Lecture 2: The CELL THE CELL A.The Cell Concept 1.Brief Historical Review 1665 Robert Hooke --using cork under simple microscope “cell” 1673 Anton Van Leeuwonhoek *Dutch biologist *first to see algae, protozoans, sperm cells & RBC==“animalcules” *high quality single lens” 1838 Matthias Schleiden *all tissue was composed of cells *plant cell develops as an independent unit 1839 Theodor Schwann *German zoologist *plant cell similar to animal cell but bounded by invisible plasma membrane 1839 Robert Brown *English botanist *opaque spot in a variety of cells= =NUCLEUS Schleiden & Schwann ---The TWO were the basis for the “THE CELL THEORY” 3 generalizations: •The Cell Theory 3 generalizations: 1.All organisms are composed of one or more cells. The Cell Theory 2.The cell is the smallest unit having the properties of life. The Cell Theory 3.The continuity of life arise directly from the growth & division of single cells. • The Cell Theory 1.All organisms are composed of one or more cells. 2.The cell is the smallest unit having the properties of life. 3.The continuity of life arise directly from the growth & division of single cells. Prokaryotes vs Eukaryotes ========================== No true nucleus true nucleus No cell organelles cytoplasmic organelles B. The Cell Structure & Functions PROKARYOTES VS EUKARYOTES Plant Cell vs Animal Cell 1.Nucleus 2.Cytoplasm & its organelles 3.Plasma or Cell Membrane 4.Specializations of the plasma membrane Plant Cell Animal Cell 1. The NUCLEUS Parts and Function of a Cell 3. Plasma or Cell Membrane 1.Plasma or Cell Membrane Fluid-Mosaic Model 1.membrane is fluid --bilipid layer 2.protein, cholesterol & glycoproteins are arranged in a very “art-like” manner--MOSAIC TYPE 3.3 The plasma membrane and how substances cross it What are some characteristics of the plasma membrane? • It is a phospholipid bilayer • It is embedded with proteins that move in space • It contains cholesterol for support • It contains carbohydrates on proteins and lipids • Selectively permeable Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Outside plasma membrane carbohydrate chain hydrophobic hydrophilic tails heads phopspholipid bilayer filaments of cytoskeleton cholesterol protein Inside 3.3 The plasma membrane and how substances cross it What does selectively permeable mean? • The membrane allows some things in while keeping other substances out Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. charged molecules and ions -+ H2 O aquaporin noncharged molecules + - macromolecule phospholipid molecule protein 3.3 The plasma membrane and how substances cross it How do things move across the plasma membrane? 1. Diffusion 2. Osmosis 3. Facilitated transport 4. Active transport 5. Endocytosis and exocytosis 3.3 The plasma membrane and how substances cross it What are diffusion and osmosis? • 1. Diffusion is the random movement of molecules from a higher concentration to a lower concentration • 2. Osmosis is the diffusion of water molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. particle plasma membrane water cell cell time a. Initial conditions b. Equilibrium conditions 3.3 The plasma membrane and how substances cross it How does tonicity change a cell? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • • Hypertonic solutions have more solute than the inside of the cell and lead to lysis (shrinking) H2O H2O Hypotonic solutions have less solute than the inside of the cell and lead to crenation (shriveling) • Isotonic solutions have equal amounts of solute inside and outside the cell and thus does not affect the cell a. Isotonic solution (same solute concentration as in cell) b. Hypotonic solution c. Hypertonic solution (lower solute concen- (higher solute concentration than in cell) tration than in cell) a: © Dennis Kunkel/Phototake 3.3 The plasma membrane and how substances cross it What are facilitated diffusion and active transport? • 3. Facilitated transport is the transport of molecules across the plasma membrane from higher concentration to lower concentration via a protein carrier • 4. Active transport is the movement of molecules from a lower to higher concentration using ATP as energy; requires a protein carrier Outside K+ K+ K+ P ATP ADP K+ Inside K+ 3.3 The plasma membrane and how substances cross it What are endocytosis and exocytosis? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • 5. Endocytosis transports molecules or cells into the cell via invagination of the plasma membrane to form a vesicle Outside Inside substances taken in vesicle a. Endocytosis • 6. Exocytosis transports molecules outside the cell via fusion of a vesicle with the plasma membrane Outside substances released vesicle Inside b. Exocytosis 2. NUCLEUS *5-10% vol. -- cell *nuclear membrane *nucleoplasm *Nucleoli=assembly area for ribosomes *chromatin= complex of DNA and protein 3. Cytoplasm *consists of the cell items outsidethe nucleus but w/in the cell membrane *3major elements 1. cytosol 2. inclusions 3. organelles Cytosol *semi-transparent fluid *water, nutrients & other solutes *half of the cell’s volume Inclusions *chemical substances *mostly nutrients or cell products *eg. fat droplets, crystals glycogen granules pigments, vacuoles 3.Cytoplasmic organelles ---all membrane bound 1. Ribosomes 2. Endoplasmic Reticulum a. rough ER = rER b. smooth ER= sER 3. Golgi Apparatus 4. Mitochondria 5. Lysosomes 6. Peroxisomes 3.4 The nucleus and the production of proteins What structures are involved in protein production? • Nucleus • Ribosomes • Endomembrane system 3.4 The nucleus and the production of proteins What is the structure and function of the nucleus? • Bound by a porous nuclear envelope • Houses DNA and associated proteins called chromatin • Contains nucleoplasm • Nucleolus region(s) that contain ribosomal RNA (rRNA) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. nuclear envelope chromatin nucleolus rough ER nuclear pores smooth ER (nuclear pores): Courtesy E.G. Pollock; (ER): © R. Bolender & D. Fawcett/Visuals Unlimiteda 3.4 The nucleus and the production of proteins What is the structure and function of ribosomes? • Organelles made of RNA and protein • Found bound to the endoplasmic reticulum and free floating in the cell • Site of protein synthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (nuclear pores): Courtesy E.G. Pollock; (ER): © R. Bolender & D. Fawcett/Visuals Unlimiteda 3.4 The nucleus and the production of proteins What is the endomembrane system? • A series of membranes in which molecules are transported in the cell • It consists of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes and vesicles 3.4 The nucleus and the production of proteins Summary of the parts of the endomembrane system? • Rough endoplasmic reticulum – studded with ribosomes used to make proteins • Smooth endoplasmic reticulum – lacks ribosomes but aids in making carbohydrates and lipids • Golgi apparatus – flattened stacks that process, package and deliver proteins and lipids from the ER • Lysosomes – membranous vesicles made by the Golgi that contain digestive enzymes • Vesicles – small membranous sacs used for transport 3.4 The nucleus and the production of proteins How does the endomembrane system function and appear? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. secretion plasma membrane secretory vesicle incoming vesicle enzyme Golgi apparatus modifies lipids and Proteins from the ER; sorts and packages them in vesicles lysosome contains digestive enzymes that break down cell parts or substances entering by vesicles protein transport vesicle takes proteins to Golgi apparatus transport vesicle takes lipids to Golgi apparatus lipid smooth endoplasmic reticulum synthesizes lipids and has various other functions Nucleus ribosome rough endoplasmic reticulum synthesizes proteins And packages them in vesicles Ribosomes *complexes of RNA & protein *workbenches on which the protein molecules are stitched together with peptide bonds 2.Endoplasmic Reticulum Endoplasmic Reticulum *flattened but layered stacks *located right after the nucleus 2 TYPES *rER = rough ER (w/ ribosomes) for protein synthesis *sER = smoothER (w/o ribosomes) for lipid synthesis Golgi Apparatus Golgi Apparatus * “packaging center” of ER products for cell usage & secretion Lysosomes * “suicide bag of the cell” or digestion vat (lysis = to destroy) *contain hydrolytic enzymes Peroxisomes *help digest fats and detoxify harmful substances *contain powerful oxidase enzymes *the enzymes use O2 to breakdown molecules by means of biochem rxns that produce Hydrogen Peroxide 3.5 The cytoskeleton and cell movement What is the cytoskeleton? • A series of proteins that maintain cell shape as well as anchors and/or moves organelles in the cell • Made of 3 fibers: large microtubules, thin actin filaments and medium-sized intermediate filaments 3.5 The cytoskeleton and cell movement What are cilia and flagella? • Both are made of microtubules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Flagellum microtubules • Both are used in movement cilia sperm plasma membrane flagellum secretory cell a. b. • Cilia are about 20x shorter than flagella flagellum c. 3.6 Mitochondria and cellular metabolism What do mitochondria do and what do they look like? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • A highly folded organelle in eukaryotic cells • Produces energy in the form of ATP • They are thought to be derived from an engulfed prokaryotic cell outer membrane intermembrane space inner membrane 200 nm matrix cristae © Dr. Don W. Fawcett/Visuals Unlimited Mitochondria * “powerhouse of the cell” * produces the ATP ; liver & heart (ATP= currency of E) * also contains DNA mtDNA = mitochondrial DNA • mtDNA = mitochondrial DNA • * in humans, maternally inherited • * Paternally inherited reported in some insects such as fruit flies, honeybees, and periodical cicadas; sheep, and in cloned cattle. • Because mtDNA is not highly conserved and has a rapid mutation rate-----• it is useful for studying the evolutionary relationships. 54 3.6 Mitochondria and cellular metabolism What happens in glycolysis – step 1 of cellular respiration? • Glycolysis – Occurs in the cytoplasm – Breaks glucose into 2 pyruvate – NADH and 2 ATP molecules are made – Does not require oxygen Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 57 TRANSITION REACTION 58 3.6 Mitochondria and cellular metabolism What happens in glycolysis – step 2 of cellular respiration? • Citric acid cycle – A cyclical pathway that occurs in the mitochondria – Produces NADH, FADH2 and 2 ATP – Requires oxygen Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. The Citric Acid Cycle 62 63 3.6 Mitochondria and cellular metabolism What happens in glycolysis – step 3 of cellular respiration? • Electron transport chain – Series of molecules embedded in the mitochondrial membrane – NADH made in steps 1 and 2 carry electrons here – 32-34 ATP are made depending on the cell – Requires oxygen as the final electron acceptor in the chain Organization of Cristae 65 3.6 Mitochondria and cellular metabolism What other molecules besides glucose can be used in cellular respiration? • Other carbohydrates • Proteins • Lipids 3.6 Mitochondria and cellular metabolism How can a cell make ATP without oxygen? • Fermentation – Occurs in the cytoplasm – Does not require oxygen – Involves glycolysis – Makes 2 ATP and lactate in human cells – Is important in humans for a burst of energy for a short time VACUOLES • Membranous sacs that are larger than vesicles – Store materials that occur in excess – Others very specialized (contractile vacuole) • Plants cells typically have a central vacuole – Up to 90% volume of some cells – Functions in: • Storage of water, nutrients, pigments, and waste products • Development of turgor pressure • Some functions performed by lysosomes in other eukaryotes 68 69 Energy-Related Organelles: Chloroplast Structure • Bounded by double membrane • Inner membrane infolded – Forms disc-like thylakoids, which are stacked to form grana – Suspended in semi-fluid stroma • Green due to chlorophyll – Green photosynthetic pigment – Found ONLY in inner membranes of chloroplast 70 Energy-Related Organelles: Chloroplasts • Captures light energy to drive cellular machinery • Photosynthesis – Synthesizes carbohydrates from CO2 & H2O – Makes own food using CO2 as only carbon source – Energy-poor compounds converted to energy rich compounds 71 72
