Chemistry, Matter, and Life Chapter 2 Chemistry, Matter, and Life

Chemistry Science that deals with composition and properties of matter Used to understand normal and abnormal functioning of body

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

Atoms Subunits of elements Smallest complete units of matter Cannot be broken down or changed by ordinary chemical and physical means

Atomic Structure Nucleus Protons (+ charge) Neutrons (no charge) Electrons (– charge)

Representation of the oxygen atom. ZOOMING IN • How does the number of protons in this atom compare with the number of electrons?

Checkpoint 2-1: What are atoms? Checkpoint 2-2: What are three types of particles found in atoms?

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

Molecules and Compounds 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

Checkpoint 2-3: What are molecules?

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

Checkpoint 2-4:What is the most abundant compound in the body?

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 Evenly distributed throughout

Checkpoint 2-5: Both solutions and suspensions are types of mixtures Checkpoint 2-5: Both solutions and suspensions are types of mixtures. What is the difference between them?

Chemical Bonds Atoms interact chemically to alter neutrality of atoms and form bonds.

Ionic bonding.

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

Checkpoint 2-6: What happens when an electrolyte goes into solution?

Covalent Bonds A chemical bond in which atoms share electrons Non-polar covalent bond Polar covalent bond

Checkpoint 2-7: How is a covalent bond formed?

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

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 7.35-7.45 pH

The pH scale. ZOOMING IN • What happens to the amount of hydroxide ion (OH–) present in a solution when the amount of hydrogen ion (H1) increases?

Buffers Chemicals that prevent sharp changes in hydrogen ion concentration and maintain relatively constant pH in body fluids

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? Checkpoint 2-9: What is a buffer?

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)

Use of Radioactive Isotopes Radioisotopes are the rays given off by some radioactive elements. Can penetrate and destroy cancer cells Can aid in diagnosis X-rays Tracers

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?

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

Organic Compounds Chemical compounds that characterize living things Contain carbon, hydrogen, and oxygen Carbohydrates Lipids Proteins

Checkpoint 2-11: Where are organic compounds found? Checkpoint 2-12: What element is the basis of organic chemistry?

Carbohydrates Monosaccharides (simple sugars) Glucose Disaccharides Polysaccharides Starch Glycogen

Examples of carbohydrates. ZOOMING IN • What are the building blocks of disaccharides and polysaccharides?

Lipids Triglycerides Glycerol (glycerin) Phospholipids Steroids Cholesterol Steroid hormones Sex hormones

Lipids. ZOOMING IN • How many carbon atoms are there in glycerol?

Checkpoint 2-13: What are the three main categories of organic compounds?

Proteins Amino acids Enzymes Catalysts Substrates

Proteins. ZOOMING IN • What part of an amino acid contains nitrogen?

Diagram of enzyme action. ZOOMING IN • How does the shape of the enzyme before the reaction compare with its shape after the reaction?

Checkpoint 2-14: Enzymes are proteins that act as catalysts Checkpoint 2-14: Enzymes are proteins that act as catalysts. What is a catalyst?