Nutrition III

Question 1

What is the general sequence of events in the rectification of hypocalcemia?

Answer 1

Low plasma Ca2+ –> increased PTH gene expression + activation of vitamin D

Leads to:

1) Enhance intestinal calcium absorption
2) Increase renal reabsorption of Ca2+
3) activate bone resorption and augment osteoclast activity

Question 2

How is calcium absorbed in the gut?

Answer 2

Ca2+ binds to calbindin and is secreted into the blood through Na/Ca2+ exchangers and Ca2+ ATPases

Question 3

Describe the relative efficacy of calcium absorption.

Answer 3

Calcium is poorly absorbed- only 30% of dairy calcium is absorbed, and even less plant calcium is absorbed

Question 4

What is oxalate?

Answer 4

A potent inhibitor of Ca2+ absorption

Question 5

What is the most abundant intracellular anion?

Answer 5

Phosphorus

Question 6

List some of the major functions of phosphorus

Answer 6

Major component of bone, component for phospholipids of cell membranes, required for energy production and storage, acid base regulation…

Question 7

What is refeeding syndrome?

Answer 7

Rapid expansion of extracellular fluid when severely malnourished individuals are given glucose and saline. This stimulates rapid glycogen synthesis, which depletes plasma phosphorus concentration.

This may result in cardiac arrhythmias and sudden death

Question 8

Iron is transferred in what state? What is it bound to?

Answer 8

Ferric iron (Fe3+) binds to transferrin for transfer through the blood.

Question 9

Iron is stored in what state? What is it bound to for storage?

Answer 9

Ferrous iron (Fe2+) binds to ferritin for storage.

Question 10

Animal foods contain what type of iron (heme-iron vs non-heme iron)?

Answer 10

Heme-iron and non heme-iron

Question 11

Plant food contains what type of iron (heme iron vs. non-heme iron)?

Answer 11

Non-heme iron

Question 12

How does vitamin C affect the absorption of iron?

Answer 12

Vitamin C increases the absorption of iron - it aids in the reduction of Ferric iron to ferrous iron

Fe2+ is absorbed via a putative heme receptor,. Fe3+ is absorbed in a much more complicated way.

Question 13

How are transferrin and ferritin affected by an iron deficiency?

Answer 13

Transferrin receptor is upregulated and ferritin is downregulated

Question 14

How are transferrin and ferritin affected by an iron excess?

Answer 14

Transferrin receptor is downregulated and ferritin is upregulated

Question 15

What type of anemia is seen with an iron deficiency?

Answer 15

Microcytic, hypochromic anemia

Without sufficient iron, hemoglobin synthesis is inhibited at the ALA dehydrogenase step. The cells continue to divide and end up as smaller red cells.

Question 16

Differentiate red blood cells resulting from an iron deficiency from red blood cells resulting from a folic acid or b12 deficiency.

Answer 16

Folic acid/b12: megaloblastic

iron: microcytic, hypochromic

Question 17

What is the most prevalent nutritional deficiency in the world?

Answer 17

Iron deficiency anemia (defined as abnormally low plasma hemoglobin)

Question 18

What information does testing for plasma ferritin levels give us?

Answer 18

Ferritin is an indicator for iron storage levels

Question 19

How is the total iron binding capacity affected by iron deficiency?

Answer 19

TBIC is increased in an iron deficiency - the saturation of transferrin is low and can therefore accept more iron