vitamins

Question 1

water soluble and fat soluble vitamins; characteristics

Answer 1

water soluble: B/C; not stored extensively; not toxic in excess
fat-soluble: A/D/E/K; stored; toxic in excess

Question 2

B1 name; sources; drv; role; associated diseases due to deficiency

Answer 2

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

Question 3

beri-beri types and symptoms

Answer 3

infantile: sudden onset/ cardio problems
acute cardiac: heart failure/ enlarged liver/ engorged neck veins
chronic dry: ataxia/neuropathy

Question 4

wenicke’s encephalopathy/korsakoff’s syndrome symptoms; vulnerable group; why

Answer 4

wenicke’s: ataxia/ polyneuropathy
untreated wenicke’s-> korsakoff’s
vulnerable group: alcoholics; because alcohol inhibits AT of thiamin + enzyme that converts thiamin-> thiamin pyrophosphate

Question 5

why are alcoholics susceptible to vitamin D deficiencies/ why dont they have enough vitamins

Answer 5

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

Question 6

B2 name; sources; characteristics; role; deficiency symptoms

Answer 6

riboflavin; 
in milk; 
precursor of FAD/FMN 
sensitive to UV 
angular stomatitis/ cheilosis; cataracts

Question 7

B3 name; vitamers; sources; role; deficiency

Answer 7

niacin 
nicotinic acid / nicotinamide
cereals/ formed from tryptophan 
NAD/NADP
pellagra (maize eaters in eu and usa)/ dermatitis/ diarrhoea/ dementia

Question 8

B6 name; vitamers; role; deficiency; therapeutic uses

Answer 8

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

Question 9

B12 name; sources; absorption; function; metabolic role

Answer 9

cobalamin; meat; combines with intrinsic factor (glycoprotein from gastric cells); carrier of methyl groups;
homocysteine-> methionine
branched aa metabolism

Question 10

what is pernicious anaemia caused by; treatment

Answer 10

lack of intrinsic factor-> can’t absorb B12; treated with raw liver

Question 11

B9 name; active form; how is active form maintained; sources; function; metabolic role

Answer 11

folate; tetrahydrofolate; maintained by dihydrofolate reductase; green veg/liver/whole grains; carrier of 1C units; purine&pyrimidine synthesis/ aa metabolism

Question 12

types of 1c units in what compound

Answer 12

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

Question 13

folate/ B12 relationship

Answer 13

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

Question 14

b9/12 deficiencies

Answer 14

inadequate myelin synthesis( neuro changes)
megaloblastosis
neural tube defects
cardiovascular mortality (hyperhomocysteinaemia)
alzheimers

Question 15

symptoms of inadequate myelin synthesis due to lack of B9/12

Answer 15

numbness in fingers hands forearms/ tingling/ataxia/dizziness

Question 16

why do b9/12 deficiencies result in megaloblastosis

Answer 16

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

Question 17

B9/12 deficiency causes

Answer 17

B9: malabsorption/ drugs/ ethanol
B12: absent IF/ defective IF/ gastric atrophy/ gastrectomy / crohn’s disease /coeliac disease

Question 18

B5 name/ role

Answer 18

pantothenic acid

component of CoA

Question 19

B7 name/sources/role

Answer 19

biotin
peanuts/chocolates/bacteria
co-enzyme in PYRUVATE CARBOXYLASE (pyruvate-> oxaloacetate in GLUCONEOGENESIS); in ACETYL COA CARBOXYLASE (acetyl coa-> malonyl coa in FA SYNTHESIS)

Question 20

vitamin C name; sources; role; deficiency

Answer 20

ascorbic acid;
citrus/tomatoes/berries;
antioxidant-> maintains Fe2+ needed for proline/lysine hydroxylase -> collagen formation ; reduces Fe3+ in small intestine for absorption
scurvy

Question 21

causes of fat-soluble vitamin deficiency

Answer 21

dietary deficiency
low fat diet
fat malasbsorption

Question 22

intestinal absorption of adek

Answer 22

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

Question 23

vitamin a name; sources; absorption and ratio

Answer 23

retinol
animal liver/ millk/ eggs/beta carotene
carotenoids cleaved into 2 retinol molecules; carotene: retinol= 6:1

Question 24

retinol active forms and functions of each active form;

Answer 24

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

Question 25

retinol transport and storage; deficiency; toxicity

Answer 25

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

Question 26

vitamin e sources; potent form; function

Answer 26

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

Question 27

free radical scavenging and how vitamin E helps with this

Answer 27

free radicals attack PUFA-> other radicals generated
FA radicals + oxygen -> peroxyl radical -> chain reaction
reaction with vitamin E-> vitamin E becomes radical-> stable

Question 28

vitamin E deficiency

Answer 28

in infants as vit e doesnt cross placenta 
haemolytic anaemia (RBC Membranes are fragile)

Question 29

vitamin D3 name; function; formation

Answer 29

cholecalciferol; like a steroid hormone, maintains ca/p levels in blood-> mineralisation of bone; formed in skin by UV on 7-dehydrocholesterol

Question 30

vitamin d 2 name; sources; formation

Answer 30

ergocalciferol; plants/fungi/mould; maintains correct levels of ca/p in blood-> mineralisation of bone; UV on ergosterol

Question 31

vitamin d deficiencies

Answer 31

rickets : mineral:matrix ratio decreases ; bending of long bones; kyphosis; delayed tooth eruption
osteomalacia: muscle weakness/ bone pain/ decalcification of long bones

Question 32

vitamin d toxicity

Answer 32

hypercalcaemia/ GI disturbances/ soft tissue calcification

Question 33

vitamin k sources; deficiency and symptoms

Answer 33

green leafy veg/milk/meat; infants suffer deficiency as vitamin does not cross placenta easily; impaired blood clotting