What is the chemical basis of life?

• What are some of the ideas central to the chemistry of life?

• (Key concepts of the chemical basis of life)

How does water do all this?What allows water to facilitate life at the

cellular and global level?

Hydrogen Bonds

• A weak force of attraction between the H on one molecule and a highly electronegative atom on another molecule

Extraordinary Properties of Water

• Versatile Solvent-------due to polarity

• Adhesion and Cohesion---due to H bonds

• High Specific Heat --------due to H bonds

• High Heat of Vap. ---------due to H bonds

• Expands when freezing ---due to H bonds

Ideas central to the chem of life

• Based on covalent bonding• Carbon is the “backbone” of biomolecules• Simple building code• Variation on common theme in extreme• Only 4 fundamental types of biomolecules• Enzymes make and break the covalent bonds in

the chemical reactions in the cell• Isomers and polymers• Condensation and Hydrolysis

Famous ions in Biology

• Hydronium H3O+ and Hydroxide OH-

• Potassium K+ ions

• Sodium Na+ ions

• Calcium Ca2+ ions

• Hydrogen H+ ions (protons)

pH SCALEpH SCALE

• measures degree of measures degree of alkalinity or acidity alkalinity or acidity

• Ranges from Ranges from 0 to 140 to 14

• 0 – 6 acid0 – 6 acid

• 7 neutral7 neutral

• 8-14 base8-14 base

ACIDS & BASESACIDS & BASES

• Acids: always (almost) begin with "H" Acids: always (almost) begin with "H" because of the excess of H+ ions (hydrogen)because of the excess of H+ ions (hydrogen)

– Ex: lemon juice (6), stomach acid (1.5), acid rain Ex: lemon juice (6), stomach acid (1.5), acid rain (4.5), normal rain (6)(4.5), normal rain (6)

• Facts about AcidsFacts about Acids

• Acids usually taste Acids usually taste SOUR/BITTERSOUR/BITTER. .

• You eat acids daily (coffee, vinegar, soda, You eat acids daily (coffee, vinegar, soda, spicy foods, etc…)spicy foods, etc…)

ACIDS & BASESACIDS & BASES• Bases: always (almost) end with -OH because Bases: always (almost) end with -OH because

of the excess of hydroxide ions (Oxygen & of the excess of hydroxide ions (Oxygen & Hydrogen)Hydrogen)

– EX: oven cleaner, bleach, ammonia, sea water, EX: oven cleaner, bleach, ammonia, sea water, bloodblood

• Facts about BasesFacts about Bases

• Bases usually feel Bases usually feel SLIPPERYSLIPPERY to touch and to touch and taste taste BITTERBITTER. .

Elements Essential to Life

• About 25 of the 92 natural occurring elements are essential to life

• CHON = 96% liv mat• CHONPS = > 99%

Review of Chemical Equation

Example:

H2O + CO2 H2CO3

reactants products

A continuum view of bonding

• Atoms complete their valence shell in a continuum of:

• Nonpolar covalent with equal sharing of e-– Examples: H—H O = O

• Polar covalent, unequal sharing of e-– Examples: H2O NH3

• Ionic, with complete transfer of e-– Examples: NaCl Al2O3

Weak Bonds are Bio’ly Important

• H bonds, hydrophobic interactions, etc

• Can form between different parts of a single large molecule or between molecules

• Help stabilize 3D shape of proteins & Nas

• Function in chemical signaling

• Hold enzymes to substrates

Biological Building Codes

• Covalent Bond= shared pair of electrons between 2 nonmetals

• H, 1 unpaired e-• O, 2 unpaired e-• N, 3 unpaired e-• C, 4 unpaired e-

Versatility of Carbon

• 4 valence electrons• Compatibility with many

different elements• Forms single, double or

triple bonds• Makes large, complex

molecules possible– Strait chains– Branched chains– Rings

• (poly = many; mer = part)• Large molecules

consisting of many similar subunits connected together

• Monomer = subunit or building block of polymer

Macromolecules are Polymers

• Carbohydrates = polymer of monosaccharides

• Lipids = polymer of fatty acids & glycerol

• Proteins = polymer of amino acids

• Nucleic Acids = polymer of nucleotides

Polymers & Molecular Diversity

• Unity in life: Only about 40 or 50 common monomers build macromolecules

• Diversity in life: New properties emerge when these monomers are arranged in different ways

Sucrose Synthesis

Hydrolysis

Making & Breaking Polymersanimation

• Dehydration synthesis• Link monomers

• Via removal of H2O

• 1 water per link (out)• One monomer lose

OH, other loses H• Any assembling of

molecules in cells

• Hydrolysis• Disassemble polymers

• Via addition of H2O

• 1 water per link (in)• One monomer gains

OH, other gains H• Any disassembly of

molecules in cells