Respiration
Renewing ATP energy by
breaking down simple sugars
Honors Biology
Milton HS, GA
Summary equation
C6H12O6 + 6 O2 + 36-38 ADP + 36-38 Pi
 6 CO2 + 6 H2O + 36-38 ATP
glucose + oxygen + ADP + Pi
 carbon dioxide + water + ATP
• Just a summary above – respiration is NOT a onestep chemical reaction
How awesome is respiration?
• Amazingly efficient: ~ 40% of glucose energy
transferred to ATP energy
(more efficient than human-designed
combustion engines)
• Remarkably clean: CO2 and H2O gas products
(compared to soot from coal / oil combustion)
How transport high energy e-s?
• NAD+ = “empty” shuttle seeking e-s
• NADH = “full” with 2 high energy e-s
Glycolysis
• Enzyme pathway in cytoplasm
• Conserved over
evolutionary time – all
organisms possess
• In: glucose, ADP, Pi
NAD+
• Out: 2 pyruvates (smaller)
ATP, NADH
Krebs Cycle
x2
• Also called the citric
acid cycle
x2
x2
• In: pyruvates, ADP,
NAD+
• Out: CO2, ATP,
NADH
• Note: more pyruvates
can be added to keep
making ATP / NADH
x2
x2
x2
x2
Step 3: Electron transport chain
•
NADH delivers e-s to mitochondrial transport
proteins (leaves as NAD+ back to glycolysis /
citric acid cycle)
•
Transport proteins use up electron energy to
actively transport H+ to one side of membrane
Electron transport chain
intermembrane
space
inner
mitochondrial
membrane
mitochondrial
matrix
Step 3
• H+ wants to come back in
• Recall: electricity =
movement of charged
particles
• H+ rushes back through
ATP synthase, force of
rushing through powers
ADP + Pi  ATP
Summary
Alternatives to glucose …
• Cells can use MORE than just glucose
Fermentation alternative
• What if O2 is unavailable?
Fermentation
• No additional ATP
generated (after
glycolysis)
• Purpose: recycle
NADH generated in
glycolysis back to
NAD+
• Produces slightly
toxic products
Fermentation
Goal: give yeast access to sugar, but deny them O2
NOT a long-term solution for us
• Muscles can work in fermentation (short-term)
• Many other body cells cannot (not enough ATP
produced)
Summary of ways to cut up sugar