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Flashcards in Nutrition III Deck (19):
1

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

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

2

How is calcium absorbed in the gut?

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

3

Describe the relative efficacy of calcium absorption.

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

4

What is oxalate?

A potent inhibitor of Ca2+ absorption

5

What is the most abundant intracellular anion?

Phosphorus

6

List some of the major functions of phosphorus

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

7

What is refeeding syndrome?

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

8

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

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

9

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

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

10

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

Heme-iron and non heme-iron

11

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

Non-heme iron

12

How does vitamin C affect the absorption of iron?

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.

13

How are transferrin and ferritin affected by an iron deficiency?

Transferrin receptor is upregulated and ferritin is downregulated

14

How are transferrin and ferritin affected by an iron excess?

Transferrin receptor is downregulated and ferritin is upregulated

15

What type of anemia is seen with an iron deficiency?

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.

16

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

Folic acid/b12: megaloblastic
iron: microcytic, hypochromic

17

What is the most prevalent nutritional deficiency in the world?

Iron deficiency anemia (defined as abnormally low plasma hemoglobin)

18

What information does testing for plasma ferritin levels give us?

Ferritin is an indicator for iron storage levels

19

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

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