Organic Molecules by Doctor-dr

by Microbiology Doctor-dr (doctor-dr)(doctor_dr)

ORGANIC MOLECULES

The word "organic" refers to the vast majority of compounds that include carbon, especially C-C or C-H bonds. Remember that carbon atoms only have four electrons in their outer shell; the octet rule needs four electrons. As a consequence, each carbon atom may build millions of molecules of all sizes and forms by joining with four other atoms. There are four primary categories of organic compounds in the human body:

1. Carbohydrates

2. Proteins

3. Lipids

4. Nucleic acids

1. Carbohydrates:

Carbon, hydrogen, and oxygen are found in all carbohydrate molecules, and the carbon atoms are bonded to create chains of different lengths. Carbohydrates, which comprise sugars and starches, are the major source of chemical energy required by every cell in the human body. Carbohydrates also have a structural role in the creation of crucial molecules like RNA and DNA, which are essential in cell reproduction and protein synthesis. Carbohydrates are classified into three groups based on the length of their carbon chains. The three kinds are referred to as:

1. Monosaccharides (simple sugars) 

2. Disaccharides (double sugars)

3. Polysaccharides (complex sugars)

Monosaccharides 

Simple sugars, or monosaccharides, have short carbon chains. Glucose is the most essential simple sugar. It has the formula CH12O6 and is a six-carbon sugar. Each molecule of glucose has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms, according to the chemical formula. It's termed a hexose because it has six carbon atoms (hexa, "six"). When glucose is dry, it exists as a "straight chain," but when it is dissolved in water, it becomes a "cyclic" molecule. Figure 2-1 shows a three-dimensional representation of the molecule with straight chain and cyclic configurations. It's crucial to remember that all types of glucose are the same molecule, regardless of how they're depicted in models or representations.

Fructose and galactose are two more significant hexoses, or six-carbon simple sugars, in addition to glucose. However, not all monosaccharides are hexoses. Some are pentoses (penta, "five"), which get their name from the fact that they have five carbon atoms. Ribose and deoxyribose are pentose monosaccharides that play an important role in the body; we'll go over them in more detail when we talk about nucleic acids. Ribose and deoxyribose, like other monosaccharides, are sugars, but odd sugars in that they aren't sweet.

FIGURE 2-1 Structure of glucose. A, Straight chain, or linear model, of glucose. B, Ring model representing glucose in solution. C, Three-dimensional, or space filling, model of glucose.

Disaccharides and polysaccharides

Disaccharides (double sugars) and polysaccharides (complex sugars) are carbohydrates made up of two or more simple sugars linked together by a synthesis process that removes water. Disaccharides include sucrose (table sugar), maltose, and lactose. Each is made up of two monosaccharides that have been bonded together. The production of sucrose from glucose and fructose is seen in Figure 2-2. It's worth noting that a hydrogen atom from the glucose molecule joins forces with a hydroxyl group (OH) from the fructose molecule to produce water, leaving an oxygen atom to link the two subunits together.

Many monosaccharides are chemically linked to create straight or branched chains in polysaccharides. As the numerous monosaccharide subunits are linked, water is withdrawn once more. A polymer is a big molecule made up of numerous similar tiny units. Glycogen is sometimes referred to as animal starch. Polysaccharides are polymers of monosaccharides. It is the body's primary polysaccharide and has a molecular weight of several million, making it a true macromolecule.

FIGURE 2-2 Formation of sucrose. Glucose and fructose are joined in a synthesis reaction that involves the removal of water.

QUICK CHECK

1. List the four major groups of organic substances. 

2. Identify the most important monosaccharide, or simple sugar. 

3, Identify a carbohydrate polymer and explain how it is formed