digestive 1b

Question 1

why is iron needed

Answer 1

for formation of hemoglobin, myoglobin, cytochromes, cytochrome oxidase, peroxidase, catalase, etc

Question 2

men excrete about ____ mg or iron daily, most via the ____

Answer 2

0.6 mg

feces

Question 3

women who are between puberty and menopause average ____ mg of iron loss daily.

Answer 3

1.3

Question 4

excreted iron must be replaced by

Answer 4

ingestion

Question 5

the body’s handling of iron involves:

____ ____ protein (which when combined with iron is ____ )

____ ____ protein ( ____ )

the regulation of the rate of intestinal iron ____

Answer 5

intracellular storage protein (combined with iron → ferritin)

plasma transport protein (transferrin)

absorption

Question 6

the regulation of the rate of intestinal iron absorption is accomplished by

Answer 6

the down- or up-regulating of the ferritin gene and by a hormone (hepcidin) that controls the membrane transporter that moves iron out of the SI mucosal epithelial cells

Question 7

of the approximately ____ grams of iron in the body, about ____ % is in hemoglobin and myoglobin and cytochromes and enzymes; ____ % is in the blood as transferrin; and 15-30% is stored for later use (mostly by the ____ and less so in the ____ ____ as ferritin)

Answer 7

5

70%

0.1%

liver

bone marrow

Question 8

about 10% of the ingested iron is absorbed into the ____ daily

Answer 8

blood

Question 9

absorption of iron occurs in various way, including via the protein ____ in the luminal plasma membranes of SI mucosal epithelial cells

Answer 9

DMT 1

Question 10

after iron absorption into enterocytes, iron exists these cells via the protein ____ , and is then moved into blood capillaries

Answer 10

ferroportin

Question 11

inside cells (both body cells and intestinal cells), some of the iron is incorporated into ____ , but some of this is released back into the intestinal lumen when cells:

this iron is excreted in ____

Answer 11

ferritin

at the tips of intestinal villi disintegrate

excreted in feces

Question 12

some of the absorbed iron ions enter the plasma where they combine with a plasma protein (a beta globulin called apotransferrin) to form ____ , which is transported in the plasma

Answer 12

transferrin

Question 13

excess iron in the blood is deposited

Answer 13

in liver hepatocytes and bone marrow reticuloendothelial cells

Question 14

small amounts of iron are stored in a very insoluble form called

Answer 14

hemosiderin

Question 15

when the amount of iron in the plasma falls, some iron in the ____ storage pool is removed and transported in the form of ____ in the plasma to body areas where it is needed (iron is loosely bound in transferrin and can be released to any tissue cell at body locations)

Answer 15

ferritin

transferrin

Question 16

when worn out RBCs are destroyed in the ____ and ____ , the hemoglobin that is released is ingested by ____ ;

this releases iron that is bound in plasma to transferrin or stored in the ferritin pool to be used as needed for:

Answer 16

liver and spleen

macrophages

the formation in bone marrow of new hemoglobin/RBCs

Question 17

regulation of iron:

when the body’s amount of iron is sufficient, the increased level of free iron in the blood and in SI epithelial cells leads to

Answer 17

increased transcription of the gene encoding the ferritin protein in the SI epithelial cells

Question 18

when the body’s amount of iron is sufficient, the increased level of free iron in the blood and in SI epithelial cells leads to increased transcription of the gene encoding the ferritin protein in the SI epithelial cells:

the resulting increased ferritin leads to an increased:

Answer 18

binding of iron in the intestinal epithelial cells and a decrease in the amount of iron released into the blood

Question 19

when body iron is low, the production of ferritin in intestinal epithelial cells ____ , leading to:

Answer 19

falls

a decrease in the amount of iron bound to ferritin, thus increasing the unbound iron released into the blood

Question 20

iron regulation also involves ____, a hormone produced by the liver , and ____ a transmembrane protein that transports iron from the insides to the outsides of SI mucosal epithelial cells (and other cells)

Answer 20

hepcidin

ferroportin

Question 21

when systemic iron stores and concentration are high, ____ release is increased

hepcidin binds to ____ on SI epithelial cells, resulting in the ____ molecule’s being moved to the insde of the cell and degraded

hepcidin thereby prevents iron from being ____ and the iron is sequestered in the SI cells rather than being moved into the blood

Answer 21

hepcidin

ferroportin ferroportin

exported

Question 22

a lack of iron lead to

Answer 22

anemia

Question 23

too much iron can cause ____ which can result in:

Answer 23

hemochromatosis

abnormal skin pigmentation, diabetes, liver disease, and heart and reproductive problems