Exam 2: Sample Questions Flashcards
provide 6 functions of the PPP
- NADH
- prevents oxidative stress
- major route of glucose metabolism
- xenobiotic metabolism
- scrambles glucose carbons
- nucleotide synthesis
what are the 2 modes of the PPP?
- cellulose division
- fatty acid synthesis
the cellulose division mode of the PPP requires?
R-5-P
what are the metabolic event that occur in the cellulose division mode of the PPP.
glycolysis intermediate is used to make more R-5-P
the fatty acid synthesis mode of the PPP requires?
more NADPH
the fatty acid synthesis mode of the PPP includes what metabolic event?
parts of gluconeogenesis is used to make more G-6-P
what is the regulatory step of the PPP?
G-6-P
what enzyme regulates G-6-P?
dehydrogenase
dehydrogenase is inactivated by….
- increase in NADPH
- decrease in NADP+/NADPH ratio
what hormone activates dehydrogenase?
cortisol
what rxns are unique to gluconeogenesis?
- pyruvate carboxylase
- moving OAA to the cytosol
- PEPCK
- F16BiPhosphate
- G-6-phosphatase
what role does translocase play in fatty acid metabolism?
during exchange step of setting up fatty acids it exchanges carnitine far acyl carnitine
How many FADH2 and NADH molecules would be formed from an 8 carbon fatty acid through fatty acid oxidation?
3 FADH2
3 NADH
describe how unsaturated fatty acid oxidation differs from saturated fatty acid
saturated fatty acid oxidation forms FADH2 and NADH and consecutively undergoes β-oxidation until making acetyl CoA
unsaturated fatty acid oxidation cis-trans isomerase flips fatty acid if necessary then it undergoes β-oxidation until making acetyl CoA
both saturated and unsaturated fatty acids go through hydration by enoyl-CoA hydratase to form…
L-β-hydroxyacyl-CoA
D-β-hydroxyacyl-CoA
what is the prosthetic group of pyruvate carboxylase?
biotin
what is the significance of biotin in fatty acid oxidation?
it increased utilization of glucose for fat synthesis
provide 4 reasons why the production of ketone bodies is important?
- less toxic
- more soluble
- bypass regulatory points
- spares glucose
provide 3 conditions under which amino acids would be oxidized
- diet excess
- starvation
- cellular situations (diabetes)
what role does pyruvate carboxylase play in gluconeogenesis?
adds bicarbonate to pyruvate to form oxaloacetate
provide 3 ways that organisms can deal w/ ammonia & excess nitrogen
ammonia
- ammoniotelic
- 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 is the preferred methyl carrier metabolically and why?
- SAM (S-adenosyl methionine)
b/c it contains a sulfonium ion
provide 3 reasons why sugar nucleotides are used in metabolism.
- irreversible
- increase enzyme interactions
- good leaving group: nucleotide
- resource allocation
what is the rate limiting enzyme in glycogenolysis?
glycogen phosphorylase
glycogen phosphorylase requires what coenzyme to be active?
pyridoxal phosphate
what is the summarized mechanism for glycogen phosphorylase?
removes end glucose on glycogen to generate G-1-P
what are the 4 steps in the mechanism of glycogen phosphorylase?
- 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
what is the 1st reaction for many amino acids?
transamination reaction
what is the actual reaction for the transamination reaction?
converting α-keto acid to glutamate
by transfer of amino group to carbon atom of α-ketoglutarate
what coenyme do transaminases require?
pyridoxal phosphate (PLP)
what molecule plays an important role in getting fatty acids into the MTCH?
carnitine acyl transferase I (CATI)
what effect does fructose-2,6-biphosphate have on gluconeogenesis and glycolysis?
- gluconeogenesis: inhibits
- glycolysis: stimulates
what is the significance of CoA to fatty acid oxidation?
thiolytic cleavage uses CoA
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 ultimately decides if a molecule is glucogenic or ketogenic?
determined based on whether the carbon skeleton can be made into glucose or acetyl CoA
describe the hormonal regulation of acetyl CoA carboxylase
- inactivated through dephosphorylation by insulin
- activated through phosphorylation by glucagon
list the 3 major activities of the fatty acid synthesis complex
- entry/condensation
- reduction of = bond (master step)
- release of molecule
describe the role of vitamin B12 in amino acid metabolism
rearranges the carbon skeleton
provide 3 ketone bodies that can be formed
- acetoacetate
- acetone
- hydroxybutyrate
how does odd-chain fatty acid oxidation differ from even chain fatty acid oxidation?
- odd-chain produces benzoate
- even-chain produces phenylacetate
what is the role of hormone sensitive lipase in fatty acid metabolism?
- to break down triglycerides into:
glycerol & 3 fatty acids
describe the Cori Cycle
process of transporting lactate from cell undergoing anaerobic respiration to liver where it is used to provide glucose back to cells
transporting liver energy
what are the organs involved in the Cori Cycle?
liver & muscle
what are the major molecules of the Cori Cycle?
- lactate
- glycogen
- glucose
list 3 arachidonic acid products
- prostaglandins
- thromboxane
- prostacyclin
- leukotrienes
what are the effects of prostaglandins?
- transit of RBCs
- decrease gastric acid production
what is the effect of thromboxane
- blood clotting
what is the effect of prostacyclins
- basodialators
- decrease platelet aggregation
what is the effect of leukotrienes?
- allergic reactions
- promote inflammation
what is the source of all the carbons found in cholesterol?
acetyl CoAs
what is the role of HDL and LDL in regards to cholesterol transport?
HDL: transports cholesterol to the liver
LDL: transports cholesterol to tissues
what are the 5 stages of cholesterol synthesis?
- mevalonate production
- isoprenoids
- squalene
- cyclize squalene to lanosterol
- formation of cholesterol
what is a similarity of chylomicrons and VLDL?
- both aid in transport of triglycerides through the blood
what is a difference between chylomicrons AND VLDL?
chylomicrons: dietary lipids seen in the GI tract
VLDL: endogenous — seen in the liver
what is the 3 carbon carrier used in fatty acid synthesis?
acyl carrier protein (ACP)
what role does thioesterase play in determining the fatty acid that a particular cell produces?
dictates if a molecule is palmitate or something else during the cleavage stage of fatty acid synthesis
what are the 2 types of attachment for glucose molecules in glycogen?
- α 1,4 linkage —–main chain
- α 1,6 linkage——-branching points of main chain
what are the 2 glycogen storage diseases?
- Pompe’s
- Anderson’s
the disease Pompe’s occurs in the ______________ and leads to _________________
lysosomes
respiratory failure
the disease Anderson’s occurs in the ____________ and leads to ___________
liver
liver failure
name two amino acids that can undergo direct deamination. Why?
- serine
- threonine
- they contain an OH group
what are the 2 sources of nitrogen in the urea compound?
- glutamate/glutamine
- aspartate
what effect does dietary nitrogen have on enzymes in the urea cycle?
- it down regulates the enzymes
- ex: too much protein in civil war & concentration camps
diagram the glucose/alanine cycle
- glucose converted to alanine in muscle
- alanine spills into the blood
- alanine converts to glucose in liver
- glucose is transported into muscle
what role does pyridoxal phosphate play in amino acid synthesis?
- cofactor for aminotransferases
- forms Schiff-base linkage w/ specific lysine group of aminotransferase enzyme
overall reaction for synthesis of palmitate
8AcCoA + 7ATP + 14NADPH ————–> palmitate + 14NADP+ + 6H2O + 7ADP + 7Pi + 8CoA
what are the 2 enzymes that metabolize/modify arachidonic acid?
- cyclooxygenase
- lipoxygenase
what types of molecules are formed by cyclooxygenase?
- prostaglandins
- prostacyclin
- thromboxane
what types of molecules are formed by lipoxygenase?
- leukotrienes
what types of molecules are formed by lipoxygenase?
- leukotrienes
fatty acids can be modified into their ____________ and _________________ forms
ester
thioester
what are the 3 sources of NADPH for fatty acid synthesis?
- PPP
- hexose monophosphate
- malic enzyme
what are the 2 modifications that can be made to fatty acids? what are the enzymes responsible for this?
- elongate ———–elongase
- desaturation —————desaturase
what is the overall reaction for the PPP?
G-6-P + 2NADP+ + H2O ——————> R-5-P + 2NADPH + 2H+ + CO2
