Glucose Utilization
PATHWAYS: 4 W’sWhat = Net ReactionWhy = Purpose(s) of Pathway
Where = Organism/Tissue/Organelle
When = Regulation of Pathway
Glucose
AcetylCoA
Pyruvate
NADH/FADH2
KrebsCycle
C6
C4
C5
C4
ATP
Glycolysis
Bridging Rx.
Oxidative PhosphorylationADP
O2
NAD+/FAD
Metabolic Mainstreet
GLUCOSE + 2ADP + 2NAD+
2PYRUVATE + 2ATP + 2NADH
GLYCOLYSIS: Net Reaction (What)
10 Enzymes
Glucose gets oxidized - NAD+ gets reducedTwo ADP molecules get phosphorylated
Glycolysis is a a) catabolic b) anabolic pathway?
Do bacteria have a glycolysis pathway? a) yes b) no c) only anaerobic bacteria
1. Generate ATP a. immediate (2 “anaerobic” ATP) b. future - more ATP from pyruvate & NADH
GLYCOLYSIS: Purpose (Why)
2. Provide intermediates/pyruvate for synthesis reactions
Where?All Organisms: bacteria, plants, animalsAll Cell Types: liver, muscle, neurons, adipose, etc.
Cytoplasm
Low Energy Charge phosphofructokinase (-) ATP
(+) F2,6-BP hexokinase (-) G-6-P pyruvate kinase (-) ATP
When?
HO
OH
OOH
OH
OH
OH
O
OH
HO
OH
OH
a - Glucose b - Fructose
CH2 – OH |CH – OH |CH2 – OH glycerol
CHO | CH – OH | CH2 – OHglyceraldehyde
COO-
| CH – OH | CH2 – OH glycerate
COO-
|CH – OH |CH2 – O - PO3
2-
Name this molecule.
a) Glycerol phosphate b) Glyceraldehyde 3 phosphate c) 3 – phosphoglycerate d) 1 - phosphoglycerate
COO-
| C=O | CH3 pyruvate
COO-
| C-OH || CH2 enol pyruvate
CH2 - OH | C=O | CH2 - OH Dihydroxy acetone
GLYCOLYSIS
Glucose
Glucose-6-Phosphate
Fructose-6-Phosphate
Fructose 1,6 Bisphosphate
DHAP + Glyceraldehyde-3-P
Glyceraldehyde-3-P
Pyruvate
PEP
2-Phosphoglycerate
3-Phosphoglycerate
1,3-BPG
2 ATP → 2 ADP
C6 → 2C3
2 NAD+ reduced → 2 NADH 4 ADP → 4 ATP
Glucose in
2 pyruvate out
Glycolysis: The Preparatory Phase
Glycolysis: The Payoff Phase
GLUCOSE + 2ADP + 2NAD+
2PYRUVATE + 2ATP + 2NADH
GLYCOLYSIS: Net Reaction (What)
10 Enzymes
Glucose gets oxidized - NAD+ gets reducedTwo ADP molecules get phosphorylated
What is the limiting reagent for glycolysis?a) Glucose b) ADP c) NAD+
fuel in
SH2 NADH ATP
S NAD+ ADP
work output
Glucose
AcetylCoA
Pyruvate
NADH/FADH2
KrebsCycle
C6
C4
C5
C4
ATP
Glycolysis
Bridging Rx.
OP
ADP O2
Metabolic MainstreetNAD+
NADH
Lactate
Aerobic~ 36 ATP
How do you supplyNAD+ to glycolysisWhen a lack of O2
Prevents OP!
GLUCOSE + 2ADP + 2NAD+
2PYRUVATE + 2ATP + 2NADH
GLYCOLYSIS: Anaerobic
10 Enzymes
COO-
|NAD+ + H - C - OH | CH3
COO-
| C = O + NADH | CH3
Muscle
Liver
Lactate
Lactate Dehydrogenase (LDH)
GLYCOLYSIS : Side Reactions
Glucose
Glucose-6-Phosphate Glycogen R-5-P/Glucose Fructose-6-Phosphate 2,3 BPG Fructose 1,6 Bisphosphate
DHAP + Glyceraldehyde-3-P
Glyceraldehyde-3-P
Pyruvate
PEP
2-Phosphoglycerate
3-Phosphoglycerate
1,3-BPG Glycerol
GLYCOLYSIS: Regulation
Glucose (-) G-6-P 2nd
Glucose-6-Phosphate Glycogen
Fructose-6-Phosphate (-) ATP 1st
Fructose 1,6 Bisphosphate
DHAP + Glyceraldehyde-3-P
Glyceraldehyde-3-P
Pyruvate(-) ATP PEP
2-Phosphoglycerate
3-Phosphoglycerate
1,3-BPG
S PE
Metabolic Regulation
1. How Much Enzyme - Regulation of gene expression
2. Activity of Available EnzymeAllosteric EnzymesCovalent ModificationsProenzymes
Conditions in the cell (Goldilocks and the three Bears) a) Too much P – slow down pathway b) Too little P – speed up pathway c) [P] is just right – maintain steady state
Allosteric Enzymes R state (relaxed) – active: S → P T state (tense) – inactive (or less active): very little P formed
T ↔ R + S ↔ R + P
A negative regulator (-) will bind selectively to the less active form of an enzyme, shifting the conformational equilibrium toward this form and decreasing activity.
[T] increases and [R] decreases
T- ↔ (- regulator) + T ↔ R + S ↔ R + P
A positive regulator (+) will bind selectively to the more active form of an enzyme, shifting the conformational equilibrium toward this form and increasing activity. [T] decreases and [R] increases
T ↔ R + S ↔ R + P + (+ regulator) ↔ R+ + S
Glucose
AcetylCoA
Pyruvate
NADH/FADH2
KrebsCycle
C6
C4
C5
C4
ATP
Glycolysis
Bridging Rx.
OP
ADP O2
Metabolic MainstreetNAD+
NADH Aerobic~ 36 ATP
How do you supplyNAD+ to glycolysisWhen a lack of O2
Prevents OP!
Lactate
GLYCOLYSIS: Regulation
Glucose (-) G-6-P 2nd
Glucose-6-Phosphate Glycogen
Fructose-6-Phosphate (-) ATP 1st
Fructose 1,6 Bisphosphate
DHAP + Glyceraldehyde-3-P
Glyceraldehyde-3-P
Pyruvate(-) ATP PEP
2-Phosphoglycerate
3-Phosphoglycerate
1,3-BPG
1(-) G-6-P
3(-) ATP
Phosphofructokinase has distinct active and allosteric sitesATP is a negative allosteric regulator as well as a substrate.
Muscle (M4) - ↑ATP decreases PFK activity
[Glu]blood
Meal
Insulin
Glucagon
Fed
Fast early
late fast
Glycogen gone
6-12 hrs1-2 hrs
3 daysLong Term Fast
↑Liver Glycolysis
↓Liver Glycolysis
Liver Glycogenolysis provides glucose to blood/brain.
Liver Gluconeogenesis provides glucose to blood/brain.
Liver Glycolysis Regulation
Phosphofructokinase has distinct active and allosteric sitesATP is a negative allosteric regulator as well as a substrate.
Muscle (M4) - ↑ATP decreases PFK activity
Liver (L4)PhosphofructokinaseActivity in Glycolysis
Fixed [ATP]
↑[citrate] also enhances ATP (-) effect (signals sufficient building blocks)The liver runs glycolysis in the Fed state and blocks glycolysis in the Fasting State.This initially seems counterintuitive but …….
↑ATP decreases PFK activity↑ F-2,6-bP blocks ATP allosteric effect and ↑activityThe ↑F-2,6-bP is tied to insulin release (and high blood sugar)
Rat hepatocyte
Insulin & Fed state
GLUCONEOGENESIS ― What?
2Pyruvate + 4ATP + 2NADH 2GTP
Glucose + 4ADP + 2NAD+
2GDPto blood
Where? LiverWhy? To maintain blood [glucose] after glycogen is used upWhen? Fasting state – (particularly late fast) ↑ [acetylCoA] and glucagon
[Glu]blood
Meal
Insulin
Glucagon
Fed
Fast early
late fast
Glycogen gone
6-12 hrs1-2 hrs
3 daysLong Term Fast
Liver Gluconeogenesis provides glucose to blood/brain.
Gluconeogenesis
Glucose
AcetylCoA
Pyruvate
NADH/FADH2
KrebsCycle
C6
C4
C5
ATP
Glycolysis
Bridging Rx.
OP
ADP O2
NAD+/FAD
Metabolic Mainstreet
oxaloacetate
Gluconeogenesis - Bypass Enzymes
Glucose oxaloacetate Glucose-6-Phosphate
Fructose-6-Phosphate
Fructose 1,6 Bisphosphate
DHAP + Glyceraldehyde-3-P
Glyceraldehyde-3-P
Pyruvate
PEP
2-Phosphoglycerate
3-Phosphoglycerate
1,3-BPG
Pyruvate carboxylase
PEP carboxykinase
Fructose 1,6-bis phosphatase
Glucose 6-phosphatase (-) ATP
(-) ATP
(-) G-6-P
Gluconeogenesis - Bypass Enzymes
pyruvate + CO2 + ATP + H2O oxaloacetate + ADP,Pi + 2H+
oxaloacetate + GTP PEP + GDP + CO2
10. Pyruvate carboxylase & PEP carboxykinase (+) acetylCoA & (-) ADP
3. Fructose 1,6-bisphosphatase (-) fructose 2,6-bisphosphate (low fasting – high Fed) (-) AMP
fructose 1,6 bisphosphate + H2O fructose 6-phosphate + Pi
1. Glucose 6-phosphataseglucose 6-phosphate + H2O glucose + Pi
Where does Pyruvate come from?
Amino Acids
Pyruvate
Oxaloacetate
DHAP
Glucose
Glycerol
Lactate
Glucose
AcetylCoA
Pyruvate
NADH/FADH2
KrebsCycle
C6
C4
C5
ATP
Glycolysis
Bridging Rx.
OP
ADP O2
NAD+/FAD
Metabolic Mainstreet & fasting state
oxaloacetate
Protein
amino acids
Transamination & oxidative deamination
Fat
Fatty acids
Liver Regulation
Fructose-6-Phos
Fructose 1,6 Bisphos
PEP
Pyruvate oxaloacetate
(-) ADP(+) AcetylCoAPyruvate carboxylase
(-) ADPPEP carboxykinase(-) ATP
(-) Alanine(+) F-1,6 BPPyruvate kinase
(-) ATP(-) citrate(+) F-2,6 BP(+) AMPphosphofructokinase
(-) AMP (-) F-2,6 BP (+) citrateFructose 1,6-bisphosphatase
GlycolysisFed State
insulin GluconeogenesisFasting State
glucagon
Cori Cycle : Recycling Lactate
Muscle
Glucose
Lactate
Glucose
Lactate
Glycogen Glycogen
Liver
← LDH (Lactate Dehydrogenase) →
Glycolysis (all cells) & Gluconeogenesis (liver only)
Gluconeogeneis occurs in liver to provide glucose to blood during the fasting state.
It uses 4 separate enzymes to bypass all the ‘irreversible’ steps of glycolysis.Otherwise it shares the same enzymes with glycolysis.
The regulation of Gluconeogenesis and Glycolysis are coordinated and opposite.Glycolysis: on – Fed state with insulin and ↑F-2,6-bP, ↑AMP
off – Fasting state with ↑EC/ATP, ↑citrate Gluconeogeneis: on – Fasting State with glucagon, ↑acetylCoA/citrate
off – Fed state with insulin & ↑AMP/ADP, ↑F-2,6-bP
Glucose + 2NAD+ 2Pryruvate + 2NADH 2ADP → 2ATP
4ADP + 2GDP ← 4ATP + 2GTP
Today’s Topics: Cori Cycle & Gluconeogenesis reviewGlycogen Metabolism – Glycogenesis & GlycogenolysisPhosphorylase vs. Glycogen SynthaseHormones and Metabolic Regulation: Insulin vs. glucagonThe glucagon/epinephrine cascades
This pathway is negatively regulated by high ATP levels a) glycolysis b) gluconeogenesis c) both
This pathway is negatively regulated by high F-2,6-bP levels. a) glycolysis b) gluconeogenesis c) both
This pathway is negatively regulated (liver) during the fasting state. a) glycolysis b) gluconeogenesis c) both
Pentose Phosphate Pathway
To be covered with Fatty Acid Metabolism And ROS.