Exam 1 Flashcards
A rxn. in a catabolic pathway is found to have a large -Gibbs free enerfy. How likely is it that this rxn is a regulatory step in the pathway?
Very likely. Large -Gibbs Free energy means rxn. is further from equilibrium making it more irreversible (better regulatory step)
what are some likely general products of a catabolic pathway?
- ATP
- GTP
- NADH
- FADH2
- Acetyl CoA
list the control steps for the TCA cycle
- citrate synthase
- isocitrate dehydrogenase
- a-ketoglutarate dehydrogenase
provide the allosteric activators and inactivators of pyruvate dehydrogenase enzyme.
inactivators: ATP, acetyl CoA, NADH
activators: AMP, CoA, NAD+
how does citrate help tie glycolysis activity to the TCA cycle?
- in TCA cycle Acetyl-CoA reacts w/ oxaloacetate to make citrate
- citrate buildup in MTCH causes spilling into the cytosol
- citrate in cytosol inhibits PFK-1
- inhibition indicates no need for the breakdown of glucose b/c MTCH is high energy
provide 5 ways to regulate a metabolic pathway
- amount of enzymes
- catalytic activity
- compartmentalization
- energy charge
- isoenzymes
what are all the fates of G-6-P in non-liver cells?
- glucosamine
- PPP
- glycolysis
- glycogen
list similarities between pyruvate dehydrogenase and a-ketoglutarate dehydrogenase
- control scheme
- thioester produces
- products
- 3 enzymes
list the 3 control steps in glycolysis. which one is considered the pacemaker?
- HK/GK
- PFK-1
- pyruvate kinase
PFK-1 is the PACEMAKER
provide 2 differences between anabolic and catabolic processes
catabolic
- enzymes are activated by phosphorylation
- makes ATP
anabolic
- enzymes are inactivated by phosphorylation
- uses ATP
14). List the two shuttles responsible for transferring reducing equivalents from glycolysis into the mitochondria. What is the major difference between these two?
- matate-asparatate shuttle
- glycerol-3-phosphate shuttle
difference: malate is slower but more efficient & produces more ATP b/c electrons are transferred to NAD+ instead of FAD
15). Write the overall reaction for glycolysis and explain where the other two protons come from.
- phosphorylation of glucose to G-6-P
- phosphorylation of F-6-P to F-1,6-BiP
16). Fully describe the mechanism for phosphoglycerate mutase
- phosphoenzyme with His residue at the active site binds w/ 3-phosphoglycerate
- phosphoenzyme transfers phosphate group from HIS residue to 2 position of 3-phosphoglycerate making 2-3 biphosphoglycerate
- phosphate at 3 position of 2-3biphosphoglycerate is + to HIS residue. Making 2-phosphoglycerate. regenerating phosphoenzyme
Which of the following is not an intermediate of the citric acid cycle?
A) oxaloacetate
B) citrate
C) α-ketoglutarate
D) succinyl-CoA
E) pyruvate
pyruvate
18). Use an example from one glycolysis or the TCA cycle to briefly explain the concept of isozymes.
different structure but catalyze the same rxn. HK and GK both catalyze the phosphorylation of glucose
19). Use an example from glycolysis and the TCA cycle that we have discussed so far to briefly describe the term flux.
- flux is net metabolite movement
- crucial in pathways that change with varying conditions
- Glycolysis: phosphofructokinase serves as control step
- TCA cycle: isocitrate dehydrogenase serving as control step
20). Describe the term substrate level phosphorylation and provide 3 examples discussed in class.
- substrate-level phosphorylation is the transfer of phosphate to ADP from another phosphorylated compound
- succinyl-CoA synthetase
- phosphoglycerate kinase
- pyruvate kinase
21). Explain how kinases use induced fit as well as magnesium to catalyze their reactions.
- induced-fit: prevent unwanted hydrolysis of ATP by H2O (closes the H2O active site)
- magnesium: acts as cofactor allowing facilitated rxn between ATP and glucose
22). Provide three functions for GTP in cells.
important to the formation of
- proteins
- cAMP
- ATP
Explain why succinate dehydrogenase is called the mixer reaction and the role it plays in linking the TCA cycle to the ETS.
- mixer rxn. b/c the label is lost w/ the formation of fumerate
- links: oxidizes succinate to form fumerate & causes the regeneration of FADH2
