Introduction to Biology VP 2024 PDF

GENERAL CONCEPTS: HOMEOSTASIS What does homeostasis mean? Self-regulating process by which biological systems maintain internal stability while adjusting to changing external conditions  Keeping the Balance The maintenance of a relatively stable internal environment is achieved through the action o...

GENERAL CONCEPTS: HOMEOSTASIS What does homeostasis mean? Self-regulating process by which biological systems maintain internal stability while adjusting to changing external conditions  Keeping the Balance The maintenance of a relatively stable internal environment is achieved through the action of physiological reflexes:  involuntary processes involving long-distance cell-cell communication and feedback loops Units work as open systems to exchange heat, gases, nutrients, waste, information. GENERAL CONCEPTS Prokaryotic vs. Eukaryotic cells  Membrane-bound organelles (nucleus) Prokaryotes → NO nucleus, smaller and simpler cells, unicellular organisms Eukaryotes → biological membranes, membrane-bound organelles for uni and multicellular organisms.  Membranes keep cell selective permeability with many proteins, glycocalyx, receptors. eukaryotic COMPONENTS OF BIOLOGICAL MEMBRANES o Lipids (phospholipids, glycolipids, cholesterol)  Cholesterol (generally not present in most prokaryotes) o Proteins (integral, peripheral) o Carbohydrates o Water o Divalent cations (Calcium) THE EUKARYOTE CELL: A ”MEMBRANOUS UNIT” Cellular compartmentalization = Functional separation within the cell 1. Plasma membrane 2. Nuclear membrane (inner and outer) 3. ER and Golgi apparatus membrane 4. Mitochondrial membrane (inner and outer) 5. Peroxisomes and Lysosomes Color scanning electron micrograph of an acinar (exocrine) pancreatic cell. Acinar cells produce and excrete digestive enzymes to the small intestine, via the pancreatic ducts. Steve Gschmeissner https://www.sciencephoto.com/ FUNCTIONS OF MEMBRANOUS COMPARTMENTS Cell nucleus - Genetic information, transcription, nuclear receptors Endoplasmic Reticulum (ER) Synthesis of proteins, lipids, stores Ca++, proteins posttranslational modifications Golgi apparatus - Protein processing, posttranslational modifications, polysaccharide synthesis, phosphorylation, packaging of proteins for transport Mitochondria - Oxidation of carbohydrates and lipids Lysosomes - Digestion of macromolecules (lysozyme) Peroxisomes - Oxidation of organic molecules (peroxide H₂O₂ → water and oxygen) ENERGY SOURCES IN LIVING ORGANISMS Cells constantly use energy to: ✓ Maintain their structures, grow, divide, transport substances, change their shape, synthesize proteins…  Cellular energy metabolism describes the transfer and utilization of energy in biological systems  IF energy metabolism is blocked, cells die instantly Key Cellular metabolism players: ✓ Glycolysis ✓ The citric acid cycle(TCA)/Krebs Cycle ✓ The electron transport chain (ETC)  Metabolic intermediates such as NADH & FADH2 (electron carriers) also play a role in ATP production ENERGY SOURCES IN LIVING ORGANISMS Energy-rich molecules like glucose and lipids ✓ Metabolized by a series of oxidation reactions yielding ATP, CO2 & H2O The currency for energy in the cell is: ATP (Adenosine TriPhosphate)  Stable energy-carrier molecule composed of: o Adenine (nitrogenous base) o Ribose (sugar) o Three phosphate radicals ENERGY SOURCES IN LIVING ORGANISMS When ATP releases its energy, a phosphoric acid radical is split away forming:  Adenosine Diphosphate (ADP) ✓ Released energy is used for many purposes in the cell o transport o enzyme activity o muscle contraction ENERGY SOURCES IN LIVING ORGANISMS Glucose Fatty acids Amino acids Ketone bodies Volatile Fatty Acids ✓ Glycolysis ✓ Tricarboxylic Acid Cycle (TCA) ✓ Oxidative Phosphorylation (ETC) ✓ ß-Oxidation ✓ Gluconeogenesis Enzymes Messengers Cofactors