Macrominerals

Question 1

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?

Answer 1

intestinal absorption is a key regulatory step in mineral homeostasis.

Question 2

Where does the vast bulk of mineral absorption occur?

Answer 2

Small Intestine **absorption are for calcium and iron, deficiencies of which are significant health problems throughout the world

Question 3

Where is majority of Ca stored? What is the ratio to Phosphorus?

Answer 3

Ca stored in the animal is in the skeleton; Occurs in a ~ 2:1 ratio with P (as hydroxyapatite crystals);

Question 4

What are the 4 Functions of Calcium?

Answer 4

1.   Structural = bones (skeleton);
2.   Nerve & muscle excitability;
3.   Blood coagulation;
4.   Intracellular signaling

Question 5

What minerals are included in Macrominerals?

Answer 5

Calcium Phosphorus Magnesium Sulfur And Electrolytes

Question 6

What is included in Electrolytes?

Answer 6

Sodium, Chlorine and Potassium

Question 7

Calcium absorption occurs in what 2 ways ?

Answer 7

Active, transcellular absorption

Passive absorption

Question 8

Where does active transport of Calcium occur and under what circumstance?

Answer 8

occurs only in the duodenum; when calcium intake has been low

Question 9

The process of active absorption for Calcium involves what? Import? Transport? Export?

Answer 9

This process involves import of calcium into the enterocyte, transport across the cell, and export into extracellular fluid and blood.

Question 10

The rate limiting step in transcellular calcium absorption is? What is it enhanced by? What vitamin is it totally dependent on?

Answer 10

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

Question 11

Passive Absorption occurs where for Ca?

Answer 11

occurs in the jejunum and ileum, and, to a much lesser extent, in the colon when dietary calcium levels have been moderate or high

Question 12

Passive transport of Ca depends on what?

Answer 12

Such transport depends on having higher concentrations of free calcium in the intestinal lumen than in blood.

Question 13

Calcitonin in Ca homeostasis does what?

Answer 13

Reduces Ca uptake in intestine Reduces Ca uptake in to kidneys Stimulates Ca deposit in bones

Question 14

PTH (Parathyroid Stimulating Hormone) in Ca homeostasis does what?

Answer 14

Increases Ca uptake in intestine Increases Ca uptake in to kidneys Stimulates Ca release in bones

Question 15

Main symptoms of Ca deficiency affect the skeleton causing?

Answer 15

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)

Question 16

 Severe Ca deficiency results in

Answer 16

hypocalcemia - tetany & convulsions; (e.g. “milk fever” in dairy cows) BLOOD [Ca] is not a good indicator of moderate deficiency

Question 17

Ca toxicity (Excess Ca) causes

Answer 17

1. 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.

Question 18

Where is majority of Phosphorus found? And where is the rest found?

Answer 18

• ~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)

Question 19

3 Functions of Phosphorus?

Answer 19

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)

Question 20

Phosphorus absorption occurs through?

Answer 20

Active transport and passive diffusion

Question 21

What enhances P absorption? Excess P can depress what?

Answer 21

Vitamin D can enhance P absorption Depresses Ca absorption

Question 22

Deficiency of P leads to what 2 main things?

Answer 22

Leads to rickets (just like Ca) and Pica (chewing on wood or other inappropriate objects)

Question 23

Bioavailability of plant P tends to be high or low in nine-ruminants?

Answer 23

quite low in non-ruminants

Question 24

Phosphorus metabolism and homeostasis Primary mechanism for controlling blood [P] is? This is coordinated by what?

Answer 24

Through excretion from the kidneys  Coordinated by parathyroid hormone (PTH) and 1,25-dihydroxy vitamin D along with blood [Ca]

Question 25

Deficiency of P leads to?

Answer 25

Rickets

Pica (chewing on inappriate items)

Question 26

Phosphorus Toxcity

Answer 26

• Nutritioal secondary hyperparathyroidism
• Excessive bone-resorption that may lead to lameness
• Laxatative effect may lead to diarrhea

Question 27

What two nutrients are serious environmental pollutants?

Answer 27

Phosphorus and Nitrogen

Question 28

What two forms do animals consume phosphorus?

Answer 28

Organic (plant or animal origin)

Inorganic (dicalcium phosphate)

Question 29

Phosphorus in plant material is bound inside a molecule called?

Answer 29

Phytate

Question 30

Releasing the phosphorus from phytate requires what intestinal enzyme?

What type of animals lack this enzyme?

Answer 30

Phytase which most non-ruminants lack

Question 31

Why is Phosphorus a major pollution concern in our lakes and streams?

Answer 31

Much dietary P is excreted in waste and high levels of Phosphate support over production af algae and water weeds

Question 32

Functions of Magnesium?

Answer 32

Bone development (50% in bones)

Oxidative phosphorylation rxns. in mitochondria;

Activation of many enzymes associated with use of ATP

Question 33

Mg absorption mostly takes place where?

Excretion is mostly through?

Answer 33

Absorption- Ileum (55-60%)

Excretion - Urine (95%) reamainder = feces

Question 34

Mg Deficiency

Answer 34

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

Question 35

Magnesium toxicity

Answer 35

Toxicity is not a common problem

Can occcur by accident

Results in diarrhea and anorexia

Question 36

Sulfur functions

Answer 36

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

Question 37

Sulfur absorption is?

Answer 37

active transport

Question 38

Organic absorption vs. inorganic absorption?

Answer 38

Organic is readily absorbed and efficieint

Inorganic is poorly absorbed and inefficient

Question 39

Bulk of body S is present in what?

Answer 39

Amino Acids

Question 40

Urinary excretion of S is mainly as?

Tends to be parallel to what other nutrient?

Answer 40

S is mainly excreted as inorganic SO4 ^2-

Tends to be parallel to N excretion

Question 41

Toxicity?

Answer 41

Not a practical problem because intestinal absoorption of inorganic S is so low

Question 42

Inorganic S is not essential in what type of animal

Answer 42

non-ruminants

but its absence in the diet mat increase the requirement for S-containing amino acids

Question 43

Ruminants fed NPN may show a growth respons to added inorganic S because?

Answer 43

Microbial synthesis of S-containing amino acids can become limiting

Question 44

Inorganic S is needed by rumen microbes to do what?

Answer 44

to make S-containing amino acids