Download Chemistry of Life

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 Life
Part 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
–
–
–
–
–

MonosaccharideDisaccharidePolysaccharideC, 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 (nonpolar)
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 longhence 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