Electron Transport System
Step 3 In Cellular Respiration
Chapter 5.6
Life needs constant energy in
order to survive and function
efficiently
Review:
• Step 1: Glycolysis
• In cytoplasm
• Step 2: Kreb’s Cycle
• In mitochondria matrix
• Step 3: Electron Transport
System
• In mitochondria inner
membrane
Inner membrane
matrix
Outer membrane
Electron Transport System
• Purpose: Use NADH and FADH2
produced in Kreb’s cycle to produce more
energy
• Requires oxygen
• Consists of cytochromes: proteins and
enzymes making up electron transport
system
• Give cells their color
Step 1:Transfer e-
NADH
• Takes hydrogen atoms from NADH and FADH2
• Splits hydrogen atoms into protons and electrons
H+
eNADH
NAD+
• Takes hydrogen atoms from NADH and FADH2
• Splits hydrogen atoms into protons and electrons
H+
H+
eNADH
eNAD+
• Electrons transferred along chain of cytochrome
proteins
• Releases free energy
• Used to “actively” push protons across membrane
into intermembrane space
H+
H+
H+
eNADH
e-
e-
NAD+
• Electrons transferred along chain of cytochrome
proteins
• Protons build up in space between outer and inner
membrane
H+
H+
H+
H+
eNADH
e-
e-
e-
NAD+
• Terminal cytochrome: last cytochrome protein
• Adds electrons and protons with oxygen to form
water
H+
H+
H+
H+
e-
e-
e-
eO2
H2O
• Terminal cytochrome: last cytochrome protein
• Adds electrons and protons with oxygen to form
water
Step 2a: ATP synthesis
H+
H+
H+
H+
e-
e-
e-
e-
ATP
synthetase
enzyme
complex
• High concentration of protons in
intermembrane space
• There is an ATP synthetase enzyme complex
Step 2b: ATP synthesis
H+
H+
H+
H+
e-
e-
e-
e-
ATP
synthetase
enzyme
complex
• Protons tend to diffuse back into matrix
through intermembrane space
• Through ATP synthetase enzyme complex
• ATP complex synthesizes ATP from ADP
Aerobic Respiration
• Produces 38 ATP total
• Glycolysis
• 1 glucose makes 2 ATP and 2 pyruvate
• Prep between Glycolysis and Kreb’s Cycle
• 2 pyruvate
− Makes 2 CO2 and 2 NADH
• Kreb’s Cycle:
• 2 pyruvate makes 2 Carbon Dioxide, 2 ATP, 2 FADH2, and 6
NADH
• Electron Transport System:
• makes 34 ATP
Bacteria Cellular Respiration
• Bacteria don’t have mitochondria
• Glycolysis and kreb’s cycle take place in
cytoplasm
• Electron Transport System take place in cell
membrane
Cell
Membrane
Cytoplasm
Facultative Aerobes Bacteria
• Bacteria can survive for long
periods with or without oxygen
• Switch back and forth
fermentation and aerobic
respiration
• Ex. Yeast
• In presence of oxygen, aerobic
• Without oxygen, switch to anaerobic
fermentaiton
Obligate Anaerobic
• Bacteria
• Carry on anaerobic respiration
• Actually poisoned by oxygen
• Ex. Tetanus bacteria
• Causes lockjaw
Obligate Aerobes
• Animals and plants
• Cannot survive without oxygen
• “obligate”=forced to commit
• Ex. You, a human
Antibiotics
• Some antibiotics work by
interfering with bacteria’s
ability to metabolize food