Nicotinamide adenine dinucleotide is a co-enzyme. It is required for the fundamental biological process that make life possible. It is called dinucleotide because it consists of two nucleotides joined together through their phosphate groups.

The three major antioxidant vitamins are beta-carotene, vitamin C and vitamin E. Beta carotene is an antioxidant that gets converted to vitamin A and plays a very important role in health. It's responsible for the red, yellow, and orange coloration of some fruits and veggies.

Vitamins are accessory food factors, which are required in small quantity for controlling metabolism and body functioning. Vitamins are of two types- fat soluble (A, D, E, K) and water soluble (B and C). Vitamins like minerals are not digested but directly absorbed from ingested food. They play role in metabolism and growth.

Deficiency diseases are diseases which are caused due to deficiency of a critical nutrient in diet. The nutrient cannot be synthesized in body and must be present in diet. Scurvy, Rickets and Beriberi are some of the common deficiency diseases in man. Scurvy is caused due to deficiency of vitamin C. The common symptoms are bleeding gums, loose teeth, anaemia, painful and swollen joints, delayed healing of wound, and emaciation. Beriberi is caused due to deficiency of vitamin B$ _{1}$. Its symptoms are loss of appetite. Fatigue, muscle atrophy paralysis, mental confusion, cardiac oedema. Rickets is caused due to deficiency of vitamin D and minerals like phosphorous and calcium in children. Its symptoms are defective mineralization or calcification of bones potentially leading to fractures and deformity.

• A vitamin is an organic molecule that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. 
• Essential nutrients cannot be synthesized in the organism, either at all or not in sufficient quantities, and therefore must be obtained through the diet.
• Best food sources of vitamin B:     Whole grains (brown rice, barley, millet)

• Sprouting is the natural germination process by which seeds or spores put out shoots, plants produce new leaves or buds, or other newly developing parts experience further growth. Hence, A good source of vitamins of B groups is Germinated seeds.

In the large intestine, water is absorbed into the blood as the waste materials move through the colon. The symbiotic bacteria such as E. coli and Streptococcus faecalis, normally residing in the healthy human colon, feed on protein contents of chyle breaking them into amino acids which are absorbed into the blood. The colon bacteria also synthesize vitamins B1, B2, biotin, folic acid and K which are absorbed. They also convert bile pigments into brown pigments which give colour to faeces. 

• A vitamin is an organic molecule that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism.
• Fat-soluble vitamins(A, D and K) are stored in different organs of the body and especially in the liver.
• Vitamin A, VitaminK and Vitamin E are stored in the liver because they are fat soluble vitamins.
  
• So, the correct answer is 'All the above'.

Nicotinamide or Niacin is also known as anti pellagra vitamin. It is a component of NADP, NADP+ and is important for energy transfer reactions. Yeast, pulses, green vegetables, cereals, milk, egg yolk, liver, milk, fish, meat are rich sources of niacin. Crypts of lieberkuhn occur throughout small intestine and produce intestinal juice or succus entericus. Steapsin is pancreatic lipase and acts on fats and converts fats into fatty acids, glycerol, mono and diglycerides.

Vitamins are important nutrient supplements required in small amounts. They usually serve as coenzymes in metabolic reactions. Vitamin B$ _{1}$ is also called as Thiamine and its coenzyme form is thiamine pyrophosphate. Vitamin B$ _{5}$ is pantothenate. It is an important component of coenzyme A. Vitamin B$ _{3}$ or Niacin is important for synthesis of nicotinamide adenine dinucleotide or NAD and nicotinamide adenine dinucleotide phosphate or NADP. Vitamin A is also called retinol. It is essential for vision. Vitamin E is also called tocopherol. It is an important for fertility factor.

Vitamins are important nutritional supplements for body. They are required for normal body metabolism. Vitamins can be grouped into two categories- fat soluble (vitamins A, D, E and K) and water soluble vitamins (vitamin B complex and vitamin C). The fat soluble vitamins can be stored in body fat but water soluble vitamins cannot be stored in body.

Vitamins do not help to increase the amount of calories or energy required for the human body. Instead vitamins which are used in small quantities helps human beings to stay healthy. While the daily requirements of vitamins may differ from individual to individual, the necessary amounts can be met through intake of healthy food.

Vitamin A - carotene, the precursor of Vitamin A is found in most orange and green vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables. It has been shown in research that -carotene protect the lungs against toxins that are linked to lung cancer. Another study found that ex-smokers who ate green and yellow vegetables high in beta carotene daily decreased their risk of stomach and lung cancer.
Vitamin ${B _{17}}$ - The anti-tumour agent Vitamin ${B _{17}}$ (commonly known as Amygdalin or Laetrile) therapy is one of the most popular and best known alternative cancer treatments. It is very simple to use and is very effective when used in high enough doses with product of high quality combined with an effective cancer diet and key supplements. Laetrile works by targeting and killing cancer cells and building the immune system to fend off future outbreaks of cancer. The greatest concentration is found in the seeds of the rosaceous fruits, such as the apricot pits and other bitter nuts.
Vitamin C - Vitamin C has shown great promise in the fight against cancer, both in prevention and disease-management. Some properties of the vitamin C may make it toxic to cancer cells. Vitamin C is an antioxidant,it also enhance the immune system by stimulating the activities of natural killer cells (a type of white blood cell) and anti-cancer agents. Vitamin C is also said to prevent tumors from spreading, help the body heal after cancer surgery, enhance the effects of certain anti-cancer drugs, and reduce the toxic effects of other drugs used in chemotherapy. It also boost the effectiveness of other cancer treatments. Vitamin C is found in many vegetables and fruits, especially oranges, grape fruits, and peppers.

Vitamins are important nutritional components. Vitamins are grouped into two categories fat soluble (vitamin A, D, E and K) and water soluble (vitamin B complex and C). Many component vitamins of vitamin B complex act as coenzymes during metabolic reactions example thiamine is the precursor of thiamine pyrophosphate (TPP), niacin is the precursor of nicotinamide adenine dinucleotide (NAD), riboflavin is the precursor of flavin adenine dinucleotide (FAD) etc. 

Vitamins are important for healthy living. They are required for normal body metabolism as many enzymes required coenzymes for their activity. The coenzymes are derived from vitamins. The vitamins are divided into two categories- fat soluble (vitamin A, D, E and K) and water soluble (vitamin B complex and C).

Almost all food is processed in some way before it is eaten. Commercially, the main reasons to process food are to eliminate micro-organisms (which may cause disease) and to extend shelf life. Simply cooking or combining a food with other foodstuffs to create a recipe is also considered a form of food processing. Whatever the case, the nutrient value of any food is often altered by the processing. Some vitamins are more stable (less affected by processing) than others. Water-soluble vitamins (B-group and C) are more unstable than fat-soluble vitamins (K, A, D and E) during food processing and storage. The most unstable vitamins include: folate, thiamine and vitamin C. More stable vitamins include: niacin (vitamin B3), vitamin K, vitamin D etc. So, maximum amount of vitamins are lost during food processing compared to carbohydrates, fats and proteins. 

Vitamins does not generate energy inside the body but are still essential.

Vitamins are essential compounds that must be acquired through the diet because the body can't synthesize them. One of the reasons vitamins are needed is because they play an indirect role in catalysis, in which enzymes speed up chemical reactions. However, most vitamins can't help enzymes on their own. In order to participate in catalytic reactions, most vitamins have to change into coenzymes that are small "co-pilot" molecules that pair up with enzymes. These coenzymes are extremely useful because they stay the same after catalysis, so they're recycled and reused multiple times.

Vitamins with some enzymes act as coenzyme. Coenzymes are organic molecules that are required by certain enzymes to carry out catalysis. They bind to the active site of the enzyme and participate in catalysis but are not considered substrates of the reaction.

Vitamin D is not one chemical but many. The natural type is produced in the skin from a universally present form of cholesterol, 7-dehydrocholesterol. Sunlight is the key: Its ultraviolet B (UVB) energy converts the precursor to vitamin D3. In contrast, most dietary supplements are manufactured by exposing a plant sterol to ultraviolet energy, thus producing vitamin D2. Because their function is almost identical, D2 and D3 are lumped together under the name vitamin D, but neither will function until the body works its magic. The sun’s energy turns a chemical in your skin into vitamin D3, which is carried to your liver and then your kidneys to transform it to active vitamin D. 

Biological assimilation, is the combination of two processes to supply cells with nutrients. The first is the process of absorbing vitamins, minerals, and other chemicals from food within the gastrointestinal tract. In humans this is done with a chemical breakdown (enzymes and acids) and physical breakdown. The second process of bio assimilation is the chemical alteration of substances in the bloodstream by the liver or cellular secretions. Although a few similar compounds can be absorbed in digestion bio assimilation, the bio-availability of many compounds is dictated by this second process since both the liver and cellular secretions can be very specific in their metabolic action. This second process is where the absorbed food reaches the cells via the liver.

Casimir Funk was a Polish biochemist and is credited with being among the first to formulate the concept of vitamins, which he called as vital amines or vitamins.
Therefore, the correct answer is option A.

The amount of nitrogen in the atmosphere remains fixed. Nitrogen cycle keeps the atmospheric. nitrogen more or less constant. Atmospheric nitrogen cannot be taken directly by plants and animals various steps process are done by microbes to convert it into usable forms. Vitamins contain nitrogen.

Monoglycerides and fatty acids enter absorptive cells in the small intestine through micelles; they leave micelles and recombine into chylomicrons, which then enter the bloodstream. Fat soluble vitamins are absorbed in the same manner as lipids; water soluble vitamins can be directly absorbed into the bloodstream from the intestine.

A vitamin is an organic molecule that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism.
A mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life.
 Essential nutrients and minerals cannot be synthesized in the organism, either at all or not in sufficient quantities, and therefore must be obtained through the diet.
 They are present in foods (like leafy or yellow vegetables, citrus fruits, meat, milk, eggs). Food which contains adequate amounts of vitamins, minerals, and high-quality proteins is a protective food. And it also protect against the development of a deficiency disease (as pellagra, beriberi, scurvy). Hence, the vitamins and minerals containing foods are together referred to as protective food.

• The end product of protein digestion is amino acids.
• The most common source of Vitamin C is citrus fruits.
• The stomach mucosa’s epithelial lining consists only of surface mucous cells, which secrete a protective coat of alkaline mucus. A vast number of gastric pits dot the surface of the epithelium, giving it the appearance of a well-used pincushion, and mark the entry to each gastric gland, which secretes a complex digestive fluid referred to as gastric juice. Chief cells—Located primarily in the basal regions of gastric glands are chief cells, which secrete pepsinogen, the inactive proenzyme form of pepsin. HCl is necessary for the conversion of pepsinogen to pepsin.
• Fish oil contains enough vitamin A and D.

Vitamins with some enzymes act as coenzyme. Coenzymes are organic non protein molecules that bind with the protein molecule (apoenzyme) to form the active enzyme (holoenzyme). A number of the water-soluble vitamins such as vitamins B$ _1$, B$ _2$ and B$ _6$ serve as coenzymes.

Co-factor is a non-protein chemical compound that is required for the protein's biological activity. These molecules are commonly enzymes and co-factors can be helper molecules that assist in biochemical transformations such as vitamins.
Co-factors can be subdivided into either one or more inorganic ions , or a complex organic or metallo-organic molecule, called as a co-enzyme, most of which are derived from vitamins.
An inactive enzyme without the co-factor is called an apoenzyme while the complete enzyme with the co-factor is called as a holoenzyme.

In 1911, Casimir Funk isolated a concentrate from rice polishings that cured polyneuritis in pigeons. He named the concentrate vitamin because it appeared to be vital to life and because it was probably an amine.

Non-protein components of certain enzymes are called cofactors. If the cofactor is organic, then it is called a coenzyme. Coenzyme is relatively small molecules compared to the protein part of the enzyme and many of the coenzymes are derived from vitamins