Found in carrots, yellow vegetables, liver, egg yolk, milk products.
?-carotene ---> vitamin A
Exists in three forms:
retinol and
retinoic acid - binds to intracellular protein receptors --> regulates gene expression retinal - prosthetic group of rhodopsin-involved in dark adaption and night vision.
Vitamin D
Exists as several lipids;
D3 - made in skin exposed to sunlight.
D2 - additive in fortified milk
Deficiency causes rickets in children or osteomalacia in adults --> insufficient Ca phosphate deposition in bone.
Vitamin E or tocopherol
Is an antioxidant that scavenges free radicals.
Vitamin K or phylloquinone
Found in plants.
Required for synthesis of proteins involved in blood coagulation.
Ubiquinone or coenzyme Q
Ring with hydrophobic tail --> inserted into membranes.
Transports e- between enzyme complexes in inner mitochondrial membrane.
Related molecule is plastiquinone - found in thylacoid membrane of chloroplasts.
Cytochromes
Heme-containing protein coenzyme Fe3+ <--> Fe2+.
Classified as a, b, c based on absorption spectra.
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