BIOL 201 lec 4 note
G. Brown office hours: Friday, 3:00 ‐4:30, N5/11 Stewart
Glycolysis • The stages of glycolysis • Regeneration of NAD+ from NADH • Readings: Berg et al., pp.426‐443.
Glycolysis • The part of the breakdown of glucose that can occur in the absence of oxygen (anaerobic) • Sometimes called fermentation • In muscle, product of fermentation is lactic acid • In yeast, fermentation product is ethanol • Present in nearly all organisms
O2 absent or limiting yeast
muscle
Fermentation: metabolic process with organic compound as end product
Invest energy (2 ATP)
Recover investment “with interest” (2 x 2ATP)
Stage 1 features two kinases Kinases: enzymes that transfer © phosphoryl group of ATP to acceptor
ATP has high phosphoryl transfer potential: ΔG0´ ATP → ADP + Pi = -7.3 kcal/mol ΔG0´ RPO32- → ROH + Pi = -2.5 to -3 kcal/mol ΔG0´ ATP + ROH → ADP + RPO32- = -4.5 kcal/mol (avg.) Keq > 103, formation of products strongly favored
Stage 1: Glucose → F‐1,6‐BP
“traps” glucose in cell
“Pacemaker” enzyme Can be converted to two 3Cphospho compounds
Stage 2: F‐1,6‐BP cleavage, triose phosphate salvage Fructose-1,6-bisphosphate
Stage 3: NADH, ATP and pyruvate generation GAL3P (GAP)
High phosphoryl transfer potential
ΔG =
ΔG0 ´
+ 2.303 RT log
[C][D] [A][B]
A + B → C + D
Fructose‐1,6‐bisphosphate
NAD+
ADP + Pi
NADH
ATP ADP + Pi pyruvate
ATP
Overall: Glucose + 2ADP + 2 Pi + 2 NAD+ → 2 Pyruvate + 2 ATP + 2NADH + 2H+ + 2H2O
O2 absent or limiting yeast
muscle
Metabolic fates of pyruvate
Acetaldehyde → Ethanol Pyruvate → Lactate
allow recycling of NADH back to NAD+
Glycolysis occurs in cytosol. Further catabolism of pyruvate (to acetyl CoA and beyond) occurs in mitochondria.
Glycolysis • The stages of glycolysis • Regeneration of NAD+ from NADH • Readings: Berg et al., pp.426‐443.
Glycolysis • The part of the breakdown of glucose that can occur in the absence of oxygen (anaerobic) • Sometimes called fermentation • In muscle, product of fermentation is lactic acid • In yeast, fermentation product is ethanol • Present in nearly all organisms
O2 absent or limiting yeast
muscle
Fermentation: metabolic process with organic compound as end product
Invest energy (2 ATP)
Recover investment “with interest” (2 x 2ATP)
Stage 1 features two kinases Kinases: enzymes that transfer © phosphoryl group of ATP to acceptor
ATP has high phosphoryl transfer potential: ΔG0´ ATP → ADP + Pi = -7.3 kcal/mol ΔG0´ RPO32- → ROH + Pi = -2.5 to -3 kcal/mol ΔG0´ ATP + ROH → ADP + RPO32- = -4.5 kcal/mol (avg.) Keq > 103, formation of products strongly favored
Stage 1: Glucose → F‐1,6‐BP
“traps” glucose in cell
“Pacemaker” enzyme Can be converted to two 3Cphospho compounds
Stage 2: F‐1,6‐BP cleavage, triose phosphate salvage Fructose-1,6-bisphosphate
Stage 3: NADH, ATP and pyruvate generation GAL3P (GAP)
High phosphoryl transfer potential
ΔG =
ΔG0 ´
+ 2.303 RT log
[C][D] [A][B]
A + B → C + D
Fructose‐1,6‐bisphosphate
NAD+
ADP + Pi
NADH
ATP ADP + Pi pyruvate
ATP
Overall: Glucose + 2ADP + 2 Pi + 2 NAD+ → 2 Pyruvate + 2 ATP + 2NADH + 2H+ + 2H2O
O2 absent or limiting yeast
muscle
Metabolic fates of pyruvate
Acetaldehyde → Ethanol Pyruvate → Lactate
allow recycling of NADH back to NAD+
Glycolysis occurs in cytosol. Further catabolism of pyruvate (to acetyl CoA and beyond) occurs in mitochondria.
