Stuff I Forget Flashcards
Which vitamin deficiencies can cause anemia?
1) pyroxidine (B6)–promotes RBC production
2) ascorbic acid–helps in the reduction of iron (Fe+3–>Fe+2)
3) Cu–ceruloplasmin (Cu) helps oxidize iron so it can bind to transferrin
Which enzymes need cobalamin as a cofactor?
1) methylmalonyl CoA mutase (MMCoA mutase)–converts methylmalonyl CoA–>succinyl CoA, so all amino acids that follow this path need cobalamin (valine, isoleucine, threonine, methionine)
2) homocysteine methyltransferase–needs cobalamin to convert N5-methyl-THF back into THF, and to convert homocysteine back into methionine
Which enzyme deficiencies can cause homocysteinuria?
1) homocysteine methyltransferase (makes homocysteine into methionine)
2) cystathionine beta-synthetase (makes homocysteine into cystathione, then cysteine)
Which enzymes do NOT remove ammonia?
1) alanine transaminase (produces pyruvate and glutamate)
2) glutaminase (glutamine–>glutamate + ammonia)
3) serine dehydrogenase (serine–>pyruvate and free ammonia)
4) aspartate transaminase (NH3 still stuck to structure, no change)
Which enzymes remove ammonia?
1) glutamine synthase (glutamate+ammonia–>glutamine)
2) glutamate dehydrogenase (ammonia + alpha-ketoglutarate +NADPH–>glutamate+NADP+)
How are 1-carbon groups generated?
1) serine+THF–>glycine+N5, N10-methylene-THF
2) serine loses 1 carbon as it becomes glycine
3) glycine can become CO2 and NH4+
4) N5, N10-methylene-THF carries extra carbon group–this carbon used in rxns catalyzed by thymidylate synthase***
5) when N5, N10-methylene-THF loses the carbon group, it becomes N5-methyl-THF (rxn reversible only in methionine synthesis)
Why does thymidylate synthase need dihydrofolate reducatse for max activity?
1) dUMP+N5, N10-methylene-THF–>dTMP+dihydrofolate, rxn catalyzed by thymidylate synthase
2) dihydroflate must be reconverted into THF via dihydrofolate reductase
3) THF then reacts with serine to form N5, N10-methylene-THF (generates glycine), so cycle can begin again!
What’s a general summary of lipid metabolism?
1) chylomicrons deliver dietary-derived lipids to periphery, remnants returned to liver (apoE helps them get in liver)
2) VLDLs carry lipids made in liver to body cells
3) LDLs carry cholesterol around the body
4) LDLs receive cholesterol from CETP transfer of cholesterols from HDL (once LDL is still a part of VLDL)
5) LDL also carries some cholesterol back to liver
6) HDLs carry cholesterol from body back to liver for excretion (pick up cholesterol via LCAT/apoAI activity)
7) HDL not endocytosed; it binds to SR-B1 (on liver, steroid-producing cells) which allows selective re-uptake of cholesterol esters from HDL
8) TGs can be degraded by hepatic lipase
What’s different between lipoprotein particles and mixed micelles?
1) LP particles have lots of TG, not a lot of NEFA
2) mixed micelles have lots of NEFA, not much TG
What does pancreatic lipase need?
1) colipase (secreted inactively by pancreas, activated in duodenum)
2) with copliase’s action, pancreatic lipase is an esterase taht partially hydrolyzes TGs into 2-MAG and 2 NEFAs
What can bind to the LDL receptor?
1) ApoE-containing particles, chylomicrons, LDL
2) LDL NOT associated with apoE, endocytosed by receptor
3) LDLR recognizes ApoB100, apoE
Which amino acids are the highest concentration inside the cells and serum?
1) glutamate (more than)/glutamine inside CELLS–transaminases converge on it, ox deam makes energy from removing ammonia group
2) alanine in BLOOD–ammonia disposed, carbons sent to liver for glucose
Which kind of rxn is pyroxidal phosphate (B6) NOT a cofactor for?
ribonucleotide reductases
Which is NOT a function of the urea cycle? What treatment would you give someone with hyperammonia?
1) to generate carbamoyl phosphate for pyrimidines
2) making arginine/forming urea (highly soluble ammonia compound) ARE functions
3) 3 ATP used in cycle
4) protein-free diet (arginine becomes essential**), lots of glucose, sodium benzoate/sodium phenylacetate–do NOT starve them!!
Transaminations occur in making or degrading all of which amino acids?
1) alanine
2) arginine
3) aspartate
4) isoleucine, leucine, valine (use common alpha-keto transam rxn)
5) NOT threonine! (threonine–>glycine via threonine dehydrogenase, irreversible–makes threonine essential)
Which enzyme is created/degraded in same path?
1) proline–>glutamic acid–>glutamate–>alpha-ketoglutarate
2) arginine generated through urea cycle (the ornithine made too just goes through cycle again), but it becomes glutamate–NOT made/broken down through same path
3) fun fact: proline, ornithine, arginine, glutamate can all be derived from alpha-ketoglutarate skeleton (NOT histidine, since it’s essential)
How is serine made?
1) either from glycine or by 3-phosphoglycerate path
2) will become pyruvate
What’s deficient in alkaptonuria?
1) homogentisate oxidase
2) homogentisate can’t be ocnverted to 4-maleylacetate
What are some things to know about tetrahydrobiopterin?
1) needed for DOPA synthesis
2) required cofactor for phenyalanine hydroxylase
3) must be regenerated by dihydrobiopterin reductase
4) synthesized by body
What are the forms of cobalamin in the methylmalonyl CoA mutase and the homocysteine methyltransferase rxns?
1) MMAM–adenosyl version (a in MMAM for adenosyl!)
2) HMT–hydroxy version (h in HMT for hydroxy!)
What’s important stuff about folate?
1) folic acid–>THF via dihydrofolic acid reductase, enzyme inhibited by methotrexate–THF active form in body, one-carbon group donor
2) N5-methyl-THF is most reduced form–this guy gets trapped in folate trap, when B12 reduced (methylene intermediate, formyl/formino/methenyl most oxidized)
What causes the spinal cord degeneration and neurological problems in a B12 deficiency?
1) methylmalonyl CoA–>succinyl CoA doesn’t happen
Which rxns use 1-carbon fragments?
1) formation of methionine
2) synthesis of purines and pyrimidines
3) glycine synthesis
4) NOT heme synthesis!!
Which rxns does azaserine block?
1) it’s a glutamine analog–blocks amide transfer from glutamine (blocks amination rxns)
2) blocks 2 steps in purine synthesis (blocks amination rxns)
3) blocks IMP–>GMP synthesis
4) blocks UTP–>CTP synthesis
What’s needed to make purines?
1) aspartate
2) formate (from N10-formyl-THF)
3) CO2
4) glutamine
5) glycine
6) ATP
What’s needed to make pyrimidines?
1) carbamoyl phosphate (NOT from urea cycle, made in cytosol from glutamine and CO2)
2) aspartate
3) people with a urea cycle OTC deficiency can build up lots of pyrimidines**
Which enzyme is restricted to the liver?
G6Pase, for gluconeogenesis
Are all NTPs created equally?
Yes! ATP=GTP=CTP=GTP
How does pyruvate carboxylase work?
1) pyruvate–>OAA
2) requires biotin cofactor, requires ATP to activate bicarb
3) pyruvate carboxylase ONLY in mitochondria–where gluconeogenesis must begin
4) leucine/lysine, acetyl CoA from fatty acids/amino acids CANNOT contribute to gluconeogenesis
5) activated by acetyl CoA
How does PEPCK (PEP carboxykinase) work?
1) OAA–>PEP+CO2
2) requires GTP
3) PEPCK in mitochondria, PEP has transporter
4) activated by glucagon’s increase in cAMP, decreased by insulin
What about OAA in fatty acid synthesis? (NADPH required!!!***)
1) citrate+ATP–>OAA + acetyl CoA (cytosol)
2) OAA+NADH–>malate via malate dehydrogenase
3) malate+NADP+–>pyruvate+NADPH, via malic enzyme
4) pyruvate–>citrate, NADPH used as the reducing agent for fatty acids
5) oxidizing malate to make OAA is endergonic, so lots of malate is in equilibrium with OAA–this is good, because malate can go to the cytoplasm for gluconeogenesis
What about OAA in gluconeogenesis?
1) asparagine and aspartate also become OAA
2) must be converted into malate or aspartate to enter/leave mitochondrial matrix
