Macrominerals Flashcards
(45 cards)
Minerals are required for health and most also are quite toxic when present at higher than normal concentrations. What is the key regulatory step in mineral homeostasis?
intestinal absorption is a key regulatory step in mineral homeostasis.
Where does the vast bulk of mineral absorption occur?
Small Intestine **absorption are for calcium and iron, deficiencies of which are significant health problems throughout the world
Where is majority of Ca stored? What is the ratio to Phosphorus?
Ca stored in the animal is in the skeleton; Occurs in a ~ 2:1 ratio with P (as hydroxyapatite crystals);
What are the 4 Functions of Calcium?
- Structural = bones (skeleton);
- Nerve & muscle excitability;
- Blood coagulation;
- Intracellular signaling
What minerals are included in Macrominerals?
Calcium Phosphorus Magnesium Sulfur And Electrolytes
What is included in Electrolytes?
Sodium, Chlorine and Potassium
Calcium absorption occurs in what 2 ways ?
Active, transcellular absorption
Passive absorption
Where does active transport of Calcium occur and under what circumstance?
occurs only in the duodenum; when calcium intake has been low
The process of active absorption for Calcium involves what? Import? Transport? Export?
This process involves import of calcium into the enterocyte, transport across the cell, and export into extracellular fluid and blood.
The rate limiting step in transcellular calcium absorption is? What is it enhanced by? What vitamin is it totally dependent on?
Transport across the epithelial cell is the limiting step
which is greatly enhanced by the carrier protein calbindin, the synthesis of which is totally dependent on vitamin D
Passive Absorption occurs where for Ca?
occurs in the jejunum and ileum, and, to a much lesser extent, in the colon when dietary calcium levels have been moderate or high
Passive transport of Ca depends on what?
Such transport depends on having higher concentrations of free calcium in the intestinal lumen than in blood.
Calcitonin in Ca homeostasis does what?
Reduces Ca uptake in intestine Reduces Ca uptake in to kidneys Stimulates Ca deposit in bones
PTH (Parathyroid Stimulating Hormone) in Ca homeostasis does what?
Increases Ca uptake in intestine Increases Ca uptake in to kidneys Stimulates Ca release in bones
Main symptoms of Ca deficiency affect the skeleton causing?
Main symptoms affect the skeleton…
Rickets in young animal;
osteomalacia in old animals;
Ca def. = vit. D deficiency = 2 degree PTH dysfunction
Lameness & spontaneous bone fractures are frequent
(faster the animal grows the faster symptoms will be visible)
Severe Ca deficiency results in
hypocalcemia - tetany & convulsions; (e.g. “milk fever” in dairy cows) BLOOD [Ca] is not a good indicator of moderate deficiency
Ca toxicity (Excess Ca) causes
- May create a hypercalcemia with subsequent calcification of soft tissues; 2. More practical problem is that it reduces utilization/uptake of other minerals, such as Zn, Mg, Fe, I, Cu.
Where is majority of Phosphorus found? And where is the rest found?
• ~80% of body’s P is in the bone; (part of hydroxyapatite w/ Ca) • The other 20% is mostly in organic forms; (e.g., ATP, phosphorylated proteins, phospholipids, RNA & DNA)
3 Functions of Phosphorus?
1. Structural - skeleton w/ Ca and cell membrane PLs; 2. Energy metabolism - AMP, ADP and ATP along with creatine phosphate; 3. Component of various enzymes and signaling pathways (e.g., NADP, insulin and growth factor signaling)
Phosphorus absorption occurs through?
Active transport and passive diffusion
What enhances P absorption? Excess P can depress what?
Vitamin D can enhance P absorption Depresses Ca absorption
Deficiency of P leads to what 2 main things?
Leads to rickets (just like Ca) and Pica (chewing on wood or other inappropriate objects)
Bioavailability of plant P tends to be high or low in nine-ruminants?
quite low in non-ruminants
Phosphorus metabolism and homeostasis Primary mechanism for controlling blood [P] is? This is coordinated by what?
Through excretion from the kidneys Coordinated by parathyroid hormone (PTH) and 1,25-dihydroxy vitamin D along with blood [Ca]
