Chemistry When it Comes to Nutrition, Terms

Chemistry

When it comes to nutrition, terms like carbohydrate, lipid, monosaccharide, protein and cholesterol can sound almost like a foreign language. With all the conflicting reports of what affects your body and what does harm, it is no wonder that people are so confused. Yet the importance of these substances is so vital that by understanding what these things are, as well as how they are used by our bodies can certainly benefit our health and overall well being.

Carbohydrates:

By definition, a carbohydrate is group of chemical compounds that exist when hydrogen and oxygen (H2O) are then combined with carbon (Ed., Encarta). Carbohydrates are the largest group of organic compounds found in nature (Encarta). Humans, animals, plants and bacteria all use carbohydrates, and the uses for them varies depending on the organism using them. Plants use them for structural uses - as in the cellulose and hemicellulose that are their main structural elements (Encarta). The cell coatings of the connective tissues in vertebrate animals have carbohydrates in them; both animals and plants use various forms of carbohydrates to store energy (Encarta). Chitin is a carbohydrate, and is the primary ingredient for the exoskeleton of invertebrate animals (Encarta).

Saccharides:

Monosaccharides are sugars, basically, with the same molecular formula, though each have different molecular structures (Kimball, Carbohydrates). There are three primary types of monosaccharides, and they are:

1- glucose (sugar used for energy for cellular respiration)

2- galactose (sugar found in milk, yogurt, dairy)

3- fructose (sugar found in honey)

Kimball, Carbohydrates).

Disaccharides are also sugars; they differ from the monosaccharides in that they are more complex sugars, while the former are commonly referred to as the simple sugars (Kimball, Carbohydrates). According to Kimball, the three most common disaccharides are:

1- sucrose (table sugar glucose + fructose)

2- lactose (milk sugar glucose + galactose)

3- maltose (product of starch digestion glucose + glucose)

Polysaccharides are not sugars, but one of three things - starches, glycogen or cellulose (Kimball, Carbohydrates). Potatoes, rice, breads, and corn are just a few of the sources of starches. When starches are digested, glucose and maltose are produced in varying mixtures (Kimball, Carbohydrates).

Glycogen is most often found in animals because this is where their excess glucose is polymerized and then stored (Kimball, Carbohydrates). Whenever energy is again in need, the glycogen is broken back down into its original form - glucose (Kimball, Carbohydrates).

Cellulose is the major component of the foundation of plants - wood is primarily cellulose, as is paper, and cotton (Kimball, Carbohydrates). Cellulose is a tough material, perfect for the cell walls of plants.

Lipds:

Lipids are fats, and are one of the vital nutrients of animal, and human nutrition (Haas, Fats, Lipids and Oils). Like carbohydrates, they are used primarily as stored energy though lipids are also used an insulation for the body (Haas). Lipids are divided into four subclasses:

1- Saturated fats - like animal fats (butter)

2- Monounsaturated - olive, and peanut oil

3- Polyunsaturated - corn oil, soy bean oil, sunflower oil, cottonseed oil, safflower oil

4- Trans Fats - partially hydrogenated fats with fewer double bonds

Haas).

Cholesterol:

Cholesterol is one of the more complex compounds found in the body, and is made up of alcohol, animal fat and oil (Haas). Cholesterol is related to an entire group of compounds called sterols - steroids (Kimball, Fats). Cholesterol certainly has it's positive uses, but it can cause major, life-threatening problems if not monitored. Cholesterol can crystallize to form gall stones, or even worse - it can cause fatty deposits to build up along the walls of the blood vessels, which can lead to severe heart attacks (Kimball, Fats). The relationship between atherosclerosis and cholesterol seems to be linked to the levels of LDLs that are present in excess of what the body actually needs (Kimball, Fats).

Protein:

Proteins are polymers of amino acids (Chang, 711). Proteins play a major role in almost all biological functions (Chang, 711). They transport and store vital substances in the body, lend mechanical support, protect the body against disease, help coordinate body motions, as well as set processes into motion (Chang, 711-713). Proteins are made up of one or more chains of amino acids, and on average, each protein contains around 300 amino acids (Kimball, Proteins). It is estimated that the human body has about 100,000 different kinds of protein molecules in it at any given time (Chang, 713). Proteins are the basis for life and involved in almost everything imaginable that happens within the body.

Enzymes, which are the catalysts for many biochemical reactions, are proteins

Cells are made up of proteins (i.e collagen)

Receptors for hormones, and other molecules that send out signals are proteins

Proteins are nutritionally essential for heterotrophs

Contractile proteins are responsible for the movement and travel of cells and organisms

Body fluids are transported via proteins

Kimball, Proteins). As you can see, proteins are truly involved in everything.

Shape is vital to proteins - the shape of a protein is what determines the function of a protein (Chang, 713). The shape of a protein is determined by what is called its primary structure, which is actually the sequence of amino acids (Kimball, The Rules of Protein Structure). This influential sequence of amino acids is determined by the sequence of nucleotides found in the gene that is encoding the protein - this cannot be altered without having the protein cease functioning (becoming denatured) (Chang, 716).