AV Ch 11 open book

Which two minerals are the major part of the crystal, hydroxyapatite, formed in ossification of bone?​

calcium, phosphorus

One of the two mechanisms involved in calcium absorption in the small intestine is ____.​

diffusion

During which period of the life cycle does peak bone mass occur?​

early adulthood

The majority of magnesium in the plasma/serum is ____.​

found free in its ionic form

Choose one of the following choices that is not one of calcium's nonosseous functions.​

hair growth IT IS: b. ​skeletal muscle contraction c. ​changes in membrane permeability d. ​generating action potentials in nerves

Which substance can improve calcium absorption?

lactose

Deficiency of which major mineral is usually associated with muscular weakness, neuromuscular hyper-excitability, and tetany?​

magnesium

Which mineral has as its primary function to bind phosphate groups in ATP and ATP-dependent enzyme reactions?​

magnesium

Which mineral participates in all aspects of energy metabolism including glycolysis, beta-oxidation, and the TCA cycle?​

magnesium

Calcium-sensing receptors (CaSR) are located on the ____.​

parathyroid glands

Which hormone both increases release of bone phosphorus into the blood and promotes urinary excretion of phosphorus?​

parathyroid hormone

A dietary mineral that is an important component of DNA and RNA is ____.​

phosphate

In the renal system, which mineral regulates body fluid pH by reacting with secreted hydrogen ions, releasing sodium ions in the process?​

phosphorus

Malnourished individuals being refed who exhibit the "refeeding syndrome" may have low serum concentrations of ____.​

phosphorus

Which mineral is LEAST likely to be deficient in anyone's diet?​

phosphorus

The Tolerable Upper Limit for phosphorus drops after age 70 due to ____.​

​a greater likelihood of impaired renal function

Most phosphorus, regardless of its dietary form, is absorbed from the gastrointestinal tract ____.​

​as free inorganic phosphate ions

Magnesium is absorbed in the small intestine through diffusion and ____.

​carrier-mediated active transport

​Uptake of phosphorus into cells is thought to occur via ____.

​passively, driven by the chemical gradient

A factor that enhances calcium absorption is ____.

​protein intake

​Kyphosis as a result of osteoporosis leads to shortness of breath and abdominal pain due to ____.

​reduction in the spaces of the chest and abdominal cavities

calcium ​phosphorus ​magnesium ​iron ​sulfur

​required for blood clotting ​forms part of the linear backbone of DNA ​forms a complex with ATP for use in glycolysis ​absorption inhibited by excessive calcium ​found as part of structures of vitamins and some amino acids

​calcium ​phosphorus ​magnesium ​iron ​sulfur

​rickets, osteoporosis, tetany ​osteomalacia, neuromuscular, cardiac, and hematologic ​neuromuscular hyperexcitability, and CNS effects ​affects oxygen carrying capacity ​a deficiency of methionine or cysteine, both containing this element, that might lead to alkalosis

Dietary protein promotes bone growth by providing amino acids needed for bone protein and by ____.​

​stimulating insulin-like growth hormone 1

Premature infants are at risk for phosphorus deficiency due to ____.​

​their higher need for the mineral and the insufficient amount in human milk

By what mechanism is vitamin K thought to protect bone health?​

​used for the formation of Gla protein in bone

Regardless of age, the level of calcium absorption is the same.​

Infants, children, adolescents, and women during lactation and pregnancy exhibit a greater calcium absorption level than other age groups.​

____ is secreted in response to low plasma calcium concentrations and acts on the kidney to increase synthesis of ____, which promotes renal reabsorption of calcium.

Parathyroid hormone; calcitriol

Phosphorous absorption takes place in the small intestine but predominantly in the jejunum.​

True

Phosphorous is second to calcium in abundance in the body.​

True

Vitamin D, fructose, and oligosaccharides may increase magnesium absorption.​

True

A deficiency of magnesium may lead to hypocalcemia due to ____.​

a reduction in PTH levels

About 99% of the body's calcium is found in ____.​

bones and teeth

Calcium is transported in the blood in three ways with the exception of ____.​

bound to hemoglobin IT IS: b. ​bound to proteins c. ​complexed with anions d. ​ionized in the free form

Calcitriol can stimulate the absorption of calcium from the intestines by enhancing synthesis of ____and related proteins.

calbindin

The active form of vitamin D in the body is ____.

calcitriol

Rickets is caused by a deficiency in ____.​

calcium

The most abundant divalent cation in the body is ____.

calcium

Which mineral, when combined with unabsorbed dietary fat, forms soaps that cannot be absorbed and are excreted in the feces?​

calcium

A magnesium deficiency might contribute to the disruption of the cell membrane. ​

True

Absorption of magnesium decreases with increased intracellular magnesium concentrations.​

True

Calcium is the most abundant divalent cation in the body.

True

​What conditions may lead to a phosphorus deficiency? How is a deficiency manifested in the individual?

Although phosphorus deficiency is rare, it is seen in premature infants because they have a higher need for it and human milk has a low level of the mineral. In addition, malnourished individuals who are being fed through a tube or intravenously must receive additional phosphorus or they will develop a deficiency. Alkalosis (elevated pH of the blood), critical illnesses, and alcoholism are all associated with hypophosphatemia. Genetic disorders associated with hypophosphatemia include X-linked hypophosphatemia and hypophosphatemic rickets. Both conditions are caused by defects in phosphorus reabsorption in the kidneys and lead to excess phosphorus in the urine. Because bone is composed mainly of calcium and phosphorus, a deficiency will have serious effects. Rickets occurs in infants and children due to inadequate mineralization of the bone matrix and growth plate cartilage. If a phosphorus deficiency is severe, the individual will suffer from reduced oxygen transport and delivery, reduced cardiac output, arrhythmias (irregular heartbeats), respiratory failure, damage to heart and skeletal muscles and neurological problems.

How is calcium status assessed?​

Because of the precise regulation of serum calcium, there is no routine biochemical method of serum calcium status. In certain disease states, abnormal serum calcium levels develop. This is particularly true in cases of cancer and renal failure. Also, changes in blood pH and albumin may bring about changes in serum calcium concentrations. So, checking serum albumin levels is important. If serum albumin is normal, the ratio between bound calcium and ionized calcium remains constant. If albumin levels drop, protein-bound calcium will also drop and treatment is needed to correct the situation. Another means of assessment is measuring bone mineral density since most calcium is found in the bones. This is done using dual-energy X-ray absorptiometry (DEXA or DXA), computerized tomography (CT), and single-photon absorptiometry.

What effect does taking a calcium supplement have on iron absorption, and what advice would you give to maximize the benefit from both minerals?

Calcium supplements inhibit the absorption of iron, especially nonheme iron, likely by causing the ferroportin protein to disengage from the basolateral membrane, diminishing iron absorption. Because this lower iron absorption has been shown to be temporary, an adaptation likely occurs that does not affect the iron status of the body.

Describe the process by which serum calcium concentrations increase in response to the removal of ionized calcium from the blood.

Calcium-sensing receptors on the parathyroid glands and some other tissues monitor blood calcium concentrations. When a drop in serum calcium concentration occurs, the parathyroid gland releases PTH into the blood. This will increase serum calcium concentrations via actions in the kidneys and the bones. In the kidneys, the hormone stimulates transcription of 1-hydroxylase yielding synthesis of calcitriol from 25-OH vitamin D. This leads to increased renal absorption of filtered calcium by interacting with nuclear vitamin D receptors to induce transcription of the gene that codes for calbindin D28k. In the bones, PTH attaches to receptors on osteoblasts. These cells can differentiate into osteoclasts that degrade bone. They promote the release of calcium from the bones into the blood, which brings about an increase in serum calcium levels. The calcitriol that was produced acts in the small intestine to increase calcium absorption by interacting with nuclear vitamin D receptors to induce transcription of the gene that codes for calbindin D9k. This substance binds protein to allow for transport of calcium through the cytosol. In addition, calcitriol enhances calcium absorption at the brush border of the enterocytes by increasing TRPV6 channels and, at the basolateral membrane, by increasing calcium ATP-ase pumps.

Meats and grains are poor sources of calcium.​

True

A chronic phosphorous deficiency in children will cause the development of osteomalacia. ​

False A chronic phosphorous deficiency in children causes rickets. Osteomalacia occurs in adults.​

​Calcitriol enhances calcium reabsorption in the kidneys.

False Calcitriol enhances the reabsorption of phosphorous in the kidneys.​

Calcium absorption occurs in the large intestine.

False Calcium absorption takes place in the small intestine by active transport and diffusion.

ingestion of calcium, magnesium, and aluminum, along with phosphorus, will enhance its absorption.

False Ingestion of these minerals along with phosphorus will form insoluble complexes with the phosphorus and impair its absorption.​

A majority of the calcium in the body is responsible for a variety of nonosseous functions.​

False Only 1% of the nonosseous calcium in the body is involved in functions such as regulation of cellular events and metabolic processes.​

​Thyroid hormone increases serum calcium concentrations.

False Parathyroid hormone (PTH) increases serum calcium concentrations.​

Aluminum and magnesium hydroxides and calcium carbonates and acetates are used today for the treatment of hyperphosphatemia in individuals with renal failure.​

False Those treatments were used several years ago. Today, nonionic binders are used.​

Which of the following statements is true?

In smooth muscle contraction, the roles of calcium and magnesium are antagonistic, with calcium promoting the process and magnesium being the inhibitor if bound to sites that are normally occupied by calcium.

Choose which one of the following statements is not correct.

Magnesium metabolism is regulated by several hormones.

How is magnesium associated with bone mineralization?

Most of the body's magnesium is found in the bones in several forms including Mg(OH)2 and Mg3(PO4)2. Approximately 30% of bone magnesium is on the surface of the bones in an amorphous form and is used as an available pool that maintains plasma magnesium concentrations. The remainder of magnesium is found with calcium and phosphorus in the crystal lattice within the bone. It is most likely that this magnesium is deposited when the bone is formed and plays a crucial role in mineralization.

​a deficiency of methionine or cysteine, both containing this element, that might lead to alkalosis

Paracellular absorption of calcium occurs by diffusion where no carriers or energy are needed. It occurs throughout the small intestine, predominantly in the jejunum and ileum and is concentration dependent. This kind of absorption occurs between cells and is affected by tight junctions that are controlled by occludins and claudins and appear to exhibit properties similar to ion channels. This type of absorption occurs when high calcium concentrations are present in the lumen, creating a gradient of calcium concentrations between the lumen and the basolateral side of the enterocyte. Permeability is increased through the junctions by a series of reactions and calcium absorption is facilitated.

How does phosphate regulate acid-base balance?​

Phosphate acts as an intracellular buffer to help regulate acid-base balance. In the kidneys, secreted hydrogen ions react with filtered phosphate causing the release of sodium ions according to the following reaction: Na2HPO4 + H+ --> NaH2PO4 + Na+ Because this reaction removes free hydrogen ions, the pH increases. An additional reaction also increases the pH: HPO2- + H+ --> H2PO4 + Na+ If the pH drops, these reactions may be reversed.

Compare calcium, phosphorus and magnesium as to their physiological functions, symptoms of a deficiency and some of their food sources. You may write out your response or set it up in table form

calcium: milk and yogurt, seafood with bones, bone mineralization, blood clotting, rickets, osteoperosis; phosphorous: meat poultry fish eggs, bone mineralization, energy transport, nucleic acid formation, rare, infants and refeedig syndrome; magnesium: nuts seeds whole grains, bone mineralization, enzymatic reactions, glycolysis, TCA, blood clotting, arrythmia

Food sources of calcium include ____.​

canned sardines

Major minerals include calcium, phosphorus, magnesium, sodium, potassium, and ____.​

chloride

​Magnesium deficiency may develop due to mutations in ____.

claudin-16

By what mechanism is vitamin C thought to protect bone health?

contributing to the integrity of bone collagen

Per serving, the best source of phosphorus would be ____.​

milk and yogurt

Paracellular absorption of calcium ____.

occurs by diffusion mainly in the jejunum and ileum

Which cells are considered the bone-building cells?

osteoblasts

The condition associated with decreased bone strength accompanied by the deterioration of the microarchitecture of bone tissue and low mineral density is ____.​

osteoporosis