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Chapter 2Chemistry, Matter, Chemistry, Matter,

and Lifeand Life

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ChemistryChemistry

• Science that deals with composition and properties of matter

• Used to understand normal and abnormal functioning of body

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ElementsElements

• 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

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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

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Atomic Structure

• Nucleus– Protons (+ charge)– Neutrons (no charge)

• Electrons (– charge)

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• 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.

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• 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

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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

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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

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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.

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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

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

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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

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• 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.

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Chemical BondsChemical Bonds

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

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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

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Ionic bonding.

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

They release ions (charged atoms)

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Covalent Bonds

• A chemical bond in which atoms share electrons

• Non-polar covalent bond

• Polar covalent bond

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ZOOMING IN • How many electrons are needed to complete the energy level of each hydrogen atom?

A nonpolar covalent bond.

Two

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

• The bond is formed by sharing electrons between the atoms in the molecule.

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Compounds: Acids, Compounds: Acids, Bases and SaltsBases 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

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The pH ScaleThe 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

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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

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Buffers

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

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• 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.

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Isotopes and RadioactivityIsotopes 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)

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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

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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

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Chemistry of Living MatterChemistry 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

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Organic Compounds

• Chemical compounds that characterize living things

• Contain carbon, hydrogen, and oxygen– Carbohydrates– Lipids– Proteins

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Chemical composition of the body by weight.  

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Checkpoint 2-11: Where are organic compounds found?• In living things

Checkpoint 2-12: What element is the basis of organic chemistry?

• Carbon

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Carbohydrates

• Monosaccharides (simple sugars)– Glucose

• Disaccharides

• Polysaccharides

• Starch– Glycogen

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

Monosaccharides

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Lipids

• Triglycerides – Glycerol (glycerin)

• Phospholipids

• Steroids– Cholesterol– Steroid hormones– Sex hormones

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

3

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

compounds?

• Carbohydrates

• Lipids

• Proteins

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Proteins

• Amino acids are building blocks– Enzymes

• Catalysts• Act on substrates

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

Amino group

Proteins

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ZOOMING IN • How does the shape of the enzyme before the reactioncompare with its shape after the reaction?

Diagram of enzyme action.

It’s the same

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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.