Exam next Friday
• Proposal:
– 60 point 4th exam over chapters 10 (Lipids),
11 (Membranes), 13 (Bioenergetics (ATP &
redox)
– 140 point final: ~40 points new stuff (general
concepts in glycolysis, TCA, electron
transport), ~100 points “comprehensive”
– Review sheet (4th exam) this weekend
– Review for 4th exam on Tuesday(?)
– Review for final ~ couple of days next week
Nutrients:
Fats/Carbohydrates/Proteins (highly reduced compounds)
Glycolysis, TCA/Krebs cycle
Breakdown of nutrients
Harvesting of energy as
(some) ATP, lots of reducing power (NADH)
Oxidative phosphorylation (Electron transport)
Harvesting of energy from reducing agents
Generation of (lots of) ATP
Usable (bioavailable) chemical energy:
ATP (other phosphorylated cpds), reducing agents (eg. NADH)
Aerobic respiration of glucose (etc)
• Glycolysis:
– Start with glucose (6 carbon)
– Generate some ATP, some NADH, pyruvate (2 x 3 carbon)
• TCA cycle
– Start with pyruvate
– Generate acetate
– Generate CO2 and reduced NADH and FADH2
• Electron transport
– Start with NADH/FADH2
– Generate electrochemical H+ gradient
• Oxidative phosphorylation
– Start with H+ gradient and O2 (and ADP + Pi)
– Generate ATP and H2O
Glycolysis
• Pathway for D-glucose
degradation
• Generation of pyruvate
• Anerobic (no O2 required)
– Occurs in most every living cell
– Eukaryotes→ in cytosol
• Pyruvate has different fates
– Aerobic→CO2→ ATP
– Anerobic
• Fermentation to EtOH
• Fermentation to lactate
Glycolysis
• 5 step preparatory
phase
– Energy requiring
– 2 ATP invested
1. Phosphorylation
2. Isomerization
3. Phosphorylation
4. Cleavage
5. Isomerization
Why phosphorylation?
1. Coupled transfer of phosphate to/from ATP
2. Intermediates “trapped” within the cell
•
•
Energy required to keep ‘naked’ glucose in the cell
(vs. chemical gradient)
Phosphate groups (neg charge) easily retained
3. Binding energy
•
Enzymes take advantage of negative charge to
increase affinity/specificity
Glycolysis
• 5 step payoff phase
– 4 ATP generated (net
2 gained)
– 2 NADH gained
– 2 pyruvate
– Series of oxidation
and phosphorylation
steps
Glucose  2 NAD  2pyruvate  2 NADH  2H 
2ADP  2Pi  2ATP  2H 2 O
G o '  146kJ / mol
G o '  2(30.5kJ / mol )
G o '  85kJ / mol
Step 1: Glucose phosphorylation by
hexokinase
Step 2: Conversion to Fructose-6-P
Step 3:Phosphorylation to F-1,6-bisP
phosphofructokinase
*Committed step*
Regulatory enzyme
Step 4: Cleavage of F-1,6-bP
6 carbon sugar →
Two 3 carbon sugars (triose phosphates)
Step 5: isomerization of
dihydroxyacetone
Both 3 carbon sugars are
now the same
(glyceraldehyde 3-P)
“Payoff phase”
Step 6: oxidation
(phosphorylation) of G-3-P
Step 7: ATP formation
Steps 6 & 7
Overall: transfer of Pi from
glyceraldehyde 3-P to ATP with
1,3-BPG as an intermediate
“Substrate-level phosphorylation”
Step 8: Rearrangement to 2phosphoglycerate
Step 9: Dehydration of 2phosphoglycerate to PEP
Step 10: Phosphoryl transfer to
ADP