what rxns are unique to gluconeogenesis?
- pyruvate carboxylase
- PEPCK
- F16BiPhosphate
- G-6-phosphatase
list the roles of the pentose phosphate pathway
- generates NADH
- prevents oxidative stress
- glucose metabolism
- xenobiotic metabolism
- scrambling of carbons
- production of nucleotides
what enzyme catalyzes the oxidative decarboxylation step in the pentose phosphate pathway?
6-phosphogluconate dehydrogenase
what is the regulatory step of the pentose phosphate pathway and how is it regulated?
G-6-P
regulated by dehydrogenase (NADP+/NADPH ratio & hormones)
inactivated: increase NADPH activated: decrease in ratio
explain the role of glycogenin in glycogen synthesis
- glycogenin attaches glucose molecule to tyrosine residue
- complex is formed between glycogenin and glycogen synthase (allows attachment of glucose molecules)
- finally glycogen synthesis forms a large chain
what are the 3 sources of NADPH for fatty acid synthesis?
- PPP
- malic enzyme
- isocitrate dehydrogenase
what molecule is used as the building block for every round of fatty acid synthesis? which one is used for the first round?
every round: malonyl CoA
1st round: acetyl CoA
How can PEPCK function differ between animals?
- PEPCK can be found in the MTCH or cytosol
- if found in the cytosol it involves moving reducing equivalents out of the MTCH into the cytosol
describe 3 major steps that fatty acid synthase uses to produce fatty acids and name one enzyme associated with each step
- entry/condensation
- acetyl transferase
- B-ketoacyl synthase - reducing = bonds (master step)
- B-ketomalonyl transacylase
- dehyrotase
- enoly reductase - release of molecule
- thioesterase
what are the 2 modifications that can be made to fatty acids? what are the enzymes responsible for this?
- elongate ———–elongase
- desaturation —————desaturase
what determines the ratio between acetoacetate and B-hydroxybutyrate during ketogenesis?
NAD+/NADH ratios
provide 3 ways that organisms can deal w/ ammonia/ excess nitrogen
ammonia
- ammoneotelic
- uricotelic
- ureotelic
nitrogen
- urea cycle
what molecule links the TCA cycle to the urea cycle?
fumerate
Describe how glutamate (GLU) and glutamine (GLN) metabolism are involved in pH homeostasis.
- At normal pH: Gln = Glu production
- At acidic pH: there’s a decrease in the production of Gln -> Glu + NH4+
- At basic pH: there is a increase in the production of Gln -> Glu+ NH4+
what ultimately decides if a molecule is glucogenic or ketogenic?
whether the carbon backbone is formed into pyruvate for glycolysis or acetyl CoA for fatty acid synthesis
glucogenic molecules have to be conserves throughout a cycle
describe hoe acetyl CoA carboxylase is regulated through covalent modification
- inactivated by dephosphorylation of insulin: increases polymerization
- activated by phosphorylation of glucagon: decrease acetylCoA carboxylase (AMP dependent kinase, PKA)
what role does vitamin B12 play in fatty acid metabolism?
allows for mutase to generate succinyl CoA
provide 3 reasons why sugar nucleotides are used in metabolism.
- irreversible
- increase enzyme interactions
- good leaving group: nucleotide
- resource allocation
what mode of the PPP would a rapidly dividing cell opt for and why?
scrambling phse
- attempts to generate increased ribose and deoxyribose
what are the 4 steps in the mechanism of glycogen phosphorylase?
removes end glucose on glycogen to generate G-1-P
- donates proton to 4C on glycogen chain
- donates protein to inorganic phosphate
- forms carbonium ion intermediate
- Pi attacks intermediate forming G-1-P
proton is given back to pyridoxal phosphate
in amino acid catabolism, the first reaction for many amino acids is a
- transamination requiring pyridoxal phosphate
what 2 molecules play an important role in getting fatty acids into the mitochondria?
- compound: carnitine
- protein: translocase
what is the role of phosphorylase kinase in glycogen metabolism
regulate glycogen metabolism
- phosphorylate glycogen phosphorylase leads to activation
