Water soluble vitamins Flashcards
Where is thiamine stored in the body?
Half of the thiamine in the body is in muscles. There is high thiamine in liver and kidneys
In what forms does Thiamine (B1) exist in food?
in free form, diphosphate, or bounded to proteins
• Thiamine is absorbed in upper part of small intestine
Absorption of thiamine?
Absorbed small intestines
Some can be made by GM
What is an important role of Thiamine (B1)?
- co-factor for pyruvate dehydrogenase and α-ketoglutarate
dehydrogenase - also important for activity of transketolase in biosynthesis of ribose
What causes beriberi?
Long term thiamine deficiency
What is beriberi associated with?
Disturbance in nerve system
divided into dry and wet
What can decrease Thiamine uptake?
Alcohol and metication
alcohol also produce more urine and therefore more thiamine is excreted
What is mostly effected by lack of Thiamine?
Organs depending most in carbohydrate metabolism
Sources of thiamine?
Meat, peas and beans
In sweden cereal products most important
Sources of riboflavin (B2)?
Different animal and food products. (more in animal)
ex. milk products main source in sweden
Riboflavin is sensitive to what?
Basic condition and light
Absorption of niacin (B3 or B5)
Absorbed in upper part of small intestine
- in cereal products is bounded to a protein and should be released before in order to be absorbed
Can also be synthesized by the gut microbiota
In what way does Niacin exist in all cells?
in the form of co-enzymes
is used in biosynthesis of NAD and NADP
which are important for central carbon and energy metabolism
What causes pallagra?
Niacin deficiency
In what form does riboflavin usually occur?
Apart of FAD
Why is riboflavin important?
Riboflavin is central for the energiproduction of the cells and is needed for carbohydrate-, fat- and proteindigestion
Niacin can be made from what?
Tryptophan
3 other B vitamins also necessary then
Why do you need to eat more Niacin when you are physicaly active?
Since niacin is important for energy metabolism
Pyridoxine (B6) exist is several form ex…
Pyridoxine
Pyridoxal
Pyridoxamine
Who does Pyridoxine (B6) exist in the body?
In free and phosphate forms
What happens to the phosphorylated forms?
B6
They are broken down during cooking and digestion
then rephosphorylated
What is pyridoxine involved in?
Mainly involved in transamination and decarboxylation of amino acids
- also involved in reaction to break down glycogen
Pyridoxine in body is related to what?
protein intake
What is the relationship between B6 and alpha-ketoglutarate ?
Pyridoxine alpha ketoglutarate (PAK) is a combination of Vitamin B-6 and alpha ketoglutarate. In the liver it is converted to pyridoxal phosphate - the biologically active form of B-6. This acts as a coenzyme in the metabolism of protein, carbohydrates, and fats.
What does alpha-ketoglutarate do
The NADH can enter into the mitochondria and be converted to ATP
Pyridoxine is sensitive to what? and what can have during food processing?
sensitive towards light, oxygen and basic conditions.
during food processing can react with cysteine in food and get inactivated
- there are several B6-antagonists that can prevent biological activity
Which vitamin can cause neurological symptoms when consumed in high doses?
Pyridoxine
Where does biotin exist in the body?
In tissues it is bound with a protein
As a cofactor in enzyme participating in carboxylation
Why not eat raw egg white if you want to take up biotin`?
Egg white has a glycoprotein that can bpund to biotin and prevent its absorption. However it is denatured when cooked so then it is ok!
Do we need alot of biotin through diet?
No!
It is one of the most active vitamins in the body so just need very low concentrations.
A part also made by the gut microbiota
Function of biotin
Biotin is a cofactor responsible for carbon dioxide transfer in several carboxylase enzymes:
Biotin is important in fatty acid synthesis, branched-chain amino acid catabolism, and gluconeogenesis.
Why is pantothenic acid necessary for any kind of energy production in the body?
Because it is an important part of coenzyme A (CoA)
And important in acyl transfer. Making sure Acetyl CoA goes into krebs cycle
Foods rich in Panthothenic acid and absorption?
Animal products, whole grain, peas and beans are rich sources.
Thought to be absorbed passively
Ascorbic acid can easily be oxidized to dehydroascorbic acid, what could happen then?
Dehydroascorbic acid is unstable and can be converted to 2,3-Diketogulonic which does not have vitamin C effect and cannot be converted back to vitamin C
How is the absorption of ascorbic acids ?
Active way in small intestine
What need more vitamin c?
Organs with high metabolic rate.
Highest is in the adrenals
A few ways ascorbic acid is important
- important role in hydroxylases e.g. conversion of proline to hydroxyproline
- can increase ironabsorption by reducing Fe3+ to Fe2+
Vit C is sensitivee to what?
heat and oxidation
How many forms of folate are there that have different functions in the body?
Three
THF - carbon carrier (natural in food)
5,10-methylene-THF
5-methyl- THF
The 1C metabolic pathway involves a set of reactions that generate and transfer activated one carbon (1C) units for de novo nucleotide synthesis, compartmentalize amino acids, and contribute to redox homeostasis.
What is the fole of THF
The co-factor tetrahydrofolate (THF) is the carrier that mediates 1C transfer reactions for de novo nucleotide synthesis. Catabolizes serine (3C) (to generate glycine(2C)) in the mitochondria and synthesizes serine in the cytosol.
How are folate and b12 connected?
Both part in converting homocystein to metionin
if high homocystein values docotor will give you both vitamins
Absorption of folate
Absorbed upper part pf intestine
In intestine glutamate chain is released. So just mono-glutamated form enters blood
Absorption varies between 40-90% depending on the food and folate.
Folate involved in which metabolisms?
Amino acid
purine
pyrimidine
Lack of folate can cause
problem with cell division and protein metabolism
increase homocysteine levels (riskfactor for CVD)
Absorption of cobalamin (B12)
Needs a (inner factor) glycoprotein which is produced in the stomach. Joining vitamin and protein helps vitamin to bind to a receptor in lower part of intestine for absorption. - Vitamin absorbed in intestinal cells is then delivered to a protein which is carrying vitamin molecule in the blood. - Considereing mechanism of absorption, dividing intake to several portions increase absorption
Where is cobalamin stored?
Liver
In which reactions are cobalamin (B12) important?
Cobalamin is important for reactions including transferring methyl group in connection with folate (e.g. homocysteine, conversion of ethanolamine to choline)
Methionine - Homocycteine cycle
role of b12
- MTHF gives carbon to B12 – which give carbon to homocysteine and produce methionine
methionine activated to S-adenosylmethionine (SAM)
B12 is coenzyme to which enzyme in which reaction?
Mutase
catalysis of methylmalonyl CoA to succinyl CoA.
Which vitamin is important for the activity of
transketolase
and cofactor of pyruvate dehydrogenase and alpha-ketoglutarate
Thiamine B1
Riboflavin exists to a higher degree in what organs?
Liver and kidney
Important about riboflavin
important in electron transfer ex. FAD
Which vitamin is cofactor in all cells, used in biosynthesis of NAD and NADP
Niacin (B3)
What can cause pellagra?
Niacin deficiency
Main role of pyridoxine
Mainly involved in transamination and decarboxylasion of amino acids
Transamination is when move amino group to keto acid to form new amino acid
Pyridoxine’s relation to electon transport chain
Malate-aspartate shuttle.
Help move NADH into the mitochondria. Where it is made into ATP during electron transport chain.
How is b12 connected to citric acid cycle?
Co-factor in conversion of propionyl CoA to Succinyl-CoA
