copyright © 2004 lippincott williams & wilkins chapter 2 chemistry, matter, and life
TRANSCRIPT
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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.