College of Osteopathic Medicine - Introduction to Cell Biology PDF

College of Osteopathic Medicine Session Name: SF01: Introduction to Cell Biology Instructor: Dr. Marcos Garza Course: Scientific Foundations Session Objectives 1. Understand the general structure of the endoplasmic reticulum and appreciate its contribution to the complex endomembrane system. 2. De...

College of Osteopathic Medicine Session Name: SF01: Introduction to Cell Biology Instructor: Dr. Marcos Garza Course: Scientific Foundations Session Objectives 1. Understand the general structure of the endoplasmic reticulum and appreciate its contribution to the complex endomembrane system. 2. Describe the concept and composition of the cytoplasm. 3. Specify the function, structure and inter-relationships of the organelles involved in the secretory pathway. 4. Explain the structure and function of ribosomes 5. Explain the structure and function of the Golgi complex 6. Explain the structure and function of lysosomes. Organelles Levels of Organization Atoms->Molecules- >Organelles->Cells->Tissues- >Organ Systems->Organism- >Ecosystem Function at each level depends on the elements below. The function of the cell depends on the organelles and their components. Notice the interactions between proteins and lipidic membranes. Boron. Medical Physiology (3 ed.). Fig. 2-10  Component Primary Function Cytosol Metabolism, protein synthesis (free ribosomes) Cytoskeleton Cell shape and movement, intracellular transport Nucleus Genome (22 autosomes and 2 sex chromosomes), DNA and RNA synthesis 2+ Mitochondria ATP synthesis by oxidative phosphorylation, Ca storage 2+ Smooth endoplasmic reticulum Synthesis of lipids, Ca storage Free ribosomes Translation of mRNA into cytosolic proteins Rough endoplasmic reticulum Translation of mRNA into membrane associated proteins or for secretion out of the cell Lysosome Intracellular degradation Endosome Cellular uptake of cholesterol, removal of receptors from the plasma membrane, uptake of small molecules and water into the cell, internalization of large particles (e.g., bacteria, cell debris) Golgi apparatus Modification, sorting, and packaging of proteins and lipids for delivery to other organelles within the cell or for secretion out of the cell Proteosome Degradation of intracellular proteins Peroxisome Detoxification of substances Berne & Levi Physiology (7 ed.). Tab. 1.1 The Secretory Pathway Proteins that will leave the cell follow the secretory pathway. 1. Synthesis in RER Ribosomes. 2. Transport to SER and modifications. 3. Transport through Golgi with further modification. 4. Placement in secretory vesicles. Will talk about the molecular mechanisms in SF-14. Boron. Medical Physiology (3 ed.). Fig. 2-18 Ribosomes Site of Translation (RNA -> Protein) 2 Subunits in animal cells (named through sedimentation) 60S 40S Sites of interaction with Amino Acids A-site: binds incoming (accepting) aminoacyl- tRNA directed by the codon occupying the site. P-site: codon is occupied by peptidyl-tRNA, which carries the chain of amino acids (process). E-site: empty-tRNA about to exit. Chandar. Cell and Molecular Biology (3 ed.) Lippincott. Fig. 9.8 Chandar. Cell and Molecular Biology (3 ed.) Lippincott. Fig. 9.10 Endoplasmic Reticulum Note that the Endoplasmic Reticulum membrane extends from the Nucleus (not show in picture). Destiny of proteins translated on the RER: Inside organelles (i.e. enzymes). Membranes (cellular or organelles). Secretion (hormones, extracellular matrix, etc.) N-linked glycosylation in eNdoplasmic R. Smooth ER makes steroids and breaks down toxins (Cytochrome P450 enzymes located in membrane of SER). Large in steroid hormone producing cells and Liver cells (Hepatocytes) Guyton Textbook of Medical Physiology(14 ed.) Fig. 2.14 Golgi Apparatus (or Complex) & Lysosomes Golgi is a distribution center: adds signals for sorting and sends vesicles towards the cell membrane (trans) and back towards the ER (cis). Post-translational modifications (SF11): Adding O-oligosaccharides on Serine & Threonine. Modifying N-oligosaccharides on Asparagine. Tagging proteins for final destinations. Lysosomes Degrade contents. Formed out of an endosome by addition of digestive enzymes and pH regulating membrane channels. Can fuse with other vesicles (i.e. phagosomes, autophagosomes) for digestion. Read as a refresher: Guyton and Hall Textbook of Medical Physiology (14th ed.) Chapter 2: The Cell and Its Functions. Clinical Key. Key aspects of this lecture Remember the structure and function of cellular organelles. You have a sample/patient with a defect in X area, which is the organelle most likely affected? You have a sample/patient with a defect on Y organelle, which finding is most likely? Example: You are studying a tissue sample from a patient and find abnormalities in the glycans bound to Serine. In which of the following organelles is the error taking place? A) Nucleus C) Mitochondria B) Rough ER D) Golgi Rationale: Best answer is Golgi, because O- glycosylation of Serine takes place in Golgi. E) Lysosome