Chapter 4: Carbon

Why study Carbon? All of life is built on carbon Cells ~72% H 2 O ~25% carbon compounds carbohydrates lipids proteins nucleic acids ~3% salts Na, Cl, K…

Carbon: The Backbone of Life Carbon enters the biosphere through the action of plants, which use solar energy to transform atmospheric CO 2 into the molecules of life. These molecules are passed along to animals that feed on plants.

Learning Targets 1.I can explain how carbon’s electron configuration accounts for its ability to form complex molecules. I can describe how carbon skeletons may vary and explain how this variation contributes to the diversity and complexity of organic molecules. I can describe the basic structure of a hydrocarbon and explain why these molecules are hydrophobic.

Properties of Carbon Organic chemistry Study of carbon compounds C atoms are versatile building blocks 4 valence electrons = ability for 4 covalent bonds Can be single, double, or triple

Learning Targets 1.I can explain how carbon’s electron configuration accounts for its ability to form complex molecules. I can describe how carbon skeletons may vary and explain how this variation contributes to the diversity and complexity of organic molecules. I can describe the basic structure of a hydrocarbon and explain why these molecules are hydrophobic.

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

Diversity of Organic 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 (C 2 H 6 ) ethanol (C 2 H 5 OH)

Learning Targets 1.I can explain how carbon’s electron configuration accounts for its ability to form complex molecules. I can describe how carbon skeletons may vary and explain how this variation contributes to the diversity and complexity of organic molecules. I can describe the basic structure of a hydrocarbon and explain why these molecules are hydrophobic.

Hydrocarbons Combinations of C & H only non-polar not soluble in H 2 O Hydrophobic Can undergo reactions that release a relatively large amount of energy

Crash Course: That’s Why Carbon is a Tramp

Learning Targets 2. I can identify the different functional groups and outline the chemical properties of the organic molecules in which they occur.

Isomers Same molecular formula but different structures different chemical properties different biological functions 6 carbons

Form affects function Alanine (amino acid) L-alanine used in proteins D-alanine is not Dopa (medicine) L-version treats Parkinson’s D-version does not Thalidomide (medicine) L-version treats morning sickness D-version causes birth defects

Functional groups Parts of organic molecules involved in chemical reactions Hydroxyl Amino Carbonyl Sulfhydryl Carboxyl Phosphate

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

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

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

Sulfhydryl –SH S bonded to H compounds with SH = thiols SH groups stabilize the structure of proteins

Phosphate –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.

Figure 4.9_a STRUCTURE CHEMICAL GROUP Hydroxyl NAME OF COMPOUND EXAMPLE Ethanol Alcohols (Their specific names usually end in -ol.) (may be written HO—) Carbonyl Ketones if the carbonyl group is within a carbon skeleton Aldehydes if the carbonyl group is at the end of the carbon skeleton Carboxyl Acetic acid Acetone Propanal Carboxylic acids, or organic acids FUNCTIONAL PROPERTIES Is polar as a result of the electrons spending more time near the electronegative oxygen atom. Can form hydrogen bonds with water molecules, helping dissolve organic compounds such as sugars. A ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal. Ketone and aldehyde groups are also found in sugars, giving rise to two major groups of sugars: ketoses (containing ketone groups) and aldoses (containing aldehyde groups). Found in cells in the ionized form with a charge of 1  and called a carboxylate ion. Nonionized Ionized Acts as an acid; can donate an H + because the covalent bond between oxygen and hydrogen is so polar:

Figure 4.9_b AminoSulfhydrylPhosphateMethyl Methylated compounds Organic phosphates (may be written HS—) Thiols Amines Glycine Cysteine Acts as a base; can pick up an H + from the surrounding solution (water, in living organisms): NonionizedIonized Found in cells in the ionized form with a charge of 1+. Two sulfhydryl groups can react, forming a covalent bond. This “cross-linking” helps stabilize protein structure. Cross-linking of cysteines in hair proteins maintains the curliness or straightness of hair. Straight hair can be “permanently” curled by shaping it around curlers and then breaking and re-forming the cross-linking bonds. Contributes negative charge to the molecule of which it is a part (2– when at the end of a molecule, as above; 1– when located internally in a chain of phosphates). Molecules containing phosphate groups have the potential to react with water, releasing energy. Arrangement of methyl groups in male and female sex hormones affects their shape and function. Addition of a methyl group to DNA, or to molecules bound to DNA, affects the expression of genes. Glycerol phosphate 5-Methyl cytidine