Catalyst
Catalyst: A substance that speeds up a chemical reaction but is not consumed or altered in the process. Catalysts are of immense importance in chemistry and biology. All enzymes are catalysts that expedite the biochemical reactions necessary for life. The enzymes in saliva, for example, accelerate the conversion of starch to glucose, doing in minutes what would otherwise take weeks.
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- Cataplexy
Cataplexy: A debilitating condition in which a person suddenly feels weak and collapses at times of strong emotion such as during laughter, anger, fear, or surprise. In so collapsing, people with cataplexy may injure themselves. For example, laughter and other emotions may trigger a reflex that can bring many of the muscles of the body […]
- Cataplasm
Cataplasm: A poultice or plaster. A soft moist mass, often warm and medicated, that is spread over the skin to treat an inflamed, aching or painful area, to improve the circulation, etc. From the Greek kataplasma, poultice, from kataplasso, to spread over. See also: Mustard plaster; Poultice.
- Cataract
A clouding or loss of transparency of the lens in the eye as a result of tissue breakdown and protein clumping. There are many causes of cataracts, including aging, cortisone medication, trauma, diabetes, and other diseases. Cataracts affect most people who live into an old age. Symptoms include double or blurred vision and sensitivity to […]
- Cataract surgery
Removal of the clouded (cataractous) lens in its entirety via surgery and replacement of the lens with an intraocular lens (IOL) made of plastic. A typical cataract operation takes about an hour, requires local anesthesia only, and usually does not require hospitalization.
- Cataract with poikiloderma atrophicans
Cataract with poikiloderma atrophicans: Also known as the Rothmund-Thomson syndrome, this is an hereditary disease characterized by progressive degeneration (atrophy), scarring and abnormal pigmentation of the skin together with stunting of growth, baldness, cataracts, depressed nasal bridge, and malformations of the teeth, nails and bone. Poikiloderma atrophicans with cataract (the Rothmund-Thomson syndrome) is inherited as […]