Exam 3- Mineral Metabolism

Question 1

what properties of calcium and phosphate make them well suited to altering the conformation and functional properties of proteins?

Answer 1

calcium: positive charge
phosphate: negative charge

Question 2

what form of calcium is biologically active and what percentage of the total calcium in blood does it make up?

Answer 2

ionized calcium
about 50%

Question 3

true/false: the amount of calcium in interstitial fluid bound to proteins is higher than the amount in blood

Answer 3

false: very little protein in interstitial fluid to begin with

Question 4

free intracellular calcium concentrations must remain ______

Answer 4

low

Question 5

what abnormality causes an increase in free, ionized calcium in blood?

Answer 5

acid-base abnormalities

Question 6

what do changes in plasma protein concentration do to calcium levels in plasma?

Answer 6

increase total plasma calcium concentration, but not ionized calcium concentration

Question 7

how do changes in anion concentration affect calcium?

Answer 7

change fraction complexed with anions: raises phosphate concentration, increasing calcium complexed to phosphate, decreasing the amount of free, ionized calcium

Question 8

where is most of the phosphate that is not stored in bones located?

Answer 8

intracellularly

Question 9

what happens to plasma phosphate in the kidney?

Answer 9

freely filtered and more than 85% reabsorbed

Question 10

how do plasma phosphate concentrations trigger hormonal regulation?

Answer 10

decreased phosphate leads to calcitriol

Question 11

what three organ systems take part in calcium homeostasis?

Answer 11

gastrointestinal tract
bone
kidney

Question 12

what is the main determinant of intestinal absorption of calcium?

Answer 12

calcitriol (active vitamin D)

Question 13

how does parathyroid hormone impact calcium homeostasis?

Answer 13

lower plasma calcium levels leads to release
increases bone resorption and decreases bone deposition
increases reabsorption calcium in the kidneys
increases absorption calcium in gastrointestinal tract through activation vitamin D

Question 14

where is most of the body’s calcium stored?

Answer 14

in the skeleton: about 99%

Question 15

how is 99% of the bone calcium and phosphate stored?

Answer 15

calcium phosphate crystals: hydroxyapatite
important structural component of bone

Question 16

where is the rest of the calcium and phosphate in bone stored?

Answer 16

salts in equilibrium with interstitial fluid

Question 17

how much of the skeleton does cortical/compact bone make up?

Answer 17

80%

Question 18

cortical bones is composed of repeating units called __________

Answer 18

osteons

Question 19

where is extracellular fluid stored in bone?

Answer 19

canaliculi between lacunae (osteocytes within)

Question 20

what are the four types of cells in bone tissue?

Answer 20

osteoblasts
osteocytes
osteogenic stem cells
osteoclasts

Question 21

what cells take part in bone remodeling?

Answer 21

osteoblasts build up and osteoclasts resorb

Question 22

from where are osteoclasts derived?

Answer 22

monocyte/macrophage lineage (not osteogenic precursor cells)

Question 23

how do osteoclasts resorb bone?

Answer 23

release organic acids which dissolve crystals of calcium phosphate and proteolytic enzymes which dissolve collagen

Question 24

what does the bone cells layer have?

Answer 24

osteocytes
has calcium and phosphate transporters which are hormonally regulated

Question 25

how is calcium absorbed from the intestinal lumen (what routes)?

Answer 25

paracellular and transcellular

Question 26

how is calcium absorbed transcellularly?

Answer 26

Ca-ATPase pump and Ca/Na exchanger

Question 27

where is calcium reabsorbed in the kidney and is it regulated?

Answer 27

60% in proximal tubule: paracellular and unregulated distal convoluted tubule: transcellular and regulated

Question 28

true/false: calcium bound to protein is handled by the kidneys

Answer 28

false: only ultrafilterable

Question 29

what does parathyroid hormone do to activate or inactivate vitamin D?

Answer 29

stimulates 1-alpha hydroxylase in the epithelial cells of the proximal tubule of the kidney to form biologically active form of vitamin D

Question 30

what cells release parathyroid hormone?

Answer 30

chief cells of the parathyroid gland

Question 31

how does parathyroid hormone affect phosphate handling?

Answer 31

indirectly decreases plasma phosphate levels

Question 32

what causes a release of calcitonin?

Answer 32

increased plasma calcium

Question 33

what does calcitonin do?

Answer 33

inhibits osteoclasts and bone resorption

Question 34

true/false: the concentration of calcium in milk is 3-4x higher than plasma

Answer 34

true

Question 35

what is calcium important in?

Answer 35

excitable cells role in blood coagulation role in regulating function of enzymes and secretion of hormones component of 2nd messenger systems

Question 36

what is phosphate important in?

Answer 36

structural component of nucleic acids and phospholipids inorganic phosphate needed for synthesis organic phosphates- ATP many biological pathways kinases are enzymes that attach phosphate groups phosphatases are enzymes that remove phosphate groups

Question 37

how do the ratios of calcium bound to proteins, bound to complexes, and free, in plasma and interstitial fluid compare?

Answer 37

most in both is free a lot in plasma is bound to proteins too more, but still small, bound in complexes in interstitial fluid

Question 38

how does an intracellular calcium signal arise?

Answer 38

ion channels in cell membrane endoplasmic reticulum releases

Question 39

where are lacunae and what is in them?

Answer 39

between concentric lamellae osteocytes

Question 40

what are osteoblasts formed from?

Answer 40

osteogenic stem cells

Question 41

what do osteocytes do?

Answer 41

maintain bone tissue

Question 42

what separates the bone fluid from the plasma?

Answer 42

osteocyte layer with calcium and phosphate transporters that are hormonally regulated

Question 43

where is calcium reabsorbed in the kidney passively and paracellularly? what percent?

Answer 43

proximal tubule 60%

Question 44

what is the reabsorption of calcium in the distal convoluted tubule like?

Answer 44

transcellular and regulated

Question 45

true/false: about 5% of filtered calcium is excreted in urine

Answer 45

false: 1-3%

Question 46

what does the active form of vitamin D do?

Answer 46

binds to intracellular receptors in target tissues to regulate transcription of genes related to Ca++ transport

Question 47

what does parathyroid hormone do to phosphate blood levels?

Answer 47

lowers them

Question 48

do mammary epithelial cells have a lot of free calcium in the cytosol?

Answer 48

no

Question 49

what do kinases do?

Answer 49

attach phosphate groups

Question 50

what do phosphatases do?

Answer 50

remove phosphate groups

Question 51

how much of the calcium in blood is free and ionized?

Answer 51

50%

Question 52

how can calcium move across membranes?

Answer 52

primary or secondary active transport

Question 53

how do acid-base abnormalities change free ionized calcium?

Answer 53

changes amount bound to albumin: increased H+ means less calcium bound to albumin means increased free ionized calcium

Question 54

what is the most important effect of calcitriol?

Answer 54

increases absorption of calcium from the intestine