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Review1BIO155fall2010 - BIO155 Review 1 Jessica Pamment •...

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Unformatted text preview: BIO155 Review 1 Jessica Pamment • Biology today • Basic chemistry • Molecules of life • The cell • Energy and life Overview • Respiration & Photosynthesis The Characteristics of life Order Response to the environment Evolutionary adaptation Regulation Energy processing Reproduction Growth and development Biology’s Unifying Theme EVOLUTION Explains unity of all living things despite phenotypic diversity The central organizing concept in biology is that all of life has a common origin and has changed and developed through the process of evolution Science • Verifiable observations are prerequisites • Not only about accumulating facts • But it is theories that advance science • Theories tie together a number of observations that previously seemed unrelated Types of Scientific Inquiry • Discovery science: describes nature • Hypothesis­driven: explains nature • Most scientific studies combine both approaches Ch.2 Essential Chemistry • Atomic structure • Formation of bonds • Water and its unusual properties Atomic Structure • Atom is the smallest unit of matter that still retains properties of an element • Subatomic particles: neutrons, electrons, and protons • Atomic number: number of protons 2He • Mass number: sum of protons and neutrons 4He • Atoms neutral in charge have equal number of electrons as protons Arrangement of Electrons around the Nucleus First electron shell (can hold 2 electrons) Electron Outer electron shell (can hold 8 electros) Hydrogen (H) Atomic number = 1 Carbon (C) Atomic number = 6 Nitrogen (N) Atomic number = 7 Oxygen (O) Atomic number = 8 The Role of Electrons • Only electrons are directly involved in the chemical reactions between atoms • Electrons are found in different electron shells, each with a specific energy level (LINK to electron transport chain) Chemical Bonds, the Glue of Life 1. Ionic bonds 1. Covalent bonds 1. Hydrogen bonds Ionic Bonds • Charge­charge interactions formed between charged ions atoms salts • Results from the transfer of electrons between • Compounds formed by ionic bonds are called Electron Transfer and Ionic Bonding Na Cl Na Sodium atom Cl Chlorine atom Electron Transfer and Ionic Bonding Na Cl Na Cl Na Sodium atom Cl Chlorine atom Na+ Sodium ion (a cation) Cl– Chloride ion (an anion) Sodium chloride (NaCl) Covalent Bonds • Results from the sharing of a pair of electrons by two atoms • Oxygen is very electronegative, resulting in H2O being a polar molecule (LINK importance of O2’s electronegativity in pulling electrons down transport chain) Covalent Bonds in Water Name and Molecular Formula Electrondistribution Diagram Lewis Dot Structure and Structural Formula Spacefilling Model (c) Water (H2O) Polar Covalent Bonds in a Water Molecule δ– O H H2 O H δ+ δ+ Weak Chemical Bonds • Essential to life due to reversability • Hydrogen bonds Water • Unique properties due to structure • The medium of life, makes life habitable • Exists in solid, liquid, gaseous states • Constitutes 70­95% of cells Hydrogen Bonds between Water Molecules δ– δ+ Hydrogen bond H δ+ δ– δ+ —— δ– O —— H δ+ δ– Properties of Water • Cohesion • Moderation of temperature • Expansion upon freezing • Solvent Ch.3 The Molecules of Life • Importance of carbon • Biomolecules: 1. Carbohydrates: simple sugars and polysaccharides 2. Proteins 3. Lipids: are all hydrophobic 4. Nucleic acids Biomolecules • Carbohydrates, proteins and nucleic acids are polymers • Polymers are long molecules consisting of monomers that are covalently bonded • Lipids are not true polymers • Basis for diversity in polymers is arrangement of units HO 1 2 3 H HO H Unlinked monomer H2O HO 1 2 Polymer 3 4 H (a) Dehydration reaction in the synthesis of a polymer The Synthesis and Structure of a fat, or triglyceride The Synthesis and Structure of a fat, or triglyceride HO 1 2 3 4 H Hydrolysis adds a water molecule, breaking a bond H2O HO 1 2 3 H HO H (b) Hydrolysis of a polymer Carbohydrates Carbohydrates • Literally means hydrated carbon • Sugars (monosaccharides and disaccharides) • Polymers of sugars (polysaccharides) Lipids • Not big enough to be considered macromolecules behavior • They show hydrophobic (‘water fearing’) • 1. 2. 3. Three most important types in biology: Fats Phospholipids Steroids Proteins • Account for more than 50% of dry mass of most cells • Essential for almost every biological function • • • • • Functions include: Enzymes as catalysts Storage proteins Contractile proteins Antibodies as defensive proteins Four Levels of Protein Structure • Primary: the list of amino acids in the proper order • Secondary: structural elements common to • Tertiary: the 3D shape obtained once the helices and sheets are coiled and folded many proteins, alpha helices and beta sheets • Quartenary: joining of more than one polypeptide in some proteins Nucleic Acids • Store and transmit hereditary information • Macromolecules that exist as polynucleotide polymers • Two types: DNA and RNA DNA vs. RNA DNA vs. RNA • Sugar: deoxyribose in DNA, ribose in RNA • Bases: RNA uses Uracil where DNA uses Thymine • RNA is usually single­stranded, DNA is double­stranded Summary for Biomolecules • Carbs, proteins and nucleic acids are MACROmolecules, lipids are not • They are all made by dehydration reactions • They are all essential as building blocks in living organisms • Organisms can make biomolecules and break them down Ch.4 Cells • Microscopes to study cells • Prokaryotic vs. Eukaryotic cells • Organelles of the endomembrane system • Organelles that are sites of energy conversion Cell is basic unit of living organisms Different views of a protist, Euglena Differences between bacteria and eukaryotes Character Bacteria/archae Eukarya a Nuclear Envelope Absent Present Membrane­ enclosed organelles Circular chromosome Absent Present Present Absent Similarities between bacteria and eukaryotes • Bound by a plasma membrane • Contain cytosol in the area enclosed by plasma membrane • Contain chromosomes • Contain ribosomes The Mitochondrion The Chloroplast Ch.5 The Working Cell • Energy concepts • ATP and cellular work • Enzymes and chemical reactions • Membrane function Forms of Energy • Energy is the capacity to do work • Kinetic energy: energy associated with the relative motion of objects • Potential energy: energy associated with location or arrangement of object • Chemical energy: energy that matter possesses due to stored energy in bonds of atoms and molecules (a type of potential energy) ATP • • 1. 2. 3. Powers cellular work. Stores energy from food, releasing it when required Cell does three types of work: Chemical work Transport work Mechanical work ATP is the mediator of all work in the cell ATP Structure ATP Structure • Adenosine triphosphate: adenosine + 3 phosphate groups • ATP is a form of POTENTIAL energy • Energy currency in the cell • Loss of a phosphate group releases energy Enzymes • Enzymes act as biological catalysts • Enzymes lower the energy activation barriers required for metabolic reactions to take place SubstrateSpecificity • Essential to enable thousands of biological reactions to take place simultaneously • Active site is region of enzyme that binds substrate only few amino acids long • As substrate binds, active site changes to result in ‘induced fit’ Induced Fit between an Enzyme and its Substrate Substrate Active site Enzyme (a) (b) Enzyme-substrate complex Factors that affect Enzyme Activity • Substrate concentration • Temperature and pH • Inhibitors Cell Membranes Cell Membranes • Fluid mosaic model of lipids and proteins, all with hydrophobic and hydrophilic regions • Dynamic, fluid structures • Fluidity and function depend on composition • Lipid bilayer is asymmetrical Transport Mechanisms Transport Mechanisms • Passive Transport­ includes both simple and facilitated diffusion. No energy requirement as solutes move down concentration gradient • Active Transport­ requires energy to move solutes against their concentration gradient Bulk Transport Bulk Transport • • Refers to transport of large molecules across membranes Two main mechanisms: 1. Exocytosis 1. Endocytosis Ch.6 Cellular Respiration • Cellular respiration: 3 stages • Anaerobic respiration: doesn’t utilize oxygen, uses electron transport chain • Fermentation: doesn’t utilize oxygen, doesn’t utilize electron transport chain Cellular Respiration Cellular Respiration • The aerobic harvesting of chemical energy from organic fuel molecules • Oxygen in the air we breathe in is required for cellular respiration • Carbon dioxide is a by product found in the air we exhale 3 Stages of Respiration 3 Stages of Respiration • Respiration is a metabolic pathway • 3 main metabolic stages: 1.Glycolysis 2.Citric acid cycle 3.Electron transport The three stages of cellular respiration The three stages of cellular respiration Glycolysis Glycolysis • Means sugar splitting • Anaerobic process • Takes place in cytosol • One molecule of glucose is converted to two of pyruvate and net two of ATP glucose • Releases less than 25% of chemical energy stored in The Citric Acid Cycle The Citric Acid Cycle • A.K.A Kreb’s Cycle • Takes place in the mitochondrial matrix • Oxidizes organic fuel derived from pyruvate • The cycle generates 1 ATP per turn • Most energy is transferred to NAD+ and FAD+ REDOX reactions REDOX Redox Reactions Redox Reactions • Reduction­oxidation reactions • Reactions that transfer electrons between reactants • A substrate that gains electrons is said to have been reduced • A substrate that has lost electrons is said to have been oxidized The role of The role of oxygen in harvesting food energy Electron Transport Electron In the absence of oxygen…. In the absence of oxygen…. • Cells can oxidize organic fuel and 1. Anaerobic respiration 1. Fermentation generate ATP without the use of oxygen: Fermentation Fermentation • A method of harvesting chemical energy without the use of an electron transport chain • Fermentation is an expansion of glycolysis that allows continuous generation of ATP by direct phosphate transfer • A way of regenerating NAD+ from NADH made during glycolysis in the absence of the electron transport chain Lactic Acid Fermentation Lactic Acid Fermentation Alcohol Fermentation Alcohol Fermentation Ch. 7 Photosynthesis • Importance of photosynthesis for life as we know it • Chloroplasts • 2 stages: light reactions and Calvin cycle ...
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