BIOLOGIC CHEMISTRY

Chapter 2 – Part 1The Chemistry of Life

CP BiologyPaul VI Catholic High School

BIOLOGIC CHEMISTRYNATURE OF MATTER:

ATOMS: “Basic unit of matter”

An atom is the smallest portion of a substance that still retains the unique properties of that substance.

• PROTONS: Positive charge (1.009 DALTONS)

• NEUTRONS: No Charge (1.007 DALTONS)

• ELECTRONS: Negative charge (1/1840 DALTONS)

1 DALTON = 1.66054X10-24 kilograms

(1/12 the mass of Carbon)

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NUCLEUS:• CENTER OF ATOM• CONTAINS PROTONS AND NEUTRONS

ORBITALS:• CONTAIN ELECTRONS

In a neutral atom, the number of protons equals the number of electrons

BIOLOGIC CHEMISTRYELECTRON CONFIGURATION:

ENERGY LEVELS CONTAIN:2, 8, 18, 32 electrons

ENERGY SUBLEVELS:s level: 2 electronsp level: 6 electronsd level: 10 electronsf level: 14 electrons

Periodic chart (including Bohr models)

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• Periodic means repeating in a pattern

The Periodic Table of Elements

…is the arrangement of elements according to repeating changes in properties .

• The boxes for the elements are arranged in order of their atomic numbers.

• Vertical columns are groups or families.• Horizontal rows are called periods.

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ELEMENT:Atomic Number = protons Atomic Mass = protons + neutrons

ISOTOPES:Vary in number neutronsSame Chemical PropertiesSome Radioactive

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Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 2 Atoms and Molecules: The Chemical Basis of Life

Carbon Isotopes

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RADIOACTIVE DECAY:α wavesβ wavesγ waves

CARBON DATING:“Half-Life” 5600 years

BIOLOGIC CHEMISTRYCHEMICAL COMPOUNDS:

Substances formed by the combination of two or more different elements in a fixed ratio. They are “pure” substances.

MOLECULE:

Smallest unit of covalently bonded compound.

BIOLOGIC CHEMISTRY A chemical formula uses the symbols for the elements in the compound.

Na + Cl → NaCl

Some formulas include subscripts to show ratios of more than one atom.

2 H + 1 O → H20

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CHEMICAL FORMULA: Shorthand expression describing chemical composition

SIMPLEST FORMULA CaN2O6

(Empirical Formula)

MOLECULAR FORMULA Ca(NO3)2

STRUCTURAL FORMULA

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BIOLOGIC CHEMISTRYCHEMICAL BONDS:

Bond energy is the energy necessary to break a chemical bond.

• COVALENT BOND • holds molecule together by sharing electrons

• IONIC BOND • holds molecule together by transfer of electrons

• VAN DER WAALS FORCES • temporary dipole attraction between molecules • Results in higher boiling points

• HYDROGEN BONDS• Attraction between molecules with partially positive

and partially negative areas

Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 2 Atoms and Molecules: The Chemical Basis of Life

Covalent bonds

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Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 2 Atoms and Molecules: The Chemical Basis of Life

Ionic bonding

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Hydrogen

Bonding

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• Hydrogen bonds- partially positive charged “H”end of a molecule is attracted to partially negative charged end of another molecule

BIOLOGIC CHEMISTRYCHEMISTRY OF WATER:

ATOMIC STRUCTURE:10 Protons10 ElectronsCovalent BondPolar Structure

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PROPERTIES OF WATER:1.COHESION: Attraction between molecules of the same substance.

2. ADHESION: Attraction between different substances.

3. HIGH SPECIFIC HEAT: 1Cal./gm/oC

4. HIGH HEAT OF VAPORIZATION: (Heat energy required to change 1 gm. liquid water to gas.)

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SOLUTION: Homogeneous (uniform) mixture of a liquid.

solvent- dissolving agentsolute- substance that is dissolvedaqueous solution- solution with water as solvent

MIXTURE: Substance composed of two or more elements or compounds that are together BUT are not chemically combined.

SUSPENSION: Composed of nonpolar molecules in water. Water acts to exclude them.

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BIOLOGIC CHEMISTRYCOLLOIDS: Heterogeneous mixtures containing particles intermediate in size between suspensions and solutions.

TYNDALL EFFECT – light scattering effect in colloids

BIOLOGIC CHEMISTRYACID / BASE / pH

pH: (“pouvoir hydrogene”)

Calculated from the spontaneous dissociation of water

Negative logarithm of the [H+]

Each change in a pH unit is a tenfold change in concentration

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ACIDS:

Any substance that dissociates in water to increase the H+ concentration

BASES:

Any substance that dissociates to decrease the H+ concentration.

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Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition CHAPTER 2 Atoms and Molecules: The Chemical Basis of Life

pH valuesof commonsolutions

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BUFFERS:Substance that acts as reservoir for H+.

• Carbonic Acid Buffer System

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