234 OLIVE OILS AND HEALTH CARBOXYLATED In organic chemistry, carboxylation is the reaction in which a carboxyl group is added to a compound by substituting a hydrogen atom. Carboxyl group C: carbon O: oxygen H: hydrogen; R: in fatty acid esters, it represents the hydrocarbon chain that identifies the specific acid. The carboxyl group is a functional group with the following structure: –COOH. - carboxylated Refers to a compound that has undergone carboxylation. CARCINOMA Carcinoma is a general term for a malignant tumour (cancer) that develops in epithelial cells, which cover the inside or outside of many body structures (hollow organs, glands, internal linings of cavities, ducts, etc.). There are different types of carcinomas, and they represent the most common form of cancer. (see also “Neoplasia”) CARDIOVASCULAR (See PHYSIOLOGY / Cardiovascular system) CARDIOVASCULAR SYSTEM (See PHYSIOLOGY) CAROTENES (See CAROTENOIDS) CAROTENOIDS According to their chemical structure, carotenoids can be classified into carotenes (non-oxygenated) and xanthophylls (oxygenated derivatives of carotenes). These are fat-soluble pigments responsible for most of the yellow, orange, and red colours found in many fruits and vegetables (carrots, spinach, broccoli, green beans, oranges, tomatoes, maize, some mushrooms, bell peppers, paprika, saffron, etc.), and also for the orange tones in some animals (flamingos, salmon, trout, crustaceans, egg yolk, etc.). Animals cannot synthesise carotenoids and must obtain them through the diet, although they can convert some types into others, albeit with certain limitations. Carotenoids are also found in algae, bacteria, and fungi. Generally, xanthophylls give yellow colour, while carotenes are orange or red. They are found alongside chlorophylls in plant leaves. Roughly 10% of carotenoids act as precursors of vitamin A (provitamin A), the most abundant in the human diet being β-carotene. Carotenoids may also function as antioxidants, although this remains under debate. The presence of carotenoid-rich foods in the diet has been o 11 _,,e, R 'OH L__·__II _-_-_-_-_-_-_-_-_-_-_-=
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