Module 1. Altered Cellular/Tissue Biology

8/31/23 Module 1 Altered Cellular/Tissue Biology Prokaryotes and eukaryotes are a broad kinds of cell types Prokaryotes don't have any membrane bound organelles where eukaryotes do Prokaryotes are straight forward. Simpler cells in terms of how they function and what they have to do to carry out their life functions ' Eukaryotes are little more complex because w/ complexity Difference Between Prokaryotes and Eukaryotes ● Prokaryotes Ø No distinct nucleus (single, circular chromosome) Lack histones, organelles Ø Cyanobacteria, bacteria, chlamydia and rickettsia Ø ● Eukaryotes Ø Complex cellular organization Membrane-bound organelles Well-defined nucleus with several chromosomes Ø Higher animals, plants, fungi, protozoa, and algae Ø comes the need to have membrane bound organelles so that each organelle is given a task of doing something Bc you have different organelles doing different functions there's a need to make sure that one organelle doesn't g0 off track and does more than it should and makes other ones shut down Ø ● Differences in biochemical activity: Ø Protein synthesis Ø Transport across the outer cell membrane Enzyme content Ø In eukaryotes the protein synthesis steps are a little different In prokaryotes protein synthesis takes place in the cytoplasm bc there is no organelle membrane so the DNA get converted to RNA and RNA translated into protein everything is happening in the cytoplasm so it can happen simultaneously In eukaryotes the DNA is sitting inside the nucleus which is where RNA is produced = transcription Cellular Functions Specialized through differentiation or maturation Ø Ø Ø Ø Ø Ø Ø Ø Movement Conductivity Metabolic absorption Secretion Excretion Respiration Reproduction Communication 1 8/31/23 The largest membrane bound organelle Eukaryotic Cell: Nucleus in it called nuclear ports • through these ports the RNA gets out from inside the nucleus into the cytoplasm Consists of the plasma membrane, cytoplasm, and intracellular organelles Ø Has a membrane called nuclear membrane which has holes Nucleus • Largest membrane-bound The liquid inside the nucleus is called nucleoplasm also inside organelle Cell division Genetic information the nucleoplasm will be another small structure called nucleolus. within thenucleolus you have RNA synthesis and some protein regulation mechanisms going on In eukaryotic cells it 'S the nucleus that houses the genetic information Eukaryotic Cell: Cytoplasm ● ● ● ● Cytoplasmic matrix Ø Fills space between the nucleus and plasma membrane Cytosol Outside the nucleus you have the cycloplasm where the organelles set in different locations Function Cytoplasmic organelles The glogi complex helps in processing of the proteins when proteins are freshly synthesized< that strand of polypeptide is referred to a the primary structure Endoplasmic reticulum has 2 kinds • rough- it's called rough cause it has ribosomes on it and appears rough • s mooth-a looks smooth The rough is involved in protein synthesis the smooth is in protein ,maturation, and storage of nutrients 7 Eukaryotic Organelles ● Ribosomes ● RNA protein complexes Ø Synthesized in nucleolus Ø ● ● Sites for cellular protein synthesis Cisternae Ø Synthesis, folding, and transport of proteins and lipids Ø ● Network of smooth membranes Ø Processing and packaging of proteins Ø Secretory vesicles Ø Cytoskeleton Ø “Bones and muscles” of cell Network of protein filaments Ø Forms cell extensions Ø ● Cellular injury causes enzyme release that leads to cellular self-destruction Peroxisomes Ø Golgi complex Ø ● Ø Endoplasmic reticulum Ø Lysosomes Saclike structures Ø Contain enzymes for digestion Ø Contain oxidative enzymes Break substances down into harmless products Mitochondria Cellular energy metabolism Ø ATP generation Ø Has role in: • Osmotic regulation • pH control • Calcium homeostasis • Cell signaling The primary structure cannot do any function but it needs to get folded multiple times and the first time it folds in a certain configuration it is called secondary structure even that's not functional then the 3rd fold is called tertiary structure, the 4th fold is called quaternary structure this level is what makes protein function again Cytoskeleton are filaments that tried to help keep the organelles in their positions so that when the organism is moving or carrying out other functions things are not hitting the cell wall or messing with other cells or try to breakout Lysosomes are bags filled with enzymes that will be functional indigestion, peroxyzymes which have filled bags with oxidative enzymes Ø Mitochondria plays a role in energy production and metabolism 2 8/31/23 Plasma Membrane ● ● ● ● Controls the composition of a space or compartment it encloses Function Ø Cell-to-cell recognition Ø Cellular mobility Ø Cellular shape Ø Movement of molecules Composition Ø Lipid bilayer • Solid-gel phase • Fluid-liquid crystalline phase • Liquid-ordered phase Lipids Ø Amphipathic (hydrophobic and hydrophilic) • O 2 and CO 2 diffusion • Barrier to the diffusion of water Ø Molecular glue ● ● Proteins Ø Perform most of the plasma membrane tasks Ø Functions • Receptors • Transport channels/carriers • Enzymes • Surface markers • Cell adhesion molecules (CAMs) • Catalysts Carbohydrates Ø Protection Ø Lubrication Ø Recognition Ø Adhesion it is either passive transport or active transport The primary difference between passive and active transport is in passive, no energy is used but in active energy is used Plasma membrane protein functions Plasma membrane is the outermost boundary in contact with the environment or the other cells will function to recognize other cells.it helps movement, cellular shape to som e extent moving molecules across, back and forth and the plasma membrane is semi-permeable Semi-permable = is to allow to things move back and forth Plasma membrane will have receptors or markers and receptors are used for signaling but they can be hijacked by microorganisms to bind to like viruses and get into the cell and infected it. Cell surface markers or specific proteins or molecules Plasma Membrane: Protein regulation (proteostasis) ● ● Main role is to minimize protein misfolding and protein aggregation Regulated by: Ø Ribosomes (makers) Chaperones (helpers) Proteolytic systems • Lysosomes • Ubiquitin-proteasome system (UPS) Malfunction associated with human disease Ø Ø ● 3 8/31/23 Cellular Receptors ● ● Ligands Ø Bind with cellular receptors to activate or inhibit the receptor’s associated signaling or biochemical pathway Plasma membrane receptors Ø Determine response to binding Cell-to-Cell Adhesions ● Basement membrane Ø Specialized type of extracellular matrix Ø Sheet of matrix: thin, tough, flexible Located: • Beneath epithelial cells Ø • Between two cell sheets • Around individual muscle, fat, Schwann cells ● Cell junctions Ø Symmetrical • Tight junctions—barriers • Desmosomes and belt desmosomes—unite cells • Gap junctions—communication Ø ● Asymmetrical • Hemidesmosomes Gating: Enables uninjured cells to protect themselves from injured neighbors Cell-to-Cell Adhesions ● ● Formed on plasma membranes Held together by: Ø Extracellular membrane Cell adhesion molecules Specialized cell junctions Extracellular matrix—secreted by cell Ø Ø ● Fibrous proteins in gel substance Produced by fibroblasts Ø Diffusion of water, nutrients Ø Ø Ø Composed of: Collagen, Elastin, Fibronectin Ø Regulates cell growth, movement, and differentiation 4 8/31/23 Cell-to-Cell Adhesions: Extracellular Matrix Cellular Communication ● Plasma membrane-bound receptors Intracellular receptors Gap junctions (contact signaling) ● Chemical signaling ● ● Ø Ø Ø Ø ● Paracrine Autocrine Hormonal Neurohormonal Neurotransmitters Signal Transduction ● Cells communicate via receptor protein Ø Signals molecules to activate protein kinases • Instructs cells to grow and reproduce, die, or differentiate 5 8/31/23 Cellular Metabolism Metabolism Ø Chemical tasks of maintaining essential cellular functions Ø Anabolism • Energy using Ø Catabolism • Energy releasing Adenosine Triphosphate (ATP) ● ● ● ● Fuel for cell survival Created from the chemical energy contained within organic molecules Used in the synthesis of organic molecules, muscle contraction, and active transport Stores and transfers energy Cellular Energy ● ● ● Digestion Ø Extracellular breakdown of proteins, fats, and polysaccharides to subunits Glycolysis Ø Intracellular breakdown of subunits to pyruvate, then to acetyl CoA Ø Limited ATP produced Citric acid cycle Ø Also called Krebs cycle or the tricarboxylic acid cycle (TCA) Much ATP is produced via oxidative phosphorylation if oxygen present Ø Waste products excreted Oxidative phosphorylation Ø ● 6 8/31/23 Cellular Energy Oxidative phosphorylation Ø Occurs in the mitochondria ● Mechanism producing energy from fats, carbohydrates, proteins Ø Involves the removal of electrons from various intermediates via a coenzyme such as nicotinamide adenine dinucleotide (NAD) to transfer electrons Ø Anaerobic glycolysis: if oxygen is not available, carbohydrates (like glucose) are converted to pyruvic acid (pyruvate) in the cytoplasm with the production of two ATP molecules, which is insufficient for energy needs; pyruvate then converted to lactic acid Ø Process reverses when oxygen becomes available and lactic acid is converted back to either pyruvic acid or glucose, which moves into the mitochondria and enters the citric acid cycle Ø Membrane Transport: Introduction ● Cellular intake and output Ø Cells continually take in nutrients, fluids, and chemical messengers from the extracellular environment and expel metabolites, or the products of metabolism, and end products of lysosomal digestion Ø Transporters Ø Channels Membrane Transport: Transporters ● Passive transport Molecules move easily from a region of high concentration to a region of low concentration Ø Requires no energy Ø Osmosis, hydrostatic pressure, and diffusion Ø Active transport Flows “uphill” Ø Requires energy ● Ø Ø Pumps, endocytosis, and exocytosis Mediated transport Ø Moves solute particles singly or two at a time ● Ø Symport: two molecules moved simultaneously in one direction Ø Antiport: two molecules moved simultaneously in opposite directions Uniport: single molecule moved in one direction Ø 7 8/31/23 Membrane Transport: Electrolytes ● Electrolytes Ø Account for ~95% of solutes in body fluids Ø Electrically charged • Cations (positive charge) • Anions (negative charge) Ø Measured in milliequivalents per liter (mEq/L) or milligrams per deciliter (mg/dl) • Milliequivalent indicates the chemical-combining activity of an ion, which depends on the electrical charge, or valence (number of plus or minus signs) • Monovalent—one charge (+) • Divalent—2 charges (++) Passive Transport ● ● Diffusion Ø Movement of solutes from area of greater concentration to area of lesser concentration Ø Rate of diffusion influenced by difference of electrical potential across the membrane • Also influenced by size of molecules and lipid solubility ● Filtration Ø Movement of water and solutes through a membrane because of greater force on one side than on the other • Hydrostatic pressure • Blood pressure Osmosis Ø Movement of water down a concentration gradient • Membrane must be more permeable to water than solutes • Concentration of solutes on one side greater than the other Ø Controls the distribution of water between body compartments Osmotic pressure Related to hydrostatic pressure and solute concentration Ø Oncotic pressure or colloid osmotic pressure Ø Tonicity Osmolality: Concentration of molecules per weight (kg) of water Osmolarity: Concentration of molecules per volume (mL) of solution Ø Ø Active Transport ● ● Transport system for Na + and K + Uses direct energy of ATP Ø ATPase Process leads to electrical potential Transport of macromolecules Ø Endocytosis Ø ● • Vesicle formed and moves into the cell • Pinocytosis—ingestion of fluids • Phagocytosis—ingestion of large particles Ø Exocytosis • Replaces plasma membrane removed by endocytosis • Releases synthesized molecules into the extracellular matrix 8 8/31/23 Electrical Impulses ● ● Resting membrane potential Action potential Ø Depolarization Ø Threshold potential • Hyperpolarized vs. hypopolarized Ø Repolarization Ø Refractory period • Absolute and relative Propagation of an Action Potential The Cell Cycle ● ● Mitosis vs. cytokinesis Four phases Ø G1 phase • Period between M phase and Ø Ø Ø the start of DNA synthesis S phase • DNA synthesized G2 phase • RNA and protein synthesis M phase (M=mitosis) • Nuclear and cytoplasmic division 9 8/31/23 The Cell Cycle: Mitosis ● M Phase Ø Prophase Ø Metaphase Ø Ø Anaphase Telophase Control of Cell Division and Growth ● ● Organ and body size depends on: Ø Cell growth Ø Cell division Ø Cell survival Regulated by extracellular signal molecules Ø Mitogens Ø Growth factors Ø Survival factors Tissue Formation ● ● ● ● Intercellular recognition and communication, adhesion, and memory Specialized patterns of gene expression Terminally differentiated cells Stem cells 10