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Chapter 2. The Chemistry of Life. Introduction. Cells, tissues and organs composed of chemicals Chemical reactions important for function Chemistry is the study of: Elements, compounds, chemical reactions, molecular structure. Atomic Structure. Atomic Structure (cont’d.). Atoms
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Chapter 2 The Chemistry of Life
Introduction • Cells, tissues and organs composed of chemicals • Chemical reactions important for function • Chemistry is the study of: • Elements, compounds, chemical reactions, molecular structure
Atomic Structure (cont’d.) • Atoms • Smallest particles of elements • Maintain all characteristics of element • Nucleus contains protons and neutrons • Electrons orbit nucleus in shells
Elements, Isotopes, Compounds (cont’d.) • Element: atoms contain same numbers of protons and electrons • Compound: contains two or more elements • Isotope: number of neutrons varies • Periodic table of the elements • Arranges elements by increasing atomic number
Elements, Isotopes, Compounds (cont’d.) • Orbital: area where electron is found • Energy levels: grouping of orbitals • Represented as concentric circles surrounding nucleus
Bonds and Energy (cont’d.) • Ionic: one atom gains and one atom loses electrons • Covalent: atoms share electrons • Hydrogen: weak bonds, hold water molecules together • Electron donors vs. acceptors vs. carriers • Bonds are energy containing
Water • Most abundant substance in cells • Universal solvent • Transport of materials • Absorbs and reduces heat • Protects body structures
Carbon Dioxide • Waste product of cellular respiration • Used in photosynthesis to produce usable energy sources • Must be removed quickly from cells • Carbon in molecules comes from carbon dioxide gas
Molecular Oxygen • Formed from covalent bond of two oxygen atoms • Required by all organisms that breathe air • Necessary to convert food into ATP • Level in atmosphere is 21%
Ammonia • By-product of amino acid breakdown • Amino acids are building blocks of proteins • Amino acids contain nitrogen • Converted to urea in the liver
Mineral Salts • Composed of small ions • Calcium: muscle contraction and strong bones • Phosphate - ATP synthesis • Sodium, potassium, and chloride are necessary for muscle contraction and nervous transmission
Carbohydrates • 1:2:1 ratio of carbon, hydrogen and oxygen • Five- and six-carbon simple sugars are smallest • Five-carbon: deoxyribose and ribose • Six-carbon: glucose and fructose • Functions: energy storage and cell structure
Lipids • Insoluble in water • 95% of fats in body are triacylglycerols • Saturated fat: fatty acids have single covalent bonds • Unsaturated fat: fatty acids have one or more double covalent bonds • Functions: energy, insulation and protection
Proteins • Contain carbon, oxygen, hydrogen, nitrogen and sulfur • Amino acids are building blocks of proteins • Functions: energy and structure • Enzymes: protein catalysts for chemical reactions
Proteins (cont’d.) • Structure • Primary: amino acid sequence • Secondary: determined by hydrogen bonds • Tertiary: folding caused by interactions within peptide bonds and sulfur atoms • Quaternary: determined by spatial relationships between units
Nucleic Acids • Deoxyribonucleic acid: genetic material of the cell • Ribonucleic acid: protein synthesis • Messenger RNA • Transfer RNA
Nucleic Acids (cont’d.) • Structure • DNA: double helical chain • RNA: single chain
Nucleic Acids (cont’d.) • Nucleic acids are made up of chains of nucleotides • Nucleotide: nitrogen base, sugar and phosphate group • Nitrogen bases: purines (two) and pyrimidines (three)
Adenosine Triphosphate • Fuel for cell function and maintenance • Molecule consists of sugar, adenine, and three phosphates • Energy is stored in the second and third phosphates • Breakdown of glucose provides energy to make ATP
Introduction • Plasma membrane is selectively permeable • Only selected materials can enter and exit • This is because of chemical structure • Water can enter and exit with ease
Diffusion • Movement of molecules from area of high concentration to low concentration • Brownian movement: random collision of diffusing molecules • Accelerated by increased temperature • O2 - CO2 exchange is an example of diffusion
Osmosis • Movement of water through semipermeable membrane from high concentration to low concentration • Isotonic solution: salt concentration is the same outside the cell as inside • Hypotonic solution: salt concentration inside cell is higher than outside cell
Osmosis • Movement of water through semipermeable membrane from high concentration to low concentration • Hypertonic solution: salt concentration higher outside the cell than inside
Osmosis (cont’d.) • Active transport • Used by cells to obtain sugars, amino acids, larger proteins and fats • Needs energy in the form of ATP • Molecules move from areas of low concentration to areas of high concentration
pH (cont’d.) • Negative logarithm of hydrogen ion concentration • Acids: pH values below 7 • Bases: pH values above 7 • Buffers: help maintain pH levels
Summary • Discussed basic chemical concepts such as bonds and energy and how they apply to living systems • Discussed specific chemical substances and how they are used in living systems
Summary (cont’d.) • Described three ways that substances move into and out of cells • Introduced pH and acids/bases