Learning objectives: purines, pyrimidines, B12, folate

Question 1

Identify the key points pertaining to the de nova purine synthesis, emphasizing input metabolites, key regulated steps, and significance for physiology and metabolism

Answer 1

start w/ sugar scaffold and add to it

PRPP + glutamine –> (use THF)–> IMP –(use GTP or ATP, respectively)–> AMP or GMP

Question 2

Identify the key points pertaining to the de nova pyrimidine synthesis, emphasizing input metabolites, key regulated steps, and significance for physiology and metabolism

Answer 2

pyrimidine = “primitive,” start with primitive building blocks (glutamine, CO2, ATP)

ATP+CO2+Gln –>(use CPSII)–>Orotate–>(use UMP synthase) –>UMP–>UTP–(use CTP synthase, glutamine)–>CTP

Question 3

Identify the functions of B12

Answer 3

regenerate THF (useful version of folate), which you need to make purines and therefore DNA for cell replication, esp in blood cells

promote generation of SAMS (an important methyl donor), which is important to make myelination for nerves

Question 4

Explain the role of intrinsic factor in vitamin B12 absorption

Answer 4

intrinsic factor in the gut is essential for absorbing Vitamin B12

as you age (or if part of intestine removed), have less intrinsic factor

this can lead to Vitamin B12 deficiency