Introduction To Cell PDF

INTRODUCTION TO CELL Dr. Ervin T. Jandoc Department of Histology TOPICS: I: Introduction II: Cell Membrane III: Cytoplasm and Its Organelles IV: Nucleus INTRODUCTION: CELL Cell-is the basic functional unit of all organism Is a mass of protoplasm separated from the externa...

INTRODUCTION TO CELL Dr. Ervin T. Jandoc Department of Histology TOPICS: I: Introduction II: Cell Membrane III: Cytoplasm and Its Organelles IV: Nucleus INTRODUCTION: CELL Cell-is the basic functional unit of all organism Is a mass of protoplasm separated from the external environment by plasma membrane. Main1.Components Cytoplasmof Protoplasm: 2. Nucleus 1. Cytoplasm: contains Numerous organelles. Mitochondria Endoplasmic Reticulum ( Soft and Rough ER) Golgi Apparatus Ribosome , Lysosomes, Peroxisomes Cytoskeleton: Microfilaments, Intermediate Filaments, Microtubule. Centrosome, Centrioles Cytoplasmic Inclusions 2. Nucleus: houses the Genome of the cell. I:CELL MEMBRANE AKA: Plasma Membrane/ Plasmalemma Structure: -7.5 nanometers (nm) thick -consists of a lipid bilayer and associated proteins. Integral Proteins Phospholipids Peripheral Proteins Cholesterol Glycolipids I:CELL MEMBRANE Function : 1. It envelops the cell and maintains its structural and functional integrity. 2.It acts as a semipermeable membrane between the cytoplasm and the external environment. 3.It permits the cell to recognize (and be recognized by) other cells and macromolecules. 4. It transduces extracellular signals into intracellular events. A. PHOSPHOLIPIDS A. PHOSPHOLIPIDS Each phospholipid are made up of: (a) a single polar Head (that either project outside the cell or into the cytoplasm. (b) two non- polar FATTY ACYL (tail that projects the center of cytoplasm facing one another. Phospholipid molecule is amphipathic B. CHOLESTEROL Constitute 2% of plasma membrane C. GLYCOLIPIDS AND GLYCOPROTIENS CONSTITUTE 5% OF THE PLASMA MEMBRANE LIPIDS. ARE AMPHIPATHIC IN NATURE LOCATED ON THE EXTRACELLULAR PART OF THE OUTER LEAFLET. CARBOHYDRATE SIDE CHAIN FROM GLYDOLIPIDS AND GLYCOPROTIENS FORM THE “FUZZY MATERIAL OUTSIDE THE CELL MEMBRANE CALLED GLYCOCALYX D. MEMBRANE PROTEINS a. Integral proteins- aka; “transmembrane Proteins” Function: Membrane Receptors and Transport Protein b. Peripheral proteins - Do not extend into lipid bilayer, they usually located on the cytoplasm Function:as part of cytoskeleton or as part of an Intracellular Second messenger system. D. MEMBRANE PROTEINS E: GLYCOCALYX-“CELL COAT” - Sugar coat located on the outer surface of the plasmalemma. - Appearance: fuzzy - Thickness: 50nm - Composition: polar oligosaccharide side chain linked covalently to most proteins and some lipids - also contains: Proteoglycans ( can bound to integral protein) II: Plasma Membrane Transport Processes A. Passive transport- NO ENERGY REQUIRED because molecule move across the plasma membrane from Higher concentration to Lower concentration or electrochemical gradient. a. Simple Diffusion Transport- transport of small non-polar (e.g) O2, N2) and small unchanged polar molecule (e.g) H20, Co2, Glycerol. It exhibit little specificity and diffusion rate id proportional to the concentration gradient of diffusing molecule II: Plasma Membrane Transport Processes b.Facilitated Diffusion- occurs via ion channels and /or carrier proteins, structures that exhibit specificity for the transported molecule. Ion Channels protiens- Are Multi-pass transmembrane protein that form small aqueous pore across membrane through which specific small water- soluble molecule and ion pass down electrochemical gradient. (passive Transport) Carrier Protiens- Are Multi-pass transmembrane protein that undergo reversible conformational changes to transport specific molecule across the membrane , these proteins function both passive and active transport. II: Plasma Membrane Transport Processes c. Osmosis- Diffusion of water across a selected permeable membrane Direction is determined by relative solute concentration. It continuous until equilibrium is reached. II: Plasma Membrane Transport Processes B. Active Transport-is an ENERGY REQUIRING process that transports a molecule against an electrochemical gradient via CARRIERS. a. Na+-K+ Pump- involved the anti-port transport of Na+ and K+ mediated by carrier protein -ATPase b. Glucose transport- Involves the Symport movement of glucose across an epithelium (Transepithelial Transport) II: Plasma Membrane Transport Processes C: Vesicular Transport-vesicle formed or lost as material is brought into cell or release from the cell a.Exocytosis- Bulk movement of substance out of the cell by fusion of secretory vesicle with the plasma membrane b. Endocytosis- Bulk movement of substance into the cell by vesicles forming at the plasma membrane. c. Phagocytosis-type of endocytosis in which vesicles are formed as particulate material external to the cells are engulf by pseudopodia. (cell eating) d. Phinocytosis-type of endocytosis in which vesicles are formed as interstitial fluids taken up by the cell. (Cell drinking) Receptor mediated endocytosis- plasma receptor first bind specific substance or receptor before taken up by the cell. II: Plasma Membrane Transport Processes C: Vesicular Transport II:Cytoplasm Contains 3 main structural Components: a. Organelles b. Inclusions c. Cytoskeleton II:Cytoplasm: Structural Components: Organelles A. Ribosomes- 12nm wide and 25 nm long. Contains small and large sub-units Sub-Units- are composed of several types of ribosomal ribonucleic acid and numerous proteins. Function: 1. Site where mRNA is translated into protein/ protein synthesis. II:Cytoplasm: Structural Components: Organelles B. RER ( Rough Endoplasmic Reticulum) is a system of sac like or cavities bounded by membranes. Outer surface is studied with Ribosomes Interior region : Cisterna Function : 1. Site where membrane-packed proteins are synthesized, including secretory, plasma membrane, and lysosomal protein. 2. RER monitors the assembly, retention and even the degradation of certain proteins. II:Cytoplasm: Structural Components: Organelles C: SER ( Smooth Endoplasmic Reticulum) - is an irregular network of membrane-bounded channels that lacks ribosomes on its surface (thus appearing smooth). - It usually appears as branching anastomosing tubules, or vesicles, whose membranes do not contain ribophorins. Function: SER has different functions in different cell types. (1) Steroid hormone synthesis (Leydig cells of the testis) (2) Drug detoxification (hepatocytes ) (3) Muscle contraction and relaxation (Muscular Muscles) II:Cytoplasm: Structural Components: Organelles D. Mitochondria- Rod-shaped organelles, 0.2 Micrometer wide and 7 p.m long. they posses outer membrane and inner membrane subdivided into an inter-membrane compartment, and an inner matrix compartment Granules within the matrix bind the divalent cations Mg2+ and Ca2+. It Contains : Krebs [tricarboxylic acid (TCA)] cycle. Elementary particles (ATP synthase, Phosphorylation of ADP to ATP Genetic apparatus II:Cytoplasm: Structural Components: Organelles Mitochondria: Origin and proliferation : Mitochondria may have originated as symbionts (intracellular parasites). According to this theory, anaerobic eukaryotic cells endocytosed aerobic microorganisms that evolved into mitochondria, which function in oxidative processes Mitochondria proliferate by division (fission) of preexisting mitochondria and typically have a 10-day life span. II:Cytoplasm: Structural Components: Organelles E. Golgi complex-consists of several membrane-bounded cisternae (saccules) arranged in a stack and positioned and held in place by microtubules. Cisternae- are disk-shaped and slightly curved, with flat centers and dilated rims. Regions : a. Cis face of the Golgi complex- (now:CGN(cis Golgi Network) it is located at the side of the Golgi stack facing a separate endoplasmic reticulum-Golgi-intermediate compartment. b. Medial compartment-is comprised of a few cisternae lying between the cis and trans faces. c.Trans face -is composed of the cisternae located at the side of the stack facing vacuoles and secretory granules d. Trans Golgi network (TGN) -lies apart from the last cisterna at the trans face and is separated from the Golgi stack. It sorts proteins for their final destinations. II:Cytoplasm: Structural Components: Organelles F. Lysosomes: Structure: are dense, membrane-bound organelles of diverse shape and size that function to degrade material. possess special membrane proteins and ( about) 50 acid hydrolases, which are synthesized in the RER. ATP-powered proton pumps in the lysosome membrane -maintain an acid pH (=5) Types of lysosomes: a. Multivesicular bodies —are formed by fusion of an early endosome containing endocytic vesicles with a late endosome b. Phagolysosomes —are formed by fusion of a phagocytic vacuole with a late endosome or a lysosome. II:Cytoplasm: Structural Components: Organelles c. Autophagolysosomes —are formed by fusion of an autophagic vacuole with a late endosome or lysosome. Autophagic vacuoles —are formed when cell components targeted for destruction become enveloped by smooth areas of membranes derived from the RER d. Residual bodies —are lysosomes of any type that have expended their capacity to degrade material. They contain undegraded material (e.g., lipofuscin and hemosiderin) and eventually may be excreted from the cell. II:Cytoplasm: Structural Components: Organelles G. Peroxisomes-(aka: Microbodies)-are membrane-bound, spherical, or ovoid organelles that may be identified in cells by a cytochemical reaction for catalase. contain a nucleoid, a crystalline core consisting of urate oxidase (uricase):(the human peroxisome lacks a nucleoid.) (0.15-0.25 i.un in diameter) peroxisome divides by fission; it has a life span of approximately 5-6 days Function: contain a variety of enzymes whose functions vary: from the oxidation of long chain fatty acids, to the synthesis of cholesterol, to the detoxification of substances such as ethanol. II:Cytoplasm: Structural Components:Inclusions 1. Glycogen 2. Lipid droplets 3. Lipofuscin 4. Centrosome Fig.1 Fig.2 Fig.4 Fig.3 II:Cytoplasm: Structural Components:Inclusions 4. Centrosome Functions: a. Major microtubule organizing center in the cell. b. Pericentriolar cloud of material contains hundreds of ring- shaped structures composed of -y-tubulin, and each ring serves as a starting point for the polymerization of one microtubule c. Although it play no role in nucleating microtubules, It help to maintain the organization of the centrosome. d. It forms a pole ( during S-Phase) for mitotic spindle where microtubule originates and converge. II:Cytoplasm: Structural Components:Cytoskeleton Cytoskeleton- Structural framework within cytosol. Function: Maintain shape, Stabilized Cell attachment, Facilitate Endocytosis and Exocytosis, Cell Motility. Major Components : 1. Microtubules 2. Microfilaments 3. Intermediate Filaments II:Cytoplasm: Structural Components:Cytoskeleton 1. Microtubule-straight, hollow tubules 25 nm in diameter and made of tubulin. they have a rigid wall composed of 13 proto-filaments, each of which consists of a linear arrangement of tubulin dimers. Each dimer consists of nonidentical alpha and beta tubulin subunits it has microtubule-associated proteins (MAPs), which stabilize them and bind them to other cytoskeletal components and organelles they also are associated with kinesin and cytoplasmic dynein, two force- generating proteins, which serve as "motors" for vesicle or organelle movement. Function: Maintain cell shape, aid in transport of macromolecule within the cytosol, Promote Movement II:Cytoplasm: Structural Components:Cytoskeleton 2. Microfilaments: (aka F actin or Actin Filaments) -7nm in diameter Composition: Globular actin Monomer (Actin) linked into Double Helix. abundant at the periphery of the cell where they are anchored to the plasma membrane via one or more intermediary proteins (e.g., a-actinin, vinculin, talin) Function: Establish focal contacts between the cell and the extracellular matrix,Locomotion of nonmuscle cells, Formation of the contractile ring (in dividing cells), and the folding of epithelia into tubes during development. II:Cytoplasm: Structural Components:Cytoskeleton 3. Intermediate Filaments: 8-10nm in diameter. constitute a population of heterogenous filaments that includes: Keratin, Vimentin, Design, Glial Fibrillary acid proteins, lamia and Neurofilaments They lack polarity and do not require GTP or ATP for assembly, which occurs along the entire length of the filament. III: Nucleus The largest Organelle of the cell —contains the genetic material encoded in the deoxyribonucleic acid (DNA) of chromosomes. Includes: Nuclear Envelope Nucleolus Nucleoplasm Chromatin Function: It directs protein synthesis in the cytoplasm via, ribosomal ribonucleic acid (rRNA), messenger RNA (mRNA), and transfer RNA (tRNA). All forms of RNA are synthesized in the nucleus.  NUCLEAR ENVELOPE: Surrounds the nuclear material and consist of 2 parallel membrane -These membranes fuse at intervals, forming openings in the nuclear envelope called nuclear pores. 6nm thick -Nuclear pore -Outer Membrane 80 nm in diameter -Inner Membrane 6nm thick Perinuclear cisterna  NEUCLEAR PORE COMPLEX Cytoplasmic ring MIDDLE RING nucleoplasmic ring  NUCLEOLUS 4 Distinct regions: 1. FIBRILLAR CENTER 2. PARS FIBROSA 3. PARS GRANULOGA 4. NUCLEOLAR MATRIX  NUCLEOPLASM is the protoplasm within the nuclear envelope. Consist of: a. Nuclear Matrix and b. Nuclear particle A. Nuclear Matrix- acts as a scaffold that aids in organizing the nucleoplasm. B. Nuclear Particle- contains: a. Interchromatin granules -are clusters of irregularly distributed particles (20-25 nm in diameter) that contain RNP and various enzymes. b. Pericromatin Granules-are single dense granules (30- 50 nm in diameter) surrounded by a less dense halo. They are located at the periphery of heterochromatin and exhibit a substructure of 3-nm packed fibrils.  CHROMATIN it consists of double-stranded DNA complexed with histones and acidic proteins. It resides within the nucleus as heterochromatin and euchromatin. Function. Chromatin is responsible for RNA synthesis. a. Heterochromatin: (condensed inactive Chromatin) - are concentrated at the periphery of the nucleus and around the nucleolus, as well as scattered throughout the nucleoplasm. it corresponds to one of two X chromosomes and is therefore present in nearly all somatic cells of female mammals.  CHROMATIN B. Euchromatin-is the transcriptionally active form of chromatin that appears in the LM as a lightly stained region of the nucleus. It appears in transmission electron microscope (TEM) as electron-lucent regions among heterochromatin, and is composed of 30-nm strings of nucleosomes and the DNA double helix. End of Lecture Thank You