A good index fossil is one with four characteristics: it is distinctive, widespread, abundant, and limited in geologic time. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms

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2 years ago

Scurvy is a disease that until the nineteenth century was common among sailors and others whose diets were deficient in vitamin

alina1380 [7]

<h2>Scurvy </h2>

Explanation:

(a) Collagen is the major structural component of cartilage,bones and tendons

The basic unit of collagen is tropocollagen and each tropocollagen consists of three coiled left handed polypeptide chains called α chains
Generally each α chain consists of a repeating tripeptide sequence called: G-X-Y
Here G represents glycine; X represents proline and Y represents hydroxyproline
Rigidity of collagen molecule is due to presence of proline and hydroxyproline
Hydroxylation of proline is catalysed by prolyl hydroxylase enzyme which use ascorbate,α ketoglutarate and oxygen
α ketoglutarate is oxidatively decarboxylated to form carbon dioxide and succinate
Sequence of events leading from a dietary vitamin C deficiency to symptoms such as bruising and breakdown of supporting tissues includes: tissue levels of ascorbic acid is low; enzyme prolyl hydroxylase is inactive; proline is not hydroxylated; the triple helix is inadequately stabilized; collagen breaks down; defects in tissues that depend on collagen ; tissues that depend on collagen are subject to breakdown and bruising

(b) Sailors are no longer susceptible to scurvy because fresh fruits which are the source of vitamin C source are available now

British sailors called "limeys" to this day,this term reflects the British navy's use of limes

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2 years ago