protein molecule corresponds to the sequence of DNA nucleotide triplets (codons), a property known as collinearity. Recoding of Genetic information occurs during Protein Biosynthesis. At The First stage (Transcription), information is complementarily copied from a DNA molecule to an mRNA molecule, which carries this information from The Nucleus to the Cytoplasm to the site of protein biosynthesis—the Ribosomes. At the ribosomes, the genetic information contained in the mRNA is read by tRNA (translated from the language of nucleotides into the language of amino acids) and transferred to the polypeptide being synthesized there.

Before each Cell Division, the flow of information is directed from the parent DNA molecule to two daughter DNA molecules that are formed on it and serve as its exact copies (DNA Replication).