Copyright © 2004 Lippincott Williams & Wilkins Chapter 2 Chemistry, Matter, and Life

Copyright © 2004 Lippincott Williams & Wilkins Chemistry Science that deals with composition and properties of matter Used to understand normal and abnormal functioning of body

Copyright © 2004 Lippincott Williams & Wilkins Elements Make up all matter 92 occur in nature Identified by names or chemical symbols (abbreviations of modern or Latin names) Identified by number (based on structure of subunits or atoms) Described and organized in periodic table

Copyright © 2004 Lippincott Williams & Wilkins Atoms Subunits of elements Smallest complete units of matter Cannot be broken down or changed by ordinary chemical and physical means All matter is composed of atoms

Copyright © 2004 Lippincott Williams & Wilkins Atomic Structure Nucleus –Protons (+ charge) –Neutrons (no charge) Electrons (– charge)

Copyright © 2004 Lippincott Williams & Wilkins Representation of the oxygen atom. ZOOMING IN How does the number of protons in this atom compare with the number of electrons? They are equal, indicating that the atom is neutral.

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-1: What are atoms? –They are the smallest complete units of matter; they cannot be broken down or changed by ordinary chemical and physical means Checkpoint 2-2: What are three types of particles found in atoms? –Protons, neutrons and electrons

Copyright © 2004 Lippincott Williams & Wilkins Energy Levels Distances from nucleus where electrons orbit Higher energy levels can hold more electrons Electrons in farthest level give atom its characteristics (positive or negative charge) Valence of element is number of electrons lost or gained by atoms of element in chemical reactions

Copyright © 2004 Lippincott Williams & Wilkins Water Molecule Molecules and Compounds Molecules –Formed when two or more atoms unite on the basis of their electron structures –Can be made of like atoms or atoms of different elements Compounds –Composed of two or more elements –Smallest subunits of a compound

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-3: What are molecules? –A molecule is formed by the union of two or more atoms; it is the smallest unit of a compound.

Copyright © 2004 Lippincott Williams & Wilkins The Importance of Water Most abundant compound in body Critical in all physiologic processes in body tissues Deficiency (dehydration) can threaten health Universal solvent Stable liquid at ordinary temperatures Participates in chemical reactions in body

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-4:What is the most abundant compound in the body? –Water

Copyright © 2004 Lippincott Williams & Wilkins Mixtures: Solutions and Suspensions Solution components Indistinguishable from one another Evenly distributed throughout (homogeneous) Suspension components Separate from solvent Settle out (heterogeneous or non-uniform) Colloid components Separate from solvent Evenly distributed throughout

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-5: Both solutions and suspensions are types of mixtures. What is the difference between them? –Solution contents are evenly distributed throughout (homogeneous) whereas suspension contents separate from solvent and settle out.

Copyright © 2004 Lippincott Williams & Wilkins Chemical Bonds Atoms interact chemically to alter neutrality of atoms and form bonds.

Copyright © 2004 Lippincott Williams & Wilkins Ionic Bonds Electrons transferred between atoms form ionic bonds. Electrolytes— ionic bonds form compounds that release ions when they are in solution –Influence homeostasis (stable condition of normal organism) –Conduct electronic current

Copyright © 2004 Lippincott Williams & Wilkins Ionic bonding.

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-6: What happens when an electrolyte goes into solution? They release ions (charged atoms)

Copyright © 2004 Lippincott Williams & Wilkins Covalent Bonds A chemical bond in which atoms share electrons Non-polar covalent bond Polar covalent bond

Copyright © 2004 Lippincott Williams & Wilkins ZOOMING IN How many electrons are needed to complete the energy level of each hydrogen atom? A nonpolar covalent bond. Two

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-7: How is a covalent bond formed? The bond is formed by sharing electrons between the atoms in the molecule.

Copyright © 2004 Lippincott Williams & Wilkins Compounds: Acids, Bases and Salts Compounds are chemical substances with specific properties Acid can donate hydrogen ion (H+) Base (alkali) can accept hydrogen ion (H+) Salt is formed by a reaction between an acid and a base

Copyright © 2004 Lippincott Williams & Wilkins The pH Scale Represents relative concentrations of hydrogen and hydroxide ions in a solution Scale from 0 (most acidic) to 14 (most basic) Each unit represents a 10-fold change Body fluids usually pH

Copyright © 2004 Lippincott Williams & Wilkins ZOOMING IN What happens to the amount of hydroxide ion (OH – ) present in a solution when the amount of hydrogen ion (H+) increases? The number of hydroxide ions decrease The pH Scale

Copyright © 2004 Lippincott Williams & Wilkins Buffers Chemicals that prevent sharp changes in hydrogen ion concentration and maintain relatively constant pH in body fluids

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-8: The pH scale is used to measure acidity and alkalinity of fluids. What number is neutral on the pH scale? What kind of compound measures lower than this number? Higher? –7.0 is neutral –Acids measure lower than 7.0 –Bases (alkalis) measure higher than 7.0 Checkpoint 2-9: What is a buffer? –A buffer is a chemical that prevents sharp changes in pH. They are important in maintaining the pH of body fluids.

Copyright © 2004 Lippincott Williams & Wilkins Isotopes and Radioactivity Elements can exist in several forms (isotopes). Same number of protons and electrons Different number of neutrons Different atomic weights May be stable or unstable (radioactive)

Copyright © 2004 Lippincott Williams & Wilkins Use of Radioactive Isotopes Radioisotopes are the rays given off by some radioactive elements. Can aid in diagnosis –X-rays –Tracers Can penetrate and destroy cancer cells

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-10: Some isotopes are stable; others break down to give off atomic particles. What word is used to describe isotopes that give off radiation? Radioisotopes

Copyright © 2004 Lippincott Williams & Wilkins Chemistry of Living Matter Living matter contains 26 of 92 natural elements. 96% of body weight—four elements 4% of body weight—nine elements 0.1% of body weight—13 elements

Copyright © 2004 Lippincott Williams & Wilkins Organic Compounds Chemical compounds that characterize living things Contain carbon, hydrogen, and oxygen –Carbohydrates –Lipids –Proteins

Copyright © 2004 Lippincott Williams & Wilkins Chemical composition of the body by weight.

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-11: Where are organic compounds found? In living things Checkpoint 2-12: What element is the basis of organic chemistry? Carbon

Copyright © 2004 Lippincott Williams & Wilkins Carbohydrates Monosaccharides (simple sugars) –Glucose Disaccharides Polysaccharides Starch –Glycogen

Copyright © 2004 Lippincott Williams & Wilkins Examples of carbohydrates. ZOOMING IN What are the building blocks of disaccharides and polysaccharides? Monosaccharides

Copyright © 2004 Lippincott Williams & Wilkins Lipids Triglycerides –Glycerol (glycerin) Phospholipids Steroids –Cholesterol –Steroid hormones –Sex hormones

Copyright © 2004 Lippincott Williams & Wilkins Lipids. ZOOMING IN How many carbon atoms are there in glycerol? 3

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-13: What are the three main categories of organic compounds? Carbohydrates Lipids Proteins

Copyright © 2004 Lippincott Williams & Wilkins Proteins Amino acids are building blocks –Enzymes Catalysts Act on substrates

Copyright © 2004 Lippincott Williams & Wilkins ZOOMING IN What part of an amino acid contains nitrogen? Amino group Proteins

Copyright © 2004 Lippincott Williams & Wilkins ZOOMING IN How does the shape of the enzyme before the reaction compare with its shape after the reaction? Diagram of enzyme action. It’s the same

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 2-14: Enzymes are proteins that act as catalysts. What is a catalyst? Catalysts speed up the rate of chemical reactions; the names of catalysts usually end with –ase.