BIO146

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Chapter 4
Chapter 4

Organic chemistry is key to the origin of life

4.1

Organic chemistry - organic compounds range from simple molecules, such as methane (CH4), to colossal ones, such as proteins, with thousands of atoms

The major elements of life - C, H, O, N, S, and P

➡️ CO2 is not an organic compound - it does not have Hydrogen in it

Stanley Miller’s classic experiment demonstrated the abiotic synthesis of organic compounds, who was trying to make amino acids

4.2 Carbon atoms can form diverse molecules by bonding to four other atoms

The Formation of Bonds with Carbon

Carbon usually shares 4 electrons with other atoms so that 8 electrons are present

each pair of shared electrons constitutes a covalent bond

in organic molecules, carbon usually forms single or double covalent bonds

→ they have the hydroformed

→ the organic compounds end with -ane have single covalent bonds between carbons

→ the organic compounds end with -ene have at least one double covalent bond between carbons

→ the organic compounds end with - yne have at least one triple covalent bonds between

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valence - the number of covalent bonds it can form; the number of electrons required to fill the valence shell of an atom

In carbon dioxide molecule (CO2), a single carbon atom is joined to two atoms of oxygen by double covalent bonds

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Urea, CO(NH2)2 is an organic compound found in urine - one carbon atom participates in both single and double bonds.

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Molecular Diversity Arising from Variation in Carbon Skeletons

hydrocarbons - organic molecules consisting of only carbon and hydrogen

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Isomers

Isomers - compounds that have the same atoms of the same elements but different structures and hence different properties; same molecular formula but different structures and properties)

structural isomers - differ in the covalent arrangements of their atoms

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cis-trans isomers (aka geometric isomers) - carbons have covalent bonds to the same atoms, but these atoms differ in their spatial arrangements due to the inflexibility

single bonds allow the atoms they join to rotate freely about the bond axis without changing the compound

double bonds do not permit such rotation

cis isomer: the two Xs are on the same side

trans isomer: the two Xs are on opposite sides

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Enantiomers - isomers that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon, one that attached to four different atoms or groups of atoms

enantiomers are important in the pharmaceutical industry

two enantiomers of a drug have different properties

S is the left image; R is the right imagine

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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

The Chemical Groups Most Important in the Processes of Life

functional groups - chemical groups are directly involved in chemical reactions

each has certain properties (valence # of the elements)

→ shape and charge - cause it to participate in chemical reactions in a characteristic way

→ hormones are lipids that cannot dissolve in the water

seven important chemical groups in biological processes

> hydroxyl

> carbonyl

> carboxyl

> amino

> sulfhydryl

> phosphate

> methyl groups

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ATP: An Important Source of Energy for Cellular Process

Adenosine triphosphate (ATP) - consists of an organic molecule called adenosine attached to a string of three phosphate groups

three phosphates are present in series

→ one phosphate may be split off as a result of a reaction with water

having lost one phosphate, ATP becomes adenosine diphosphate (ADP)

ATP is sometimes said to store energy, but it is more accurate to think of it as storing the potential to react with water or other molecules

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