Food Composition

Foods have energy and non-energy components called nutrients. Both are essentially required for growth and survival of living organisms.

The energy components of food include:

• carbohydrates (sugars and starches)

• proteins

• lipids (fats)

The non-energy components include:

• vitamins

• minerals

• dietary fibre

• water

Functions of Nutrients

The important functions of nutrients include:

• They are the main source of energy for the body.

• They help in building and repairing body tissues.

• Increases the absorption of fat-soluble vitamins.

• Helps in the synthesis of collagen.

• Provides proper structure to the blood vessels, bones and ligaments.

• They also help in maintaining the homeostasis of the body.

Carbohydrates

Carbohydrates, or carbs, are sugar molecules. Along with proteins and fats, carbohydrates are one of three main nutrients/macronutrients found in foods and drinks. 

Human body breaks down carbohydrates into glucose. Glucose, or blood sugar, is the main source of energy for your body's cells, tissues, and organs. Glucose can be used immediately or stored in the liver and muscles as glycogen for later use.

There are three main types of carbohydrates:

• Sugars. They are also called simple carbohydrates because they are in the most basic form. They can be added to foods, such as the sugar in candy, desserts, processed foods, and regular soda. They also include the kinds of sugar that are found naturally in fruits, vegetables, and milk.

• Starches. They are complex carbohydrates, which are made of lots of simple sugars strung together. Your body needs to break starches down into sugars to use them for energy. Starches include bread, cereal, and pasta. They also include certain vegetables, like potatoes, peas, and corn.

• Fiber. It is also a complex carbohydrate. Your body cannot break down most fibers, so eating foods with fiber can help you feel full and make you less likely to overeat. Diets high in fiber have other health benefits. They may help prevent stomach or intestinal problems, such as constipation. They may also help lower cholesterol and blood sugar. Fiber is found in many foods that come from plants, including fruits, vegetables, nuts, seeds, beans, and whole grains.

Common foods with carbohydrates include:

• Grains, such as bread, noodles, pasta, crackers, cereals, and rice

• Fruits, such as apples, bananas, berries, mangoes, melons, and oranges

• Dairy products, such as milk and yogurt

• Legumes, including dried beans, lentils, and peas

• Snack foods and sweets, such as cakes, cookies, candy, and other desserts

• Juices, regular sodas, fruit drinks, sports drinks, and energy drinks that contain sugar

• Starchy vegetables, such as potatoes, corn, and peas

Some foods don't have a lot of carbohydrates, such as meat, fish, poultry, some types of cheese, nuts, and oils.

Protein

Proteins are very large molecules composed of basic units called amino acids. Proteins contain carbon, hydrogen, oxygen, nitrogen, and sulphur.

Protein molecules are large, complex molecules formed by one or more twisted and folded strands of amino acids. Proteins are highly complex molecules that are actively involved in the most basic and important aspects of life. These include metabolism, movement, defense, cellular communication, and molecular recognition.

Functions of Proteins

Positive negative attractions between different atoms in the long amino acid strand cause it to coil on itself again and again to form its highly complex shape. Folded proteins may combine with other folded proteins to form even larger more complicated shapes.

The folded shape of a protein molecule determines its role in body chemistry. Structural proteins are shaped in ways that allow them to form essential structures of the body. Collagen, a protein with a fibre shape, holds most of the body tissues together. Keratin, another structural protein forms a network of waterproof fibres in the outer layer of the skin.

Functional proteins have shapes that enable them to participate in chemical processes of the body. Functional proteins include some of hormones, growth factors, cell membrane receptors, and enzymes.

Classification of Proteins

Protein molecules are large, complex molecules formed by one or more twisted and folded strands of amino acids. Each amino acid is connected to the next amino acid by covalent bonds.

• • • 1. Primary (first level) – Protein structure is a sequence of amino acids in a chain.

      2. Secondary (secondary level) – Protein structure is formed by folding and twisting of the amino acid chain.

      3. Tertiary (third level) – Protein structure is formed when the twists and folds of the secondary structure fold again to form a larger three dimensional structure.

      4. Quaternary (fourth level) – Protein structure is a protein consisting of more than one folded amino acid chain.

Proteins can bond with other organic compounds and form “mixed” molecules. For example, glycoproteins embedded in cell membranes are proteins with sugars attached. Lipoproteins are lipid-protein combinations.