Properties of vitamin A

The term vitamin A is generally used to refer to a group of compounds that possess the biological activity of all-trans retinol.

Vitamin A actually an assembly of unsaturated and double bonded organic compounds in which carbon is major element of its structure, it is known as retinol, retinal and retinoic acid (because of their structure and position of its atoms).

Vitamin A is a group of fat-soluble compounds that can be differentiated into two categories, depending on whether the food source is an animal or a plant:
• Vitamin A found in foods that come from animals is called preformed vitamin A or retinol
• Vitamin A found in fruits and vegetables is called provitamin A carotenoid

Animal source derived vitamin A is known as Preformed Vitamin A (retinol) is chiefly found as retinly palmitate in the major of supplements of Vitamins, fortified foods and in the livers of animals.

Proformed is actually the inactive form of vitamin A that are present in plants, approximately fifty Provitanin A is carotenoids that are actually α-carotene, β-carotene and β-cryptoxanthin. β-carotene is less easily absorbed than retinol and must be converted to retinal and retinol by the body.

Two micrograms (mcg) of β-carotene in oil provided as a supplement can be converted by the body to 1 mcg of retinol giving it an RAE (retinol activity equivalent) ratio of 2:1. However, 12 mcg of β-carotene from foods are required to provide the body with 1 mcg of retinol, giving dietary β-carotene an RAE ratio of 12:1.

Food rich in retinol include meat, butter, retinol-enriched margarine, dairy products and eggs, while foods rich in β-carotene include vegetables and fruits (e.g. sweet potatoes, carrots, dark-green leafy vegetables, sweet red peppers, mangoes, melons).

The main physiological active forms of vitamin A are retinaldehyde and retinoic acid, both of which are derive from retinol.

The vital biological roles of vitamin A compounds include normal cell growth, cell differentiation, vision and immunology.
Properties of vitamin A

Physical properties of proteins

Nearly half of the dry weight of a typical animal cell is protein. Structural components of the cell, antibodies, and many of the hormones are proteins but as much as 90% of cellular proteins are the enzymes upon which fundamental cellular function depends. They may be as many as 1000 different enzymes in a single cell.

The protein molecule is a polymer of amino acids joined in peptide linkages. Although the molecular weight is usually high, there is a vast range in both structure and complexity of protein molecules. Hemoglobin for example, has a molecular weight of about 64,500; myosin, a muscle protein is estimated to have a molecular weight of about 489,000.

It is not uncommon for peptide structures of fairly low molecular weight (less than 10,000 and containing less than 100 amino acids) to be designated polypeptides rather than proteins. On the average, about 20 different amino acids occur in most proteins, the amino acids present, their position in the molecule, and the spatial arrangement of the molecule all determine the proteins and characteristics of the proteins. In turn the function of a protein depends, in large measure, on its structure.

Other physical properties of proteins
*Dissociation
*Denaturation: denaturation refers to the changes in the properties of a protein. In other words, it is the loss of biologic activity. In many instances the process of denaturation is followed by coagulation— a process where denatured protein molecules tend to form largeaggregates and to precipitate from solution.
*Optical Activity
*Solubility, Hydration and Swelling Power
*Foam Formation and Foam Stabilization
*Emulsifying Effect
*Colour and taste: Proteins are colorless and usually tasteless. These are homogeneous and crystalline
*Shape and size: the proteins range in shape from simple crystalloid spherical structuresto long fibrillar structures.
Physical properties of proteins

The properties of vitamin C

Vitamin C is a small molecule, a white crystalline substance similar in structure to glucose. It is a highly polar, it is therefore soluble in aqueous conditions.

Vitamin C consists of a single molecule, called ascorbic acid or ascorbate, composed of six carbon atoms, six oxygen atoms, and eight hydrogen atoms, all linked to greater by chemical bonds.

Vitamin C is a water-soluble nutrient essential for life and is used by the human body for many purposes. The term vitamin C is generally used to describe all compounds that qualitatively exhibit the biological activity of ascorbate, including ascorbate and DHA.

All animals and plants synthesize their own vitamin C, except for a small number of animals, including guinea pigs, humans, apes, the red-vented bulbul, a fruit eating bat and a species of trout, that cannot.

Vitamin C is heat labile, and is destroyed by alkali solutions but stabilized by acid solution. It absorbs light whereupon it is destroyed.

The active part of the substance is the ascorbate ion, which can express itself as either an acid or a salt of ascorbate, that is neutral or slightly basic.

Commercial vitamin C is often a mix of ascorbic acid, sodium ascorbate and/or other ascorbates. Absence of vitamin C causes scurvy, leading to spongy gums, loosed teeth, bruising, and bleeding into the mucous membranes.

The properties of vitamin C

Proteins and Amino Acid

The word protein comes from the Greek ‘proteios’ which means ‘of the first rank or importance’.

Nearly half of the dry weight of a typical animal cell is protein. Structural components of the cell, antibodies, and many of the hormones are proteins but as much as 90% of cellular proteins are the enzymes upon which fundamental cellular function depends. They may be as many as 1000 different enzymes in a single cell.

Protein are essential components of muscle, skin, cell membranes, blood, hormones, antibodies, enzymes and genetic material and almost all other body tissues and components.

The protein molecule is a polymer of amino acids joined in peptide linkages. Nitrogen molecules are combined with hydrogen molecules to make what is called an amino group.

Although the molecular weight is usually high, there is a vast range in both structure and complexity of protein molecules.

Hemoglobin for example, has a molecular weight of about 64,500; myosin, a muscle protein is estimated to have a molecular weight of about 489,000.

On the average, about 20 different amino acids occur in most proteins, the amino acids present, their position in the molecule, and the spatial arrangement of the molecule all determine the proteins and characteristics of the proteins. In turn the function of a protein depends, in large measure, on its structure.

Proteins play a critical role in virtually every physiological and biochemical process in the body.

Protein serves as cell communicators through the action of neurotransmitters. They are also essential for blood clotting, immune system development and formation of milk during lactation.
Proteins and amino acids

What are vitamins?

Vitamins have been defined as organic substances present in minute amounts in natural foodstuffs that are essential to normal metabolism and lack of which in the diet causes deficiency diseases.

Vitamins are required in trace amounts in the diet for health, growth and reproduction.

As the chemical structure of the vitamin became known through its isolation and synthesis; it was given a chemical name. When the chemical name was assigned, it was assumed that the name applied to one substance with one specific activity.

Some of the vitamins occur in foods in a form known as precursors or provitamin. Once inside the body, these are transformed chemically to one or more active vitamin forms.

Now it is evident that a vitamin may have a variety of functions and that vitamin activity may be found in several closely related compounds known as vitamers. An excellent example of this is vitamin A, which has several seemly unrelated functions and encompasses not only retinol but also retinal and retinoic acid.

The vitamins can further classified into two classes: fat soluble and water soluble. Soluble confers vitamin many of their characteristics. It determines how they are absorbed into and transported by the bloodstream.

The fat soluble vitamins are represented by vitamins A, D, E, and K absorbed and transported by conventional lipid transport.

For water-soluble vitamins, respective solubility coefficients are major factors that dictate the availability and ease of absorption.
What are vitamins?

What is starch?

The commonest digestible polysaccharide in plants is starch. Starch can be found in all organs of most higher plants, organs and tissues containing starch granules include pollen, leaves, stems, woody tissues, roots, tubers, bulbs, rhizomes, fruits, flowers and the pericarp, cotyledons, embryo and endosperm of seeds. 

Starch molecules are polymers of anhydroglucose and occur in both linear and branched form. The amylose molecule is a linear, unbranched structure in which the glucose residues are attached solely through a-1,4 glycosidic bonds.

Amylopectin, on the other hand, is a branched-chain polymer, the branch points occurring through a-1,6 glycosidic bonds.

The stored starch provides the plants with a spruce of energy when they need it later, keeping them alive though the winter and fueling their reproduction the following spring. It’s what makes starchy vegetables, legumes and grains so healthy to eat.

The enzymes in human saliva and intestine breaks down the long carbohydrate chains, turning them back into simple sugars.

Food starches are commercially manufactured and available for use in products such as baked food, beverages, canned, frozen, and glassed foods, confections, dairy products, dry goods, meat products and snack food.
What is starch?

Starches in food

Plant cells store glucose as starches – long branches or unbranched chains of hundreds or thousands of glucose molecules linked together.

It is a plant polysaccharide stored in roots and seeds of plants and is in the endosperm of a grain kernel. It provides humans with energy 4 cal per gram and is hydrolyzed to glucose.

It occurs in the form of granules, which are usually an irregular rounded shape, ranging in size from 2 to 100um. Both the shapes and sizes of the granules are characteristics of the species of plant and can help to identify the origin of a starch or flour.

Starch from plants is used to produce various foods such as bread and pasta. Many vegetables such as corn and potatoes also contain starch.

Starch is made up to two molecules, amylose and amylopectin, whose parts are connected by glycosidic linkages. Amylose molecules typically make up approximately one-quarter of starch.

Most starches have 20-25% amylose. However, pea starch is 60% amylose.

In foods products, modified starch thickens readymade sauces; adds a sheen to cake frostings, jelly beans and wine gums; and improves the texture, or ‘mouth feel’, of puddings, pie fillings and even baby foods.

Starches in food