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Biochem Exam 6

One-Carbon Metabolism

What can carry carbon groups and force them to go somewhere else Folates and s-adenosylmethionine (SAM)
Pteridine ring + PABA + glutamate forms what molecule Folate
Folates can have many chemical forms with a chain of what attached Glutamates
Can folates be synthesized in the body No
What synthesizes folates Bacteria and higher plants
What must ingested folates have done to them Activation
What form of folate is absorbed in the intestine using a specfic transporter Monoglutamate
What form of folic acid is found in supplements Monoglutamate
Folate is reduced to FH2 then FH4 and this is catalyzed by Dhydrofolate reductase
Where does the reduction of folate primarily Intestinal cells
Where is FH4 reconjuaged to the polyglutamate form Liver
Conjugated FH4 can accept On carbon groups
Where does FH4 usally accept one carbon groups At N5 or N10
What is the primary carbon source that donates a carbon group to FH4 Serine
Folates with carbon groups attached are called the One-carbon pool
What are three important reactions that folates are involved in Purine synthesis, dTMP synthesis, Methylcobalamin synthesis, Serine syntehsis
What is the most reduced and stable form of folates N5-methyl-FH4
What is the only thing the carbon of N5-methyl-FH4 can do Transfer to vitamin B12
What is another name for Vitamin B12 Cobalamin
Corrin ring + cobalt make what molecule Vitamin B12 (cobalamin)
Cobalt can form bonds with Carbons
B12 is only synthesized by Bacteria
What form of vitamin B12 is fround in most supplements but does not occur in nature Cyanocobalamin
After ingesting B12 is converted to Methyl cobalamin or deoxyadenosylcobalamin
What does B12 generally enter the small intestine boudn to Haptocorrin (Transcobalamin I, R-binders)
Proteases digest Haptocorrin and other proteins releasing B12
B12 binds what to enter enterocytes as a complex Intrinsic factor
Within the enterocytes, B12 is released from IF and binds what to be secreted as a complex Transcobalamin II
What takes up and stores B12 Liver
B12 is secreted by the liver in Bile
What two reaction require B12 Transfer of methyl group from N5-methyl-FH4 to homocystein to form methionine, Conversion of methylmalonyl-CoA to Succinyl CoA
Methylmalonyl CoA --> Succinyl CoA Adenosyl B12
Methylene-FH4 --> N5-Ch3-Fh4 Methylenetetrahydrofolate reductase (MTHFR)
Homocysteine --> Methionine Met synthase
Homocystein --> Cystathionine Cystathionine synthase and PLP
Met is essential because there are no good dietary sources of Homocysteine
DNA methyltransferases and histone methyltransferases require what as the methyl donor SAM
DNA methylation is important for Gene silencing and regulating dynamic gene expression
What could cause hyperhomocysteinemia B6, B12, or Folate deficiencyMet synthase, MTHFR or cystathionine synthase mutations
Mild hyperhomocysteinemia is associated with Increased risk of coronary artery disease and thrombosis
How can homocysteine levels be reduced B12, B6 or folate supplementation Betaine and Choline supplementation
B12 or folate deficiencies can lead to Macrocytic anemia
Red blood cells are larger than normal but fewer in number Macrocytic anemia
Caused by enlarged hematopoietic precursor cells in bone marrow; Slowed cell division but normal growth rate so cells are larger than normal Macrocytic anemia
Neurological symptoms occurs in B12 deficiency due to Hypomethylationin the nervous system
Anemia occurs in B12 deficiency due to Inhibition of DNA replication
B12 causes macrocytic anemia because need folate to get methylcobalmin and need B12 to recycle N5-Ch3-FH4 If B12 or met synthases are deficient, N5-methyl-Fh4 will build up resulting in a functional folate deficiency folate in a form that can’t be used Methyl trap hypothesis
Folate deficiency during pregnancy increases the risk of Neural tube defects
Dietary insufficiency and Chronic alcoholism are associated with Folate and B12 deficiency
Abdominal surgery can cause a decrease in IF production, GI Disease, Intestinal parasites, certain drugs, and IF deficiency are associated with B12 deficiency
Intrinsic factor deficiency results in Pernicious anemia
Created by: mhaynes