BIBC 120 Lecture Notes - Lecture 24: B Vitamins, Gut Flora, Gastric Pits
24 May 2018
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Week 9.1
• vitamins: critical (usually) essential micronutrients (some may be nonessential or
conditionally essential)
• animal vs. plant based foods provide different sets of nutrients; i.e.
- iron and calcium mainly from animal sources (meat/dairy)
- Vit. C from mainly plant sources
• lots of processed foods are either fortified or enriched with vitamins; vitamins often
removed by processing
- fortified: any addition of nutrients
- enriched: nutrient content claim regulated by the FDA; must contain certain
levels of thamin B1, niacin B3, riboflavin B2, folate, iron; ONLY for grain based
foods – do’t eed to ko speifi utriets
• when to take vitamin supplements? recommended during times when deficiencies can
have serious consequences (pregnancy) or eating a diet that restricts food variety
(vegan)
• textbook p 452-453
WATER SOLUBLE VITAMINS
• hydrophilic, absorption from solution in small intestine, all function as coenzymes
• less potential than fat soluble vitamins for toxicity from overconsumption, excess
itai gets flushed out of ody i urie, ad does’t oetrate i adipose tissue like
fat soluble
• Vitamin B complex (B1; B2; B3; B5; B6; B7; B9; B12)—all coenzymes (small molecules
that participate in enzyme catalytic actions)
• Vitamin C—Electron donor coenzyme (Antioxidant?)
• Choline and carnitine are conditionally essential nutrients
VITAMIN B12 – cobalamin
• contains cobalt
• synthesized only by bacterial sources (gut microbiota), only available from animal
dietary sources (in animals B12 produced by microbiota and absorbed into their body
tissues)
• need intrinsic factor (protein synthesized by parietal cells in the gastric pits stomach) to
absorb B12 (the extrinsic factor) – intrinsic factor binds to B12, protects it from being
degraded in the stomach, IF-B12 complex then is absorbed in small intestine (cannot
absorb free vit.B12)
• sources of B12: MEATS clams, beef liver, crab, dairy products; not in plants
• ROLE AS A COENZYME
1) coenzyme for methionine synthase (methionine is an essential AA, glucogenic AA?)
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