Exam 2 Flashcards
B12 -digestion and absorption -functions -causes of deficiency, deficiency disease/symptoms Vitamin C - Functions - Sources - Deficiency disease/symptoms - RDA & UL General characters of fat soluble vitamins Vitamin A: Sources Digestion, absorption, storage - transport - Hypervitaminosis - Function Specific retinoid associated with each function - Deficiency symptoms/disease - UL - toxicity - RAE - calculation - Carotenoids Vitamin K -Sources - Function - Vitamin K c
B12 absorption and digestion
HCl Separates b12 from food proteins. Combines with intrinsic factor in the stomach for absorption.
B12 functions
Methylcoblamin: Used as a co-enzyme to convert homocysteine to methionine.
Adenosylcobalamin: required for methylmalonyl CoA mutase which converts L-methylmalonyl CoA to succinyl-CoA
B12 deficiency disease, symptoms, and causes
Prevents megaloblastic macrocytic anemia (Large amounts of folate can hide this)
Pernicious anemia is a condition where instrinsic factor is not made and B12 cannot be absorbed well.
Causes: impaired pancreatic exocrine function which impairs B12 release. Impaired gastric and intestinal function, parasitic competition, use of Nitrous oxide
C function
Antioxidant; hydroxylating enzymes involved in synthesis of collagen, carnitine, norepinephrine.
C sources
Papaya, OJ, cataloupe, broccoli, brussels sprouts, green peppers, grapefruit juice, strawberries.
C deficiency disease and symptoms
Scurvy: fatigue, depression, inflammation of gums, skin discoloration.
C RDA + UL
RDA / UL
Men: 75mg
Women: 90mg
Smokers:
A sources
Liver, dairy, sweet potato, carots, spinach, butternut squash, greens, broccoli, cantaloupe
A Digestion and absorption
Hydrolyzed by pepsin and other upper small intestine enzymes (pancreatic esterases) before absorption.
Retinol and carotenoids become part of micellar particls with other lipids and are taken into duodenal and jejunal cells for absorption
A storage and transport
Circulates as retinol bound to retinol binding protein.
A deficiency symptoms and diseases
Xerophtlamia: Night blindness is the most common deficiency symptom.
A UL and toxicity
High intake of preformed A can lead to dizziness nausea, headaches, coma, and even death. Can also cause birth defects in pregnant women.
High amounts of beta-carotene can cause skin discoloration
3,000 mcg (10,000 IU) = UL
A Functions and associated retinoid
Synthesis of rhodopsin and other light receptor pigments; metabolites involved in growth, cell differentiation, bone development, and immune function.
K sources
Synthesized by intestinal bacteria; green leafy vegetables, soy beans, beef liver
K function
Activates blood clotting factors by gamma(?)-carboxylating glutamic acid residues; carboxylates other proteins.
K cycle
-Quinone (quinone reductases: dithiol or NADPH) -Dihydroquinone (y-glutamyl carboxylase) -2,3 epoxide (epoxide reductase) -Quinone
K deficiency and UL
Deficiency is associated with hemorrhaging. There is no UL, but the synthetic form (Menadione) has been shown to cause liver damage in large amounts (also hemolytic anemia).
E active forms, dietary form, and supplements
a-tocopherol (active)
y-tocopherol
Supplements can be gamma (y)-tocopherol or tocotrienols
E transport
- Secreted from liver as a-tocopherol
- Solubilized by bile acids, absored by small intestinal epithelial cells, incorporated into chylomicrons, and transported via blood lymphatics.
- Sent to liver in chylomicron remnant
- Sent from liver packaged in VLDL
- Alpha-tocopherol transfer protein (ATTP, biologically active form)
- Excreted as tocopheronic acid
E sources
Vegetable seed oils
E toxicity and deficiency
Deficiency symptoms include: myopathy (skeletal muscle pain, anemia, and neuropathy
Toxicity: reduced clotting
E RDA and UL
UL = 1500 IU, 1000mg a-tocopherol
RDA 15mg alpha-tocopherol
E RDA and UL
UL = 1500 IU, 1000mg a-tocopherol
RDA 15mg alpha-tocopherol
Lack of intrinsic factor can lead to what disease?
Pernicious anemia
How are fat soluble vitamins primarily excreted?
Bile to feces
Active form of vitamin D?
Calcitriol
Storage form of A?
Retinyl ester
Retinoid form importan to visual cycle?
11-cis retinal
Retinoid form for cell differentiation
retinoic acid
RAE for A
1 RAE = 1ug retinol = 12ug B-carotene = 24 a-carotene
Vitamin important to proline or lysine hydroxylation
C
Plant origin vitamin D
Cholecalciferol
Synthetic vitamin e forms
all rac-a-tocopherol
