Medical Biology (Theory) Past Paper 2024-2025 PDF

Lec. 2 Al Safwa University College Medical Biology (Theory) 2024-2025 st st (1 Stage 1 Semester) Cell Cells are the structural and functio...

Lec. 2 Al Safwa University College Medical Biology (Theory) 2024-2025 st st (1 Stage 1 Semester) Cell Cells are the structural and functional unit of all living organisms, from the unicellular organisms, like amoeba, which are the body made up of one cell to the multicellular organisms, such as human, whom their body made up of 50-100 trillion cells. The cell has been known in the 6th century by Robert Hook with the discovery of the light microscope. A typical cell under light microscope consists of two major parts are nucleus and cytoplasm Cell Theory I. All living things are composed of one or more cells. II. Cells are the basic units of structure and function in an organism. III. Cells come only from the replication of existing cells. The Cells, which represents the structural and functional unit of body, consists of mass of protoplasm surrounded by plasma membrane. The protoplasm is a living material of the cell, which considered as the life itself, has two compartments, the cytoplasm and nucleoplasm. Protoplasm is mainly composed of six basics substances including water, electrolytes, protein, lipids, and carbohydrates. Assistant lec. Ali M. Rayshan Water Water is the most abundant component of the living cells, which represent 70-85% of the total chemical components. Electrolytes Electrolytes represent 2-3% of the chemical components are dissociated as anions, such as Cl-, and cations, such as Na+ and K+. The anion and cation are important in maintaining the osmatic pressure and acid-base equilibrium of the cell. Protein Protein represent 10-20% of the chemical component of a dry cell and composed chains of different types of amino acids. Lipids Lipids (15%) are insoluble in water, the most important lipids in the cell including phospholipids, cholesterol, neutral fat (triglyceride), glycolipids, steroids, and terpenes. Carbohydrates Carbohydrates (1%) are group of poly saccharides, contain C, H, O in a ratio of 1:2:1. The smallest carbohydrates are the simple sugar (trioses, pentoses and hexoses), depending on the number of the carbon atoms. Nucleic acid Nucleic acid (2%) are of two types DNA and RNA, which are formed of repeating units called nucleotides. Each nucleotide is composed of nitrogen base, pentose sugar, and a phosphate group. The living properties of the protoplasm 1. Conductivity: It is the transmission of waves of excitation throughout the cell from the point of stimulus, as that of the nerve and muscle cells. 2. Contraction: Contraction is a property of change in size to achieve locomotion of an organism as that of contraction of skeletal muscle tissue. 3. Respiration: Respiration is a process whereby oxygen and food substances within the cell interact chemically to produce energy, carbon dioxide and water. 4. Absorption: Is the capacity of the living cell to get in a substance from its environment (columnar epithelium of small intestine). 5. Secretion: It is a process by which a cell extrudes materials. These materials may be a useful (secretion) or useless product (excretion) e.g. digestive enzymes and hormones or urea. 2