Carbon Pool

Question 1

_____ is the most oxidized one-carbon form that is transferred by biotin in carboxylation reactions

Answer 1

CO2

Question 2

_______ is produced in cells via the reduction of dietary folate

Answer 2

tetrahydrofolate (FH4)

Question 3

_______ is synthesized by bacteria and higher plants from the bicyclic pteridine ring, p-amino-benzoic acid (PABA) and glutamate

Answer 3

Folate

Question 4

why don’t sulfa drugs affect human cells?

Answer 4

because they block the synthesis of PABA for folate synthesis, which human cells can’t do

Question 5

Enzymes of brush border epithelium cleave how many of the glutamate residues before absorption?

Answer 5

all but one

Question 6

what was the first class of drugs to be discovered that could treat bacterial infection

Answer 6

sulpha drugs

Question 7

Folate is reduced to dihydrofolate and then to tetrahydrofolate by what enzyme and what else is needed??

Answer 7

dihydrofolate reductase and NADPH

Question 8

what drug targets dihydrofolate as an anticancer agent?

Answer 8

methotrexate

Question 9

B12 deficiency can cause what to occur?

Answer 9

the methyl folate trap, in which THF is converted into a resivoir that has no way of being metabolized, resulting in a folate deficiency

Question 10

Tetrahydrofolate (FH4) obtains one carbon units from what 5 things as part of their catabolism?

Answer 10

serine, glycine, histidine, formaldehyde, and formate

Question 11

These 1-carbon units that are attached to FH4 for their catabolism are ______ and ______

Answer 11

oxidized and reduced

Question 12

once the 1-carbon units that are attched to FH4 for their catabolism are reduced they can/cannot be reoxidized

Answer 12

cannot

Question 13

further reduction of the CH3 groups to methane (CH4) from serine, glycine, histidine, formaldehyde, and formate can be done by _____

Answer 13

intestinal bacteria, but not humane cells

Question 14

what is the major source of 1-carbon groups carried by FH4?

Answer 14

serine

Question 15

serine’s hydroxymethyl group is transferred to act as a 1-carbon group by a reversible reaction that uses pyridoxal phosphate and generates what?

Answer 15

generating N5,N10-methylene-FH4 and glycine

Question 16

Since serine can be synthesized from ______, dietary _____ serves as a source of carbon for the 1-carbon pool

Answer 16

glucose,carbohydrate

Question 17

the reversible reaction between glycine and serine is catalyzed by what enzyme?

Answer 17

serine hydroxymethyl transerase

Question 18

dUMP acts as a 1-carbon recipient when catalyzed by what enzyme into what product?

Answer 18

catalyzed by thymidylate synthase into dTMP

Question 19

how does methotrexate act as an anticancer agent?

Answer 19

it has essentially the same structure as FH4 (except methrotrexate has an additional amino group)so it prevents the conversion of FH2 (folate) to FH4 (tetrahydrofoloate)

Question 20

explain how 5-FU (5-fluorouracil) blocks DNA replication and cell growth

Answer 20

since 5-FU is a pyrimidine analog, the cell inserts it into DNA where thymine should be, thus disrupting cell growth and DNA replication, this is especially import for tumor cell which have a greater rate of cell division than normal healthy cells

Question 21

5-FU gets converted into cells to _____ which causes “_____death”

Answer 21

FdUMP, thymineless

Question 22

what enzyme plays the role of catabolizing most naturally occurring pyrimidines (uracil and thymine) as well as 5-FU (the anticancer agent) into metabolically active forms?

Answer 22

dihydropyrimidine dehydrogenase (DPD)

Question 23

dihydropyrimidine dehydrogenase (DPD) converts 5-FU from an inactive metabolite into an active one through an enzymatic process that is irreversible or reversible?

Answer 23

irreversible

Question 24

__________inactivates uracil reductase (DPD), the enzyme that rapidly degrades 5-FU in cancer patients. Thereby improving the efficacy, the therapeutic index, and the oral bioavailability of 5-FU in laboratory animals.

Answer 24

Eniluracil (5-ethynyluracil)

Question 25

The combination therapy, Cytefuran, combines what two drugs for the Tc of solid tumors?

Answer 25

5-FU and eniluracil

Question 26

In the absence of B12, all of the folate is eventually trapped as the THF-CH3 (N5-methyl FH4), resulting in what conidition?

Answer 26

megaloblastic anemia

Question 27

define megaloblastic anemia

Answer 27

is an anemia that results from inhibition of DNA synthesis during red blood cell production, can result from the absence of B12

Question 28

Folate deficiencies in early pregnancy can result in defects such as _________

Answer 28

spina bifida

Question 29

_______ is a developmental congenital disorder caused by the incomplete closing of the embryonic neural tube. This condition can be a result of ______ deficiencies early in pregnancy

Answer 29

spina bifida, folate

Question 30

deficiencies of what two things can cause megaloblastic anemia?

Answer 30

folate and b12

Question 31

Is FH4 required for cell division?

Answer 31

yes, because it is required for the synthesis of purine bases, which are needed for DNA replication

Question 32

________ is an abnormal growth of tissue, and when also forming a mass is commonly referred to as a tumor

Answer 32

neoplasm

Question 33

what is N-formiminoglutamate and it’s significance?

Answer 33

it is an intermediate in the metabolism of histidine, so it is used for 1-carbon donation to THF, resulting in N5-Formimino THF

Question 34

what enzyme does methotrexate inhibit?

Answer 34

dihydrofolate reductase

Question 35

5-FU is metabolized by what enzyme?

Answer 35

dihydropyrimidine dehydrogenase

Question 36

what blocks the conversion of dUMP to dTMP?

Answer 36

5-FU

Question 37

another name for Vit B12?

Answer 37

Cobalamin