Term
| Niacin is the general term for what? |
|
Definition
| nicotonic acid & nicotinamide |
|
|
Term
True or False
Niacin can be produced in the liver from tryptophan in small amounts |
|
Definition
|
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Term
| What is the active form of NADP? What is the active form of NAD? |
|
Definition
NADPH is active (reduced NADP)
NAD+ is active (oxidized NAD) |
|
|
Term
| How many electrons are transferred between the oxidized and reduced forms of NADP & NAD? |
|
Definition
|
|
Term
| What are the main biological functions of niacin? |
|
Definition
Enzymatic Cofactor -NAD+ accepts electrons in catabolic pathways -NADPH donates eletrons in anabolic pathways
Post Translational Modification -mono & poly (ADP) ribosylation
Intracellular calcium signaling molecules -cADPR & NAADP |
|
|
Term
| What condition(s) result from niacin deficiency? |
|
Definition
Pellegra
-dermatitis, diarrhea, dementia, death |
|
|
Term
True or False
A corn-based diet may lead to a niacin deficiency because it lacks tryptophan and the existing niacin is tightly bound to proteins |
|
Definition
|
|
Term
| Which classification of B vitamins is niacin? |
|
Definition
|
|
Term
| Which classification of B vitamins is riboflavin? |
|
Definition
|
|
Term
| What are some dietary sources of riboflavin? |
|
Definition
food from animal sources
eg milk, meat |
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|
Term
| How is protein-bound riboflavin absorbed? |
|
Definition
| HCl in stomach acid frees it for absorption |
|
|
Term
|
Definition
| converted to free riboflavin |
|
|
Term
| How is cellular production of FAD/FMN regulated? |
|
Definition
| positive regulation by T3 hormone, which activates the enzyme flavokinase |
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|
Term
| What effect will increased FAD/FMN production have on metabolic rate? |
|
Definition
| metabolic rate will increase |
|
|
Term
| How many electrons are exchange in reduction/oxidation of FMN & FAD? |
|
Definition
2 electrons
FMN -> FMNH2
FAD -> FADH2 |
|
|
Term
| What is the precursor of FMN & FAD? |
|
Definition
|
|
Term
| What biochemical pathways is riboflavin involved in? |
|
Definition
B-oxidation
Kreb's Cycle
ETC |
|
|
Term
| Describe the function of FAD & FADH2 in the glutathione reductase reaction |
|
Definition
| 1. NADPH passes 2 e- to FAD, NAD & FADH2 are produced 2. FADH2 passes 2 e- to GSSG, FAD & GSH are produced (glutathione) |
|
|
Term
True or False
Riboflavin is continuously excreted in the urine |
|
Definition
|
|
Term
| What are some common symptoms of a riboflavin deficiency? |
|
Definition
cracked & red lips
inflammation of the lining of the mouth & tongue
mouth ulcers
cracks @ corners of the mouth |
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|
Term
| Which classification of B vitamins is thiamin? |
|
Definition
|
|
Term
True or False
Cooking foods in hot water will lead to a loss of thiamine |
|
Definition
|
|
Term
| What form of thiamin exists in plants? Animals? |
|
Definition
Plants: free thiamin
Animals: thiamin pyrophosphate (TPP) |
|
|
Term
|
Definition
| phosphate must be removed prior to absorption |
|
|
Term
| What disease results from a thiamin deficiency? |
|
Definition
|
|
Term
True or False
A diet of polished/white rice will likely lead to pellegra disease |
|
Definition
False
Beriberi disease is characteristic of this type of diet |
|
|
Term
| What are the biological roles of thiamin? |
|
Definition
-acts as TPP in pyruvate & a-ketoglutarate dehydrogenase reactions
-involved in transketolase pathway/hexose monophosphate shunt (NADPH production & ribose synthesis)
-oxidant defense
-TTP is plays a role in nervous transmission |
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|
Term
| What enzymes are involved in the pyruvate dehydrogenase complex? |
|
Definition
pyruvate carboxylase
transacetylase
dehydrogenase |
|
|
Term
| What are the symptoms of a thiamin deficiency? |
|
Definition
Beriberi disease
wasting
neural dysfunction
irritability
edematous swelling in limbs
difficulty walking
risk of heart failure |
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|
Term
| Where is the majority of pantothenic acid found in food? |
|
Definition
|
|
Term
| What form is pantothenic acid found in the blood? |
|
Definition
|
|
Term
| What is the metabolic function of pantothenic acid? |
|
Definition
assists in the formation of acetyl CoA
CoASH + pyruvate -> acetyl CoA, which is essential in the Krebs cycle |
|
|
Term
| What is the RDA for biotin? |
|
Definition
|
|
Term
| What reactions are dependent on biotin? |
|
Definition
1. conversion of pyruvate to oxaloacetate
2. acetyl coa -> Malonyl CoA (FA synthesis)
3. propionyl CoA -> succinyl CoA -> glucose |
|
|
Term
| What is the relationship of biotin & the enzyme pyruvate carboxylase? |
|
Definition
| biotin acts as a cofactor for this enzyme |
|
|
Term
True or False
acetyl CoA supports glucose synthesis |
|
Definition
False
acetyl CoA is strictly ketogenic |
|
|
Term
| What does pyruvate carboxylase do? |
|
Definition
| converts pyruvate to oxaloacetate for the krebs cycle, or for gluconeogenesis |
|
|
Term
| What does pyruvate dehydrogenase do? |
|
Definition
| converts pyruvate to acetyl CoA for the krebs cycle |
|
|
Term
True or False
Folate & folic acid are interchangeable |
|
Definition
False
Folate is the reduced form of Vit B12
Folic acid is the oxidized form of Vit B12 |
|
|
Term
| Which is found naturally in foods, folate or folic acid? |
|
Definition
|
|
Term
| What are the 3 components of folate? |
|
Definition
pterin ring
PABA
glutamic acid |
|
|
Term
|
Definition
| folate is a polyglutamate, must be broken down to monoglutamtes for absorption |
|
|
Term
| How is folic acid absorbed? |
|
Definition
| folic acid is a monoglutamate and can be readily absorbed |
|
|
Term
| What might inhibit enzymes from breaking polyglutamate down into monoglutamates? |
|
Definition
| alcohols and enzyme inhibitors |
|
|
Term
| Compare the bioavailability of folic acid to that of folate |
|
Definition
Folic acid: 100% bioavailable
Folate: 50% bioavailable |
|
|
Term
| What form of Vit B are cobalamins associated with? |
|
Definition
|
|
Term
True or False
It is easy to exceed the UL of folate |
|
Definition
|
|
Term
|
Definition
|
|
Term
| What is the best dietary source of Vit B12? |
|
Definition
animal products
e.g. meat (esp. from ruminants) & milk |
|
|
Term
| What is required for effective absorption of B12? |
|
Definition
| secretion of an "intrinsic factor" binding protein which will chaperone B12 through the GIT & bring it to a receptor in the SI for absorption |
|
|
Term
| Is Vit B12 easily stored? |
|
Definition
| yes, can be stored in the liver up to 10 years |
|
|
Term
| What effects will be observed in a folate deficiency? |
|
Definition
impaired DNA synthesis & DNA repair
uracil misincorporation
megaloblastic anemia
teratogenesis |
|
|
Term
| What are the effects of excess folate in the diet? |
|
Definition
increased cancer cell growth
tumour progression |
|
|
Term
| What is the best indicator of a Vit B12 or folate deficiency? |
|
Definition
|
|
Term
| What is megoblastic anemia? |
|
Definition
a condition where there are few large RBCs overstuffed with hemoglobin
-due to a folate deficiency |
|
|
Term
| Describe the absorption & utilization of folate, assuming Vit B12 is present |
|
Definition
1. polyglutamate side chains are removed to form monoglutamates (in SI)
2. intestinal mucosal cells methylate folate to N5-methyl form & release into bloodstream
3. Vit B12 removes N5-methyl group when folate reaches target cells, releasing free folate (THF)
4. B12 transfers methyl groups to SAM cycle (imp. for metabolism)
5. THF is also reduced to N5-methyl form to feed SAM cycle |
|
|
Term
| Describe the absorption & utilization of folate when in a Vit B12-deficient state |
|
Definition
1. polyglutamate side chains are removed to form monoglutamates (in SI)
2. intestinal mucosal cells methylate folate to N5-methyl form & release into bloodstream
3. B12 is not available, so folate is trapped in N5-methyl form
4. B12 deficiency leads to a functional folate deficiency |
|
|
Term
| What isomers of Vit B6 are found in foods? |
|
Definition
| all isomers are readily available, B6 deficiency is rare |
|
|
Term
True or False
A B12 deficiency is sometimes mistaken for a folate deficiency |
|
Definition
|
|
Term
True or False
Increasing folate intake can overcome all implications of a B12 deficiency |
|
Definition
False
Megoblastic anemia can be cured, but neural degeneration & death will eventually occur |
|
|
Term
| How is vitamin B6 absorbed? |
|
Definition
| dephosphorylation must occur prior to absorption, followed by passive diffusion in the jejunum |
|
|
Term
| What is the metabolically active form of Vit B6? |
|
Definition
|
|
Term
| What is the major storage site of PLP? |
|
Definition
|
|
Term
True or False
As protein intake decreases, demand for B6 increases |
|
Definition
False
as protein intake increases, demand for B6 increases |
|
|
Term
| What are the functions of Vit B6? |
|
Definition
1. Transamination
2. 1st step in porphyrin synthesis
3. Synthesis of neuroactive amines |
|
|
Term
| What are the neuroactive amines synthesized by vit B6? |
|
Definition
| epinephrine, norepinephrine, serotonin, histamine, GABA |
|
|
Term
| What are some symptoms involved with a B6 deficiency? |
|
Definition
- convulsive seizures
- microcytic anemia
- dermatitis |
|
|
Term
| What are some symptoms of Vit B6 toxicity? |
|
Definition
- peripheral nerve damage
- numb feet/hands
- tingling |
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