Zinc

Question 1

Where is zinc absorbed

Answer 1

upper portion of SI

Question 2

Zinc absorption may involve formation of complexes with ____?

Answer 2

ligands (e.g. citric acid, histidine, other AA)

Question 3

Is zinc absorbed through passive or active absorption

Answer 3

active

Question 4

How is Zn absorption regulated

Answer 4

GI mucosal cells

Question 5

What is metallothionein

Answer 5

Zn-binding protein involved in regulation

Question 6

Zn absorption rate

Answer 6

30-50%

Question 7

What affects the bioavailability of Zn absorption

Answer 7

1. pregnancy/lactation
2. excess amounts of Ca, Fe, Cu, fiber
3. factor in human milk to enhance Zn absorption in infants

Question 8

How is Zn transported

Answer 8

bound to albumin primarily (2/3) & AA/a-2 macroglobulin

Question 9

How is Zn excreted

Answer 9

Feces (primarily)

Question 10

Metabolic Roles of Zn

Answer 10

1. co-factor for a large # of enzymes
2. influences protein synthesis

Question 11

Describe zinc fingers

Answer 11

loop of amino acids that protrude from the zinc-binding site; Cys2/His2 finger

Question 12

What are zinc fingers’ roles

Answer 12

act as a transcription factor to enhance or inhibit gene expression

Question 13

Name some of Zinc’s enzymatic roles

Answer 13

1. carbonic anhydrase (RBC)
2. alkaline phosphatase
3. alcohol dehydrogenase (retinol->retinal)
4. carboxypeptidase A (pancreas)
5. aminolevulinic acid dehydratase (heme synthesis)

Question 14

what are the tissues and systems affected by Zinc

Answer 14

growth, sexual maturation, reproduction, skin, immune system

Question 15

How does zinc affect the immune system

Answer 15

structural part of thymic hormone (lymphocyte mitogen)

Question 16

What does a lymphocyte mitogen

Answer 16

causes expansion of immune cells

Question 17

Signs of zinc deficiency

Answer 17

poor appetite, dermatitis, growth failure, delayed puberty, impaired immunity and healing, loss of taste, mental lethargy

Question 18

Biochemical indicators of zinc

Answer 18

blood levels, hair content

Question 19

Zinc DRI

Answer 19

Males: 11 mg/day
Females: 8 mg/day

Question 20

Food sources of zinc

Answer 20

shellfish, beef, red meats, nuts, legumes

Question 21

In what food sources is zinc bioavailability high

Answer 21

meat, eggs, seafoods–>relative absence of compounds that inhibit zinc absorption and presence of certain AA

Question 22

Why is bioavailability of zinc lower in whole grain products

Answer 22

high content of phytic acid

Question 23

Zinc toxicity

Answer 23

relatively non-toxic; may interfere with absorption/utilization of copper/iron, may reduce HDL levels