chem w1-part2

THE CHEMISTRY OF MAJOR CLASSES OF NUTRIENTS - Carbohydrates, Proteins, Fats, Vitamins and minerals

CARBOHYDRATES

Carbohydrates are referred to as energy-giving foods. They provide energy in the form of
calories that the body needs to be able to work, and to support other functions.

Carbohydrates are needed in large amounts by the body. Indeed, up to 65% of our energy comes from carbohydrates. They are the body’s main source of fuel because they are easily converted into energy. This energy is usually in the form of glucose, which all tissues and cells in our bodies readily use.

Carbohydrates are ingested in the form of simple carbohydrates, like monosaccharides and
disaccharides, or complex carbohydrates, like oligosaccharides and polysaccharides.

• Monosaccharides are the basic building blocks of all carbohydrates and include glucose,
  fructose, and galactose.
• Glucose is the primary form to which carbohydrates become metabolized in humans.
• Disaccharides contain two sugar units and include lactose, sucrose, and maltose. Lactose is a carbohydrate found in milk, and sucrose is basic table sugar.
• Oligosaccharides consist of 3 to 10 sugar units and include raffinose and stachyose, which are in legumes.
• Polysaccharides include greater than ten sugar units and consist of starches, glycogen, and fibers, like pectin and cellulose.
• Starches like amylose are in grains, starchy vegetables, and legumes and consist of glucose monomers.
• Glycogen is the storage form of glucose in animals and is present in liver and muscle, but there is little to none in the diet.
• Fibers are plant polysaccharides like pectin and cellulose that are found in whole-grains, fruits, vegetables, and legumes but are not digestible by humans.

PROTEINS

Proteins are essential macronutrients that contribute to structural and mechanical function,
regulate processes in the cells and body, and provide energy if necessary.

Proteins are needed in our diets for growth and to improve immune functions. They also play an important role in making essential hormones and enzymes, in tissue repair, preserving lean muscle mass, and supplying energy in times when carbohydrates are not available.

Proteins are organic compounds made up of amino acids. Proteins in food are broken down during digestion to provide the amino acids needed for protein synthesis.

Proteins in the human body are the basis of many body structures, including muscles and skin. Proteins also function as enzymes that catalyze biochemical reactions, hormones that regulate body functions in other ways, and antibodies that help fight pathogens. Any amino acids from food that arenot needed for these purposes are excreted in the urine, and under certain extreme conditions, converted to glucose for energy.

The most important aspect of protein structure from a nutritional standpoint is amino acid composition. About 20 amino acids are commonly found in the human body, of which about 11 are nonessential because they can be synthesized internally. The other 9 amino acids are essential amino acids that must be obtained from dietary sources.

FATS

Lipids, commonly called fats, are organic compounds made up mainly of fatty acids. Fats in foods as well as fats in the human body, are typically triglycerides (three fatty acids attached to a
molecule of glycerol). Fats provide the body with energy and serve other vital functions, including
helping to make and maintain cell membranes and functioning as hormones.

Fats are classified into saturated and unsaturated fats. Saturated fats are usually solid at cool temperatures. Eating too much saturated fat is not good for a person’s health, as it can cause heart and blood vessel problems. Unsaturated fats are usually liquid at room temperature. These types of fats are healthy fats. Examples include fats from fish, oil seeds (sesame and sunflower), maize oil and ground nut oil and breastmilk.

As a general rule, plant sources of fats are better for a person’s health than the animal sources, because animal fats contain more saturated fats.

VITAMIINS and MINERALS

Vitamins are organic compounds that generally function as coenzymes. A coenzyme is a “helper” molecule that is required for a protein enzyme to work. In this capacity, vitamins play many roles in good health, ranging from maintaining normal vision (vitamin A) to help the blood to clot (vitamin K).

Depending on their chemical structure, vitamins can be classified as water-soluble or fat-soluble. Fat soluble vitamins are soluble in fats and fat solvents. They are insoluble in water. So these are utilised only if there is enough fat in the body. Water soluble vitamins are soluble in water and so they cannot be stored in the body.

Minerals are inorganic chemical elements that are necessary for normal body processes and
good health. Because they are inorganic and not synthesized biologically, all nutrient minerals are
considered essential nutrients. These are the substances that people need to ensure the health and
correct working of their soft tissues, fluids and their skeleton. Examples of minerals include calcium, iron, iodine, fluorine, phosphorus, potassium, zinc, selenium, and sodium.