Vitamins Flashcards
What is the definition of a vitamin?
A complex organic substance required in the diet in small amounts, compared with other dietary components. The absence leads to a deficiency disease.
Why are some vitamins A the and some B type?
A type = fat soluble factor
B type = heat labile factor
Ho many vitamins does man need?
13
Which vitamins are fat soluble?
Water soluble?
A, D, E, K
B complex and C
Explain the difference in properties between water and fat soluble vitamins
Water soluble:
- not stored extensively
- needed regularly
- generally not toxic in excess
- most function as cofactors for enzyme-catalysed reactions
Fat soluble:
- stored
- not easily absorbed
- not excreted easily
- may be toxic in excess (A&D)
How do B vitamins work?
Co-enzymes in metabolic pathways.
What food sources are good for vitamins?
Which aren’t?
Whole grain, pork, poultry, fish, vegetables, dairy produce.
Polished rice, sugar, fat and processed food.
What happens if you do not have enough thiaminases?
What is this mainly caused by?
- Biochemical role in glycolysis
- Pyruvate to acetyl CoA
- If deficient, there is accumulation of lactate
Alcoholism
What are the 3 types of vitamin deficiency and explain them?
Primary - not taking enough in diet
Secondary - taking enough but it is not used properly in body
Iatrogenic - caused by medical examination or treatment
Why may alcoholics suffer B vitamin deficiencies?
- May have adequate energy intake but as ‘empty calories’ from alcohol
- Inadequate levels of vitamins and other nutrients
- GI tract malfunctions are common
- Cirrhotic liver affects storage, transport and metabolism of many vitamins
- Storage and transport of fat soluble vitamins e.g. vitamin A, may be impaired
What is the function of riboflavin?
How is it taken in?
Functions as FAD and FMN in redox reactions.
Taken mainly in milk
Give details on the functions and sources of Niacin
Function as NAD and NAPH in redox reactions.
Source is in cereal.
Give details on pyridoxine
Essential for amino acid metabolism and harm synthesis.
Most common as a secondary deficiency, causes by antagonistic presence.
What are the dietary sources of vitamin A?
- Retinol containing foods
- Full fat dairy produce, liver and kidney
- Provitamin A containing foods
What is the function of vitamin B12 and folate?
B12 - carrier of methyl groups in mammalian metabolism
Folate - carrier of 1C units
What groups can folate call?
What is the point of this?
Can carry CHO, CH=NH, CH, CH2, CH3.
Responsible in making purines and pyrimidines.
Explain the absorption of B12/Folate
B12 is only from animal tissues. It binds to glycoproteins secreted from gastric cells (the intrinsic factor). Needed for the absorption and transport of B12.
Folate is mainly found in green vegetables and the liver. Absorbed in GI.
Explain what happens when folate enters the body
Folate becomes dihydrofolate then tetrehydroflate duding DHF reductase.
This binds to methyl groups forming methyl tetrahydrofolate.
B12 is therefore needed to get the methyl from tetrahydofolate. This means it can go back and carry more methyl groups.
Explain the symptoms of metaloblastosis (giant germ cells)
B12 and folate needed for thymidylate synthesis and DNA.
B12 dependant methionine synthesise only means of Me THF return into the folate pool.
B12 deficiency traps THF in in the Me THF form producing functional THF deficiency.
Haemopoietic cells dies in bone marrow without completing cell cycle.
Why does vitamin B12 cause neurological symptoms?
Explain these
B12 affects myelin synthesis
Numb fingers
Tingling hands
Loss of position sense
Unsteadiness, confusion, moodiness, depression
What is the function of panothothenic acid?
Component of the coenzyme A in the metabolism and transfer of carbon chains.
What is the source and function of biotin?
Normally sufficient quantities from intestinal bacterial synthesis.
It is a prothetic group for carboxylations.
Explain the source and function of Vitamin C
Source - citrus fruits, tomatoes, berries
Antioxidant. Hydroxylation of proline and lysine in collagen formation. Needed to maintain the Fe2+ necessary for proline and lysine hydroxylase activity in the reduced, active state.
What are the 3 main risks of megadoses in an individual?
Oxalate kidney stones in susceptible individuals.
Diarrhoea.
Systemic conditioning (pregnant women on high doses will have infants with exceptionally high requirements)
What is the one main affect of vitamin C deficiency on the body?
Scurvy
What are the causes of deficiency of fat soluble vitamins?
Primary:
- dietary deficiency
- low fat diet
- fat malabsorption
What are the sources of vitamin A in the body?
As retinol - animal liver, whole milk, egg yolk.
Green vegetables and fruit
What are the functions of vitamin A?
What affects happen if you have too much?
- control of protein synthesis (building a receptor protein, binds chromatin and affects synthesis of proteins involved in cell growth and differentiation)
- in vision
Hair loss, mucous membrane defects, thinning and fracture of long bones.
What is the source and function of vitamin A?
- vegetable oils
- canned and frozen fruits
Naturally occurring oxidant. Prevents oxidation of unsaturated fatty acids in cell membranes.
Destruction of it disrupts membrane structure and cell integrity.
What are the two types of vitamin D and where do we get each one?
D3
- naturally occurs in animals
- functions by binding to intracellular receptor that eventually interact with DNA
- formed in skin by UV light
D2
- derived from ergosterol widely found in plants, fungi and moulds
Vitamin D main function is to maintain correct levels of calcium and phosphate in blood so bone can be mineralised.
What are sources of vitamin K?
What does deficiency lead to?
Green leafy vegetables, milk, meat, eggs and cereal.
Blood clotting is defective. This process depends on a cascade system of interacting proteins.
