Carbon and the Molecular Diversity of Life Chapter 04

Why study Carbon? All of life is built on carbon Cells ~72% H2O ~25% carbon compounds carbohydrates lipids proteins nucleic acids ~3% salts Na, Cl, K… Why do we study carbon -- is it the most abundant element in living organisms? H & O most abundant C is the next most abundant

Carbon: The Backbone of Life Carbon enters the biosphere through the action of plants, which use solar energy to transform atmospheric CO2 into the molecules of life. These molecules are passed along to animals that feed on plants.

What type of compounds are considered organic?

Organic Chemistry The branch of chemistry that specializes in the study of carbon compounds.

What 5 atoms are most commonly combine with carbon to form organic molecules?

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur CHNOPS Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur

Carbon What are the key properties of carbon that make it a good choice for life?

It has four valence electrons Properties of Carbon It has four valence electrons

Properties of Carbon It can form up to 4 covalent bonds These can be single, double, or triple covalent bonds

Properties of Carbon It likes to bond with itself, unlike most atoms Thus it can form large molecules These molecules can be chains, branches, or ring-shaped

Variations in Carbon Skeletons How can you create variations in carbon skeletons? Change the length of the carbon skeleton. The skeleton may be straight, branched, or arranged in closed rings Alter the number and location of double bonds. Change the elements or groups with which carbon bonds.

Diversity of Molecules Substitute other atoms or groups around the carbon ethane vs. ethanol H replaced by an hydroxyl group (–OH) nonpolar vs. polar gas vs. liquid biological effects! ethane (C2H6) ethanol (C2H5OH)

Hydrocarbons Combinations of C & H only non-polar not soluble in H2O Hydrophobic Can undergo reactions that release a relatively large amount of energy methane (simplest HC)

Isomers 6 carbons 6 carbons 6 carbons Molecules with same molecular formula but different structures (shapes) different chemical properties different biological functions Same formula but different structurally & therefore different functionally. Molecular shape determines biological properties. Ex. Isomers may be ineffective as medicines 6 carbons 6 carbons 6 carbons

Types of Isomers

Structural Isomer

Geometric Isomer

Enantiomer or Stereoisomer

Form Affects Function stereoisomers Structural differences create important functional significance amino acid alanine L-alanine used in proteins but not D-alanine medicines L-version active but not D-version sometimes with tragic results… stereoisomers

Form Affects Function Thalidomide prescribed to pregnant women in 50s & 60s reduced morning sickness, but… stereoisomer caused severe birth defects

Chemical Groups There are SEVEN chemical groups most important in biology Hydroxyl Carbonyl Carboxyl Amino Sulfhydryl Phosphate Methyl 6 of the 7 chemical groups are considered functional groups Methyl group is NOT a functional group because it does not participate in chemical reactions, instead it acts as a recognizable tag on biological molecules

Functional Groups parts of organic molecules that are involved in chemical reactions give organic molecules distinctive properties  hydroxyl  amino  carbonyl  sulfhydryl  carboxyl  phosphate Affect reactivity makes hydrocarbons hydrophilic increase solubility in water

Viva la difference! Basic structure of male & female hormones is identical identical carbon skeleton attachment of different chemical / functional groups interact with different targets in the body different effects For example the male and female hormones, testosterone and estradiol, differ from each other only by the attachment of different functional groups to an identical carbon skeleton.

Hydroxyl –OH organic compounds with OH = alcohols names typically end in -ol ethanol

Carbonyl C=O if C=O at end molecule = aldehyde O double bonded to C if C=O at end molecule = aldehyde if C=O in middle of molecule = ketone

Carboxyl compounds with COOH = acids –COOH fatty acids amino acids C double bonded to O & single bonded to OH group compounds with COOH = acids fatty acids amino acids

Carboxyl Group How did it get its name? COOH - This group consists of a carbon atom that is bonded to both a carbonyl and a hydroxyl group. Why is this group acidic? It donates H+ Compounds with this group are called carboxylic acids

Amino compounds with NH2 = amines amino acids NH2 acts as base N attached to 2 H compounds with NH2 = amines amino acids NH2 acts as base ammonia picks up H+ from solution

Sulfhydryl compounds with SH = thiols S bonded to H compounds with SH = thiols SH groups help stabilize protein structure through disulfide bridges

Disulfide Bridge

Phosphate connects to C through an O –PO4 P bound to 4 O connects to C through an O lots of O = lots of negative charge highly reactive transfers energy between organic molecules ATP, GTP, etc.