THE PROCESS OF SCIENCE –What is science? –The word science is derived from a Latin verb meaning “to know.” Discovery Science Science seeks natural causes for natural phenomena. –This limits the scope of science to the study of structures and processes that we can observe and measure. As a formal process of inquiry, consists of a series of steps. –The key element of the scientific method is hypothesis-driven science. Hypothesis-Driven Science

–As a formal process of inquiry, the scientific method consists of a series of steps. The key element of the scientific method is hypothesis-driven science. ObservationQuestionHypothesisPredictionExperiment Revise and repeat Figure UN1-4

Observation: My flashlight doesn’t work. Question: What’s wrong with my flashlight? Prediction: If I replace the batteries, the flashlight will work. Experiment: I replace the batteries with new ones. Experiment supports hypothesis; make additional predictions and test them. Hypothesis: The flashlight’s batteries are dead. Hypothesis-Driven Science

Theories in Science –What is a scientific theory, and how is it different from a hypothesis? A theory is much broader in scope than a hypothesis. Theories only become widely accepted in science if they are supported by an accumulation of extensive and varied evidence.

Chemistry of Life –Matter is anything that occupies space and has mass. –Matter is found on the Earth in three physical states: Solid Liquid Gas

Atoms Nucleus Protons Neutrons Electrons Nucleus Cloud of negative charge  2 electrons  –Each element consists of one kind of atom. An atom is the smallest unit of matter that still retains the properties of an element.

–Matter is composed of chemical elements. Elements are substances that cannot be broken down into other substances. Chemistry of Life Change the number of PROTONS in the nucleus and you change the ELEMENT

–Elements differ in the number of subatomic particles in their atoms. The number of protons, the atomic number, determines which element it is. An atom’s mass number is the sum of the number of protons and neutrons. Mass is a measure of the amount of matter in an object. Chemistry of Life

Periodic Table of the Elements Atomic number = number of protons within the nucleus Other nonmetals Halogens Noble gases Other metals Rare earth metals Transition metals Alkali earth metals Alkali metals Synthetic Gas Liquid Solid Legend

Chemistry of Life Carbon  C  : 18.5% Hydrogen  H  : 9.5% Nitrogen  N  : 3.3% Calcium  Ca  : 1.5% Trace elements: less than 0.01% Boron  B  Manganese  Mn  Oxygen  O  : 65.0% Magnesium  Mg  : 0.1% Phosphorus  P  : 1.0% Potassium  K  : 0.4% Sulfur  S  : 0.3% Sodium  Na  : 0.2% Chlorine  Cl  : 0.2% Cobalt  Co  Chromium  Cr  Iron  Fe  Iodine  I  Fluorine  F  Copper  Cu  Silicon  Si  Zinc  Zn  Vanadium  V  Tin  Sn  Molybdenum  Mo  Selenium  Se  –Twenty-five elements are essential to life. –Four elements make up about 96% of the weight of the human body: Oxygen Carbon Hydrogen Nitrogen

First electron shell  can hold 2 electrons  Outer electron shell  can hold 8 electrons  Hydrogen  H  Atomic number = 1 Carbon  C  Atomic number = 6 Nitrogen  N  Atomic number = 7 Oxygen  O  Atomic number = 8 Electron Chemical Properties of Atoms –Electrons determine how an atom behaves when it encounters other atoms. © 2010 Pearson Education, Inc.

Covalent Bonds –A covalent bond forms when two atoms share one or more pairs of outer-shell electrons. –Atoms held together by covalent bonds form a molecule. Name  molecular formula  Hydrogen gas  H 2  Oxygen gas  O 2  Methane  CH 4  Electron configurationStructural formulaSpace-filling modelBall-and-stick model Single bond  a pair of shared electrons  Double bond  two pairs of shared electrons 

Ionic Bonds –When an atom loses or gains electrons, it becomes electrically charged. Charged atoms are called ions. Ionic bonds are formed between oppositely charged ions. Outer shell has 1 electron Outer shell has 7 electrons The outer electron is stripped from sodium and completes the chlorine atom’s outer shell Na Sodium atom Cl Chlorine atom Complete outer shells The attraction between the ions—an ionic bond—holds them together Na  Sodium ion Cl  Chlorine ion Sodium chloride (NaCl)

Hydrogen Bonds –Water is a compound in which the electrons in its covalent bonds are shared unequally. This causes water to be a polar molecule, one with opposite charges on opposite ends. HH O  slightly   slightly – 

Hydrogen bonding Weak bonds formed between hydrogen and another atom –Surface tension of water Important as intramolecular bonds, giving shape to proteins and other biomolecules

WATER AND LIFE –Life on Earth began in water and evolved there for 3 billion years. Modern life remains tied to water. Your cells are composed of 70%–95% water.

Properties of Water Numerous properties due to the hydrogen bonding

Properties of Water Microscopic tubes Cohesion due to hydrogen bonds between water molecules Evaporation from the leaves SEM Flow of water –Water molecules stick together as a result of hydrogen bonding. This is called cohesion.

–Heat and temperature are related, but different. Heat is the amount of energy associated with the movement of the atoms and molecules in a body of matter. Temperature measures the intensity of heat. –Water can absorb and store large amounts of heat while only changing a few degrees in temperature. –Water can moderate temperatures. Properties of Water

–Surface tension is the measure of how difficult it is to stretch or break the surface of a liquid. Hydrogen bonds give water an unusually high surface tension. Properties of Water

*solution *solvent *solute *aqueous solution Water is the solvent of life

Basic solution Neutral solution Acidic solution Oven cleaner Household bleach Human blood Pure water Grapefruit juice, soft drink Lemon juice, gastric juice Household ammonia Milk of magnesia Seawater Tomato juice Urine pH scale Increasingly acidic  greater H  concentration  Increasingly basic  lower H  concentration  Neutral [ H + ]  [ OH – ] Acids, Bases and pH

Carbon and Organic Chemistry –Carbon is a versatile atom. –Carbon forms large, complex, and diverse molecules necessary for life’s functions. –Organic compounds are carbon-based molecules. Structural formula Ball-and-stick model Space-filling model

Variations in Carbon skeletons Carbon skeletons vary in length Carbon skeletons may be unbranched or branched Carbon skeletons may have double bonds, which can vary in location Carbon skeletons may be arranged in rings Carbon and Organic Chemistry

–Larger hydrocarbons form fuels for engines. –Hydrocarbons of fat molecules fuel our bodies. Hydrocarbons

The unique properties of an organic compound depend not only on its carbon skeleton but also on the atoms attached to the skeleton –These atoms are called functional groups –Some common functional groups include: Hydroxyl groupCarbonyl groupAmino groupCarboxyl group Found in alcohols and sugars Found in sugars Found in amino acids and urea in urine (from protein breakdown) Found in amino acids, fatty acids, and some vitamins Carbon and Organic Chemistry

Macromolecules –On a molecular scale, many of life’s molecules are gigantic, earning the name macromolecules. –Three categories of macromolecules are Carbohydrates Proteins Nucleic acids

*most macromolecules are polymers polymer monomer The making and breaking of polymers: Dehydration reaction:Hydrolysis: Macromolecules

Carbohydrates include Carbohydrates –Small sugar molecules in soft drinks Monosaccharides & Disaccharides –Long starch molecules in pasta and potatoes Polysaccharides

Monosaccharides are simple sugars Monosaccharides –Glucose, found in sports drinks –Fructose, found in fruit Honey contains both glucose and fructose Glucose Fructose Isomers

In aqueous solutions, monosaccharides form rings (a) Linear and ring structures (b) Abbreviated ring structure Monosaccharides

A disaccharide is a double sugar Disaccharides Disaccharides are joined by the process of dehydration synthesis Glucose Maltose

The most common disaccharide is sucrose, common table sugar –It consists of a glucose linked to a fructose –Sucrose is extracted from sugar cane and the roots of sugar beets Disaccharides

Polysaccharides (a) Starch Starch granules in potato tuber cells Glucose monomer (b) Glycogen Glycogen Granules In muscle tissue (c) Cellulose Cellulose molecules Cellulose fibril in a plant cell wall –They are long chains of sugar units –They are polymers of monosaccharides

Most animals cannot derive nutrition from fiber –How do grazing animals survive on a diet of cellulose? Polysaccharides

Proteins Proteins perform most of the tasks the body needs to function –They are the most elaborate of life’s molecules MAJOR TYPES OF PROTEINS Structural ProteinsStorage Proteins Contractile ProteinsTransport ProteinsEnzymes

All proteins are constructed from a common set of 20 kinds of amino acids The Monomers: Amino Acids Amino group Carboxyl group Side group

Carboxyl group Amino group Side group Side group Amino acid Dehydration synthesis Side group Side group Peptide bond Cells link amino acids together by dehydration synthesis Proteins as Polymers –The resulting bond between them is called a peptide bond

Primary structure –The specific sequence of amino acids in a protein Amino acid –The arrangement of amino acids makes each protein different Protein Structure

A slight change in the primary structure of a protein affects its ability to function –The substitution of one amino acid for another in hemoglobin causes sickle-cell disease (a) Normal red blood cellNormal hemoglobin (b) Sickled red blood cellSickle-cell hemoglobin Protein Structure

Proteins have four levels of structure Hydrogen bond Pleated sheet Amino acid (a) Primary structure Hydrogen bond Alpha helix (b) Secondary structure Polypeptide (single subunit) (c) Tertiary structure Complete protein, with four polypeptide subunits (d) Quaternary structure Protein Structure