Biol 1406 Chapter 4 Carbon and Molecular Diversity of Life

Although cells are 70-95% water,

the rest consists of mostly carbon-based compounds

proteins, DNA, carbohydrates, and other molecules that distinguish living matter from inorganic material are all composed of carbon atoms bonded to each other and to atoms of other elements

These other elements commonly include hydrogen (H), oxygen (o), nitrogen (N), sulfur (S), and phosphorus (P)

Organic chemistry

focuses on organic compounds containing carbon

Most organic compounds contain

hydrogen atoms in addition to carbon atoms

major elements of life

carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus

These few elements (C, H, O, N, S, AND P)

can be combined to build an inexhaustible variety of organic molecules

Variations in organic molecules can distinguish even individuals of a

single species

Jons Jacob Berzelius

was the first to make a distinction between organic compounds, thought to arise in only living organisms, and inorganic compounds that were found in the nonliving world

Vitalism

the belief that physical and chemical laws do not apply to living things

Mechanism

the belief that the same physical and chemical laws govern all natural phenomena, including the processes of life

Redefined as the study of carbon compounds, regardless of their origin

Organic Chemistry

the laws of chemistry apply to both

inorganic and organic compounds

A carbon atom has a total of 6 electrons:

2 in the first electron shell and 4 in the second shell\

Carbon has little tendency to form ionic bonds by losing or gaining 4 electrons to complete its valence shell

Carbon usually completes its valence shell by sharing electrons with other atoms in

four covalent bonds, which may include single or double bonds

- the ability of carbon to form four covalent bonds makes large, complex molecules possible

The valences of carbon and its partners can be viewed as the building code that governs the architecture of

organic molecules

although CO2 can be classified as either organic or inorganic, its importance to the living world is clear:

CO2 is the source of carbon for all organic molecules found in organisms

CO2 is usually fixed into organic molecules by the process of

photosynthesis

Carbon chains form the skeletons of most

organic molecules

Carbon skeletons:

- vary in length and may be straight, branched, or arranged in closed rings

- may include double bonds

- atoms of other elements can be bonded to the atoms of the ___________________

hydrocarbons

are organic molecules that consist of only carbon and hydrogen atoms

- are the major component of petroleum,

- fats are biological molecules that have long ______ tails attached to a nonhydrocarbon component

- petroleum and fat are hydrophobic compounds that cannot dissolve in water because of their many nonpolar carbon-hydrogen bonds

- can undergo reactions that release a relatively large amount of energy

Isomers

compunds that have the same molecular formula but different structures and, therefore, different chemical properties

Structural Isomers

have the same molecular formula but differ in the covalent arrangement of atoms

Cis-trans isomers

have the same covalent partnerships but differ in the spatial arrangment of atoms around a carbon-carbon double bond

Enantiomers

are molecules that are mirror images of each other

asymmetric carbon

A carbon that is attached to four different atoms or groups of atoms.

- enantiomers are possible because of

Functional groups

affect molecular function though their direct involvement in chemical reactions

Seven chemical groups are most important to the chemistry of life:

hydroxl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, and methyl groups

the first six chemical groups are functional groups

they are hydrophilic and increase the solubility of organic compounds in water

methyl groups are not reactive

but may serve as important markers on organic molecules

hydroxl group

(OH-) A hydrogen atom forms a polar covalent bond with an oxygen atom, which forms a polar covalent bond to the carbon skeleton

a carbonyl group

(>CO) consists of a carbon atom joined to an oxygen atom by a double bond

aldehyde

if the carbonyl group is on the end of the carbon skeleton

ketone

if the carbonyl group is within the carbon skeleton

Carboxyl group

COOH consists of a carbon atom with a double bond to an oxygen atom and a single bond to the oxygen atom of a hydroxyl group

Carboxylic acids

compounds with carboxyl groups

Amino group

(-NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton

Amines

organic compounds with amino groups

organic compounds with hydroxyl groups are alcohols,

and their names typically end with -ol

Isomers with aldehydes and those with ketones have

different properties

Carboxyl group acts as an acid because the combined electronegativities of the two adjacent oxygen atoms increase the chance of

dissociation of hydrogen as an ion (H+)

The amino group acts as a base because it can pick up a

hydrogen ion (H+) from the solution

Amino acids, the building blocks of proteins,

have amino and carboxyl groups

Sulfhydryl group

(-SH) consists of a sulfur atom bonded to a hydrogen atom to the backbone

Thiols

organic molecules with sulfhydryl groups

Phosphate group

(-OP3-2) consists of a phosphorus atom bound to four oxygen atoms (three with single bonds and one with a double bond)

- connects to the carbon backbone via one of its oxygen atoms

- are anions with two negative charges because 2 protons dissociate from the oxygen atoms

- on function is to transfer energy between organic molecules

Adenosine triphosphate, ATP

the primary energy transfer molecule in living cells

Adenosine Diphosphate (ADP)

when one inorganic phosphate ion is split off as a result of a reaction with water, ATP becomes

ATP "stores"

the potential to react with water, releasing energy that can be used by the cell