chapter 12 Flashcards
(39 cards)
glucose
occupies a central position in the metabolism of most cells
-nearly universal
glucose structure
6 carbon compound with one aldehyde group and 5 hydroxyl groups
a 6-C sugar containing a ketone is a-
ketohexose
cyclizes to form a 6-membered ring
glycolysis is a —- pathway
catabolic
-convertion of 1 molecule of glucose into 2 molecules of pyruvate
generates both ATP and NADH
Gluconeogenesis is the -
opposing pathway of glycolysis
know Glycolysis scheme
Glycolysis serves as the-
first step in the complete oxidation of glucose to CO2 and H2O
-occurs in the cytosol
- can occur under aerobic or anaerobic conditions
-typically aerobic, can only metabolize fat aerobically
-results in the net production of a small amount of ATP
-provides building blocks for synthesis of cellular molecules
glycolysis is comprised of -
10 enzyme catalyzed reactions
what are the 4 important enzymes we are learning about for glycolysis
hexokinase
phosphofructikinase-1
pyruvate kinase
glyceraldehyde 3-phosphate dehydrogenase
stage 1 for glycolusis
energy investment
-glucose needs to be activated
-small amount of enery (ATP) is utilized
-involves ‘hexose’ sugars (6 carbon)
stage 2 in glycolysis:
energy payback
-energy is harvested in the form of ARP directly
-NADH is also generated
-involves ‘triose’ sugars (3 carbons)
stage 1: glucose to glyceraldehyde- 3- phosphate
glucose (c6) -> Glyceraldehyde-3-phospate (GAP) (x2) (c3)
-2 ATP are consumed for every glucose
activation stage
rxn 1 - catalyzed by hexokinase
-first ATP investment
Glucose + ATP -> G-6-P + ADP + H+
irreversible, Exergonic, ^G «0
-Regulated
-phosphate/phosphoryl transfer reaction
coupled to ATP ‘lysis’ (hydrolysis)
coupling rxn 1
hexokinase couples the breaking of a phosphoanhydride bond (ATP) to the formation of a phosphoester bond (G-6-P)
-breaking a phosphoanhydride bond released -32 kJ/mol of energy
-forming a phosphoester bond required +14 KJ/mol of energy
rxn 2 - isomerization
glucose and fructose are structural isomers
isomerization (aldehyde to ketone)
reveribile, ^G approx 0
rxn 3: Catalyzed by PFK-1
second ATP investment
F-6-P + ATP -> F-1,6-BP + ADP + H+
-irreversible, exergonic, ^G «0
rate limiting
TIGHTLY regulated
coupled to ATP “hydrolysis”
phosphate/phosphoryl transfer reaction
the reaction catalyzed by PFK-1is the-
committed step in glycolysis
rxn 4: lysis
the lysis in glycolysis
F-1,6-BP <–> DHAP and GAP
-isomers of each other
-reversible, ^G approx 0
rxn 5: DHAP isomerization
production of two glyceraldehyde 3-phosphate molecules
reversible, ^G approx 0
2 seperate rxns (lysis and isomerization
2 molecules of GAP are produced from one molecule of fructose-1,6-biphosphate
one molecule of glucose produces
2 molecules of GAP
every rxn described from GAP to pyruvate happens twice per glucose
stage 2: glyceraldehyde-3-phosphate to pyruvate
glyceraldehyde-3-phosphate (GAP) (x2) -> pyruvate (x2)
4 ATP are generated for every glucose
rxn 6: oxidation and phosphorylation
oxidation followed by phosphorylation
-energy capture step (NADH produced)
^Go is +
^G is approx 0 -> reversible under cellular conditions
-this rxn generates 2 high energy molecules (NADH and 1,3-BPG)
rxn 7: synthesis of ATP from 1,3- BPG
-paying back the dept
-^Go is -
-^G is approx 0 -> reversible under cellular conditions
-ATP synthesis coupled to breaking acyl phosphate (mixed anhydride)
-energy capture step (ATP produced) SLP reaction
Substrate-Level phosphorylation (SLP)
a coupled reaction, a phosphate-transfer reaction and, specifically, a phosphate-transfer reaction that produces a nucleoside triphosphate
-no O2 required in the synthesis of the NTP
