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This PPT Adapted from Hole’s Human Anatomy and Physiology Eleventh Edition Shier w Butler w Lewis Chapter 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 Chapter 2 Chemical Basis of Life Why study chemistry in an Anatomy and Physiology class? - body functions depend on cellular functions - cellular functions result from chemical changes - biochemistry helps to explain physiological processes, and develop new drugs and methods for treating diseases 2 Structure of Matter Matter – anything that takes up space and has weight; composed of elements Elements – composed of chemically identical atoms • bulk elements – required by the body in large amounts • trace elements – required by the body in small amounts Atoms – smallest particle of an element 3 Atomic Structure Atoms - composed of subatomic particles: • proton – carries a single positive charge • neutron – carries no electrical charge • electron – carries a single negative charge Nucleus • central part of atom • composed of protons and neutrons • electrons move around the nucleus 4 Atomic Number and Atomic Weight Atomic Number • number of protons in the nucleus of one atom • each element has a unique atomic number • equals the number of electrons in the atom Atomic Weight • the number of protons plus the number of neutrons in one atom • electrons do not contribute to the weight of the atom 5 Isotopes Isotopes • atoms with the same atomic numbers but with different atomic weights • atoms with the same number of protons and electrons but a different number of neutrons • oxygen often forms isotopes (O16, O17, O18) • unstable isotopes are radioactive; they emit energy or atomic fragments 6 Molecules and Compounds Molecule – particle formed when two or more atoms chemically combine Compound – particle formed when two or more atoms of different elements chemically combine Molecular formulas – depict the elements present and the number of each atom present in the molecule H2 C6H12O6 H2O 7 Bonding of Atoms • bonds form when atoms combine with other atoms • electrons of an atom occupy regions of space called electron shells which circle the nucleus • each shell can hold a limited number of electrons • for atoms with atomic numbers of 18 or less, the following rules apply: • the first shell can hold up to 2 electrons • the second shell can hold up to 8 electrons • the third shell can hold up to 8 electrons 8 Bonding of Atoms • lower shells are filled first • if the outermost shell is full, the atom is stable 9 Ions Ion • an atom that gains or loses electrons to become stable • an electrically charged atom Cation • a positively charged ion • formed when an atom loses electrons Anion • a negatively charged ion • formed when an atom gains electrons 10 Ionic Bond Ionic Bond • an attraction between a cation and an anion • formed when electrons are transferred from one atom to another atom 11 Covalent Bond Formed when atoms share electrons •Hydrogen atoms form single bonds •Oxygen atoms form two bonds •Nitrogen atoms form three bonds •Carbon atoms form four bonds H―H O=O N≡N O=C=O 12 Ionic Compounds Covalent Compounds Made of metal and non-metals Two or more Non-metals Dissolve ready in water Many do not dissolve in water Dissociate into + or – ions surrounded by hydration shells Remain intact molecules Many inorganic compounds All organic compounds Electrolytes in water Non-electrolytes Crystalline structure Amorphous 13 Structural Formula Structural formulas show how atoms bond and are arranged in various molecules (covalent compounds) 14 Polar Molecules Polar Molecule ( polar covalent molecules) • molecule with a slightly negative end and a slightly positive end • results when electrons are not shared equally in covalent bonds • water is an important polar molecule 15 Polarity of Water • • • • Responsible for properties of water Adhesion, cohesion, surface tension Capillary action “Universal solvent” can dissolve ionic and some covalent compounds 16 Hydrogen Bonds Hydrogen Bond • a weak attraction between the positive end of one polar molecule and the negative end of another polar molecule • formed between water molecules • important for protein and nucleic acid structure 17 Chemical Reactions Chemical reactions occur when chemical bonds form or break among atoms, ions, or molecules Reactants are the starting materials of the reaction- the atoms, ions, or molecules Products are substances formed at the end of the chemical reaction NaCl Na+ + ClReactant Products 18 Types of Chemical Reactions Synthesis Reaction – more complex chemical structure is formed A + B AB Decomposition Reaction – chemical bonds are broken to form a simpler chemical structure AB A + B Exchange Reaction – chemical bonds are broken and new bonds are formed AB + CD AD + CB Reversible Reaction – the products can change back to the reactants 19 A + B n AB Acids, Bases, and Salts Electrolytes – substances that release ions in water NaCl Na+ + Cl- Acids – electrolytes that dissociate to release hydrogen ions in water HCl H+ + Cl- Bases – substances that release ions that can combine with hydrogen ions NaOH Na+ + OH- Salts – electrolytes formed by the reaction between an acid and a base HCl + NaOH H2O + NaCl 20 Buffers Buffers are the salts of weak acids. They can keep the pH of a solution from shifting too rapidly. The can help maintain pH within a narrow range. A buffer can neutralize either an acid or a base. With an acid it acts as a base. With a base it can act as an acid. An example is NaHCO3 21 Acid and Base Concentrations pH scale - indicates the concentration of hydrogen ions in solution Neutral – pH 7; indicates equal concentrations of H+ and OH- Acidic – pH less than 7; indicates a greater concentration of H+ Basic or alkaline – pH greater than 7; indicates a greater concentration of OH- 22 Organic Versus Inorganic Organic molecules • contain C and H • usually larger than inorganic molecules • dissolve in water and organic liquids • carbohydrates, proteins, lipids, and nucleic acids Inorganic molecules • generally do not contain C • usually smaller than organic molecules • usually dissociate in water, forming ions • water, oxygen, carbon dioxide, and inorganic salts 23 Inorganic Substances Water • most abundant compound in living material • two-thirds of the weight of an adult human • major component of all body fluids • medium for most metabolic reactions • important role in transporting chemicals in the body • absorbs and transports heat Oxygen (O2) • used by organelles to release energy from nutrients in order to drive cell’s metabolic activities 24 • necessary for survival Inorganic Substances Carbon dioxide (CO2) • waste product released during metabolic reactions • must be removed from the body Inorganic salts • abundant in body fluids • sources of necessary ions (Na+, Cl-, K+, Ca2+, etc.) • play important roles in metabolism 25 Organic Substances Carbohydrates • provide energy to cells • supply materials to build cell structures • water-soluble • contain C, H, and O • ratio of H to O close to 2:1 (C6H12O6) • monosaccharides – glucose, fructose • disaccharides – sucrose, lactose • polysaccharides – glycogen, cellulose 26 Organic Substances Carbohydrates 27 Dehydration synthesis 28 Hydrolysis 29 Organic Substances Lipids • soluble in organic solvents; insoluble in water • fats (triglycerides) • used primarily for energy; most common lipid in the body • contain C, H, and O but less O than carbohydrates (C57H110O6) • building blocks are 1 glycerol and 3 fatty acids per molecule • saturated and unsaturated 30 Organic Substances Lipids • phospholipids • building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per molecule • hydrophilic and hydrophobic • major component of cell membranes 312-25 Organic Substances Lipids • steroids • four connected rings of carbon • widely distributed in the body, various functions • component of cell membrane • used to synthesize hormones • cholesterol 32 Organic Substances Proteins • structural material • energy source • hormones • receptors • enzymes • antibodies • building blocks are amino acids • amino acids held together with peptide bonds 332-27 34 Organic Substances Nucleic Acids • carry genes • encode amino acid sequences of proteins • building blocks are nucleotides • DNA (deoxyribonucleic acid) – double polynucleotide • RNA (ribonucleic acid) – single polynucleotide 35 Organic Substances Nucleic Acids 36 DNA RNA A-T and G-C A-U and G-C Double helix Single strand Can’t leave nucleus Active in cytoplasm Replication and Transcription Translation of proteins 1 kind Many types 37 MacroElements Building blocks molecule (monomers) Example monomers Bonding Use Key vocabulary Example polymers Polymer formula Carbohydrates Glucose, Fructose, Ribose Covalent COH to COH producing -C-O-Cbonds Short term energy from Cellular respiration Disaccharides, Polysaccharides (C1H2O1)n Dehydration – (H2O)n-1 synthesis and Hydrolysis Glycerol and Essential fatty acids such as linoleic acid and alpha linoleic acid Covalent COH to COOH or POOH producing COOC or COOP bonds Long term energy storage, Insulation, Cushioning 20 essential amino acids , groups acidic, basic, neutral, and rings Covalent COH to NH2 producing C-N bond Lipids Proteins Nucleic Acids C1H2O1 CHO (P) CHON (S) CHONP Monosaccharides Or simple sugars Glycerol and fatty acids Amino Acids Nucleotides Adenine, Thymine Guanine Cytosine Uracil Covalent COC COOP and Hydrogen bonds Amylose or Plant Starch, Glycogen, Cellulose Chemistry Enzymes = -ase Low density lipids LDL High density Lipids HDL Saturated, unsaturated, polyunsaturated fatty acids Cholesterol Triglycerides, Steroids, Waxes Phospholipids Dehydration synthesis and Hydrolysis Energy use, enzymes, Transport, cell markers, muscle Dipeptides, Polypeptides, Enzymes, Transport proteins, Hormones Linear proteins, globular proteins Making DNA and RNA, informatio n storage Double Helix, Genes, Genomes, Ribosomes DNA, mRNA NA tRNA, rRNA, and other RNA’s Enzymes = -ase (Aa)n – (H2O)n-1 Dehydration synthesis and Hydrolysis Enzymes = -ase Dehydration synthesis and Hydrolysis 38Enzymes = -ase