Physiology of Cells & Tissues PDF

PHYSIOLOGY OF CELLS AND TISSUES PREPARED BY: THEO MD DEPT. OF BIOCHEMISTRY CONTENTS 1. Plasma Membrane 5. Response to Tissue Injury a. Membrane Function a. Inflammation b. Membrane Lipids b. Repair c. Membrane Proteins 2....

PHYSIOLOGY OF CELLS AND TISSUES PREPARED BY: THEO MD DEPT. OF BIOCHEMISTRY CONTENTS 1. Plasma Membrane 5. Response to Tissue Injury a. Membrane Function a. Inflammation b. Membrane Lipids b. Repair c. Membrane Proteins 2. Membrane transport a. Passive Transport b. Active Transport 3. Cell Division and Apoptosis 4. Cellular Basis of Aging and Cancer PLASMA MEMBRANE  MEMBRANE LIPIDS Functions of Lipid Bilayer: 1. Distributing molecules within the plasma membrane 2. Repair to slight damage 3. Fluid nature enables membranes to fuse with one another. Phospholipids – forms the lipid bilayer Cholesterol – stability and fluidity  MEMBRANE PROTEINS Types: 1. Integral Proteins – penetrate deeply into the lipid bilayer 2. Peripheral Proteins – attached to either inner or outer surfaces of the lipid bilayer FUNCTIONS OF MEMBRANE PROTEINS  MAJOR CLASSES OF TRANSPORT PROTEINS 1. CHANNEL PROTEINS Leak Ion Channels – always open Gated Ion Channels: 1. Ligand-gated ion channels o Ligand - chemical signal molecule used by cells to communicate with each other 2. Voltage-gated ion channels o Based on membrane potential alteration  MAJOR CLASSES OF TRANSPORT PROTEINS 2. CARRIER PROTEINS Uniport – movement of one specific ion or molecule across membrane Symport/Cotransport – movement of 2 different ions or molecules in the same direction across plasma membrane Antiport/Countertransport – movement of 2 molecules in different direction  MAJOR CLASSES OF TRANSPORT PROTEINS 3. ATP-POWERED PUMPS – transport proteins that require cellular energy to move specific ions or molecules from one side of the plasma membrane to the other.  RECEPTOR PROTEINS Membrane proteins or glycoproteins that have an exposed receptor site on the outer cell surface. Cells commonly use receptors and chemical signals they bind as part of an intercellular communication system that coordinates activities among the various parts of the body The binding acts as a signal that triggers a response  TYPES OF RECEPTOR PROTEINS 1. LINKED TO CHANNEL PROTEINS Some help form ligand-gated ion channels Chemical signal (ligands) bind to these receptors Alters 3D-structure of the proteins of the ion channels to open or close Result is a change in the permeability of the plasma membrane to the specific ions  TYPES OF RECEPTOR PROTEINS 2. LINKED TO G-PROTEIN COMPLEXES G Protein Complex acts as an intermediary between a receptor and other cellular proteins Three components : Alpha (α), Beta (β), and Gamma (γ) The complex interacts with a receptor protein when a chemical signal is bound to the receptor protein G-PROTEIN COMPLEX-RECEPTOR INTERACTION Activated α subunit can stimulate a cell response in at least three ways: 1. Intracellular chemical signals 2. Opening of ion channels in the plasma membrane 3. Activation of enzymes associated with the plasma membrane. MEMBRANE TRANSPORTS  CELL MEMBRANE TRANSPORT They are Selectively Permeable Types of Cell transport: 1. Passive Transport – cell does not expend metabolic energy 2. Active Transport – mediated transport process that requires energy by ATP Vesicular Transport - subtype SUMMARY OF CELL MOVEMENT  PASSIVE TRANSPORT a. SIMPLE DIFFUSION Movement of solutes from a higher to lower solute concentration (downhill) Random motion of the solutes until an equilibrium is reached Rate is influenced by Magnitude of concentration gradient Temperature Size of the Solutes Viscosity of the Solvents Membrane thickness Ex. O2, CO2, Lipid soluble  PASSIVE TRANSPORT b. OSMOSIS Diffusion of water (solvent) across a selectively permeable membrane (i.e. plasma membrane) in a downhill process Some cells use water membrane channels called Aquaporins OSMOTIC PRESSURE force required to prevent osmosis ↑ concentrated solution = ↑ osmotic tendency = ↑ osmotic pressure needed Based on the same concentration of the solute particles: Isosmotic Hyperosmotic Hyposmotic  PASSIVE TRANSPORT c. FACILITATED DIFFUSION Downhill process Mediated by a channel and carrier (transporter) protein Rate is directly proportional to their concentration gradient up to the point of saturation Ex. Amino acids and glucose  ACTIVE TRANSPORT a. PRIMARY ACTIVE ATP-Powered pumps bind to substances and move them across the plasma membrane Move against their concentration gradients (uphill) Ex. Sodium-Potassium (Na+–K+) ATPase pump  ACTIVE TRANSPORT b. SECONDARY ACTIVE Uses an active transport of a substance to establish a concentration gradient (uphill process) The facilitated diffusion of that transported substance in a downhill process provides the energy to transport a second substance Cotransport Countertransport VESICULAR TRANSPORT Use vesicles to move large substances across the plasma membrane Large water soluble substances, whole cells, and small pieces of matter Requires ATP 2 types: Endocytosis & Exocytosis  ENDOCYTOSIS Uptake of material through the cell membrane by the formation of a vesicle Role: Nutrient intake, Immune response, and Cell recycling Can exhibit Specificity EXOCYTOSIS & TRANSCYTOSIS Secretory vesicles accumulate materials for release from the cell Examples: Digestive Enzymes, Hormones, and Neurotransmitters Transcytosis – a combination of both endocytosis and exocytosis to move substances “through” the cell Endothelial cells of blood capillaries CELL DIVISION & APOPTOSIS CELL DIVISION Formation of daughter cells from a single parent cell 2 major types: MITOSIS – for somatic cells MEIOSIS – for reproductive cells 2 major events in Mitotic Cell Division: MITOSIS PROPER (4 PHASES) CYTOKINESIS  INTERPHASE Phase between cell divisions Where all cells spent their lives Preparation for cell division DNA replication occurs (S Phase) Other organelles DNA appears as thin threads in the nucleus  MITOSIS The division of a cell’s nucleus into two new nuclei, each containing the same amount and type of DNA MITOTIC CHROMOSOMES chromatin becomes very densely coiled to form compact structure  MITOSIS HAS FOUR PHASES 1. PROPHASE 2. METAPHASE Mitotic Chromosomes formation Chromosomes align in the center Replication of Centrioles and moves to each pole Spindle fibers extends Nucleolus and Nuclear envelope disappears  MITOSIS HAS FOUR PHASES 3. ANAPHASE 4. TELOPHASE Chromatids separate Nuclear envelopes form around Each set of chromosomes has each set of chromosomes to reached an opposite pole of form two separate nuclei. the cell Chromosomes begin to uncoil Cytokinesis begins Cytokinesis continues  CYTOKINESIS The division of the cell’s cytoplasm to produce two new cells Cleavage furrow – first sign of cytokinesis A contractile ring pulls the plasma membrane inward COMPLETE CYTOKINESIS  APOPTOSIS Programmed cell death Normal process where cell numbers are regulated by specific genes (p53, bcl-2 and BAX) Where does it occur? Developing Fetus Adult Damaged, Infected, and Potentially Malignant Cells  APOPTOSIS Initiated by the proteins encoded by the specific genes Mitochondrial Proteins → Cytosol → activate other proteins https://www.genome.gov/sites/default/files/tg/en/illustration/apoptosis.jpg CELLULAR BASIS OF AGING & CANCER  CELLULAR AGEING Effect of Cellular changes: Condensation of chromatin and nuclear shrinkage MAJOR HYPOTHESES Degeneration of cytoplasmic 1. Cellular clock organelles Insufficient production of 2. Death genes Enzymes 3. DNA damage Accumulation of pigments and 4. Free radicals free radicals Change in level of hormones 5. Mitochondrial damage Low antibody protection and weak immune response Low rate of cell division  TUMORS Abnormal mass of tissue that occurs usually in an uncontrolled cell proliferation Can be benign or malignant Cancer A malignant, spreading tumor that results into illness.  TUMORS CANCER CELLS Results when a cell or group of cells breaks away from the normal control of growth and differentiation Multifactorial causes: Hereditary, Viruses, and Toxins Promising Anti-cancer therapy: Immunomodulators Anti-angiogenesis drugs TISSUE RESPONSE TO INJURY  INFLAMMATION Inflammation Initial response to Tissue damage and used as defense mechanism of the body Produces the Five Cardinal signs: SYMPTOMS PHYSIOLOGICAL BASIS Redness (Rubor) Vasodilation and Increased blood flow Heat (Calor) Swelling (Tumor) Increased vascular permeability Pain (Dolor) Physical & chemical stimulation of nociceptors Loss of function (Functio laesa) Increased pain/swelling  INFLAMMATION Chemical mediators Released or activated by injured tissue or adjacent blood vessels like Histamine & Prostaglandins Some induce dilation of blood vessels → heat & redness Also stimulates pain receptors and increases the permeability of blood vessels → Clotting proteins & White blood cells moves out of the blood vessel → water follows them → Edema  TISSUE REPAIR It is the process of substitution of viable cells for dead cells by regeneration or replacement Regeneration – new cells are the same type of the cell that was destroyed Replacement – new type of tissue develops  TISSUE REPAIR Cells can be divided into 3 groups according to their ability to regenerate: 1. Labile cells - Continually divide throughout life 2. Stable cells - do not normally divide after growth stops, but they may do so if injury occurs 3. Permanent cells - are not able to replicate and, if killed, are usually replaced by a different type of cell  SKIN REPAIR PROCESS 1st process: Formation of Clot and Scab Clot – contains fibrin, which binds the edges of the wound together to stop bleeding Scab – the surface of a dried clot to seal the wound and prevent infection  SKIN REPAIR PROCESS 2nd process: Inflammatory response and Epithelial regeneration Fibrin and white blood cells such as neutrophils move into the wounded tissues Pus formation – dead neutrophils, other dead cells, and fluids Epithelium at the edge of the wound starts proliferating and migrates into the scab  SKIN REPAIR PROCESS 3rd process: Granulation Formation Granulation tissue – delicate, granular-appearing connective tissue that consists of fibroblasts, collagen, and capillaries 4th process: Scar formation By a month, most granulation tissue is converted to a scar Appears bright red then turned into white  THANK YOU FOR LISTENING PREPARED BY: THEOMD DEPT. OF BIOCHEMISTRY