The Chemical Basis of Life Chapter 2 REVIEW The Chemical Basis of Life

Basic Chemistry-Review Matter, Mass, and Weight Matter: Anything that occupies space and has mass (liquid, solid or gas) Mass: The amount of matter in an object Weight: The gravitational force acting on an object of a given mass Elements and Atoms Elements: The simplest type of matter with unique chemical properties Atoms: Smallest particle of an element that has chemical characteristics of that element

Atomic Structure Atoms: composed of subatomic particles Nucleus Neutrons: no electrical charge Protons: positive charge Electrons: negative charge Nucleus Formed by protons and neutrons Most of volume of atom occupied by electrons

Atomic Number and Mass Number Atomic Number: Equal to number of protons in each atom which equals the number of electrons Mass Number: Number of protons plus number of neutrons

Isotopes and Atomic Mass Isotopes: Two or more forms of same element with same number of protons and electrons but different neutron number (important in medical imaging) 3 types of hydrogen Denoted by using symbol of element preceded by mass number as 1H, 2H, 3H Atomic Mass: Average mass of naturally occurring isotopes

Electrons and Chemical Bonding Ion: When an atom loses or gains electrons and become charged Cation: Positively charged ion Anion: Negatively charged ion Ionic Bonding Cations and anions are attracted to each other

Covalent Bonding Atoms share one or more pairs of electrons Single covalent: Share one pair of electrons Double covalent: Share two pairs of electrons Nonpolar covalent: Electrons shared equally (Methane- CH4) Polar covalent: Electrons shared unequally (Water-H2O)

Molecules and Compounds Molecules: Two or more atoms (same or different) chemically combined to form an independent unit Examples: H2, H2O Compounds: A substance composed of two or more different types of atoms chemically combined Example: Glucose (C6H12O6) Molecular Mass: Determined by summing atomic masses of its atoms or ions Example: NaCl (22.99 + 35.45)

Intermolecular Forces Result from weak electrostatic attractions between oppositely charged parts of molecules, or between ions and molecules Weaker than forces producing chemical bonding

Intermolecular Forces Hydrogen Bonds Water: Positively charged hydrogen atoms bond with negatively charged oxygen atoms of other water molecules Important role in determining shape of complex molecules

Intermolecular Forces Solubility: Ability of one substance to dissolve in another Example: Sugar dissolves in water Dissociation or Separation Ionic compounds in water Cations are attracted to negative end and anions attracted to positive end of water molecules

Intermolecular Forces Electrolytes: Cations (+) and anions (-) that dissociate in water Capacity to conduct an electric current Currents can be detected by electrodes Nonelectrolytes: Molecules that do not dissociate form solutions that do not conduct electricity

Chemical Reactions & Energy Chemical Reactions: Atoms, ions, molecules or compounds interact to form or break chemical bonds Metabolism: An organism’s total chemical reactions. Managing the material and energy resources of a cell Examples: Catabolism Anabolism

Chem. Reactions & Energy (continued) Catabolism: Decomposition reactions that break down molecules into smaller parts Hydrolysis: Reactions that use water to decompose Anabolism: Build complicated molecules from simpler ones for growth, maintenance, and repair of the body Synthesis reactions: Produce molecules characteristic of life - ATP, proteins, carbohydrates, lipids, and nucleic acids

Synthesis and Decomposition Reactions Synthesis Reactions Two or more reactants chemically combine to form a larger product Anabolism: All body’s synthesis reactions Decomposition Reactions Reverse of synthesis reactions Catabolism: Reactions of decomposition in body

Oxidation-Reduction Reactions Loss of an electron by an atom Reduction Gain of an electron by an atom Oxidation-Reduction Reactions The complete or partial loss of an electron by one atom is accompanied by the gain of that electron by another atom

Energy Energy: The capacity to do work Potential Energy: Stored energy Kinetic Energy: Does work and moves matter Mechanical Energy: Energy resulting from the position or movement of objects Chemical Energy: Form of potential energy in the chemical bonds of a substance Heat Energy: Energy that flows between objects of different temperatures

Energy and Chemical Reactions

Speed of Chemical Reactions Activation Energy: Minimum energy reactants must have to start a chemical reaction Catalysts: Substances that increase the rate of chemical reactions without being permanently changed or depleted Enzymes: Biological catalysts – proteins that increase the rate of chemical reactions by lowering the activation energy necessary for reaction to begin

Activation Energy and Enzymes

Chemistry Inorganic Chemistry: Substances that do not contain carbon Water Oxygen Organic Chemistry: Study of carbon-containing substances

Water (The most abundant substance in the human body) Inorganic Stabilizes body temperature Protection Necessary for many chemical reactions of life Mixing Medium Mixture: Substance physically but not chemically combined Solution: Liquid, gas, or solid uniformly distributed Solvent: What dissolves the solute Solute: What is to be dissolved

Acids and Bases; Salts and Buffers Acid: A proton donor or any substance that releases hydrogen ions (H+) (HCL- H+ + Cl-) Bases: A proton acceptor or any substance that binds to or accepts hydrogen ions (OH-) (NaOH- Na+ + OH- ) Salts: An ionic compound consisting of a cation other than a hydrogen ion and an anion other than a hydroxide ion (NaCl) Buffers: A solution of a conjugate acid-base pair in which the acid and base components occur in similar concentrations (maintain body pH at ~ 7.4)

Buffer systems in the body- Homeostasis -near neutral pH (~7.4) in the body prevent large changes in acidity or alkalinity in the human body weak acids Ex. carbonic acid (H2CO3) H2CO3 H+ + HCO3+ weak bases Ex. bicarbonate ion (HCO3-) NaHCO3 HCL + NaHCO3 NaCl + H2CO3 (strong acid) (weak acid) NaOH + H2CO3 NaHCO3 + H2O (strong base) (weak base) Other buffers: phosphates, amino acids, proteins (most abundant)

The pH Scale Refers to the Hydrogen ion concentration in a solution Neutral: pH of 7 or equal hydrogen and hydroxide ions Acidic: a greater concentration of hydrogen ions Alkaline or basic: a greater concentration of hydroxide ions

Organic Chemistry Carbohydrates Lipids Proteins Composed of carbon, hydrogen, oxygen Lipids Composed mostly of carbon, hydrogen, oxygen, phosphorus, nitrogen Proteins Composed of carbon, hydrogen, oxygen, nitrogen, and sulfur Nucleic Acids: DNA and RNA Composed of carbon, hydrogen, oxygen, nitrogen, phosphorus Adenosine Triphosphate (ATP) Composed of adenosine and three phosphate groups

Carbohydrates Monosaccharides Disaccharides Polysaccharides Simple sugars: glucose, fructose, galactose Trioses, tetroses, pentoses, or hexoses Disaccharides Two simple sugars bound together by dehydration: sucrose, lactose, maltose Polysaccharides Long chains of many monosaccharides: glycogen in animals; starch and cellulose in plants

Monosaccharides

Disaccharide and Polysaccharide

Lipids Lipids: Can be dissolved in nonpolar organic solvents such as alcohol but relatively insoluble in water Fats: Ingested and broken down by hydrolysis Triglycerides: 95% of fats in the human body - composed of glycerol and fatty acids Phospholipids: Important structural component of cell membranes Eicosanoids: Importatnt regulatory molecules derived from fatty acids Steroids: Cholesterol, bile salts, estrogen, testosterone Fat-soluble Vitamins: Vitamin E

Fats (triglycerides/neutral fats) 1 glycerol + 3 fatty acids Differ- length and saturation of of carbon chains ( usually 14-18 carbon chains) Saturated fats- no double bonds between carbon atoms; animal foods - unhealthy Unsaturated fats- one or more double bonds between carbon atoms (mono/poly) – do not contribute to development of cardiovascular disease. Vegetable oils, fish oils, and olive (monounsaturated) oil. Functions Source of long-term energy; not metabolized efficiently Protection by surrounding and padding organs Insulation to prevent heat loss

Phospholipids-Cell membranes)

Steroids

Proteins Amino acids: The building blocks of protein Peptide bonds: Covalent bonds formed between amino acids during protein synthesis Structure Primary, secondary, tertiary, quaternary Enzymes: Protein catalysts Lock-and-key model Active site Cofactors – Non-protein substances necessary for some enzymes. Can be an ion or an organic molecule. Coenzymes – Organic cofactors such as certain vitamins

Peptide Bonds

Proteins Most complex and varied physiological molecules Diversity- Amino acids A+B+C+D = polypeptide A A+B+E+D = polypeptide B Denaturation- Proteins influenced by changes in temperature, pH, salt concentrations. Such changes result in nonfunctional protein.

Protein Structure and Enzyme Action

Nucleic Acids: DNA and RNA Two Types of Nucleic Acids DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid) Both DNA and RNA consist of basic building blocks called nucleotides Each nucleotide is a pentose sugar, phosphate group, and a nitrogenous base Two groups of nitrogenous bases: pyrimidines and purines Pyrimidines are cytosine (DNA & RNA), thymine (DNA only), and uracil (RNA only). Purines are guanine and adenine (both in DNA and RNA)

Nucleic Acids: DNA and RNA DNA: Deoxyribonucleic acid Genetic material of cells copied from one generation to next Contains the information that determines the structure of proteins Composed of 2 strands of nucleotides called the double helix Each nucleotide contains deoxyribose as the pentose sugar and one of the organic bases: adenine, guanine, thymine, or cystosine.

Nucleic Acids: DNA and RNA RNA: Ribonucleic acid Functions in protein synthesis Three types of RNA: mRNA, tRNA, and rRNA Similar to a single strand of DNA Pentose sugar is ribose Same nitrogenous bases as DNA except thymine is replaced with uracil

DNA Structure

Nucleotides and Nitrogenous Bases

Adenosine Triphosphate (ATP) Energy currency of the body Provides energy for chemical reactions such as anabolism or to drive cellular processes such as muscle contraction All energy-requiring chemical reactions stop when there is inadequate ATP