Vitamins Flashcards
Forms of Vitamin k
K1 - Phylloquinone (plants)
K2 - Menaquinone (bacteria)
Vitamin K Absorption
80% of K1 is absorbed
Proximal intestine
Fat soluble so enter chylomicron
Travels to Liver
How vitamin K travel to liver
50% in triglyceride 25% in LDL 25% in HDL Effectiveness depends on ApoE gene E2 best and E4 the worst
Vitamin K function
Blood coagulation
Bone protein
Vitamin K make Gla
Co-factor for carboxylase enzyme for carboxylation of pro-thrombin
Glu -> Gla
Warfarin interrupts vit K cycle and no Gla made
Leading to uncarboxylated proteins in blood
Vitamin K and blood coagulation
Factor II (prothrombin) synthesised in liver containing Gla protein So no blood clot
Vitamin K and Bone Protein
Osteoblasts produce ostocalcin which need Gla
Matric also has Gla
Protein S
Vitamin K Deficiency
Increased clotting time
Circulatin uncarboxylate prothrombin
Decreased bone density
Vitamin A forms
Retinol
Retinal
Retinoic acid
1 retinol activity
1mg pre-formed vtiamin A
2mg beta-carotene
Digestion Vitamin A
Reinyl esters hydrolysed in duodenum via pancreatic lipase
Enter cell through SR-B1 and CD36 transporter
Absorption Vitamin A
Incorporated into micelles
Retinol is re-esterified to retinyl ester (sometimes turn to trans form which is useless)
Enter target cell by facilitated diffusion by SR-B1
Cleaving beta-caretone
BCO1 - Cleaves 5-15’ creating two retinol
BCO2 - cleaves 9-10’ creating one
(we have evolved to have BCO2 as eat meat)
Deficiency vitamin A
Pupils cannot constrict mormally so night blindness
Impaired maintanence of epithelial tissues
Impaired neutrophils and macrophages
Decreased natural killer cells
Decreased T-helper cell
B vitamin overview
Water soluble vitamins with different structures but similar function. Participate in all metabolic pathways.
B1
Thiamine
Grains
Meat
B2
Riboflavin
Grains
Dairy
B3
Niacin
Grains
Meat
B5
Pantothenic acid
Eggs
Liver
B6
Pyridoxal
Meat
B7
Biotin
Egg
Liver
Salmon
B9
Folate
Grains
Fruit and veg
B12
Meat
Dairy
Thiamine Absorption
Duodenum and jejunum
Active transport or passive if high concn
Binds to albumin in blood
Absorbed in target cell via active transport
Phosphorylated to make TPP
Thiamine Coenzymes
Known as TPP
Catobolise leucine, isoleucine and valine
Involved in link reaction
Make branch amino acids
Krebs cycle - Ketoglutarate dehydrogenase
Pentose pathway
Thiamine Deficiency
Beri Beri wet and dry
Riboflavin digestion
Protease converts Riboflavin to B2
Absorbed by active transport in duodenum and jejunum
Magnesium and high dose of B2 decrease
Enters circulation as free B2
Binds to Fibrinogen and albumin in blood
Uptake into target cell via active transport
Riboflavin function
Co-enzyme flavin adenine diucleotide (FAD) and flavin mononucleotide (FMN) Electron carrier TCA Beta oxdation link reaction gluthione reductase
Riboflavin deficiency
Cracks around mouth, inflammation of lips and tongue, anaemia. Is rare as body can conserve
Niacin Absorption
Hydrolysed to free nicotinic acid
Absorbed in stomach and duodenum by facilitated diffusion (Na dependent)
High leucine and low tryptophan and niacin inhibit absorption
Transport in blood free
Cellular uptake via facillitated diffusion
Niacin function
NAD+ and NADP+ Glycolysis TCA beta oxidation link reaction Malonyl pathway
Niacin Deficiency
Pellagra cracking skin Hyperkeratosis Hyperpigmentation Dermatitis DIarrhoea Delirium
Niacin toxicity
Dilation of blood vessels
Liver damage
Pantothenic acid digestion
CoA and ACP degraded in intestine
Yield pantothenic acid
Absorbed via facilitated diffusion at low concentration
Cellular uptake mediated by SMVT and converted to CoA and ACP
Pantothenic acid function
CoA
Beta oxidation
fat synthesis
Link reaction
Pantothenic acid deficiency
Burning foot
Abdominal pain and nausea
Cramps
Alopecia
Pyridoxine Absorption
Dephosphorylated by alkaline phosphate in mucosa
Absorbed passively
Binds to albumin in plasma
Stored in muscle, liver, brain, kidney and spleen
Urine reflects intake
Pyridoxine Function
Needed to transfer amine group
Co-enzyme for homocysteine to cysteine
Glycolysis
Pyridoxine Deficiency
Caused by tuberculosis Microcytic anaemia Secondary pellagra Irritability Depression Convulsions Raised plasma homocysteine concn
Pyridoxine Toxicity
Nerve and skin damage
Biotin Absorption
Protease creates Biocytin and biotinides
These are further hydrolysed to create free biotin
Absorbed along small intestine by sodium dependent transporters
or passively at high concentration
Biotin Function
Prosthetic group for: pyruvate carboxylase (link)
acetyl CoA carboxylase
Propionyl CoA carboxylase
Beta-methylcrotonyl-CoA carboxylase
Involved in gluconeogenesis and fatty acid synthesis
Biotin Deficiency
Not severe in adults Burning foot Less coordinated In infants Dermatitis, alopecia and ketosis
Folate Absorption
Hydrolysed to monoglutamate via a zinc dependent carboxypeptidase
Absorbed by active pH transporter (needs H+)
Transported to liver via portal circulation
Released in to peripheral tissue carried by albumin
Taken up by cells via folate transporter
Folate Function
Carries methyl group
Amino acid metabolism (Homocysteine to methionine)
Pyrimidine and purine synthesis
Folate deficiency
Hyperhomocysteinemia
Megaloblastic anaemia
Reduces synthesis of neurotransmitters
First 12 weeks of pregnancy consume 400ug a day
Cobalamin Absorption
Bile constantly recirculated Bile enter small intestine B12 binds to IF 90% reabsorbed in ileum Saturate with intake higher than 1.5-2.5ug
Cobalamin Metabolism
Found as adenosycobalamin or methyl cobalamin acts as carrier of 1-C units
MeCbl needed for 5-methylTHF to tetrahydrofolate by MS Co-enzyme in the reaction of homocysteine to methionine
Co-enzyme in the conversion of propionyl CoA to succinyl CoA
Cobalamin Deficiency
Vegans
Pernicious anaemia
Demyelination nerve cells
Hyperhomosysteinemia
Vitamin E overview
fat soluble
Alpha - 3 methyl groups
Beta and yonder - 2 methyl groups
Sigma - 1 methyl group
Vitamin E Absorption
Hydrolysed by pancreatic esterase Facilitated diffusion involving SR-B1 Incorporated into chylomicron Binds to alpha-tocopherol transfer protein Delivered to VLDL Redistributed into lipoprotein
Vitamin E Structural function
Incorporated into membrane and cytoplasm
Vitamin E chemical function
Breaks oxidation chain to protect PUFA
Free radical steal hydrogen from in PUFA
Making a peroxy radical
Peroxy radical normallyt hen steal from neighbouring instead Vitamin E quenches
Makes lipid hydroperoxide
Secondary vitamin E reacts with lipid hydroperoxide to make lipid alcohol
Vitamin E Defficiency
Rare unless associated with fat malabsorption
Myopathies
Neuropathies
Vitamin C Absorption
If high concentration absorbed passively
If low concentration then active tranpost using sodium pump SVCT1
Readily transported in blood
ABsorbed into tissue with SVCT2
Vitamin C Fnction
Quenches Vitamin E radical
Maintain iron and copper as ions
Formation of adrenalin and noradrenaline
Vitamin C deficiency
Scurvy
