Acid Precipitation

Normal rainfall pH around 5.6– CO2 (atmos) + H2O → H2CO3 carbonic acid

Rain, snow, or fog with a pH lower than pH 5.6– Caused by sulfur oxides, nitrogen oxides in

atmosphere-gaseous compounds which react with water in the air to form strong acids which fall with rain or snow

– Source of oxides-burning of fossil fuels (coal,oil, gas) in factories and automobiles– Winds carry pollutants

Acid Precipitation

Damage to lakes, streams Washes away certain minerals from soil (e.g.

Calcium, Magnesium which help buffer soil and are essential nutrients for plant growth

Other minerals (e.g. aluminum) reach toxic concentrations when acidification increases solubility

Acid Precipitation Upside

Pollution control programs here, Canada, some European countries– Decrease in oxide emissions over several decades– Acid rain has decreased, but recovery is slow

Chemistry of LifeChemistry of Life

Part deuxPart deux

Chemistry of Life Outline

I. Introduction

II. Macromolecules-Large Organic Molecules

A. Carbohydrates

B. Lipids

1. glycerides

2. phospholipids

C. Proteins

D. Nucleic Acids

Inorganic vs. Organic

Inorganic compounds

Organic compounds:

Recall Carbon 6C– 4 electrons in outer shell– Can form up to 4 covalent bonds with other atoms– Recall bonds can be single, double, triple– Often bond with carbon atoms to create chains of carbons

Carbon Chemistry

Hydrocarbons:

Examples: methane-simplest hydrocarbon CH4 Hydrocarbons undergo reactions that release

relatively large amounts of energy Replace a H with a C and the backbone grows,

keep going and you get long chains, branched chains, and ring structures

No polarity to bonds, not soluble in water

Isomers

Functional Groups

Groups of atoms attached to the carbon backbone

Most chemical reactions that occur within organisms involve transferring a functional group from one molecule to another or breaking a carbon-carbon bond

Behave consistently from one organic molecule to the next

Macromolecules

Large organic molecules

3 of these are– Long molecules made up of similar or identical

building blocks linked by covalent bonds– Repeating units are called

Assembly and Disassembly

Chemical mechanism by which cells make and break polymers is the same even though monomers may be different for different macromolecules

Enzymes: special class of proteins which catalyze (speed up) reactions between specific substances

Assembly and Disassembly

Condensation: monomer connection by reaction in which 2 molecules are covalently bonded to each other through loss of H2O (dehydration)

Assembly and Disassembly

Hydrolysis: “water breaking”-polymers broken down into monomers. H from water attaches to one monomer, OH attaches to adjacent monomer

Carbohydrates

Structure– Monosaccharide-– Disaccharide-– Polysaccharide-– C, H, O in 1:2:1 ratio– Examples

Function

Important Carbohydrates

Glucose: C6H12O6 forms ring structure in solution, major nutrient for cells, carbon skeletons serve as raw material for synthesis of other types of small organic molecules– Water soluble– Often linked to form disaccharide for transport

Polysaccharides

Glycogen: storage form of glucose in animals, long chains, highly branched therefore more insoluble in solution. Easily broken down via enzyme catalyzed hydrolysis to glucose

Starch: storage form of glucose in plants

Polysaccharides

Cellulose: also made of glucose monomers but structurally different than starch. Component of tough walls that encase plant cells, not readily broken down

Chitin: structural also, used by crustaceans, insects, spiders to build their exoskeletons–

Lipids

Insoluble in water (polar) but soluble in oil (non-polar)

Types of Lipids:

Many C-H bonds Functions include

Lipids

Built from 2 subunits– Glycerol: 3-C alcohol with 3 OH groups which forms the

backbone of the lipid molecule– Fatty acids: long chains of C-H (often 16-18 carbons long-

hence the insolubility) Saturated: single bonds between carbons, chains lay flat,

decreased reactivity. Solid at room T (lard, butter) Most animal fats

Unsaturated: one or more double bonds which cause “kinks” in chains, therefore increasing reactivity. Liquid at room T (olive oil, cod liver oil) Most plant and fish fats

– 1-3 fatty acid chains per glycerol molecule

Great energy storage

Phospholipids

Glycerol backbone with 2 fatty acid tails. Phosphate group PO4

- attached

Form lipid bilayer at cell surface

Steroids

Carbon skeleton of 4 rings Vary in functional groups attached and

therefore vary in function Cholesterol:

Proteins

Account for almost 50% of dry weight of cells Instrumental for many cell functions including:

– Structural support and movement(bone,cartilage)– Storage/transport molecules (hemoglobin)– Hormones (insulin-sugar breakdown)– Enzymes (control of cellular reactions

Protein Chemistry

R groups differ for each AA

Amino acids joined together by special covalent bonds called peptide bonds

Protein Structure

Primary structure: specific and unique AA sequence

Secondary structure: parts of AA chain bonded together via hydrogen bonds into helical structure (alpha helix) or sheet structure

Tertiary structure: due to interactions of R groups-sheets often form fibers that have structural function, helical structures tend to have globular form-heavily influenced by R group

Protein Structure

Quaternary structure: Proteins that consist of more than one polypeptide chain.– Ex: Hemoglobin (carries O2 in body) globular protein

with 4 chains, collagen fibrous protein of 3 chains forming a triple helix-suits function of connective tissue in skin, bone, tendons etc.

Denaturation: change in 3D structure when chemical environment of protein changed– Exs. pH, salt concentration, temperature etc.

Nucleic Acids

Nucleotide monomer– 5 C sugar-either ribose or deoxyribose– N-containing base

Single ring Pyrimidine: C, T, U Double ring purine A, G

– Phosphate group

Deoxyribonucleic Acid (DNA)

Nucleotide has deoxyribose as 5C sugar Double helix structure (double strand of

nucleotides) Lives in nucleus of cells

Ribonucleic Acid (RNA)

Nucleotide has ribose as 5C sugar Single chain nucleotide structure (single

stranded) Directs production of proteins

– Once synthesized (via DNA), moves out of nucleus to protein synthesis machinery in cell and base sequence directs which AA’s are joined together

– 3 bases = particular AA