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Chapter #4; Carbon and the Molecular Diversity of Life - Coggle Diagram
Chapter #4; Carbon and the Molecular Diversity of Life
4.1 Organic chemistry is key to the origin of life
compounds containing carbon are said to be organic, and their study is called organic chemistry
complex organic molecules could arise spontaneously under conditions thought at that time to have existed on early earth
the overall percentages of the major elements of life; C, H, O, N, S, and P, are quite uniform from one organism to another, reflecting the common evolutionary origin of all life
4.2 Carbon atoms can form diverse molecules by bonding to four other atoms
the key to an atoms chemical characteristic is its electron configuration
The Formation of Bonds with Carbon
carbon has 6 electrons, with 2 in the first electron shell and 4 in the second shell, thus having 4 valence electrons in a shell that can hold up to 8 electrons
a carbon atom usually completes its valence shell by sharing its 4 electrons
in organic molecules, carbon usually forms single or double covalent bonds
the number of electrons required to fill the valence shell of an atom is generally equal to the atom’s valence, the number of covalent bonds it can form
there are 4 main atoms in organic molecules - carbon, hydrogen, oxygen, and nitrogen
the electron configuration of carbon gives it covalent compatibility with many different elements
Molecular Diversity Arising from Variation in Carbon Skeletons
carbon chains form the basis of most organic molecules
carbon skeletons vary in length and may be straight, branched, or arranged in closed rings
some carbon chains have double bonds, which vary in number and location
such variation in carbon chains is one important ource of the molecular complexity and diversity that characterizes living matter
Hydrocarbons
hydrocarbons - organic molecules consisting of only carbon and hydrogen
hydrocarbons are not prevalent in most living organisms
hydrocarbons can undergo reactions that release a relatively large amount of energy
Isomers
variation in the architecture of organic molecules can be seen in siomers
isomers - compounds that have the same numbers of atoms of the same elements but different structures, hence different properties
there are 3 types of isomers; structural, isomers, cis-trans isomers, and enantiomers
structural isomers
differ in the covalent arrangements of their atoms
the number od possible isomers increase tremendously as carbon skeletons increase in size
cis-trans isomers
also known as geometric isomers
in cis-trans isomers, carbons have covalent bonds to the same atoms, but these atoms differ in their spatial arrangements due to the inflexibility of double bonds
single bonds allow the atoms they join to rotate freely about the bond axis without changing the compound
double bonds don’t allow such rotation
enantiomers
isomers that are mirror images of each other and differ in shape due to an asymmetric carbon that is attached to 4 different group/ of atoms
the 4 groups can be arranged in space around the asymmetric carbon
usually only 1 isomer is bilogically active because only that form can bind to specific molecules in organisms
the concept of enantiomers is important in the pharmecutical industry because the 2 enantiomers of a drug may not be equally as effective
the differing effects of enantiomers in the bofy demonstarte that organisms are sensitive to even the smallest variation in molecular architecture
4.3 A few chemical groups are key to molecular function
the distinctive properties of an organic molecule depend not only on the arrangement of its mostly carbon skeleton, but also on the various chemical groups attached to that skeleton
these groups may participate in chemical reactions or contribute to function indirectly by their effects on molecular shape
the chemical groups most important in the process of life
estradiol and testosterone are both steroids that differ only in the chemical groups attached to the rings
the different actions of these 2 molecules on many targets throughout the body are the basis of sexual characteristics
functional groups - chemical groups are directly involved in chemical reactions
each has certain properties like shape and or charge that cause it to participate in chemical reactions in a charecteristic way
the 7 chemical groups most important in biological processes - hydroxyl group, carbonyl group, carboxyl group, amino group, sulfhydryl group, phosphate group, and methyl group
he first 6 groups can be chemically reactive; of the six, the sulfhydryl group is the only one not hydrophilic and thus increase the solubility of organic compounds in water
the methyl group is not reactive, instead it serves as a recognizable tag on biological molecules
ATP consists of an organic molecule called adenosine attached to a string of 3phosphate groups
ATP is said to store energy, but its more accurate to think of it as storing the potential to react with water