UNIT III CELL STRUCTURE FUNCTION Baby Campbell Ch
UNIT III – CELL STRUCTURE & FUNCTION • Baby Campbell - Ch 4, 5 • Big Campbell – Ch 6, 7, 11
I. DISCOVERY OF CELLS • History of Microscopes § Anton van Leeuwenhoek § Robert Hooke • Cell Theory § § §
I. DISCOVERY OF CELLS, cont. • Types of Microscopes § Compound Light Microscope Ø Magnification Ø Resolution Ø Advances in light microscopy include o o Confocal Fluorescent Phase Contrast Super-resolution § Electron Microscope Ø Scanning Electron Microscope (SEM) Ø Transmission Electron Microscope (TEM)
II. CELL TYPES • Prokaryotic Cells § Domain Ø • Eukaryotic Cells § Domain Ø Ø
III. CELL BOUNDARIES • Cell Wall § Found in § Rigid structure; protects, maintains shape of cells § Prevents excess water uptake § Plant cell wall Ø Cellulose Ø Pectin - Sticky polysaccharide found between cell walls of adjacent cells Ø Plasmodesmata - Perforations between adjacent cell walls that allow for movement of materials from one cell to another
III. CELL BOUNDARIES, cont • Cell (Plasma) Membrane § Selectively-permeable barrier found in all cells § Composed primarily of phospholipid bilayer § Fluid Mosaic Model Ø“Fluid” – Not a rigid structure. Organization due to high concentration of water inside & outside cell
III. CELL BOUNDARIES, cont • Organization of Plasma Membrane
III. CELL BOUNDARIES, cont • Fluidity of Plasma Membrane
III. CELL BOUNDARIES, cont • Cell Membrane, cont Ø Proteins - “Mosaic” – Assortment of different proteins embedded in bilayer; determine most of membrane’s specific functions. Act as channels, pumps, enzymes in metabolism, binding sites, etc o Integral Proteins – Embedded in phospholipid layer o Peripheral Proteins – Bound to surface of membrane
III. CELL BOUNDARIES, cont Membrane Proteins
III. CELL BOUNDARIES, cont • Cell Membrane, cont Ø Carbohydrates § “ID tags” that identify cell. § Enable cells to recognize each other and foreign cells. § May be bonded to lipids (glycolipids) or proteins (glycoproteins)
III. CELL BOUNDARIES, cont • Synthesis of Cell Membrane Components
III. CELL BOUNDARIES, cont • Extracellular Matrix of Animal Cells § Holds cells together, protects & supports cells § Allows for communication between cells § Composed primarily of glycoproteins – proteins with covalently-bonded carbohydrate chains attached § Must abundant glycoprotein in most animals is collagen
III. CELL BOUNDARIES, cont • Intracellular Junctions in Animal Cells § Tight Junctions – Press membranes together very tightly; prevents leakage of fluid § Desmosomes (Anchoring Junctions) – Fasten cells together in sheets § Gap Junctions – Allow for movement of cytoplasm from one cell to another; important in communication between cells
III. CELL BOUNDARIES, cont
IV. CELL TRANSPORT
IV. CELL TRANSPORT, cont • Passive Transport – Movement of materials from high to low concentration. No energy output required. § Diffusion ØRandom movement of a substance across membrane down concentration gradient ØNo net movement once equilibrium is reached
IV. CELL TRANSPORT, cont • Passive Transport, cont § Facilitated Diffusion Ø Passive transport of molecules across cell membrane with the help of transport proteins Ø Utilized by large molecules, charged particles, polar molecules Ø Water v Aquaporins
IV. CELL TRANSPORT, cont • Passive Transport, cont § Osmosis – Diffusion of water across a membrane. Tonicity refers to tendency of cell to gain or lose water. If the solution is Ø Isotonic relative to the cell – Solute concentration is same on both sides of membrane. No net movement of water. Ø Hypertonic relative to the cell – Concentration of solute is greater outside cell → water moves out of cell until equilibrium is reached. Cell may shrivel. Ø Hypotonic relative to the cell – Concentration of solute is lower outside cell → water moves into cell until equilibrium is reached. Cell may swell to bursting point.
IV. CELL TRANSPORT, cont • Passive Transport / Osmosis, cont Ø Water Potential § Used to predict the passive movement of water § Designated as Ψ § Water always moves from an area of higher water potential → lower water potential § vΨS = vΨP =
IV. CELL TRANSPORT, cont
IV. CELL TRANSPORT, cont
IV. CELL TRANSPORT, cont • Passive Transport/Osmosis, cont § Osmoregulation Ø Cells must have mechanism to prevent excess loss, uptake of water Ø Cell wall, contractile vacuole Ø Plasmolysis – Seen in plants; excessive water loss causes cell membrane to pull away from cell wall
IV. CELL TRANSPORT, cont
IV. CELL TRANSPORT, cont • Active Transport § Carrier Proteins – Na+ / K+ Pump § Movement of materials against concentration gradient. Requires energy output by cell
IV. CELL TRANSPORT, cont • Active Transport, cont § Proton Pump
IV. CELL TRANSPORT, cont • Active Transport, cont § Exocytosis Ø Secretion of biomolecules by fusion of vesicles with cell membrane. Biomolecules “spit out”. Ø Hormones, neurotransmitters, etc
IV. CELL TRANSPORT, cont • Active Transport, cont § Endocytosis – “Sucking In”. Cell membrane surrounds, engulfs particle or biomolecule, pinches in to form vesicle. ØPhagocytosis – “Sucking in” food particles ØPinocytosis – “Sucking in” fluid droplets ØReceptor-mediated Endocytosis – Very specific
IV. CELL TRANSPORT, cont Ø Receptor-mediated Endocytosis, cont v. Cholesterol
V. CELL SIZE • Metabolic needs impose both upper & lower limits on cell size • How small? Ø Must have enough space for DNA, enzymes Ø Mycoplasma sp. - < 1 μm • How large? Ø Surface Area to Volume Ratio Ø Adaptations
VI. PROKARYOTIC CELL STRUCTURES
VII. EUKARYOTIC CELL STRUCTURES § Larger, more complex § Contain true nucleus, membrane-bound organelles suspended in cytosol § Composed of Ø Nucleus Ø Ribosomes Ø Endomembrane System o ER o Golgi Apparatus o Lysosomes o Vacuoles Ø Mitochondria/Chloroplasts Ø Peroxisomes Ø Cytoskeleton
VII. EUKARYOTIC CELL STRUCTURES ________ Cell
VII. EUKARYOTIC CELL STRUCTURES, cont • Ø Control center of eukaryotic cell Ø § Double membrane that protects nucleus; continuous with ER § Contains pores Ø § Site of ribosome production Ø § DNA wrapped in protein
VII. EUKARYOTIC CELL STRUCTURES, cont • Ø Suspended in cytosol or found on rough ER Ø Site of protein production in a cell
VII. EUKARYOTIC CELL STRUCTURES, cont • Endomembrane System Ø Endoplasmic Reticulum § Interconnected network continuous with nuclear envelope § Rough ER § Smooth ER
VII. EUKARYOTIC CELL STRUCTURES, cont Endomembrane System, cont Ø § “Cell postmaster” § Receives transport vesicles from ER; modifies, stores, and ships products § Receiving side is known as the cis face; shipping side is known as the trans face
VII. EUKARYOTIC CELL STRUCTURES, cont Ø Endomembrane System, cont § Sacs containing hydrolytic enzymes § Used for recycling cellular materials, destroying pathogens
VII. EUKARYOTIC CELL STRUCTURES, cont Endomembrane System, cont Ø § Storage sac § Plants typically have large, central vacuole surrounded by membrane called tonoplast. Absorbs water and helps plant cell to grow larger § Some protists have contractile vacuole to pump out excess water
VII. EUKARYOTIC CELL STRUCTURES, cont • Ø Ø Site of oxidative respiration Contain own DNA, ribosomes Found in virtually all euk cells Enclosed by 2 membranes; inner membrane has folds called cristae to increase surface area
VII. EUKARYOTIC CELL STRUCTURES, cont • Ø Type of plastid that carries out photosynthesis by converting solar energy to chemical energy (glucose) Ø Contain membranous system of flattened sacs called thylakoids Ø Contains DNA, ribosomes
VII. EUKARYOTIC CELL STRUCTURES, cont Endosymbiont Theory
VII. EUKARYOTIC CELL STRUCTURES, cont • Ø Membrane-bound compartments that use O 2 to carry out metabolism Ø H 2 O 2 is produced; broken down by _________
VII. EUKARYOTIC CELL STRUCTURES, cont • Ø Provides structural support to cell Ø Allows for movement Ø Attachment site for organelles, enzymes Ø More extensive in animal cells Ø Composed of three types of proteins § § v. Actin § v. More fixed v. Keratin
VI. EUKARYOTIC CELL STRUCTURES, cont Cytoskeleton, cont
VIII. CELL SIGNALING • Coordinates cell activities, development v Autocrine Signaling v Paracrine Signaling o Synaptic Signaling v Endocrine Signaling
VIII. CELL SIGNALING, cont • Typically involves 3 steps: § Reception – Target cell’s detection of signal molecule due to binding of signal molecule to receptor protein in cell membrane or inside the cell. § Transduction – Binding of signaling molecule changes receptor protein; triggers a sequence of events within cell that ultimately allows the signal to elicit a cellular response § Response – Results in specific cellular response; for example, activation of genes, enzyme catalysis, etc.
VIII. CELL SIGNALING, cont • Reception § The signaling molecule acts as a ligand, a term used to describe a molecule that specifically binds to another (usually larger) molecule. § Receptors may be located in the cell membrane or intracellularly § Intracellular Receptors
VIII. CELL SIGNALING, cont § Membrane Receptors v. Ion Channel Receptors
VIII. CELL SIGNALING, cont § Membrane Receptors, cont v. G Proteins
VIII. CELL SIGNALING, cont • Transduction § Typically multi-step pathway that amplifies, distributes signal § Many of the relay molecules are kinases – enzymes that transfer phosphate groups
VIII. CELL SIGNALING, cont • Transduction, cont § Many signaling pathways use small, water-soluble molecules or ions as second messengers. § Can diffuse through cell rapidly due to small size § Most common second messenger are a nonprotein molecule known as cyclic AMP (or c. AMP) and Ca 2+
VIII. CELL SIGNALING, cont • Response § Nuclear Ø May “turn on” or “turn off” genes § Cytoplasmic Ø May regulate enzyme activity § Apoptosis Ø Controlled cell suicide
VIII. CELL SIGNALING, cont • Regulation of Cell Signaling Pathways
- Slides: 54