Cell Organelles PDF

 COURSE OBJECTIVES The objectives of this course 1) To understand the structure of cells. 2) To correlate their structures with basic functions. The Cell as the Fundamental Unit of Life: The Structure and Function of Cellular Organelles  The cell is the smallest unit of life. All...

 COURSE OBJECTIVES The objectives of this course 1) To understand the structure of cells. 2) To correlate their structures with basic functions. The Cell as the Fundamental Unit of Life: The Structure and Function of Cellular Organelles  The cell is the smallest unit of life. All organisms are composed one or more cells. New cells arise from previously existing cells.  Types of Cells Two fundamental types: Prokaryotic No Nucleus No organelles Small 100nm-5um Eukaryotic True Nucleus Membrane bound organelles 10-100um Some are larger Prokaryotic and Eukaryotic Cell Examples Eukaryotic Cells Typical Animal Cell cytoplasm DNA in nucleus plasma membrane c Animal cell (eukaryotic) Fig. 4-4b (2), p. 56  Basic Cell Structure Each cell has four common components: 1. Plasma membrane 2. Nucleus -Region containing DNA 3. Cytoplasm - Semifluid matrix + organelles - cytosol 4. Biochemical molecules & biochemical pathways Visual Summary of an Animal Cell Organelles in protein processing Nucleus ER Ribosomes Golgi complex  Nucleus Nuclear envelop -Double membrane system (lipid bilayer). - Pores (protein) permit passage of large molecules. Nucleoulus (1 or more) -protein + RNA subunits of ribosome. - Nucleolus manufactures ribosomes. Chromosome - One DNA molecule & its associated protein. Chromatin - Total collection of DNA & Their associated protein. Nucleoplasm - Fluid matrix of the nucleus. The Nucleus The Nucleus  Functions of the nucleus Contain genetic materials of cell So it control cell division. Act as control system for cell activities. Produce Ribosomes. Control protein synthesis.  Ribosomes Ribosomes are Non-membranous structures. Ribosomes are rRNA-protein complexes composed of two subunites that join and attach to messenger RNA (mRNA). -Site of protein synthesis - Assembled in nucleoli. Ribosomes attached to mRNA to form polyribosomes (polysomes). -Attached to RER (form protein for external use) - Free in cytoplasm (form proteins for internal cellular use).  The Endoplasmic Reticulum Endoplasmic reticulum (ER) – An extension of the nuclear envelope that forms a continuous, folded compartment Two kinds of endoplasmic reticulum – Rough ER (with ribosomes) makes proteins, folds polypeptides into their tertiary form – Smooth ER (no ribosomes) makes lipids, breaks down carbohydrates and lipids, detoxifies poisons The Endoplasmic Reticulum Rough and Smooth ER The Endomembrane System  Functions of the ER 1- It divides cytoplasm into compartments providing a large surface area for chemical reactions. 2- producing proteins, enzymes (rough ER). 3- producing lipids (smooth ER). 4- collecting and storing synthesized products. 5- function in glycosylation 6- Helps to transmit cell impluse from one part to other.  The Golgi Complex Golgi body A folded membrane containing enzymes that finish polypeptides and lipids delivered by the ER Packages finished products in vesicles that carry them to the plasma membrane or to lysosomes  Functioning of the Golgi Complex Responsible for modification necessary to newly synthesized proteins and converted into mature functional proteins. -Glycosylation - phosphorylation - proteolysis the trans Golgi sorts and packages the newly synthesized and modified proteins into transport vesicles. Mitochondrion  Mitochondria Mitochondrion – Eukaryotic organelle that carries out respiration (energy release from “food”) and makes the energy molecule ATP for energy storage – Contains two membranes, forming inner and outer compartments; buildup of hydrogen ions in the outer compartment drives ATP synthesis – Has its own DNA and ribosomes Mitochondrion Structure  Mitochondria Function 1- Energy production - the outer membrane controls the passage of chemicals. - the inner membrane is folded inwards, giving rise to cristae which increase the surface area on which respiratory enzymes are attached - Oxidative phosphorylation - krep’s cycle takes place in the matrix. -  Mitochondria Function 2- Role as independent unite It contain mtDNA& ribosomes for RNA production. also contain proteins and lipids in the matrix. It can self replicate or divide by fission.  Mitochondria Function 3- Function in cell survival cell survival depends on the integrity of the mitochondrial membrane. when pores occur in the membrane, Cytochrome C is released into cytosol, leading to serial reactions that lead to programmed cell death (apoptosis)  Lysosomes They are membranous organelles of various sizes with acidic medium (pH 5) Formed from Golgi complex They contain acid hydrolases (digestive enzymes). they necessary for breakdown nonfunctional macromolecules and old organells. Lysosome Function  Peroxisomes – Small, membrane-bound sacs formed from ER. – Contain powerful hydrolytic enzymes (oxidative enzymes) as catalase and uric acid oxidase. – Vesicles containing enzymes that break down hydrogen peroxide, alcohol, and other toxins. The main functions of the proxisome in liver: Breakdown (by β-oxidation) of excess fatty acids. Breakdown of hydrogen peroxide (H2o2),a potentially dangerous product of fatty-acid oxidation,it is catalyzed by the enzyme (catalase). Participates in the synthesis of cholesterol. Participates in the synthesis of bile acids. Participates in the synthesis of the lipids used to make myelin. Break down of excess of purines to uric acid. The Endomembrane System Typical Plant Cell  peroxysomes * Defect in proxisomes : - X-linked adrenoleukodystrophy Deterioration in myelin sheath of neuron owing to proper fatty-acid metabolism - zellweger syndrome.impaired transporting of peroxisomal enzymes into peroxysome