Lecture 2 NatSci II Josephine B. Guerrero, MD Asst. Professor, Department of Biology

Chemistry of LifeLecture 2 NatSci II

Josephine B. Guerrero, MD

Asst. Professor, Department of Biology

Concepts: Matter – anything that has mass and

occupies space Atomic theory – all elements are composed

of atoms; each element with a unique number of electrons, protons and neutrons

Elements – simplest form that cannot be broken down further

Compounds – composed of two or more elements joined by a chemical bond

Chemical Bonds

1. Covalent bonds

2. Hydrogen bonds

3. Ionic bonds

4. Electrostatic bonds

Elements found in living systems

What is the difference between organic and inorganic molecules?

Inorganic Molecules – made up of elements except C

Organic Molecules – made up of C except CO and CO2

Acids, Bases and Buffers Acids – release H+; proton donors

Bases – release OH-; proton acceptors

Salt – product of neutralization process between an acid and a base

Buffers – substances that help resist changes in pH; mixture of a weak acid and its conjugate base or a weak base and its conjugate acid

[H+] pH Example

Acids

1 X 100 0 HCl

1 x 10-1 1 Stomach acid

1 x 10-2 2 Lemon juice

1 x 10-3 3 Vinegar

1 x 10-4 4 Soda

1 x 10-5 5 Rainwater

1 x 10-6 6 Milk

Neutral 1 x 10-7 7 Pure water

Bases

1 x 10-8 8 Egg whites

1 x 10-9 9 Baking soda

1 x 10-10 10 Tums® antacid

1 x 10-11 11 Ammonia

1 x 10-12 12Mineral lime - Ca(OH)2

1 x 10-13 13 Drano®

1 x 10-14 14 NaOH

CO2 + H2O [H2CO3] H+ + HCO3-

produced by metabolism

always available

in equilibrium

with species on either

side

produced by metabolism

pre-existing blood buffer

directly expelled in

lung

adjusted in kidney via physiologic mechanisms unrelated

to pH

converted to products on

left by carbonic

anhydrase (RBC)

adjusted in kidney or

reacts with bicarbonate to

make products on

left

adjusted in kidney or

reacts with H+ to make products on

left

Biomolecules:

Carbohydrate

Lipids

Proteins

Nucleotides

Carbohydrates

Simple sugars or monosaccharides forming long chains of polysaccharides

Ranges from a 4C, 5C or 6C monosaccharide

Useful as an energy source: glucose

Lipids

Also known as fatty acids; composed of a glycerol molecule with three fatty acid chains

Saturated vs. unsaturated fatty acid

Useful as a energy storage material and heat insulation

Proteins

Composed of amino acids connected together by peptide bond

Either a structural molecule or one with enzymatic functions

1o, 2o, 3o, 4o forms

Primary Form

Secondary Form

Tertiary Form

Nucleic Acids

Building blocks: nucleotides Form the genetic material of living systems DNA or RNA In eukaryotic systems, dsDNA are coiled

around histone proteins which become visible during cell division as chromosomes

Nucleotide molecule

Central Dogma of Genetics