Cobalamin or Vitamin B12 Flashcards
The most biologically active form of cobalamin
cyanocobalamin
hydroxycobalamin
Cobalamin helps in the synthesis of heme.
true or false?
True
tissues in the body that contain the highest concentration of B12
kidneys testes brain spleen pancreas bone marrow muscles
Cobalamin is absobed with the aid of ___ before it can be absorbed in the ileum
Intrinsic factor IF
2 major components of pernicious anemia:
megaloblastic anemia
neurological degeneration
Vitamin B12 is a coenzyme for only two mamalian enzymes:
methionine synthase
L-methylmalonyl-coenzyme A mutase
Generic descriptor for all cobalamins that exhibit anti-pernicious anemia activity
Cobalamin
Deficiency defect from lack of cobalamin
Pernicious anemia
Manifestation of pernicious anemia
anorexia vomiting diarrhea achlorhydria abdominal pain weight loss retarded growth
Advance cases of pernicious anemia
liver and spleen enlargement yellowish skin nerve generation (spinal cord) paresthesias limbs difficulty walking
characteristics of rbc defect in pernicious anemia
hyperchromic, macrocytic anemia
abnormal size and shape of rbc
in pernicious anemia the cells fails to ____ and the total number of cells is ____.
mature
reduced
The most biologically active form of cobalamin in the blood
adenylcobamide
Cobalamin contains _____-like cobalt-centered ring molecules
porphyrin-like
Food Sources
Found in food bound to protein: kidney, milk, eggs, fish, cheese and muscle meats
Cobalamin is a Coenzyme of __________
methionine synthase (methylcobalamin)
Cobalamin Catalyses the conversion of _______to ________ and regenerates _________
homocysteine
methionine
THF Tetrahydrofuran
◦A deficiency of vitamin B12 lowers intracellular levels of ____________, which is required for DNA synthesis.
5,10-methylene-THF
cobalamin is important in conversion of _______ to succinyl-CoA
L-methylmalonyl-CoA
Cobalamin is An important intermediary in the ______ cycle
tricarboxylic acid
Cobalamin requirement _____during pregnancy and lactation
Increased
Effects of Deficient Intakes
- Impaired cell division of bone marrow and intestinal mucosa, and RBC
- neurologic abnormalities, ◦numbness, tingling, burning of the feet, stiffness and generalized weakness of the legs
megaloblastic anemia is secondary ______ deficiency
folate
malabsorption of vit B12 (gastritis to no intrinsic factor (IF); tapeworm)
Pernicious anemia
Effects of Excessive Intakes
- Has no appreciable toxicity
- Excess amounts that exceed the limited binding capacity of plasma R are excreted unchanged in the urine and in the feces
