Learning Objectives

Learning Objectives • Explain how the properties of carbon make it so important • Describe why the functional groups that are attached to the carbon skeleton have diverse properties • Explain how the behavior of organic molecules is dependent on the identity of their functional groups

Carbon & The Molecular Diversity of Life (Chapter 4)

Carbon: Organic Chemistry • Living organisms consist mostly of carbon-based compounds (element of life) • Carbon is important enough to have it’s own branch of chemistry called Organic chemistry • Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds

Miller-Urey Experiment • The Miller-Urey experiment demonstrated the abiotic synthesis of organic compounds. • Water (H2O), methane (CH4), ammonia (NH3), and hydrogen (H2) were all sealed inside a sterile array of glass tubes and flasks connected in a loop, with one flask half-full of liquid water and another flask containing a pair of electrodes.

Experimental Design: The origin of life on this planet • The liquid water was heated to induce evaporation, sparks were fired between the electrodes to simulate lightning through the atmosphere and water vapor, and then the atmosphere was cooled again so that the water could condense and trickle back into the first flask in a continuous cycle.

Experimental Design: The origin of life on this planet • Within a day, the mixture had turned pink in color, and at the end of two weeks of continuous operation, Miller and Urey observed that as much as 10–15% of the carbon within the system was now in the form of organic compounds.

Experimental Design: The origin of life on this planet • Two percent of the carbon had formed amino acids that are used to make proteins in living cells, with glycine as the most abundant. • Nucleic acids were not formed within the reaction. But the common 20 amino acids were formed, in various concentrations.

Structure of Carbon • With four valence electrons, carbon can form four covalent bonds with a variety of atoms • This ability makes large, complex molecules possible • Carbon-based molecules have three basic structures: straight chains, branched chains, and rings

Carbon Skeletons Vary • Carbon chains form the skeletons of most organic molecules • Carbon chains vary in length and shape

Hydrocarbons • Hydrocarbons are organic molecules consisting of only carbon and hydrogen • Hydrocarbons are nonpolar and do not dissolve in water

Hydrocarbons • Many organic molecules, such as fats, have hydrocarbon components • Hydrocarbons can undergo reactions that release a large amount of energy

Isomers • Isomers are compounds with the same molecular formula but different structures, thus different properties. • Structural isomers • Cis-transisomers • Enantiomers

Structural Isomers • Structural isomershave different covalent arrangements of their atoms

Cis-trans Isomers • Cis-trans isomershave the same covalent bonds but differ in spatial arrangements

Enantiomers • Enantiomers are isomers that are mirror images of each other & rotate light differently

Enantiomers in Medicine • Enantiomers are important in the pharmaceutical industry • Two enantiomers of a drug may have different effects • Usually only one isomer is biologically active • Differing effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules

Enantiomers in Medicine • Ex. Ibuprofen and albuterol – ibuprofen used for pain and inflammation, albuterol used to open airways during asthma attacks

Name that Isomer!!!

Functional Groups A few chemical groups are key to the functioning of molecules • Distinctive properties of organic molecules depend on the carbon skeleton and on the molecular components attached to it • A number of characteristic groups can replace the hydrogens attached to skeletons of organic molecules

Functional Groups • Functional groups are the components of organic molecules that are most commonly involved in chemical reactions • The number and arrangement of functional groups give each molecule its unique properties

Hydroxyl STRUCTURE Alcohols (Their specific names usually end in -ol.) NAME OF COMPOUND (may be written HO—) • Is polar as a result of the electrons spending more time near the electronegative oxygen atom. EXAMPLE FUNCTIONALPROPERTIES Ethanol • Can form hydrogen bonds with water molecules, helping dissolve organic compounds such as sugars.

Carbonyl STRUCTURE Ketones if the carbonyl group is within a carbon skeleton NAME OF COMPOUND Aldehydes if the carbonyl group is at the end of the carbon skeleton EXAMPLE • A ketone and an • aldehyde may be • structural isomers • with different properties, • as is the case for • acetone and propanal. FUNCTIONALPROPERTIES • 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). Acetone Propanal

Carboxyl STRUCTURE Carboxylic acids, or organic acids NAME OF COMPOUND • Acts as an acid; can donate an H+ because the covalent bond between oxygen and hydrogen is so polar: EXAMPLE FUNCTIONALPROPERTIES Acetic acid Nonionized Ionized • Found in cells in the ionized form with a charge of 1– and called a carboxylate ion.

Amino Amines STRUCTURE NAME OF COMPOUND •Acts as a base; can pick up an H+ from the surrounding solution (water, in living organisms): EXAMPLE FUNCTIONALPROPERTIES Glycine Ionized Nonionized •Found in cells in the ionized form with a charge of 1.

Sulfhydryl Thiols STRUCTURE NAME OF COMPOUND (may be written HS—) •Two sulfhydryl groups can react, forming a covalent bond. This “cross-linking” helps stabilize protein structure. EXAMPLE FUNCTIONALPROPERTIES •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. Cysteine

Phosphate Organic phosphates STRUCTURE NAME OF COMPOUND EXAMPLE •Contributes negative charge to the molecule of which it is a part (2– when at the end of a molecule, as at left; 1– when located internally in a chain of phosphates). FUNCTIONALPROPERTIES Glycerol phosphate •Molecules containing phosphate groups have the potential to react with water, releasing energy.

Methyl STRUCTURE Methylated compounds NAME OF COMPOUND •Addition of a methyl group to DNA, or to molecules bound to DNA, affects the expression of genes. EXAMPLE FUNCTIONALPROPERTIES •Arrangement of methyl groups in male and female sex hormones affects their shape and function. 5-Methyl cytidine

Learning Objectives Summaries

Learning Objectives