SAM Cycle (S-Adenosylmethionine Cycle)

The video tutorial discusses the critical role of methylation in biochemistry, focusing on S-adenosyl methionine (SAM) as a methyl group donor. It explains the mechanisms of methylation reactions, including the role of various enzymes like methyltransferases. The tutorial also covers the regeneration of methionine from homocysteine and the methionine synthesis pathway, highlighting the importance of these processes in cellular functions.

What is the primary role of methylation in biochemistry?

• To provide energy for cellular processes

• To synthesize carbohydrates

• To donate methyl groups for various biochemical reactions

• To break down proteins

Which molecule is commonly abbreviated as SAM in biochemical reactions?

• S-adenosyl methionine

• Adenosine triphosphate

• Nicotinamide adenine dinucleotide

• Flavin adenine dinucleotide

What type of reaction is primarily involved in methyltransferase activity?

• E1 reaction

• E2 reaction

• SN2 reaction

• SN1 reaction

What is the product when SAM transfers a methyl group?

• Methionine

• Adenosine diphosphate

• Cysteine

• S-adenosyl homocysteine

Which enzyme is responsible for regenerating methionine from homocysteine?

• Methyltransferase

• Homocysteine hydrolase

• Adenosyl transferase

• Methionine synthase

What coenzyme is required by methionine synthase for its activity?

• Vitamin C

• Vitamin K

• Vitamin B12

• Vitamin D

What is the role of inorganic pyrophosphatase in the SAM cycle?

• To synthesize ATP

• To oxidize methionine

• To cleave inorganic pyrophosphate into two phosphates

• To transfer methyl groups

How many ATP molecules are consumed per cycle of the SAM cycle?

• Four

• Three

• Two

• One

Which of the following processes does not involve methylation?

• DNA replication

• Protein synthesis

• Catecholamine degradation

• Epinephrine synthesis

Why is the SAM cycle considered energy-intensive?

• It requires multiple enzymes

• It consumes one ATP per cycle

• It involves complex reactions

• It produces heat