Protein: General structure and functions

The word protein is derived from Greek word, “proteios” which means primary. As the name shows, the proteins are of paramount importance for biological systems. Proteins are biochemical molecules consisting of polypeptides joined by peptide bonds between the amino and carboxyl groups of amino acid residues.

Proteins are made up of hundreds or thousands of smaller units known as amino acids. Most organisms use 20 naturally-occurring amino acids to build proteins. The linear sequence of the amino acids in a protein is dictated by the sequence of the nucleotides in an organisms’ genetic code. Amino acids can combine to form long linear chains known as polypeptides. Each type of polypeptide chain has a unique amino acid sequence.

The sequence of amino acids determines each protein’s unique 3-dimensional structure and its specific function such as catalysis of biochemical reactions, mechanical support and immune protection, movement, transport of ligand, transmits nerve impulses, and control growth and differentiation.

The proteins function to regulate specific steps in metabolism – one step, one protein. Hence, many proteins are needed.

The polypeptide must fold into a specific three-dimensional structure before it can perform its biological functions. The function of all proteins depends on their ability to specifically interact with other molecules. Such specificity is possible because polypeptides with different amino acid sequences fold into different tertiary structures.

Proteins are not entirely rigid molecules. They undergo conformational changes upon ligand binding. Each kind of protein evolved to interact with a specific molecule or ligand. For example, transport proteins (such as hemoglobin) bind to specific ligands (in this case oxygen) and transport the ligand to a site where it is needed. Hemoglobin, the transporter of oxygen is a tetrameric protein (alpha 2, beta 2), with each monomer having a heme unit. Binding of oxygen to one heme facilitates oxygen binding by other subunits.

Storage proteins such as myoglobin, another oxygen-binding protein, allow the cell to store higher concentrations of the ligand than otherwise would be possible.

Catalytic proteins— the enzymes—convert the ligands into other molecules. They act as biochemical catalysts. The first step in enzymatic catalysis is the binding of the enzyme to the substrate. This, in turn, depends on the structural conformation of the active site of the enzyme, which is precisely oriented for substrate binding

Many proteins have structural or mechanical functions. Structural proteins interact with specific molecules, often endowing the bound molecules with special biological properties. For instance, one class of proteins, the histones, binds to DNA to form compact nucleoprotein structures called nucleosomes, while a second class of proteins combines with RNA to form the ribonucleoprotein complex known as the ribosome.

Structural proteins collagen is the most abundant protein in mammals and is the main fibrous component of skin, bone, tendon, cartilage and teeth.

Proteins are also important in cell signaling, immune responses, cell adhesion, and the cell cycle.
Protein: General structure and functions

Nutritional value of food can be improved and maintained by additives

The use of additives can enhance the nutritive value of food. Food additives are utilized for the purpose of restoring nutrients lost or degraded during production, fortifying or enriching certain foods in order to correct dietary deficiencies, or adding nutrients to food substitutes.

Additive such as vitamins, minerals, amino acids and amino acids derivatives are utilized to increase the nutritive value of food. Vitamins and minerals are added to many common foods such as milk, flour, cereal and margarine to make up for those likely to be lacking in a person’s diet or lost in processing. When foods are processed, there may be loss of some nutrients and additives may be added to restore the original value.

A particular diet may also require the use of thickening agents, emulsifiers, sweeteners, etc. The fortification of foods began in 1924 when iodine was added to table salt for the prevention of goitre. Vitamins are commonly added to many foods in order to enrich their nutritional value. They help to increase the shelf life of the food by maintaining product consistency, wholesomeness and freshness.
Nutritional value of food can be improved and maintained by additives

Definition of food

Food is that which nourishes the body. Food may also be defined as anything eaten or drunk which meets the needs for energy, building, regulation and protection of the body.

Food  is defined by the FAO/WHO Codex Alimentarius Commission as a substances, whether processed, semi-processed, or raw, which is intended for human consumption and includes drink, chewing gum, and any substances that has been used in the manufacture, preparation or treatment of food but does not include cosmetic, tobacco or substances used only as drugs.

In short, food is the raw material form which human bodies are made. Intake of the right kinds and amounts of food can ensure good nutrition and health which may evident in human appearance efficiency and emotional well-being.

Food should be stable and must be safe. These requirements mean that the products must not endanger the health of the consumer with micro-organisms or their toxins, or deteriorate owing to enzyme or microbial activity, at any stage from production through storage and retail consumption.
Definition of food

Calcium and mechanism of muscle contraction

Calcium has a central role in muscle contractions and it is obtained from extracellular and intracellular sources.

An elevation of intracellular calcium concentrations to about 1 uM is an absolute requirement for smooth muscle contraction, and a reduction in smooth muscle calcium concentration is considered mechanism of smooth muscle relaxation.

Calcium sits at a critical location on the muscle fiber, facilitating the interaction of the muscle proteins myosin and actin.

Stimulation of muscle fibers by nerve impulses, hormones, or stretch in the fiber increases the amount of calcium in the muscle cells and causes the muscle to contract. Calcium binds to calmodulin, causing structural changes that allow calmodulin to bind and activate myosin light chain kinase.

In the presence of calcium and calmodulin, this kinase phosphorylates a light chain of myosin. This result in structural changes in the thick filament, which then allow its interaction with actin, actomyosin ATPase activity and smooth muscle contraction.

As the cells pump calcium ions back outside, the muscle relaxes.
Calcium and mechanism of muscle contraction

Calcium in transmission of nerve impulses

About 99% of the calcium ions in the body are in bones and teeth. Together with sodium and potassium, calcium also participates in transmission of nerve impulses and regulation of the heartbeat.

Calcium is a key factor in normal transmission of nerve impulses. The movement of calcium into nerve cells triggers the release of neurotransmitters at the junction between nerves.

The calcium appeared to aid the momentary fusion of the vesicle membrane and the nerve fiber membrane, prior to the bursting open of the vesicle.

The neuron releases neurotransmitters in direct proportion to the number of calcium ions that flow through the cell’s calcium channels.

Neurotransmitters are released into the synaptic cleft. They migrate to the membrane of the plasma membrane of the postsynaptic neuron where they bind to receptors embedded on the membrane.

Insufficient calcium can inhibit nerve transmissions. It can act as an anesthetic to dull nerve impulses.
Calcium in transmission of nerve impulses

Copper role in formation of collagen

All copper metalloenzymes involve molecular oxygen or oxygen species in their reactions.

Copper plays a key role in the biosynthesis of the extracellular matrix proteins, collagen and elastin, through its function as a cofactor for the enzyme lysyl oxidase.

Lysyl is a secreted enzyme and it catalyzes cross-linking of collagen, which is necessary for proper collagen formation and integrity of all connective tissue.

Copper ion is being located at its active site. Since lysyl oxidase is a copper-dependent enzyme, impaired cross-linking can occur as a result of copper deficiency.

Inhibition of lysyl oxidase has profound effects on the strength of bone and elastic tissue.

Thus, copper is essential for formation and maintenance connective tissue and skeletal mineralization.
Copper role in formation of collagen

Vitamin A and immune system

Among the micronutrients, the role of vitamin A in immune system function has probably been the most extensively characterized, and studies have shown a multifaceted role of vitamin A in many aspect of immunity.

Individuals deficient in vitamin A are more susceptible to infectious disease in general but especially viral infections.

Vitamin A deficiency is associated with increased mortality in children and pregnant women. An estimated 253 million children are at risk of immunodeficiency due to vitamin A deficiency (WHO) and millions of pregnant and lactating women are also at high risk in developing countries.

Vitamin A plays an important function in host defense mechanism, including both cell-mediated immunity and humoral immune mechanisms.

This vitamin involves in the maintenance of mucosal surfaces, in the generation of antibody responses, in hematopoiesis and in the function of T and B lymphocytes, natural killer cells and neutrophils.

Vitamin A also acts to eliminate free radicals before they can do severe cell damage, thus strengthening the immune system.

Researchers have found that children with low vitamin A had abnormally low levels of T-cells in their blood. Vitamin A makes T-cells more active and stronger.
Vitamin A and immune system

Alpha-cyclodextrin

Alpha-cyclodextrin occurs as a virtually odorless, white or almost white crystalline solid.  It is tasteless, resistant to heat, stable at pH levels generally encountered in food manufacture and able to perform inclusion complexes with appropriately sized non-polar organic compounds.

Alpha-cyclodextrin contains six glucopyranosyl units linked by α -1, 4-glycosidic bonds and is one of a family of three cyclodextrin molecules (α-, β - and γ–cyclodextrin).

Alpha-cyclodextrin

In nature, the cyclodextrins are produced as a storage form of carbohydrate by some microorganisms, but they can also be produced industrially by the enzymatic degradation of amylose by cyclodextrin-glucoltransferases, a group of amylolytic enzymes, belonging to class of α–amylases.

The properties of alpha-cyclodextrin have allowed it to be used as a carrier for the range of flavour, colors, sweeteners and fatty acids.

It is used as encapsulating agent and stabilizer. It provides exceptional protection to enclosed favors in terms of evaporation loss and oxidation.
Alpha-cyclodextrin

Glucose, the simple carbohydrate

A 6-carbon sugar, glucose is one of the simplest carbohydrates found in foods. It is one of the most important carbohydrates in plant and animal metabolism.

The compounds D-glucose or dextrose is 2,3,4,5,6-pnetahydroxyhexaldehayde, or conventionally expressed as C6H12O6 with a molecular weight of 180,6 kDa. Glucose is readily soluble in water in a powder form.

Glucose is also the primary repeating sugar unit of most complex carbohydrates or starch.

While many foods contain traces of glucose, it is found in significant amounts only in fruits, such as grapes.

Photosynthesis converts carbon dioxide and water to glucose, which is stored in leaves, stems, fruits, roots, pods and seeds, as glucose, as other sugars or as starch.

The small, amount of glucose in the blood and cells provides the energy need for human body’s daily activities. Any galactose or fructose that is absorbed into the blood is converted to glucose by enzymes present in the liver.  It is an essential energy source for the adult human brain.

Glucose is stored as glycogen, an α-link polymer, predominantly in the liver and muscles.  On average m a 70 kg man may store 500g of glycogen.
Glucose, the simple carbohydrate

Roles of calcium in blood clotting

When blood vessels rupture, the process of blood coagulation is quickly activated. Blood coagulation is adaptive response to hemorrhage involving local conversion of liquid blood to a gel, which plugs a wound.

Calcium participates in nearly every steps of the blood clotting cascade. Calcium is essential for the formation of fibrin, the fibrous protein that makes up structure of blood clots.

According to Best and Taylor’s theory, when the blood is shed from wound, thromboplastin is liberated from the damaged tissue and disintegrated platelets.

It acts on prothrombin in the present of calcium and converts it to active thrombin. Prothrombin is produced in the liver and is present in small quantities in the blood plasma. Calcium occurs as an inorganic constituent in the plasma.

Now thrombin reacts with fibrinogen and converts it into fibrin, which is insoluble. Fibrin constitutes the blood clot in which the blood corpuscles are trapped.

Blood will not clot in the absence of calcium but calcium levels in the body seldom fall low enough to significantly impair blood clotting.
Roles of calcium in blood clotting

Function of the saliva

Saliva is a mixture of secretions produced by cells in different salivary glands. Although the major composition of saliva is water, it also contains mucus, enzymes and antibodies.

Saliva performs a wide array of physiologic and protective functions, some related to its fluid properties and others to its specific content of a variety of molecules.

Being a liquid, saliva primarily lubricates the oral mucosa lining the side of the mouth and moistens food bites. It reducing the frictional damage caused by the rough surfaces of food.

It cleans the oral cavity by flushing away food debris and bacteria, helps with mastication and swallowing of the food bolus, facilitates speech.

Saliva can dissolve flavorful substances stimulating the different taste buds located on the tongue.

In addition, saliva functions in controlling bacterial flora in the mouth and protecting the oral cavity against pathogens.

Saliva also plays an important role in water intake; the sensation of dryness of the mouth as a result of low salivary secretion urges a person to drinks.

The inorganic constituents of saliva such as bicarbonate and phosphate allow buffering while phosphate and calcium function to maintain the mineral integrity of teeth.

A digestive enzyme, salivary amylase is mainly produced by the serous acini initiates the breakdown of starch into smaller carbohydrates during the short times that food is present in the oral cavity.
Function of the saliva

The meaning of condiments

According to the International Organization of Standardization (ISO), there is no clear cut division between spices and condiments and as such they have been clubbed together.

The term spices and condiments refer to the natural plant or vegetable products or their mixtures that are virtually indispensable in culinary art.

Many condiments, e.g. vinegars, pickles and chutneys, tomato ketchup, horseradish sauce, mustard and soy sauce are of plant origin.

They are used in various forms such as fresh, ripe, dried, whole, broken and powdered. They impart aroma, taste, flavor, color and pungency to food.

Condiment act principally upon the nervous system.

Some of them, for instance, excite the nerve termini of the mucous membrane of the digestive canal, whence the excitation or stimulus passes to certain centers in the intestine, or to more remote centers in the spinal cord and the brains.

The condiments used in seasoning foods make the food more delectable to the taste and therefore more digestible.

The culinary use of plants as condiment exploits all parts of a plant: leaves (age, bay, basil), stems (ginger, angelica), bark (cinnamon), rhizomes (ginger, turmeric), roots (horseradish), stolons (liquorice), flower buds (cloves).
The meaning of condiments

Amino acid of Arginine

Arginine is found in foods such as meat, dairy products, poultry and fish. The body uses arginine to create nitric oxide, a substance used to relax the blood vessel.

Arginine is a conditionally essential amino acid, which means that under most circumstances, the human body synthesis its own arginine as needed.

It is considered to be essential in newborn infants and during early childhood development when production may not occur quickly enough to keep up with requirements. 

Arginine is required for the detoxification of ammonia and amine resulting in the production of urea.

Arginine is also a precursor for nitric oxide, a simple gas made up of nitrogen and oxygen that penetrates and crosses the membranes of almost all cells in human body and helps regulates many cellular functions.

Arginine also helps the body to manufacture protein and is needed for the production of certain hormones, including growth hormones. It is one of acclaimed five amino acids and it is crucial for muscle growth.

For athlete, arginine is actually a conditionally essential a like intense training in the gym, increases body’s demand for this amino acid.

Deficiency of arginine may occur in the presence of excessive ammonia, excessive lysine, rapid growth, pregnancy, trauma, or protein deficiency and malnutrition.

Symptoms of arginine deficiency include poor wound healing, muscular weakness, impotence, hair loss, skin rash, constipation and fatty liver.
Amino acid of Arginine

Role of fats in food

Fats are important in foods as well as in the body. The unique chemical configuration of the fat molecule is the key to the uses of fats in foods.

In food, fats provide a source so essential fatty acids, add calorie density or energy, act as carriers for flavors, carry fat soluble vitamins, contribute to texture and mouthfeel. Become precursors of flavor and provide heat transfer medium in frying.

It also contributes shortening power, emulsions and influences the fats melting point, plasticity, appearance, satiety and nutritional content.

A major function of fats is their ability to act as medium for heat transfer to foods without burning them – butter in the frying pan, oil in the deep fryer, and peanut oil in the work.

Their function is particularly important in pastry and bread which little or no sugar to contribute to tenderness. Fats, being insoluble in water interfere with gluten development during mixing. Therefore, fats act as shortenings in the preparation of baked products.

High fat foods may deliver many unneeded calories in only a few bites to the person who is not expending much physical energy.

Fat is important for another reason. Some essential nutrient are soluble in fat and therefore are found mainly in foods that contain it. These nutrient are the essential fatty acids and the fat soluble vitamins – A, D, E, K. 

Fats by themselves tend to be tasteless, they absorb and retain the favor of substances that’s surround them. Fats in meat and other food pick up flavors from their environment and give those flavors to the food.
Role of fats in food

Calcium functions in human body

#99% of total body calcium is found in bones and teeth. Calcium is responsible for construction, formation and maintenance of bone and teeth. This function helps reduce the occurrence of osteoporosis.

#It serves as an intracellular regulator.

#Calcium is a vital component in blood clotting systems and also helps in wound healing. Calcium helps to produce fibrin, the protein responsible for the structure of blood clots.

#Calcium helps to control blood pressure, nerve transmission, and release of neurotransmitters. #Calcium is an essential component in the production of enzymes and hormones that regulate digestion, energy, and fat metabolism.

#It is co-factor for some enzymes, including some involved in blood clotting.

#Calcium helps to transport ions (electrically charged particles) across the membrane.

#It is an important link between electrical excitation and contraction in muscles.

# Nerve transmission requires calcium. When a nerve impulse is transmitted to the end of a motor neuron, it increases the permeability of the nerve ending to calcium.

#Calcium assists in maintaining all cells and connective tissues in the body.

Calcium functions in human body

The use of additives in food processing

Food additives play a vital role in today’s bountiful and nutritious food supply. They allow our growing urban population to enjoy a variety of safe, wholesome, tasty foods year round.

Food additives can be used to:
*Improve the taste or appearance of processed food.

*To improve or maintain nutritional value.

*Improve the keeping quality or stability of a food. It is done by adding vitamins and minerals to common foods such as milk, flour, cereal and margarine.

*Enhance flavor or impart desired color.

*Preserve food when this is the most practical way of extending its storage life. It will keep the food appetizing and wholesome. Food addictives retard product spoilage caused by mold, air, bacteria, fungi or yeast.

*To maintain product consistency. Emulsifiers give products such as peanut butter a consistent texture and prevent them from separating. Stabilizers and thickeners give ice cream a smooth, uniform texture.

Use of food additive whether an intentional or incidental one should not be permitted until its safety under conation of the proposed use has been established beyond reasonable doubt as judged by competent experts.
The use of additives in food processing

Vitamin E Sources and Functions

It was discovered in 1922 in vegetable oil given the name ‘tocopherol’. Vitamin E, of which there are four different forms, is fat soluble.

The four have the same name except with the prefixes alpha-, beta-, gamma-, and delta-, (the first four letters of the Greek alphabet).

Only alpha-tocopherol contributes toward meeting the human vitamin E requirement and it is the most common form of vitamin E in food.

It is our body’s major fat soluble antioxidant. It protects vulnerable polyunsaturated lipids in cell membranes, in blood and elsewhere throughout the body.

The richest dietary sources of vitamin E are the vegetable oils. Safflower and olive oil contain the highest proportion of alpha-tocopherol, followed by soybean oil.

Curiously enough, these oils are also the richest sources of polyunsaturated fatty acids, which vitamin E protects from oxidation.

Nuts and seeds such as sunflower seeds, are among the best food sources.

In western diet, vitamins E intake derives mainly from fats and oils contained in margarine, mayonnaise, salad dressing and desserts, and increasingly also from fortified food (e.g., breakfast cereals, milk, fruit juices).

Vitamin E helps reduce oxidation of lipid membranes and the unsaturated fatty acids and prevents the breakdown of other nutrients by oxygen.

Some scientists compare the function of vitamin E on the cell membrane to a lightening and nullifying the damage that occurs of lightening strikes. This function of vitamin E is also performed and enhanced by other antioxidants, such as vitamin C, beta-carotene, glutathione (L-cysteine), coenzyme Q and the mineral selenium.

In fact, there is a direct recycling process for vitamin E that requires the immediate presence of beta-carotene, vitamin C, flavonoids, and coenzyme Q to work.

Observational studies have suggested that high intake of antioxidant including vitamins E, may lower the risk of some chronic disease, especially heart disease.

Different forms of vitamin E, other than alpha-tocopherol, have immuno-regulatory functions,

Alpha-tocopherol is the most common form of vitamin E in plasma and tissues and the most extensively studied for its beneficial effect on immune function, probably because it is the exclusively component in most vitamin E supplements.
Vitamin E Sources and Functions

Biotin deficiency

Biotin is a water soluble vitamin that is generally classified in the B complex group. This B complex vitamin used in the formation of enzymes that fuel the human body.

Biotin is a key factor in metabolizing and utilizing fats an glucose for energy.

Deficiency of this compound is unusual, but can be demonstrated by the feeding of raw egg white, which contains the substance, avidin, which ties up biotin.

Because some anticonvulsant drugs breakdown biotin, people who take then for long periods also risk a deficiency.

Biotin deficiency also has been clearly demonstrated in biotinidase deficiency. This due to several process which involved gastrointestinal absorption, salvage of biotin at cellular level and renal loss of biocytin.

Infants born with biotinidase deficiency suffer from a rare genetic defect that leads to biotin depletion.

Decreased levels of biotin cause the metabolism to become severely impaired. When enzymes aren’t available to breakdown and build up protein, every biochemical process of the body suffers since protein are the essential building blocks of cellular composition.

The clinical findings and biochemical abnormalities caused by biotinidase deficiency are quiet similar to those of biotin deficiency: common finding include periorificial dermatitis, conjunctivitis, alopecia, ataxia, and development delay.
Biotin deficiency

Roles of Vitamin D in Our Body

Vitamin D is a fat soluble steroid hormone precursor that contributes to the maintenance of normal levels of calcium in the blood stream by increasing absorption of calcium from food and reducing urinary calcium loss (reabsorption by the kidneys).

Both effects keep calcium in the body and therefore spare the calcium that is stored in bones. When necessary, vitamin D transfers calcium from the bone into the bloodstream, which does not benefit bones.

The bones grow denser and stronger as they absorb and deposit the calcium.

Although the overall effect of vitamin D on the bones is complicated, some vitamin D is necessary for healthy bones and teeth.

Therefore, vitamin D prevent muscle aches, bone pains, chronic fatigue and osteoporosis.

Vitamin D plays a vital role in the normal functioning of the immune system and blood cell formation and also helps cells "differentiate"—a process that may reduce the risk of cancer.

From animal and human studies, researchers have hypothesized that vitamin D may protect people from tuberculosis, gum inflammation, multiple sclerosis, autoimmune arthritis, and juvenile diabetes.

Vitamin D controls the growth of normal as well as cancerous cells. It is important role in the prevention of various cancer especially cancer of the colon, prostate pancreas and breast.

Vitamin D is also needed for adequate blood levels of insulin. It stimulates the production of insulin form insulin producing cells in the pancreas.

Vitamin D isn’t actually a vitamin Vitamin D produced by the body. When the skin exposed to ultra Violet B radiation from sun, vitamin D is synthesized.

This fat soluble vitamin is transported to the liver and kidneys and become activated vitamin D.
Roles of Vitamin D in Our Body

Function of Zinc in Human Body

Zinc is an essential trace element for all forms of life. It is widely distributed in foods. Because virtually none of its is present as the free ions, bioavailability is a function of the extent of digestion.

The vast majority of zinc is absorbed by the small intestine though a transcellular process with the jejunum being the site with the greatest transport rate.

Numerous aspects of cellular metabolism are zinc-dependent. Zinc plays important roles in growth and development, the immune response, neurological function and reproduction.

Nearly 300 different metalloenzymes depend on zinc for their ability to catalyze vital chemical reactions. Among the classes of enzymes with zinc metalloenzymes are oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases.

Zinc plays an important role in the structure of proteins and cell membranes. It is because zinc ability to stabilize thiol groups and phospholipids and to quench free radicals.

Zinc influences all immune cell subsets. However, zinc especially important in the maturation and function of T cells, because zinc is an essential cofactor for the thymus hormone, thymulin.

Zinc finger proteins have been found to regulate gene expression by acting as transaction factors. Zinc fingers are protein complexes that form a tetrahedral complex with zinc and provide structural stability for small polypeptides.

Zinc also plays a role in cell signaling and has been found to influence hormones release and nerve impulse transmission.

There is also a suggestions that zinc can act as an endogenous protective factor against atherosclerosis by inhibiting the oxidation of LDL by cells or transition metals.

Other functions little known including in maintaining the integrity of the vasculature and particularly the vascular endothelium.

Because zinc is required for normal cellular repair process and because atherosclerosis is believed to begin with vessel wall injury or dysfunction.

Zinc also interacts with platelets in blood clotting, affects thyroid hormone function, and influence behavior and learning performance.
Function of Zinc in Human Body