Week 3: End of Lecture 3, plus Lectures 4 and 5
Week 3: End of Lecture 3, plus Lectures 4 and 5 01:119:115
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This 7 page Class Notes was uploaded by gtan51097 on Sunday September 25, 2016. The Class Notes belongs to 01:119:115 at Rutgers University taught by Dr. Gregory Transue in Fall 2016. Since its upload, it has received 14 views. For similar materials see General Biology I in Biological Sciences at Rutgers University.
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Date Created: 09/25/16
9/19/2016 Lipids (continued) Phospholipid o Glycerol + 2 fatty acids (hydrophobic) o Phosphate group (hydrophilic) Cell membranes Steroids o 3 rings w/ 6 C and one ring has 5 C o Ex: cholesterol in animals A. Proteins Monomer: amino acid (20) o α carbon in center o Amino group NH₂ o Carboxyl group O=C–OH o R groups: determine functions, acidity, polarity Polymer: protein or polypeptide Peptide bonds are between amino acids 4 Levels of Protein Structure 1) Primary structure: sequence of amino acids joined by peptide bonds in polypeptide chain; not a protein yet 2) Secondary structure: H bonds formed; R groups do not participate α helix = coil β pleated sheet 3) Tertiary structure Interrelationships of R groups fold into particular 3D shape All types of bonds o H, ionic, hydrophobic interactions, covalent, disulfide (type of covalent, link 2 sulfur atoms) 4) Quaternary structure: 2+ polypeptide chains form 1 macromolecule; no more folding Denaturation: loss of protein’s native structure; biologically inactive; pH, salt concentration, temperature B. Nucleic Acids Monomers: nucleotides 2 classes o DNA: deoxyribonucleic acid o RNA: ribonucleic acid o Acidic due to phosphate group Transmit hereditary info & determine protein production Lecture 4: Origin of Life; Ch. 25.1 – 25.3 I. Chemical Evolution: from living to non-living Earth is 4.6 bil yrs old Fossil evidence of microorganisms 3.5 bil years ago (bya) st But how did 1 living cells appear? Hypothesis: if life developed from non-living matter, then we expect 4 requirements to be fulfilled II. Abiotic Synth 4 requirements to have occurred: Conditions of Early Earth o Little to no free O2 O₂ breaks bonds (oxidizes) so O₂ not conductive to building Low O₂ reducing environment Oxidation is losing e-, reduction is gaining e- OILRIG If this is true, then where did O₂ in atmosphere (~21%) come from? o Source of E: to build biological molecules E to form bonds could come from violent thunderstorms, volcanic activity, meteorite bombardment, intense radiation o Presence of chem building blocks: CHON Water Dissolved inorganic materials Atmosphere contained CO₂, water vapor, CO, H₂, and N₂ Maybe NH₃, H₂S, and CH₄ o Time: for molecules react w/ one another Estimated Earth is 4.6 bya Evidence that life arose on Earth ~3.5 bya So how could life have started? o Prebiotic soup hypothesis (Opain-Haldane) Worked independently, 1920s Hypothesis: life formed near Earth’s surface + conditions of early Earth favored spontaneous formation of simple organic molecules Stanley Miller and Harold Urey Experiment o Experiment: 1953; stimulated early conditions of early Earth o Formed amino acids + other organic molecules o Recent development 2008: atmosphere may have been neutral and not reducing o Iron-Sulfur World Hypothesis Hypothesis: life formed at cracks of ocean floor hydrothermal vents Hot water, CO, and minerals such as iron and nickel sulfides released Today, these hot springs produce precursors of biological molecules III. Abiogenesis: how did life arise? 4 steps hypothesis of single cell formation 1) Formation of small organic molecules How could this have happened? Prebiotic soup hypothesis ISWH 2) Abiotic synthesis of macromolecules Formation of polymers from monomers (protein or RNA) Monomers polymerize (form chains) on hot sand, clay, or rock Neg ions bind monomers Zn^2⁺ and Fe^2⁺ In lab drip solution of aa onto hot rock form polypeptide 3) Formation of protocells In water, lipids + other organic molecules spontaneously form vesicles Organic polymers exhibit attributes of living cells o Osmosis, homeostasis, divide o No mechanisms of heredity 4) Self-replicating RNA RNA 1 NA in protocells RNA capable of replicate itself and catalyze protein synth (ribosomes) DNA evolved later Double stranded, more stable IV. Key events in the history of life No fossils for transition from nonlife to life Fossil shows only changes in kinds of organisms on earth over time Absolute ages use radiometric dating Use decay of radioactive isotopes Prokaryotic cells prolific on Earth 3.8 bya Fossil record formation o Sedimentary rocks deposited into layers called strata: 5 major strata and minor strata o Older ones on bottom, younger on top o Characteristic fossils: each layer A. Geological = standard time scale; divided into 4 eons 1) Hadean: oldest 2) Archaean: first cells 3) Proterozoic: first eukaryotes 4) Phanerozoic: includes 3 eras; you are here Between eras: major extinction events Periods and epochs – smaller divisions o Eons > Era > Period > Epoch o An age is the # of years ago 9/21/2016 B. The First Single-Celled Org Stromatolites: bacterial mats on sedimentary layers 3.5 bya: just heterotrophic bacteria Prokaryotes st o 1 Heterotrophs Use fermentation (anaerobic breakdown) couldn’t survive w/ O₂ o 2ndPhotosynthetic autotrophs: E fr/ sunlight Ex: cyanobacteria: released O₂ First one prob split H₂S since S is less electronegative, it’s easier to split from H O₂ revolution/apocalypse rise of atmospheric O₂ o 3 Aerobes: use O₂ more ATP C. The First Eukaryotes: More complex Oldest fossils: 1.8 bya Endosymbiotic theory: mitochondria and plastids (chloroplasts) were small prokaryotes Endosymbiont: cell lives w/in host cell Serial endosymbiosis: mitochondria entered first, plastids after Key evidence supporting endosymbiotic origin of (M+P) o Inner membranes o Enzymes o Own DNA o Ribosomes o Undergo binary fission o Small D. The Origin of Multicellularity Oldest fossils ~1.2-1.8 bya Edicaran period ~600 mya o Eukaryotes: soft-bodies Cambrian explosion: 535-525 mya o Fossils appear resembling modern animal o Rapid evolution new animal body plans E. The Colonization of Land ~500 mya larger forms of life on land (fungi, plants, animals) Adaptations for life on land prevent drying out or desiccation Lecture 5: Intro to the Cell: Fundamental Unit of Life Smallest unit of life Multicellular organism: cooperative specialized cells Cell theory states: all organisms are made of cells and all cells have 4 common features and a common evolutionary ancestor I. Tools and Techniques to study cells A. Parameters of microscopes How small and what do you need to see? *Refer to Figure 6.2 on page 94 B. Microscopes Light Microscope o ~2um o Stains or dyes increase contrast o Nucleus but not smaller organelles 2 kinds of electron microscope (EM) o 1 nm or less o Scanning (surface) (SEM) o Transmission (inside) (TEM) Why not use EM all the time? o Cells must be killed (sliced or covered in gold) o May alter their structure o Expensive o Tedious prep C. Cell fractionation Separates major organelles Centrifuges fractionate cells into their component parts Used to determine functions of organelles Helps correlate cell function w/ structure II. Cell Diversity and Characteristics A. Cells are classified by structures 1. Prokaryotes: ~3.5-3.8 bya “before nucleus” Domains Bacteria and Archaea 2. Eukaryotes: ~1.9-2.1 bya Means “true nucleus” Domain Eukarya Protists, fungi, animals, plants B. Common Features of Cells Basic features of ALL cells plasma membrane phospholipids cytosol semifluid substance chromosomes (carry genes, DNA) ribosomes (make proteins, RNA) 1. Prokaryotic cells No nucleus Nucleoid: DNA in unbound region No organelles 1-10um (micrometers): Typical size 2. Eukaryotic cells DNA in nucleus Membrane bound organelles Cytoplasm Size typically 10-100um 10x larger than prokaryotes C. Limits to Cell Size: Why are they small? The plasma membrane = selective barrier (O₂, nutrients, waste) Surface area to volume ratio III. Components of Eukaryotic Cells A. Nucleus DNA organized in Chromosomes DNA + proteins = Chromatin Nucleolus (plural nucleoli): ribosomes made here o RNA + proteins o No membrane Nuclear envelope o Made of 2 membranes both lipid bilayers o Nuclear pores: regulate entry and exit of molecules Lined by nuclear lamina o Composed of proteins o Maintains nucleus shape B. Ribosomes site of protein synthesis Non-membrane bound: not considered organelles Made or ribosomal RNA (rRNA) and protein Carry out protein synth in 2 locations o Free in cytoplasm make proteins that stay in cell (prokaryotes + eukaryotes) o Bound to other organelles make proteins to be shipped out of cell (eukaryotes) C. Endomembrane System Components Nuclear envelope Plasma membrane Endoplasmic Reticulum Golgi apparatus Lysosomes Vacuoles
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