v i t a m i n s

1. vitamins

2. A vitamin is an organic compound required as a nutrient in tiny amounts by an organism., and must be obtained from the diet. Vitamins are required to perform specific cellular functions.

3. Vitamins have diverse biochemical functions. • Some have hormone-like functions as regulators of mineral metabolism (e.g., vitamin D), or • regulators of cell and tissue growth and differentiation (e.g., some forms of vitamin A). • Others function as antioxidants (e.g., vitamin E and sometimes vitamin C) • The largest number of vitamins (e.g., B complex vitamins) function as precursors for enzyme cofactors, that help enzymes in their work as catalysts in metabolism

4. The term vitamin was derived from "vitamine," a combination word made up by Polish scientist Casimir Funk from vital and amine, meaning amine of life, because it was suggested in 1912 that the organic micronutrient food factors that prevent beriberi and perhaps other similar dietary-deficiency diseases might be chemical amines. This proved incorrect for the micronutrient class, and the word was shortened to vitamin.

5. Classification of vitamins

6. Water-soluble vitamins dissolve easily in water and, in general, are readily excreted from the body. Because they are not readily stored, consistent daily intake is important. Many types of water-soluble vitamins are synthesized by bacteria. • Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats). Because they are more likely to accumulate in the body, they are more likely to lead to hypervitaminosis than are water-soluble vitamins

7. Fat soluble vitamin

8. Vitamin A (retinol)

9. Vitamin D

11. Fatty fish such as salmon are dietary sources of vitamin D

12. Vitamin E

14. Vitamin K

15. Water soluble vitamin • Folic acid • Cobalamin (vitamin B12) • Ascorbic acid (vitamin C) • Pyridoxine (vitamin B6) • Thiamine (Vitamin B1) • Niacin (vitamin B3) • Riboflavin (vitamin B2) • Biotin • Pantothenic acid

16. Vitamin C (ascorbic acid)

19. Thiamin (vitamin B1)

22. Riboflavin (vitamin B2)

24. Niacin (nicotinamide, nicotinic acid, vitamin B3)

25. A man with pellagra, which is caused by a chronic lack of vitamin B3 in the diet

26. Vitamin B6 (pyridoxine, pyridoxal, pyridoxamine)

28. Folacin (folic acid)

30. Cobalamin ,Vitamin B12

32. Biotin

33. Pantothenic acid

34. Chemical Communications

35. What Molecules Are Involved in Chemical Communications? Two systems share major responsibility for regulating body chemistry the endocrine system and the nervous system. • The endocrine system depends on hormones, chemical messengers that circulate in the bloodstream. • The nervous system relies primarily on a much faster means of communication—electrical impulses in nerve cells. But the nervous system also has its chemical messengers, the neurotransmitters that carry signals from one nerve cell to another and from nerve cells to their targets, the ultimate recipients of the messages.

36. There are three principal types of molecules for communications: • Receptorsare protein molecules on the surface of cells embedded in the membrane. • Chemical messengers, also called legends, interact with the receptors. (chemical messengers fit into the receptors sites in a manner reminiscent of the lock-and-key model) • Secondarymessengersin many cases carry the message from the receptor to the inside of the cell and amplify the message.

37. If your house is on fire and the fire threatens your life, external signals- light, smoke, and heat – register alarm at specific receptors in your eyes, nose, and skin. From there the signals are transmitted by specific compounds to nerve cells, or neurons. Nerve cells are present throughout the body and, together with the brain, constitute the nervous system. In the neurons, the signals travel as electric impulses along the axons. when they reach the end of the neuron, the signals are transmitted to adjacent neurons by specific compounds called neurotransmitters. Communication between the eyes and the brain, for example, is by neural transmission.

38. What Are Neurotransmitters? Communication by neurotransmitters is also called synaptic signaling. This is because the communication occurs over a juncture (a place where two cells come into very close contact) called a synapse. The cell releasing the neurotransmitter is called the presynaptic cell and the neurotransmitter is concentrated in an axon terminal of a presynaptic nerve cell. The neurotransmitter binds with receptors on the postsynaptic cell. An example is acetylcholine released by motor neurons at the motor end plate which triggers muscle contraction. 

41. As soon as the danger signals are processed in the brain, other neurons carry messages to the muscles and to the endocrine gland, • Again, neurotransmitters carry the necessary messages from the neurons to the muscle cells and the endocrine glands. The endocrine glands are stimulated, and a different chemical signal, called a Hormone

42. What are hormones? • These chemicals are released by endocrine glands. Hormones are secreted into the interstitial fluid but then diffuse into the blood and travel to target cells throughout the body. • An example is insulin which regulates energy metabolism.

43. The distinction between hormones and Neurotransmitters is physiological, not chemical. Whether a certain compound is considered to be a Neurotransmitters or hormone depends on whether it acts over a short distance A cross a synapse (2 x 10-6 cm), in which case it is neurotransmitter, over a long distance (20 cm) from the secretary gland through the blood- stream to the target cell,, in which case it is a hormone. For example, epinephrine and norepinphrine are both neurotransmitter and hormones.