Calcium

Question 1

What percent of calcium is free? What percent is bound to proteins?

Answer 1

50% free, 50% bound

Question 2

As pH decreases, there is (more/less) bound calcium or __________.

Answer 2

less
hypercalcemia

Question 3

As pH increases, there is (more/less) bound calcium or ____________.

Answer 3

more
hypocalcemia

Question 4

As pH increases, the total calcium amount is the same but calcium replaces some of what molecule?

Answer 4

H+

Question 5

Calcium and what other molecule maintain relatively constant free concentrations since they are inversely proportional?

Answer 5

phosphate (phosphorus)

Question 6

PTH will (increase/decrease) calcium and (increase/decrease) phosphate.

Answer 6

increase
decrease

Question 7

(T/F) More calcium is lost than is rebuilt in the adult.

Answer 7

False - equal amount

Question 8

How is calcium obtained for rebuilding of bone?

Answer 8

through diet –> GI tract –> ECF –> kidneys (reabsorbed) –> bone

Question 9

What 3 major hormones control calcium levels?

Answer 9

PTH
calcitonin
calcitriol (vitamin D3)

Question 10

What is the source of parathyroid hormone (PTH)?

Answer 10

chief cells in parathyroid gland

Question 11

What is the source of calcitonin?

Answer 11

parafollicular cells (C cells) in thyroid gland

Question 12

What is the source of calcitriol?

Answer 12

skin, activated in kidney

Question 13

What are the 3 major targets for calcium control?

Answer 13

1. GI tract
2. kidneys
3. bone

Question 14

Two actions of PTH in bone

Answer 14

up calcium resorption (stim osteoclasts)
up phosphate resorption (but less than Ca)

Question 15

In the kidney, PTH acts to (increase/decrease) calcium reabsorption, (increase/decrease) phosphate reabsorption, and (increase/decrease) bicarbonate reabsorption.

Answer 15

increase
decrease
decrease

Question 16

______ converts vitamin D to its active form in what organ?

Answer 16

PTH
kidney

Question 17

As PTH increases the circulating calcium, it is absorbed the intestines and the calcium increase (stimulates/inhibits) production of PTH via (positive/negative) feedback.

Answer 17

inhibits
negative

Question 18

(T/F) High enough calcium levels will stop PTH production.

Answer 18

False - never completely stops

Question 19

Vitamin D is a _______ which can be obtained through UV light of skin as (D2/D3) or by food as (D2/D3).

Answer 19

steroid
D3
D2

Question 20

Vitamin D begins as a steroid, is converted to ________ in the liver and then a ________ in the kidney.

Answer 20

secosteroid
hormone

Question 21

In the GI tract, vitamin D (increases/decreases) calcium absorption and (increases/decreases) phosphate absorption.

Answer 21

increases
increases

Question 22

How does vitamin D increase calcium absorption in the GI tract?

Answer 22

activates calcium channel proteins

Question 23

What action does vitamin D have on bone?

Answer 23

increases osteoclasts –> calcium resorption

Question 24

What action does vitamin D have on the kidney?

Answer 24

increases calcium reabsorption

Question 25

List the last 3 steps in the synthesis of vitamin D hormone and where it takes place.

Answer 25

1. skin: 7-dehydrocholersterol in skin exposed to UV light --> cholecalciferol --> blood 2. liver: 25-hydroxylase enzyme adds OH group --> 25-hydroxycholicalciferol 3. kidney: PTH activates 1-a-hydroxylase which adds another OH group = calcitriol

Question 26

What is the structure of calcitonin? What unique link does it have which forms a loop?

Answer 26

32-amino acid polypeptide cysteine-cysteine link

Question 27

In bone, calcitonin acts to (increase/decrease) calcium resorption and (increase/decrease) phosphate resorption.

Answer 27

decrease decrease

Question 28

In the kidney, what happens to calcium and phosphate resorption in response to calcitonin?

Answer 28

decrease calcium resorption decrease phosphate resorption

Question 29

Calcitonin acts on the kidney to increase the breakdown of what?

Answer 29

vitamin D

Question 30

What 2 actions does calcitonin cause in the GI tract?

Answer 30

1. decrease gastrin secretion 2. decrease calcium reabsorption

Question 31

Calcitonin binds to a receptor on ______ to inhibit its activity. What does this mean is the main driver?

Answer 31

osteoclast osteoblasts (use calcium to build bone, reduce circulating calcium)

Question 32

What is the half-life for each? 1. calcitonin 2. PTH 3. vitamin D (active)

Answer 32

1. 5 min (short) 2. <10 min (short) 3. 4-6 hours (long)

Question 33

________ receptors are used for PTH and calcitonin while _______ receptors are used for vitamin D.

Answer 33

transmembrane nuclear superfamily