CLASSES OF ORGANIC MOLECULES

CLASSES OF ORGANIC MOLECULESWhat are organic molecules?

These are molecules that have their basic skeleton made of carbons atoms, hydrogen, oxygen and sometimes nitrogen atoms. Generally organic molecules in the body can be classified into one of four groups: carbohydrates, lipids, proteins and nucleic acid.

Carbohydrates Carbohydrates are the most abundant of the four main organic molecules. They fill numerous roles in living things, such as the storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in animals). Most carbohydrates taste sweet, and the carbohydrates include the substances known as sugars.

Cont..The simplest sugars are known as monosaccharides, a good example of a monosaccharide is glucose.

Simple sugars/monosaccharides - the basic building block molecules of the carbohydrates

Cont- all sugar, when in straight-chain form, contain a C=O group. Hydroxyl (OH) groups are attached to all the carbons except those with a double bonded oxygen.a.1. glucosea.2. galactose1.3 fructose

Cont.In addition to ordinary monosaccharides composed only of carbon, oxygen and hydrogen, there are a variety of derivative monosaccharides containing other elements.Some have a phosphate group attached to one of the carbons and others an Amino group ( a nitrogen with two hydrogen, NH2).A.1 glucoamine a.2 Glucose 6-phosphoric acid

ContGlucose is the major monosaccharide found in the blood, when two monosaccharide are linked together they form a disaccharides.

b. Disaccharides, or double sugars are composed of two single sugars bonded together through a reaction that involves a removal of a molecule of water. This kind of reaction is called condensation reaction or a dehydration reaction.

a. Maltose/Malt sugar this compound is synthesized by a condensation reaction between two molecules of glucose.2C6H12O6 C12H22O11 + H2O

b. Lactose/Milk sugar composed of glucose and galactose.Synthesized by condensation reactions, dissacharides can be broken down to their

constituent simple sugars by reverse process. This process or reaction is called Hydrolysis, involves addition of water molecule

C6H12O6 + H2O 2C6H12O6

c. Sucrose/table sugar it is synthesized by condensation reaction between molecules of glucose and a molecule of fructose.

C. Polyssacharide is a straight or branched chain of hundreds or thousands of sugar units of the same or different kinds.Most common are:

1) Starches- are the principal carbohydrate storage products of higher plants- composed of many hundreds of glucose units bonded together.

2) Glycogen the principal carbohydrate storage product in animalSometimes called animal starch. Glycogen is found in animal cells and it serves as primary short term energy storage in animal cells. It is made primarily by the liver and the muscles.3) Cellulose highly insoluble unbranched polysaccharides common in plant-major supporting material

Reactions like those that form polysaccharides are reactions in which small molecules bond together to form long chains are called POLYMERIZATION REACTIONS.

The products formed are called POLYMERS.

Lipids

Are composed of carbon, hydrogen and oxygen, but they may also contain other elements, particularly phosphorus and nitrogen.

Lipids are fat-soluble, naturally occurring molecules; unlike carbohydrates lipids are insoluble in water, but they do dissolve in nonpolar solvent such as ether.

The main biological functions of lipids include energy storage, acting as structural components of cell membranes, and participating as important signaling molecules

Lipids can be divided into subclasses:

I) Fatty acid has a long unbranched carbon with a - COOH at the end.

Each molecule of fat is composed of two a different types of building-block compounds. -An alcohol called glycerol and fatty acids.-Glycerol (also called glycerin) has a backbone of three carbon atoms, each carrying a carboxyl group (-OH group)

Fatty acids like all organic acids, contain the acid group COOH (called carboxyl group)

O

C

OH

The various fats differ in the specific fatty acids or types of fatty acids of which they are composed:

A) Saturated fats including butter and lard tend to be solids at room temperature.Saturated means all the carbon atoms in the fatty acid tails are joined by single C-C bonds and as many hydrogen atoms as possible are linked to them.

2) Unsaturated fats or oils tend to be liquid at room temperature. One or more double bonds occur between the carbon atoms in the fatty acid tails.

Oils are liquid at room temperature because the double bond create kinks that disrupt packing between tails.

B. PhospholipidsContain phosphorus in the form of phosphate it has glycerol backbone attached to the backbone are two fatty acid tails, a phosphate group and a small hydrophilic groupMain component of the cell membraneControls the movement of materials in and out of the cell.

C. Waxes- composed of fatty acids and certain alcohol- some wax secretion form coatings that help protect, lubricate and maintain the pliability of skin and hair.

2) Lipids with no fatty acids- among the lipids that have no fatty acid tails are the steroids

Cholesterol is a steroid which is a key component of animal cell membranes

Used to synthesize vitamin D which functions in the development of bones and teeth.Excess cholesterol also plays a role in ATHEROSCLEROSIS a disorder in which the lipids becomes deposited in the walls of arteries. The deposits build up, arteries narrow and blood flow may be obstructed.

Many hormones, including sex hormones are steroid. Hormones help regulate the bodys growth, development and reproduction, as well as its everyday functioning.Unfortunately, use of those steroids can lead to pronounced behavioural disorders, liver damage and other abnormalities.

ProteinsProteins are large organic compounds made up of amino acids (amino acids are organic molecules that are made of carbon, nitrogen and hydrogen atoms). These amino acids are arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.

Example illustrating the formation of a peptide bond

ContPeptide bonds are formed between the amino and carboxyl group. These bonds can be broken by hydrolysis to yield individual amino acids. The figure on the previous slide illustrates the hydrolysis of a protein.

PROTEIN STRUCTUREProteins are characterized of three types of structures namely: primary, secondary, tertiary and quaternary structure.Primary Protein Structure

The primary structure of a protein refers to the number and sequence of amino acids in the protein. The primary structure of a protein is very important in the identification of a protein.

Diagram showing the primary structure of a protein

Cont..Secondary Protein Structure

The secondary protein structure is the specific geometric shape caused by intramolecular and intermolecular hydrogen bonding of amide groups. The most common secondary structures of proteins are the alpha helices and beta sheet.

Diagram showing the secondary structure of a protein

ContTertiary Protein Structure

The third type of structure found in proteins is called tertiary protein structure. The tertiary structure is the final specific geometric shape that a protein assumes. This final shape is determined by a variety of bonding interactions between the "side chains" on the amino acids.

These bonding interactions may be stronger than the hydrogen bonds between amide groups holding the helical structure. As a result, bonding interactions between "side chains" may cause a number of folds, bends, and loops in the protein chain. Different fragments of the same chain may become bonded together.The figure on the next slide, shows the difference between primary, secondary and tertiary protein structures:

Different protein structures

Quarternary Protein StructureThe quaternary protein structure involves the clustering of several individual peptide or protein chains into a final specific shape. A variety of bonding interactions including hydrogen bonding, salt bridges, and disulfide bonds hold the various chains into a particular geometry.

Figure showing quaternary protein structure

Nucleic AcidsThese organic molecules are responsible for the storage, expression, and transmission of genetic information. It is the expression of genetic information that determines whether a cell is a muscle cell or a nerve cell. There are basically two classes of nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

Nucleic Acid are the only organic compound capable of replicating themselves Involved in the storage and transmission of energy and cellular information.The structural block of nucleic acid is the nucleotide which is comprised of a phosphate group (PO4), a five carbon sugar (ribose or deoxyribose) and a nitrogen base, either a purine ( adenine or guanine) or pyrimidine (cytosine, thymine or uracil)