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)

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