vitamins Flashcards
water soluble and fat soluble vitamins; characteristics
water soluble: B/C; not stored extensively; not toxic in excess
fat-soluble: A/D/E/K; stored; toxic in excess
B1 name; sources; drv; role; associated diseases due to deficiency
thiamin
source: fish/poultry/ vegetables
DRV: 1.4mg (male); 1 mg (female); requirement high if carb intake is high
role: as thiamin pyrophosphate in PYRUVATE DEHYDROGENASE (pyruvate-> acetylcoa)
deficiency: (accumulation of lactate in muscles) beri-beri; wenicke’s encephalopathy/korsakoff’s syndrome
beri-beri types and symptoms
infantile: sudden onset/ cardio problems
acute cardiac: heart failure/ enlarged liver/ engorged neck veins
chronic dry: ataxia/neuropathy
wenicke’s encephalopathy/korsakoff’s syndrome symptoms; vulnerable group; why
wenicke’s: ataxia/ polyneuropathy
untreated wenicke’s-> korsakoff’s
vulnerable group: alcoholics; because alcohol inhibits AT of thiamin + enzyme that converts thiamin-> thiamin pyrophosphate
why are alcoholics susceptible to vitamin D deficiencies/ why dont they have enough vitamins
they have enough energy from alcohol (empty calories)
vitamin/nutrient deficiencies common ( eg AT of B1 inhibited)
cirrhotic liver affects storage/transport/metabolism of vitamins
storage/transport of adek also affected
B2 name; sources; characteristics; role; deficiency symptoms
riboflavin; in milk; precursor of FAD/FMN sensitive to UV angular stomatitis/ cheilosis; cataracts
B3 name; vitamers; sources; role; deficiency
niacin nicotinic acid / nicotinamide cereals/ formed from tryptophan NAD/NADP pellagra (maize eaters in eu and usa)/ dermatitis/ diarrhoea/ dementia
B6 name; vitamers; role; deficiency; therapeutic uses
pyridoxine
pyridoxal/pyridoxamine
active form is pyridoxal phosphate; needed in aa metabolism + haem synthesis
deficiency caused by presence of antagonistics ( eg isoniazid used to treat TB combines with pyridoxal phosphate and renders it useless)
autism/ seizures/ down’s syndrome/PMS
B12 name; sources; absorption; function; metabolic role
cobalamin; meat; combines with intrinsic factor (glycoprotein from gastric cells); carrier of methyl groups;
homocysteine-> methionine
branched aa metabolism
what is pernicious anaemia caused by; treatment
lack of intrinsic factor-> can’t absorb B12; treated with raw liver
B9 name; active form; how is active form maintained; sources; function; metabolic role
folate; tetrahydrofolate; maintained by dihydrofolate reductase; green veg/liver/whole grains; carrier of 1C units; purine&pyrimidine synthesis/ aa metabolism
types of 1c units in what compound
CHO in N5 formyl THFA CHO in N10 formyl THFA CH=NH in N5 formimimo =CH in N5,10 methenyl CH2 in N5,10 methylene CH3 in N5 methyl
folate/ B12 relationship
folate-> dihydrofolate-> THF by DIHYDROFOLATE REDUCTASE
pool of 1C THF derivatives interconvertible except methyl THF
Methyl THF -> THF; in this process homocysteine-> met by MET SYNTHASE WHICH REQUIRES B12
1-C THF-> purines/pyrimidines/aa
b9/12 deficiencies
inadequate myelin synthesis( neuro changes)
megaloblastosis
neural tube defects
cardiovascular mortality (hyperhomocysteinaemia)
alzheimers
symptoms of inadequate myelin synthesis due to lack of B9/12
numbness in fingers hands forearms/ tingling/ataxia/dizziness
why do b9/12 deficiencies result in megaloblastosis
without B12, an essential component of Met synthase, MeTHF can’t return to 1C folate pool
lack of B12-> THF is trapped as MeTHF
lack of B9-> no 5,10 methylene THF
inhibition of synthesis of thymidylate -> lack of DNA synthesis-> haemopoietic cell die in bone marrow
B9/12 deficiency causes
B9: malabsorption/ drugs/ ethanol
B12: absent IF/ defective IF/ gastric atrophy/ gastrectomy / crohn’s disease /coeliac disease
B5 name/ role
pantothenic acid
component of CoA
B7 name/sources/role
biotin
peanuts/chocolates/bacteria
co-enzyme in PYRUVATE CARBOXYLASE (pyruvate-> oxaloacetate in GLUCONEOGENESIS); in ACETYL COA CARBOXYLASE (acetyl coa-> malonyl coa in FA SYNTHESIS)
vitamin C name; sources; role; deficiency
ascorbic acid;
citrus/tomatoes/berries;
antioxidant-> maintains Fe2+ needed for proline/lysine hydroxylase -> collagen formation ; reduces Fe3+ in small intestine for absorption
scurvy
causes of fat-soluble vitamin deficiency
dietary deficiency
low fat diet
fat malasbsorption
intestinal absorption of adek
all absorbed and transported in chylomicrons/vldl -> liver for hydrolysis of retinyl esters
vitamin E absorbed as alpha or gamma tocopherol -> in chylomicrons/VLDL-> to liver-> alpha resecreted as vldl; gamma excreted
vitamin a name; sources; absorption and ratio
retinol
animal liver/ millk/ eggs/beta carotene
carotenoids cleaved into 2 retinol molecules; carotene: retinol= 6:1
retinol active forms and functions of each active form;
retinoic acid = hormone; controls protein synthesis by binding to cytosol protein-> binds chromatin-> affects protein synthesis
retinal= vision ; in darkness, 11 cis-retinal converts light energy to impulses in rod cells of retina
beta carotene= antioxidant
retinol transport and storage; deficiency; toxicity
gut -> liver in chylomicrons
liver-> tissues in retinol binding protein + pre-albumin
deficiency: xerophthalmia (dryness of cornea) -> keratomalacia (front part of eye gets cloudy) -> blindness
toxicity: dermatitis/ alopecia/ mucous membrane defects/ hepatic dysfunction/ thinning and fracture of long bones
vitamin e sources; potent form; function
vegetable oils; alpha;
prevents oxidation of unsaturated FA/ PUFA , which are susceptible to attack by free radicals -> membrane structure preserved;
prevents oxidation of apoprotein B in LDL
precursors of PGs
free radical scavenging and how vitamin E helps with this
free radicals attack PUFA-> other radicals generated
FA radicals + oxygen -> peroxyl radical -> chain reaction
reaction with vitamin E-> vitamin E becomes radical-> stable
vitamin E deficiency
in infants as vit e doesnt cross placenta haemolytic anaemia (RBC Membranes are fragile)
vitamin D3 name; function; formation
cholecalciferol; like a steroid hormone, maintains ca/p levels in blood-> mineralisation of bone; formed in skin by UV on 7-dehydrocholesterol
vitamin d 2 name; sources; formation
ergocalciferol; plants/fungi/mould; maintains correct levels of ca/p in blood-> mineralisation of bone; UV on ergosterol
vitamin d deficiencies
rickets : mineral:matrix ratio decreases ; bending of long bones; kyphosis; delayed tooth eruption
osteomalacia: muscle weakness/ bone pain/ decalcification of long bones
vitamin d toxicity
hypercalcaemia/ GI disturbances/ soft tissue calcification
vitamin k sources; deficiency and symptoms
green leafy veg/milk/meat; infants suffer deficiency as vitamin does not cross placenta easily; impaired blood clotting
