Amino Acid Metabolism - the Methionine (SAM) Cycle (2)

The video explains the Sam Cycle, also known as the Methionine Cycle, highlighting the role of methionine in generating S-Adenosyl Methionine (SAM), a crucial methyl donor for biosynthetic reactions and DNA methylation. It details the conversion of methionine to SAM and the subsequent transformation of homocysteine back to methionine, emphasizing the importance of cofactors like folate and vitamin B12. The video also discusses the consequences of deficiencies in these vitamins, such as elevated homocysteine levels linked to cardiovascular diseases.

What is the primary role of S-adenosylmethionine (SAM) in the methionine cycle?

• To store energy

• To synthesize proteins

• To break down methionine

• To act as a universal methyl donor

Which enzyme catalyzes the conversion of methionine to S-adenosylmethionine?

• Methionine synthase

• Methionine adenosyltransferase

• Homocysteine hydrolase

• Methyltransferase

What is the role of methyltransferases in the methionine cycle?

• To transfer methyl groups to various substrates

• To break down proteins

• To convert methionine to homocysteine

• To synthesize DNA

Which cofactors are essential for the conversion of homocysteine to methionine?

• Vitamin C and iron

• Calcium and magnesium

• Zinc and copper

• Folate and cobalamin

What happens to homocysteine levels in the case of cobalamin deficiency?

• They fluctuate randomly

• They increase

• They remain unchanged

• They decrease

How is elevated homocysteine related to cardiovascular diseases?

• It is correlated with cardiovascular diseases

• It prevents cardiovascular diseases

• It directly causes heart attacks

• It has no relation to cardiovascular health

What is the consequence of being deficient in both folate and cobalamin?

• Increased synthesis of methionine

• Decreased synthesis of S-adenosylmethionine

• Improved cardiovascular health

• Enhanced DNA methylation