Transcript protein
Origin of Life 1 Sequence of Events 4.5 billion years ago---Earth formed 3.5-4 billion years ago--- Life began evidence is prokaryotic fossils in stromatolites (banded rock) 2 Sequence of Events cont’d 3 billion years ago 2 distinct groups of prokaryotes bacteria archaea pg.515 3 4 2 types of prokaryotes 1. Autotrophs - make own energy - photosynthesis (from sun) or - chemosynthetic (from inorganic compounds) 2. Heterotrophs – use organic material for energy 5 Prokaryotes cont’d 2.5 billion years ago - Production of photosynthetic prokaryotes 1.7 billion years ago - first eukaryotes - multicellular organisms - animals & plants 6 Spontaneous Generation Abiogenesis Life from non-life Pasteur’s experiment changed this 7 8 Early Earth Primitive conditions - C,H,O,N in some form - No free oxygen - Lightning - Volcanoes - Strong UV - No ozone - Reducing atmosphere 9 Experiments on abiogenisis Oparin-Haldane hypothesis - Organic matter could’ve been derived from inorganic matter in the early atmosphere (not in today’s oxidizing atmosphere) - Miller & Urey tested Oparin’s hypothesis - Pg 508-509 10 11 Miller, Urey polymerized organic molecules from inorganic material Proteinoid- the new organic molecule surrounded by a membrane-like substance and produced by abiotic means. Protobiont - collection of proteinoids Explain the role of clay pockets in the formation of protobionts. What is being discussed now due to recent findings? 12 Two Modern Day Cell Types Prokaryotes Eukaryotes 13 Prokaryotes Simple cells- extremely small Few organelles No internal membranes Nucleoid region contains DNA 14 Prokaryotes (continued) Cell wall present - Contains peptidoglycon instead of cellulose - Peptidoglycon is a sugar mol. crosslinked with polypeptides - Structure differs in each bacteria 15 Circular chromosome containing 1 strand of DNA Some have additional genes in DNA rings called plasmids DNA Contains 1/1000 of the info of eukaryotic DNA 16 17 Endosymbiont Hypothesis 2 prokaryotes living in a symbiotic relationship one within the other Over time the endosymbiont lost its independence This gave rise to the mitochondria and internal membrane 18 Prokaryotes (continued) 2 kingdoms - Eubacteria - Archaebacteria - See chart pg 566 19 Fig. 27-16 Euryarchaeotes Crenarchaeotes UNIVERSAL ANCESTOR Nanoarchaeotes Domain Archaea Korarcheotes Domain Eukarya Eukaryotes Proteobacteria Spirochetes Cyanobacteria Gram-positive bacteria Domain Bacteria Chlamydias 20 21 22 23 Eukaryotes Complex cell Internal membranes # of distinct straight chromosomes Many organelles 4 kingdoms Plants Animals Fungi Protists 24 Eukaryote Cell Parts Use chapter 6 in text 25 26 27 28 29 Eukaryote - Cell Parts cont’d Nucleus - Control center for cellular activities - Bounded by nuclear envelope- double membrane w/space in between - Contains pores which contain a ring of 8 proteins- regulates molecular entry & exit 30 Nucleus continued Contains chromosomes that carry DNA Different states of DNA - Chromatin- long stringy & can’t be seen w/ light microscope - Chromatids-short, fat appear after duplication phase of mitosis - 2 chromatids make up one chromosome 31 Nucleus continued Contains nucleolus which synthesizes ribosomes 32 33 Eukaryote – cell parts Ribosomes – assemble proteins based on DNA - Free – proteins for cytoplasm - Attached – proteins for export Ie. insulin 34 35 Cell parts Endoplasmic Reticulum (ER) - transport - 2 kinds Smooth - No ribosomes - Lipid synthesis - Carbohydrate metabolism - Detoxify drugs 36 ER continued Rough - Has ribosomes - Synthesis of secretory proteins - Membrane production 37 ER continued Cisternae membrane tubules & sacs in ER & Golgi apparatus 38 39 Cell Parts continued Golgi apparatus - Receiving and shipping - Cis face receives from ER & fuses w/Golgi - Trans face produces vesicles that pinch off & travel 40 41 LYSOSOME Hydrolytic enzymes recycle org. material Has acid environment for enzymes Can destroy cell Lots of research here. Why? 42 43 44 45 46 Vacuole (lg.) vesicle (sm) Membranous sac Food vacuoles engulf food by phagocytosis Contractile vacuoles pump out excess water in protists Central vacuole in plants stores water & org. material 47 Endomembranes 48 Peroxisome Has enzymes that transfer H from toxins to O & produce H2O2 then to H2O and O2 • Ie. Liver and plant seeds - detoxifies alcohol 49 Mitochondria Made of: - Double membrane - Outer smooth - Inner has cristae (folds in membrane) to increase surface area 50 Mitochondria (continued) Matrix - space inside of membranes - Respiration done here 51 Mitochondria (continued) Evidence for endosymbiont hypothesis - Has it’s own chromosome with DNA - Has ribosomes - pg 517 52 53 Plastids 3kinds of plastids found only in plants 1. chloroplasts 2. leukoplast – contains starch 3. chromoplast – contains pigment 54 Chloroplast site for photosynthesis Structure: - Outer membrane - Inner membrane arranged into thylakoids (flattened sacs) - Grannum - stack of thylakoids - Stroma – fluid outside of thylakoids (enzymes) 55 56 Leukoplast Colorless plastid stores starch 57 Chromoplast Contains pigment and gives color 58 CENTROSOME Microtubule organizing center for cell division Animal cells centrosome’s contain 2 centrioles per cell 59 Cytoplasm region b/w cell memb. & nucleus Cytosol semi-fluid medium Cytoskeleton mesh network of fibers that for support, motility and regulation 60 Cytoskeleton Made of 3 types of fibers - Microtubules – hollow rods made of globular proteins - Microfilaments –solid rods made of actin associated with movement ( muscle cells) - Intermediate filaments –rods which fix position of organelles 61 Microtubules Hollow rods made of globular protein called tubulin They grow by adding tubulin units 62 Microfilaments Solid rods also called actin filaments (made of actin, a globular protein) Role is to bear tension (pulling forces) Known for role in cell motility and contraction in muscles 63 Muscle Contractions Actin filaments are interdispersed with thicker filaments called myosin. Myosin acts as a microfilament-based motor protein that “walks” along the actin filament Important in cell division Cause contractions that pinch in plasma membrane and form the cleavage furrow during cell division 64 Cell Surface & Junctions 65 Plant Cell Walls Chemicals vary with species All microfibrils of cellulose in a matrix of poly’s & proteins See fig. 6.28 pg. 119 66 67 Plant Cell Surface Primary cell wall Middle lamella made of pectin – glues cells together Some have secondary cell walls Plasmodesmata – channels in cell wall connect cytoplasm of cells 68 Animal junctions - Extracellular matrix (ECM) Made of glycoproteins - pg. 120 fig. 6.30 69 70 Types of intracellular junctions 1. Tight juctions -- form belt around cell membranes 2. Desmosomes -- fasten cells together like rivets 3. Gap junctions – provide cytoplasmic channels between adjacent cells. 71 72 73 CELL MEMBRANE STRUCTURE AND FUNCTION Fig 7.7 pg. 128 74 75 Fig. 7-7 Fibers of extracellular matrix (ECM) Glycoprotein Carbohydrate Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE 76 77 78 FUNCTION Regulate passage of certain materials in and out of the cell. 79 Fluid mosaic model 1. Membrane is a mosaic of proteins bobbing is a fluid bilayer of phospholipids 2. Lateral movement creates pores 80 Components of Cell Membrane 81 Phospholipid bilayer Boundary between 2 aqueous components Amphipathic Part nonpolar - hydrophobic Part polar - hydrophilic 82 Cholesterol Located between phospholipids Reduces fluidity of membrane and prevents solidification at low temperatures 83 Integral proteins Transport proteins Not very soluble in water Over 50 kinds Protrude from both sides of memb. Part hydrophobic & part hydrophilic (b/c of size) See pg. 129 fig. 7.9 for all functions of transport proteins 84 Fig. 7-9 Signaling molecule Enzymes ATP (a) Transport Receptor Signal transduction (b) Enzymatic activity (c) Signal transduction (e) Intercellular joining (f) Attachment to the cytoskeleton and extracellular matrix (ECM) Glycoprotein (d) Cell-cell recognition 85 Fig. 7-8 N-terminus C-terminus Helix EXTRACELLULAR SIDE CYTOPLASMIC SIDE 86 Peripheral proteins Attached to integral proteins on inside surface of memb. 87 Carbohydrates & glycolipids Carb’s are usually oligosaccharides ( short poly’s) Attached to outer surface of membrane Cell to cell recognition –based on diversity of mol’s & location on memb. 88 Movement of molecules across the cell membrane. 89 What molecules need to cross? Carbs (mono’s) Oxygen Water Proteins Carbon dioxide Ions 90 What molecules can move across the membrane? Nonpolar molecules - hydrocarbons, CO2 and O2 because they’re hydrophobic can cross easily. Hydrophilic molecules will pass slowly and use transport proteins – glucose, charged ions and water 91 DIFFUSION Movement of molecules from high concentration to low concentration. (This is called a concentration gradient.) Diffusion continues until molecules reach equilibrium 92 Changing the rate of diffusion Increase molecular movement by wind, stirring, or increased temp Pressure Steepness of gradient 93 94 Fig. 7-8 N-terminus C-terminus Helix EXTRACELLULAR SIDE CYTOPLASMIC SIDE 95 OSMOSIS Diffusion of water across a selectively permeable membrane 96 TERMS 97 HYPEROSMOTIC Also called hypertonic Refers to the solution with a greater solute concentration (sugar) 98 HYPOOSMOTIC Also called hypotonic Refers to the solution with lesser solute 99 Isoosmotic Also called isotonic When solutions are at equilibrium Does water move from hyper to hypo or hypo to hyper? 100 Hypotonic to hypertonic 101 Two basic methods of molecular transport. 1. 2. Passive Transport Active Transport 102 Passive Transport Molecular movement down a gradient (from high to low naturally by diffusion) No cellular energy required (potential energy of the gradient is enough) Two types Simple diffusion through pores Facilitated diffusion 103 Facilitated diffusion (helper) Uses integral proteins in membrane Proteins are very specific like enzymes Catalyze a physical process—transport of a molecule like glucose & other polar molecules ions (i.e. aquaporins) 104 Protein may change shape as it binds with molecule - translocating binding site to other side of protein Molecule being transported itself doesn’t change shape Pg 135 fig. 7.15 105 106 Fig. 7-15 EXTRACELLULAR FLUID Channel protein Solute CYTOPLASM (a) A channel protein Carrier protein (b) A carrier protein Solute 107 Aquaporin Integral protein channel for water Water still moves with the gradient. 108 Aquaporin 109 Aquaporin http://www.ks.uiuc.edu/Research/aquaporin s/ 110 Fig. 7-17 Passive transport Active transport ATP Diffusion Facilitated diffusion 111 ACTIVE TRANSPORT Molecular movement against a gradient Also uses integral proteins Cell expends energy (ATP) Allows cell to maintain specific internal concentration regardless of environment 112 Electrogenic pumps Sodium potassium pump is main one in animal cells Proton pump is main one in plants, fungi, and bacteria. 113 114 Fig. 7-18 – ATP EXTRACELLULAR FLUID + – + H+ H+ Proton pump H+ – + H+ H+ – + CYTOPLASM – H+ + 115 Cotransport A single ATP powered pump transports a specific solute fig. 7.19 A substance that has been pumped across a membrane can do work as it moves back across the membrane by diffusion 116 Fig. 7-19 – + H+ ATP – H+ + H+ Proton pump H+ – H+ + – H+ + H+ Diffusion of H+ Sucrose-H+ cotransporter H+ Sucrose – – + + Sucrose 117 Bulk transport Exocytosis - out Endocytosis – in - phagocytosis – cell eating - pinocytosis – cell drinking - receptor mediated endocytosis 118 Fig. 7-20 PHAGOCYTOSIS 1 µm CYTOPLASM EXTRACELLULAR FLUID Pseudopodium Pseudopodium of amoeba “Food”or other particle Bacterium Food vacuole Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM) PINOCYTOSIS 0.5 µm Plasma membrane Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM) Vesicle RECEPTOR-MEDIATED ENDOCYTOSIS Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit and a coated vesicle formed during receptormediated endocytosis (TEMs) Coat protein Plasma membrane 0.25 µm 119 Fig. 7-20b PINOCYTOSIS 0.5 µm Plasma membrane Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM) Vesicle 120 Fig. 7-20a PHAGOCYTOSIS EXTRACELLULAR FLUID 1 µm CYTOPLASM Pseudopodium Pseudopodium of amoeba “Food” or other particle Bacterium Food vacuole Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM) 121 Fig. 7-20c RECEPTOR-MEDIATED ENDOCYTOSIS Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit and a coated vesicle formed during receptormediated endocytosis (TEMs) Coat protein Plasma membrane 0.25 µm 122 Fig. 7-20 PHAGOCYTOSIS 1 µm CYTOPLASM EXTRACELLULAR FLUID Pseudopodium Pseudopodium of amoeba “Food”or other particle Bacterium Food vacuole Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM) PINOCYTOSIS 0.5 µm Plasma membrane Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM) Vesicle RECEPTOR-MEDIATED ENDOCYTOSIS Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit and a coated vesicle formed during receptormediated endocytosis (TEMs) Coat protein Plasma membrane 0.25 µm 123 124 Water potential Tendency for water mol’s to diffuse Water will move from area of high water potential to area of lower water potential In the following diagram, which side of the initial tube has the greatest water potential? 125 126 Example Cell 2% salt Environment 10% salt Where is water potential higher? 127 Water potential is higher in the cell. Which way will water move? 128 Water leaves the cell Cell membrane shrinks Animal cells - crenate Plant cells - plasmolysis 129 Cytolysis Cell membrane swells Animal cells - leads to lysing ( cell bursting) 130 Cytolysis (cont) Plant cells – leads to increased turgor pressure Pressure on the cell wall from inside the plant cell 131 Fig. 7-13 Hypotonic solution H2O Isotonic solution H2O H2O Hypertonic solution H2O (a) Animal cell Lysed H2O Normal H2O Shriveled H2O H2O (b) Plant cell Turgid (normal) Flaccid Plasmolyzed 132 133 134 Fig. 7-14 Filling vacuole 50 µm (a) A contractile vacuole fills with fluid that enters from a system of canals radiating throughout the cytoplasm. Contracting vacuole (b) When full, the vacuole and canals contract, expelling fluid from the cell. 135 Water potential equation = s + p - water potential – the ability of water to move out (unit is megapascals MPa) - pure water has a = 0 s – solute potential – how solute affects the water potential - addition of solute – lowers the water potential (more solute – more negative) p - pressure potential – is 0 in an animal cell 136 137 138 Apoplast – through cell wall Symplast - through cytoplasm 139