Exam 2, thiamin Flashcards
coenzyme for: thiamin
TPP
coenzyme for: riboflavin
FAD, FMN
coenzyme for: niacin
NAD, NADP
coenzyme for: pyridoxine
PLP (pyridoxal 5’ phosphate)
coenzyme for: folate
THF (tetrahydrofolate), it’s the reduced form of folate essential for its activity b/c oxidized form (folic acid) can’t participate in reactions as well
coenzyme for: pantothenic acid
CoA
coenzyme for: biotin
biotin
coenzyme for: B12
B12
main function: thiamin
energy transformation
*thiamin + 2 phosphates -> TPP (participates in decarboxylation of pyruvate) -> 2C acetate + CO2 -> forms ACoA to enter Krebs
what can destroy thiamin*
thiaminase: destroys weak methylene bridge between thiazole and amine group
*found in betel nuts, fermented tea, raw fish, fern leaves, fish paste
*another property of thiamin is that it’s easily destroyed by heat/ oxidation too
RDI thiamin
M: 1.2 mg, F: 1.1 mg
how does thiamin digestion work?
thiamin from animal sources comes in tpp form -> intestinal phosphatases hydrolyze the phosphates (becomes free form) -> absorbed through SI -> portla blood -> liver to active TPP
*plant thaimin is in free form
inhibitors of thiamin
polyhydroxy phenols (tannic/ caffeic acid) , thiaminases, alcohol
what is the relationship between transketolase and thiamin
transketolase is TPP dependent, catalyzes pentose shunt (which is why it’s a good indicator of thiamin status)
what is the 3rd thiamin function (synthesizes ____ through the ___)
synthesis of NADPH (through PPP) -> synthesis of lipids & nucleic acids
what are non-coenzyme roles of thiamin
membrane and nerve conduction (helps maintain a healthy nervous system)
symptoms of thiamin deficiency in nervous system (3 things)
neuritis: inflammation of nerves, paresthesia (irritated nerves, feel like a bug is on you), irritability, mental depression, anorexia
Beri Beri syndrome, its symptoms
disease of the japanese navy & cured by Baron Takaki (more cooked fish and vegetables)
symptoms: unsteady gait, peripheral neuritis, irritability, depression, fear, coma, constipation
in what population has thaimin deficiency been reported*
Karen tribe, border of Thailand-Myanmar where the diet includes betel nuts, fermented tea, raw fish & fish sauce
Christian Eijkman
-THIAMIN
-won noble prize for discovery of vitamins
-noticed that when eating brown rice instead of polished rice, this deficiency decreased
-discovered that thiamin was found in the outer layer of the rice, so if it was processed/ polished -> leads to deficiency
healthy pigeon vs. with beri beri
w/ beri beri: head is retracted (looks like it is biting itself) , after thiamin shot: head perked up, normal
populations at risk for beri beri
alcoholics, low carb diets, low carb diets + tea + raw fish, places where polished rice is a staple
wet beri beri photograph
edematous edema (when you poke the ankle it leaves a mark) also enlarged heart
enlarged heart photograph
wet beri beri
dry beri beri photograph
muscle wasting, foot and toe drop (drags while walking bc nerve damage), frail and weak lower body, thin limbs bc muscle deterioration
irritable rat photograph: name of condition + what deficiency?
Wernicke-Korsakoff syndrome, goes away when you give a shot of vitamin B1 (thiamin)
Which syndrome related to vitamins might an alcoholic develop? What is the disease and what are the resulting health consequences?*
Wernicke-Korsakoff
-thiamin deficiency syndrome, related to alcoholism and/ or malnutrition (not enough thiamin or impaired utilization)
-* impairs phosphorylation of thiamin and TDP action *
-decreased thaimin absorption
-results in: malnutrition, decreased liver function, if chronic could lead to psychosis
toxicity of thiamin
-none seen with 500mg-1g/ day
-would have to be very large amounts through IV
-no tolerable INTAKE level from food, water soluble so excreted if necessary
riboflavin coenzymes & what do they do
FAD (flavin adenine dinucleotide) and FMN (flavin mononucleotide)
-accept and transfer H ions
main thiamin food source*
pork
