Glycolysis, Krebs Cycle, and
Electron Transport System
A review for the confused (like me!)
Regina Lamendella
AP Biology
December 16, 2008
What is happening while you
ingest donuts??
What is the purpose of glycolysis
and cellular respiration?
Doughnut = glucose = electrons
= Electrons
Overview Video
• Write down the major “take home
messages” from the video
Glycolysis
• 10-STEP reaction
• (Rxns 1-5) Glucose is phosphorylated and
cleaved to yield 2 molecules of triose
glyceraldehyde-3-phosphate. This process uses
two ATPs.
• (Rxns 6-10): The molecules of glyceraldehyde3-phosphate are converted to pyruvate, with
concomitant generation of four ATPs and two
NADH per glucose.
• How many net ATPs?
1 ATP
1 ATP
2 NAD+
Glycolysis
• Where are we within
the cell?
• What does ATP
stand for?
• What does NAD
stand for?
• How many carbons
does pyruvate
have?
Adenosine Tri-Phosphate
Nicotinamide Adenine
Dinucleotide
Nicotinamide Adenine
Dinucleotide H
H
Overall reaction for glycolysis
Glucose + 2 NAD+ + 2 ADP + 2 Pi 
2 NADH + 2 pyruvate + 2 ATP
Where do the pyruvate go next?
Intermediary Reaction
• Pyruvate (3-Carbon) Acetyl (2-Carbon)-CoA
• 2 Pyruvate + 2 CoA + 2 NAD+ 
2 Acetyl-CoA + 2 CO2 + 2 NADH
Overall energy production so far…
• Glycolysis: 2 ATP, 2 NADH
• Intermediate reaction: 2 NADH
Kreb’s Cycle
• Roles of the Krebs cycle
– Generate energy by oxidizing acetyl-CoA to carbon dioxide and
water
– Supply biochemical intermediates for other pathways
– Entry point of various degradative pathways for energy
generation
acetyl-CoA
Squeezing the energy
out of acetyl-CoA!!!
Krebs Cycle
•
•
•
•
•
Where are we?
What is ATP?
What is NAD?
What is FAD?
How much energy
is produced?
FADFADH2
Flavin Adenine Dinucleotide
H
H

Energy Production from Krebs Cycle
Acetyl-CoA + 3 NAD+ + ADP + Pi →
3 NADH + ATP + 2 CO2
Wait we had two pyruvates to start… have to multiply above
by 2!!
2 Acetyl-CoA + 6 NAD+ + 2 ADP + 2Pi →
6 NADH + 2 ATP + 4 CO2
Energy Production So far…
• Glycolysis: 2ATP, 2 NADH
• Intermediate Step: 2 NADH
• Kreb’s Cycle: 2 ATP, 6 NADH, 2 FADH2
• Where to next?
Electron Transport System Video
• Take notes and write down main points.
Electron Transport System
•
•
Electron transport chains are redox reactions that transfer electrons from an
electron donor to an electron acceptor.
The transfer of electrons is coupled to the translocation of protons across a
membrane, producing a proton gradient. The proton gradient is used to
produce useful work.
NADH= 3 ATP
FADH2= 2 ATP
Total energy production after ETC
• Glycolysis: 2ATP; 2 NADH= 6 ATP
• Intermediate step: 2 NADH= 6 ATP
• Krebs: 2 ATP; 6 NADH =18 ATP;
2 FADH2 = 4 ATP
• 34 ATP from ETC
• 2 ATP from Glycolysis
• 2 ATP from Kreb’s directly
• Total ATP production= 38 ATP