Exam - Calcium Flashcards
what percentage of the body’s mineral mass does calcium represent
~40%
what percentage of the calcium in the body is contained by teeth and bone
99%
what is the remaining 1% used for
it is very important for signalling pathways
supplement label for calcium
helps prevent osteoporosis and develop strong bones
what is calcium predominantly obtained from
dairy products
how does calcium present in foods
as an insoluble salt
how does calcium become soluble
the stomach acid creates it - gets activated by HCl
what percentage of dietary calcium gets absorbed in the small intestine
25-30%
how does calcium get absorbed
saturable and carrier mediated active transport
what is calcium absorption mediated by
calcitriol
what is the secondary pathway for Ca2+ uptake
diffusion via paracellular route
percentages of the 3 ways calcium gets transported around the body
40% bound to albumin
10% found complexed with sulphate, phosphate etc
50% found in free ionized form
what do minerals make up in bone
hydroxyapatite (crystal like structure)
2 functions of calcium
bone
intra/extracellular
what is ionized calcium active and used for
blood clotting
skeletal muscle contraction
nerve potential
intracellular signalling pathways
what will happen if intra/extracellular levels of Ca2+ drop
bone will be sacrificed, otherwise death occurs
how does calcium get used for blood clotting
formation of Gla residues on coagulation proteins
how does calcium get used for skeletal muscle contraction
release of calcium stores
how does calcium get used for nerve potential
acting through ion channels
what factors decrease calcium absorption
caffeine
some fibres
magnesium and zinc
what factors increase calcium absorption
pregnancy and lactation
PTH (Vit D)
what does calcium deficiency profoundly affect
bone and muscle
how does calcium deficiency affect bone
inadequate mineralization - rickets and osteomalacia
how does calcium deficiency affect muscle
causes tetany - involuntary muscle contractions
what is there evidence of calcium deficiency being associated with
hypertension
colon cancer
what occurs with calcium toxicity
constipation
bloating/gas
hypercalcemia - kidney stones