| A wide variety of the compounds(enzymes and | | | | photoreceptor in the eye, which initiate the |
| hormones) needed to keep the body working | | | | nervous signals responsible for the sense of vision |
| properly is proteins or amino acids, or they are | | | | when they absorb light, are proteins. |
| derived from proteins or amino acids. Enzymes, | | | | Epinephrine (adrenaline), a hormone secreted by |
| including those responsible for digestion, are the | | | | the adrenal gland, is derived from the amino acid |
| most obvious examples, but there are many | | | | tryptophan serves as the precursor for the |
| others. | | | | vitamin niacin and also for serotonin a vital |
| Many of the hormones (such as insulin, gastrin and | | | | neurotransmitter that is involved in transmitting |
| growth hormone like estrogen and progesterone | | | | nerve signals from one nerve cell to another. |
| in females and testosterone in males) produced | | | | Serotonin and melatonin are neurotransmitters |
| by various glands in the body are proteins and | | | | which plays major role in providing sound sleep. |
| peptides. The oxygen molecules needed to oxidize | | | | If the diet is deficient in protein, the synthesis of |
| food molecules during respiration are transported | | | | the vital of these body compounds seems to |
| through the blood by the protein hemoglobin, | | | | take priority over the synthesis of less important |
| which also gives blood its red color. | | | | proteins such as those in skin and hair. Thus a |
| Almost all of the many substances responsible for | | | | deterioration in the condition of skin and hair is |
| the clotting of blood are proteins. The | | | | one of the earliest signs of protein deficiency. |