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Biochemistry- Unit Two
Minerals (T Pierce)
52
Medical
Post-Graduate
03/09/2009

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Cards

Term
Major electrolytes of body
Definition

sodium

potassium

chloride

Term
Functions of electrolytes
Definition
  • maintain water balance
  • neutralize charges
  • establish ion gradients across membranes
Term

Classification of minerals

Definition
  • based on concentration of minerals
    • macrominerals
    • microminerals
Term
Name some macrominerals
Definition
  • sulfer
  • magnesium
  • iron
  • calcium
  • phosphorus
Term

Sulfur (in what form is it ingested? in what form is it lost?)

Definition
  • intake as Cys and Met
  • lost as sulfate
Term
Biological compounds in body sulfur is found in
Definition
  • CoA
  • proteins (Cys, Met)
  • taurine
  • proteoglycans (as chondriotin sulfate)
Term
Function of magnesium
Definition
  • form complex with nucleotide
  • cofactor for many enzymes
Term

Form iron found in in the body

Definition

Hb

Mb

cyc

non heme iron proteins

Term

Name trace elements

Definition

zinc

iodine

copper

selenium

Term
Function of zinc
Definition
  • immune function
  • wound helaing
  • protein and nucleic acid biosyn. (ex: cofactor for alcohol dehydrogenase)
  • taste and smell acuity
  • growth and development

Major cofactor for many enzymes

Term
Function of iodine
Definition
synthesis of T4 and T3
Term
Function of selenium
Definition
  • replace sulfur in Met
  • cofactor for lipid peroxidase
Term

Function of copper

Definition
  • cofactor for lysyl oxidase
Term
Name ultratrace elements
Definition

manganese

molybdenum

chromium

fluoride

Term
Function of fluoride
Definition
develop strong teeth
Term
Function of molybdenum and manganese
Definition
cofactors for enzymes
Term
Function of Chromium
Definition
  •  unknown what it is for or how much
    • believed to affect insulin function, thereby affecting metabolism
Term

Location in body of 99% of calcium. what form is it found in?

Definition
found in bone as hydroxyapatite (the other CRITICAL 1% in cells and EC fluid)
Term
Forms of calcium seen in plasma
Definition
  • protein bound (half of it, mainly to albumin)
  • chelated (bound to various anions or organic molecules)
  • free ionized calcium (physiologically important fraction that is functional)
Term
Location of 80% phosphate in body
Definition

80% found in the bone

Term
Forms phosphate found in
Definition

membrane phospholipids

nucleic acids

nucleotides

sugar phosphates

Term
Explain the role of solubility product in calcium and phosphate metabolism
Definition
  • SP = calcium conc. X phosphate conc.
  • at homeostasis in plasma, the calcium and phosphate are near saturation
  • if their is an increase that exceeds the solubility product, calcium and phosphate will precipitate separately
Term
How is calcium eliminated from the body
Definition
  • bile (eventually be part of feces)
  • urine
  • sweat
Term

Location of calcium. mech of absorption

Definition
absorbed in small intestines via transporter
Term
Effect of Vitamine D and acid on calcium homeostasis
Definition
facilitate absorption
Term

Agents that decrease absoprtion of calcium

Definition
  • fatty acids
  • phosphate
  • oxalate
  • phytate (found in plants, cereal)
  • alkali
Term
Effect of increase calcium intake
Definition

decrease uptake/absorption

Term
Why is phylate good at decreasing absorption?
Definition
Structure is such that it is very good at chelating divalent metals with its many phosphate ions
Term
Role of kidney in calcium homeostasis
Definition
  • calcium could be filtred into kidney
    • reabsorbed in distal convoluted tubule (phospate reabsorbed at PCT)
    • excreted in urine
Term
Role of bone in calcium homeostasis
Definition
  • stores majority of calcium, leading to ossification (osteoblasts)
  • can release calcium back into blood, leading to bone resorption via osteoclasts
Term
Effect of making PTH in a pre-pro form
Definition
the pre means it has the hydrophobic leader sequence so it can be recognize by a signal recognition particle (pre part cleaved off before enters vesicle)
Term
Targe tissues for PTH
Definition

osteoblasts

kidney

Term
Effect of PTH on kidney
Definition
  • decrease resoprtion of phosphate at proximal tubule (increase phosphate excretion)
  • increases reabsorption of calcium and magnesium at DCT
  • increase activity of alpha 1-monooxygenase
Term
Effect of PTH on bone
Definition
  • promote resorption
    • inhibit collagen synthesis in osteoblasts
    • stimulate osteolysis by osteoclasts
      • increase number of osteoclasts
      • enhance lysosomal activity
Term
Mechanism of forming Vit D3 (calcitrol) in skin
Definition
  • starts in skin as 7-dehydroxycholesterol
  • UV light breaks one of the bonds on one fo the hexene rings to form pre-vit D3
  • isomerization (switching of double bonds) leads to formation of Vit D3
  • since not soluble in aqueous solution, we transport Vit D3 to liver via blood
Term
Places in body that make calcitriol (Vit D3)
Definition

skin

liver

kidney

Term

Effect of liver on Vit D3

Definition
  • Liver has 25 monoxygenase
  • converts Vit D3 to 25 hydroxyvitamin D (add OH to aliphatic chain)
  • tranpsorted to kidney via blood bound to transport protein
Term
Effect of kidney on 25 hydroxyvitamin D
Definition
  • kidney has alpha 1 mono-oxygenase (activity controlled by PTH) at the PCT
  • converts 25 hydroxyvitamin to caclitrol (adds OH to hexane ring
Term
Mechanism of action of calcitrol at the cell level
Definition
  1. diffuse into nucleus
  2. binds to VDR and RXR on the DNA
  3. has affect on gene transcription (can either enhance or silence transcription)
Term
Where is VDR's found
Definition
  • intestines
  • bone
  • prostate
  • mammary gland
  • hemopoietic tissue
  • parathyroid tissue
Term
Explain physiological response of body in hypocalciemia
Definition
  1. parathyroid senses decrease in calcium in plasma
  2. stimulated to produce and secrete PTH
  3. goes to kidney and bone
    1. in kidney
      • via cAMP mechanism, decrease reabsorption of phosphate (increase excretion) at PCT
      • increase reabsorption of calcium at DCT
      • increases activity of alpha one monooxygenase (increase production of calcitriol)
    2. in bone
      • PTH bind to osteoblast, causin it to "raise up" off the bone (stop ossification)
      • when osteoclast bound by PTH, releases factor to activate osteoclasts
      • osteoclasts will increase lysosomal activity and release their lysosomal contents
      • calcium will leave bone, picked up by transport protein, carried to plasma
Term
Why do we bring down phosphate in hypocalcemia?
Definition
  • when we start to put calcium into the blood, if we dont bring phosphate down, we will get precipitation because we will exceed Solubility product
  • if we get rid of phosphate, bringing it down to similar levels of calcium, when we start putting calcium into blood, we bring both back up together, preventing from exceeding solubility product
Term

Role of GI tract when PTH released

Definition
  • increase bound calcium
  • frees up phosphate
    • in brush border, we turn on enzymes (ex: phytase increase free phosphate)
    • these enzymes increase calcium
Term
Effect of low blood phosphate
Definition
  • activates one alpha monoxygenase
Term
Symptoms of hypocalciemia
Definition
  • tetany
    • increase neuronal membrane permeability with progressive excitability
Term
Symptoms of hypercalcemia
Definition

muscle paralysis

coma

death

Term
Effect of Vitamin D deficiency in kids and adults
Definition
  • in children, causes rickets
    • bow leggedness
    • ricketa rosery (knots along rib cage)
  • in adults, causes osteomalacia (type of osteopenia)
Term
Wat separates rickets from scruvy?
Definition
  • scurvy- deficient matrix, but we have bone mineral
  • rickets- deficient mineral, but we have matrix 
  • with scurvy, you will see bleeding of the gums
Term
Cause of osteoporosis and osteomalacia
Definition
  • with osteoporosis, lost bone density and mineral
  • with osteomalacia, you lose bone mineral, but not bone density
Term
Effect of Vit D3 deficiency on GI
Definition
  • decrease CaBP
  • decrfeaser Ca transporter
  • decrease phytase
  • decrease phosphatase
Term
Range of plasma calcium concentration
Definition
2.2-2.6 mM
Term

We have a small amount of PTH and calcitrol in plasma at all times. Why

Definition
so we can have normal bone formation
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