Macrominerals Flashcards
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]
Deficiency of P leads to?
Rickets
Pica (chewing on inappriate items)
Phosphorus Toxcity
- Nutritioal secondary hyperparathyroidism
- Excessive bone-resorption that may lead to lameness
- Laxatative effect may lead to diarrhea
What two nutrients are serious environmental pollutants?
Phosphorus and Nitrogen
What two forms do animals consume phosphorus?
Organic (plant or animal origin)
Inorganic (dicalcium phosphate)
Phosphorus in plant material is bound inside a molecule called?
Phytate
Releasing the phosphorus from phytate requires what intestinal enzyme?
What type of animals lack this enzyme?
Phytase which most non-ruminants lack
Why is Phosphorus a major pollution concern in our lakes and streams?
Much dietary P is excreted in waste and high levels of Phosphate support over production af algae and water weeds
Functions of Magnesium?
Bone development (50% in bones)
Oxidative phosphorylation rxns. in mitochondria;
Activation of many enzymes associated with use of ATP
Mg absorption mostly takes place where?
Excretion is mostly through?
Absorption- Ileum (55-60%)
Excretion - Urine (95%) reamainder = feces
Mg Deficiency
Anorexia in rats
Calcification and necrosis of kidneys (death of tissue/kidneys)
Pigs - weak and crooked legs, hyperiritabilty, muscular twitching , tetany and death is possible
Grass tetany
Magnesium toxicity
Toxicity is not a common problem
Can occcur by accident
Results in diarrhea and anorexia
Sulfur functions
Required mainly as a component of various organic compounds such as
Amino Acids - Most sulfer in body*
Vitamins- biotin and thiamin (organic)
Other - Coenzyme A
Sulfur absorption is?
active transport
Organic absorption vs. inorganic absorption?
Organic is readily absorbed and efficieint
Inorganic is poorly absorbed and inefficient
Bulk of body S is present in what?
Amino Acids
Urinary excretion of S is mainly as?
Tends to be parallel to what other nutrient?
S is mainly excreted as inorganic SO4 ^2-
Tends to be parallel to N excretion
Toxicity?
Not a practical problem because intestinal absoorption of inorganic S is so low
Inorganic S is not essential in what type of animal
non-ruminants
but its absence in the diet mat increase the requirement for S-containing amino acids
Ruminants fed NPN may show a growth respons to added inorganic S because?
Microbial synthesis of S-containing amino acids can become limiting
Inorganic S is needed by rumen microbes to do what?
to make S-containing amino acids
