Energy Transfer in Living
Things Part 2
Aerobic Respiration
Mitochondria
Krebs Cycle
Electron Transport Chain
Central Questions
–What is the purpose of the Krebs
Cycle (what does the cell need)?
Where does it occur?
–Give an example of an electron
carrier. What is its purpose?
–Describe the Electron Transport
Chain. Where does it occur?
–What is the overall equation for
aerobic respiration?
Aerobic Respiration
• Last time we discussed anaerobic
respiration (without oxygen)
• Aerobic respiration is the further
breakdown of pyruvate after
glycolysis in the presence of
oxygen
• Aerobic respiration consists of
Krebs Cycle and the Electron
Transport Chain
Mitochondria
• The rest of the steps happen in the
mitochondria
• The mitochondria is a complex
organelle with an outer membrane,
and inner membrane (folded up) and
the matrix (the liquid inside the
mitochondria)
1
Krebs Cycle
• Acetyl CoA enters the cycle and
follows several reactions
• Carbon dioxide is given off as waste
products
• 2 ATP are formed, but more
importantly, lots of electrons are
obtained for the next step
• This happens in the mitochondrial
matrix
Moving Electrons
• Remember what we discussed before
• Electron carriers can accept a pair of
electrons and a hydrogen
• NAD+ (empty taxi) accepts electrons
and H+ to make NADH (full taxi)
• FAD+ (empty taxi) accepts electrons
and H+ to make FADH (full taxi)
• Where are these taxis going...?
Electron Transport Chain (ETC)
• Electrons from NADH and FADH are
dropped into the chain
• The ETC is a series of proteins in the
inner mitochondrial membrane.
• The negative charge of the moving
electron draws H+ (protons) from the
matrix into the space between the
membranes
• They ‘go back’ through a turnstile that
makes ATP
Making ATP
• Chemiosmosis is the movement of ions
across a membrane.
• The H+ gets pushed to one side of the
membrane (high concentration) and their
natural tendency to go back across (to the
low concentration) powers the conversion
of ADP to ATP
• There is some dispute about how much
ATP is made, but the electron transport
chain probably makes about 34 ATP
Wait..why do we need oxygen?
• The H+ and electrons need somewhere to
go. They combine with oxygen to form
water as a waste product.
• This gives us the overall equation for
aerobic respiration:
• C6H12O6 + O2  CO2 + H20 + ATP
2
Aerobic vs Anaerobic
Central Questions
Glycolysis (First step for both)
2 ATP and 2 Pyruvates
–What is the role of ATP in the cell?
–Describe what happens, overall, in
glycolysis.
–Where does glycolysis occur?
–What is fermentation? What is its
purpose?
–Describe the 2 main types of
fermentation.
Aerobic
CO2 + H2O
Anaerobic
Waste
Lactic Acid (Bacteria)
Ethanol and CO2(yeast)
34* ATP
36* ATP
ATP After Glycolysis
Total ATP
0 ATP
2 ATP
3