46 Questions
What is the major carbon source involved in the transfer of single carbon atoms in various biochemical reactions?
Serine
Which enzyme catalyzes the reversible reaction transferring the hydroxymethyl group from serine to FH4?
Serine hydroxymethylase
What is produced from deoxyuridine monophosphate (dUMP) by a methylation reaction involving FH4?
Thymine
In folate deficiency, what type of anemia can develop due to the inability of blood cell precursors to synthesize DNA?
Megaloblastic anemia
Which vitamin deficiency has been linked to an increased risk of neural tube defects in fetuses?
Folate
What molecule is used for the transfer of methyl groups to vitamin B12 in biochemical reactions involving one-carbon atoms?
S-adenosylmethionine (SAM)
What is the most oxidized form of FH4?
N10-formyl FH4
What is the consequence of primary folate deficiency or secondary B12 deficiency on DNA repair?
Clumping and poly segmentation seen in the nuclei of neutrophils
Which vitamin is reconjugated to the polyglutamate form within the liver?
Vitamin B12
Which vitamin participates in the conversion of L-methylmalonyl-CoA to succinyl-CoA?
Vitamin B12
What is the major form of folate in the blood?
N5-methyl-FH4
What is the role of SAM in biochemical reactions involving FH4 and vitamin B12?
SAM transfers methyl groups to various substrates
Which compound does biotin transfer in the carboxylase reaction?
CO2
What are the consequences of carbon reduction on FH4?
The carbon becomes irreversibly reduced to methyl form
Which compound carries one-carbon units from serine, glycine, histidine, formaldehyde, and formic acid in biochemical reactions?
FH4
Which of the following serve as one-carbon sources for the one-carbon pool carried by FH4?
Serine
In which vitamin are one carbon donors transferred to folate at different oxidation states?
Vitamin B12
What is the main function of FH4 in biochemical reactions involving one-carbon units?
Facilitating the transfer of single carbon atoms
What is the role of biotin in the carboxylase reactions?
Catalyzing the transfer of CO2 to malonyl CoA
Which compound forms a bridge between nitrogen N5 and N10 in the one-carbon pool?
Serine
What occurs when the methyl group is formed from FH4?
It tends to accumulate in the cell
What is the primary function of folate within the liver?
Storage of body's folate
Which compound is involved in transferring carbon sources to folate at different oxidation states?
Histidine
What is the consequence of a folate deficiency on blood cell precursors?
Decreased ability to divide
Which base is synthesized for DNA synthesis through reactions involving one-carbon transfers?
Thymine
What is the product of the reaction where deoxyuridine monophosphate (dUMP) is methylated?
Deoxythymidine monophosphate (dTMP)
What can be a consequence of primary folate deficiency on DNA repair processes?
Increased mutation rate
Which molecule serves as a carrier of one-carbon units from various sources in biochemical reactions?
S-adenosylmethionine (SAM)
What is the major carbon source involved in recycling the hydroxymethyl group to tetrahydrofolate (FH4)?
Serine
What is the most unusual feature of Vitamin B12's structure?
Presence of cobalt
How does Vitamin B12 react with the 5’-carbon of 5’-deoxyadenosine?
Forms 5’-deoxyadenosylcobalamin
How is ingested Vitamin B12 absorbed if it is bound to proteins?
It is released by digestive proteases and binds to intrinsic factor
Which compound must be digested by proteases before Vitamin B12 can bind to intrinsic factor in the small intestine?
Haptocorrins
What is the function of intrinsic factor in the absorption and transport of Vitamin B12?
Facilitates the release of Vitamin B12 from proteins
What is the consequence of a vitamin B12 deficiency, according to the text?
An accumulation of methyl-FH4
Which hypothesis is associated with the consequences of vitamin B12 deficiency?
Methyl-trap hypothesis
What is the function of vitamin B12 in the body according to the text?
Transfer of a methyl group to homocysteine
What is the major form of B12 stored in the liver?
Methylcobalamin
Which reaction involves the transfer of a one-carbon group to tetrahydrofolate?
Conversion of homocysteine to methionine
What is the role of transcobalamin II in vitamin B12 metabolism?
Facilitation of vitamin B12 absorption in enterocytes
What is the consequence of a deficiency in vitamin B12 or a defect in methionine synthase according to the text?
Accumulation of homocysteine in the blood
What is the role of choline in one-carbon metabolism as discussed in the text?
Choline is converted to betaine for homocysteine conversion
What condition leads to the accumulation of homocysteine due to inhibition of its conversion to methionine by the major route?
Vitamin B12 deficiency
What effect does a mutation in the enzyme converting N5, N10 methylene FH4 to N5-methyl FH4 have on serum homocysteine levels?
Increases homocysteine levels
In what situation does homocysteine accumulate in the blood according to the text?
If there is a deficiency in vitamin B6
What is a possible outcome of a deficiency in vitamin B6 with regard to serum homocysteine levels?
Elevated homocysteine levels
Test your knowledge on serine hydroxymethyltransferase enzyme, one-carbon metabolism, and the role of serine in producing glycine and N5, N10-methylene-FH4. Explore how transfers of one-carbon groups contribute to the synthesis of DNA and RNA bases.
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