selenium Flashcards

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1
Q

what type of element is selenium

A

a trace element

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2
Q

selenium is Present in foods bound to what protein amino acids

A

acids methionine and cystine, as selenomethionine (plants) and selenocysteine (animals)

Also selenide (H2Se), selenite (H2SeO3) and selinate (H2SeO4) found in beets, cabbage, yeast

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3
Q

selenium is absorbed through what

A

Absorbed through amino acid transporter

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4
Q

explain the varying absorption of different selenium forms in food

A

(SeMet > SeCys,
eg Plant material sources are better sources as more bioavailable and better absorbed)

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5
Q

explain why we need selenium

A

To make seleno proteins

Glutathione Peroxidase (a selino protein) :

Antioxidant enzyme – part of cellular defence system, protecting aginst free radicals and oxidative stress. It converts H2O2to water
Peroxides converted to hydroxy forms e.g. LOOH converted to LOH

In the process, 2GSH oxidised to GSSH (eg glutathione is converted into oxidised form to detoxify lipid peroxide to protect against oxidative stress)

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6
Q

what do deiodinases do

A

Remove iodine molecules from thyroxine e.g conversion of T4 to T3
T3 is biologically active. All thyroid hormones are mediated by T3

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7
Q

what are selenoproteins involved in

A

many are involved with antioxidant reactions
Selenium is important in thyroid function and protect against oxidative stress

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8
Q

what are the requirements of selenium based on and how do we measure this

A

based on glutathione peroxidase activity

we measure this by looking at saturation of enzyme, above intakes of 41 µg/day (LRNI set at 40 µg/day)

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9
Q

what are the RNI requirements for men and women and explain the difference

A

RNI in males is 75 µg/day
RNI in females is 60 µg/day

Males need more than females as are more muscular. Physical activity is associated with oxidative stress, so as more muscular they generate more free radicals from physical activity so require greater amounts of selenium

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10
Q

explain selenium deficiency

A

No clear clinical deficiency state
Selenium in soil in china is particularly low so they are at risk of deficiency as are very very low intake of selenium

Keshan disease (very dangerous as means there muscle isn’t strong enough and isn’t contracting strongly enough):
In China, intakes below 12 µg/day increased incidence of Selenium-responsive cardiomyopathy

Kashin-Beck’s disease:

what see is osteoarthropathy – so develop osteo arthritis which is sensitive to selenium

The 2 deficiency occur in different areas of china. The deficiency makes then vulnerable to something in their environment as don’t have same antioxidant defence in their cells. Rather than it causes these deficiencies, it just makes them more vulnerable to these environmental stresses. The antioxidant defences protect us from these oxidative stresses from the environment.

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11
Q

when does selenium deficiency occur

A

occurs in long term parenteral nutrition (when put nutrients straight into a vein)

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12
Q

explain symptoms of selenium deficiency

A

Poor growth (which associated with low thyroid function)
Muscle pain
Depigmentation of skin, hair

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13
Q

Serum [selenium ] inversely linked to risk of what

A

Serum [selenium ] inversely linked to risk of heart disease and some cancers e.g oesophageal; stomach.
Eg higher ur selenium level the lower ur risk in developing these diseases

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14
Q

what are some good sources of selenium

A

nuts and seeds

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