Aerobic Respiration!!
The Krebs / Citric Acid Cycle and the
Electron Transport Chain!!
Yeast! – Overview of Yeast Worksheet
Which beaker has more ‘bubbles’?
What are the bubbles made of?
Yeast experiment; Which flour sample
had sugar added to it?
Both produce CO2, but one produced many
more bubbles much more quickly. Aerobic
respiration is much more efficient than
anaerobic respiration (or fermentation) and
produced CO2 much faster as well.
Which dough had the sugar added??
Beaker B!!
Fermentation
 Occurs when O2 NOT present (anaerobic)
Called Lactic Acid fermentation in muscle
cells (makes muscles tired)
Called Alcoholic fermentation in yeast
(produces CO2 and ethanol; this is what
gives beer, wine, etc., their alcohol
content!)
Aerobic Respiration Intro Activity
• Follow instructions on the hand-out
and complete the graph.
• DON’T get any of the solution in your
mouth! Exhale into the straw at a
normal breathing pace, even after 2
minutes of exercise (slow it down!).
Speaking like a scientist:
Analyzing Data: How did exercise
affect the time it took for the
solution to change colour?
E.x. “Based on the data, exercise
(increased / decreased) the time
it took for the bromothymol blue
solution to change colour.”
**WAIT before making your final
conclusions! **
Respiration Overview:
1) Where Does Cellular Respiration
Take Place? Aerobic respiration
• It takes place in
two parts of the
cell:
Anaerobic
respiration
(Glycolysis +
fermentation)
occur in the
Cytoplasm
takes place in the
Mitochondria
2) Review of Mitochondria
Structure
• Smooth outer
Membrane
• Folded inner
membrane
• Folds called Cristae
• Space inside cristae
called the Matrix
+ Fermentation
if no O2
4) History Lesson – The Krebs Cycle!!
• Discovered by Hans
Krebs in 1937
• He received the Nobel
Prize in physiology or
medicine in 1953 for
his discovery
• Forced to leave
Germany prior to
WWII because he was
Jewish
5-7) Krebs Cycle – Also called
the Citric Acid Cycle
During a single “turn” of the Krebs cycle an
acetyl-CoA molecule is converted to a molecule
of citric acid! The citric acid molecule’s bonds
are broken and re-arranged, releasing ENERGY
and TWO CO2 molecules!
Enough energy is produced to make _______
ATP.
6) Krebs Cycle Summary
• Also during the Krebs Cycle, electrons
are attached to NAD+ and FAD+, another
electron-carrying molecule, forming
NADH and FADH2
• These molecules are then used in the
E.T.C.!
7) How many turns?
7) Each glucose molecule allows for TWO turns
of the Krebs cycle, and a total of:
6 CO2 and 2ATP are produced!!
(Remember the 2 CO2 produced from the
conversion of Pyruvic Acid to Acetyl-CoA!)
***Now you have enough information to write
your 3-sentence conclusion from the lab
before!!***
The Electron Transport Chain !!
1) The inner membrane of the
mitochondria is lined with structures
that remove the electrons and H+
from the electron transporting
molecules:
____________ and _____________!
The Electron Transport Chain !!
2) The H+ ions are forced out of the
matrix and into the inter-membrane
space (the space between the inner
and outer membrane of the
mitochondria – see text p. 259)
• H+ pumps move the H+ into the
inter-membrane space by active
transport.
The Electron Transport Chain !!
3) The H+ ions want to move from the
inter-membrane space back into the
matrix; to get back in they must travel
through an enzyme, called
_______________, that’s attached to
the inner membrane.
The Electron Transport Chain !!
3) The H+ ions want to move from the
inter-membrane space back into the
matrix; to get back in they must travel
through an enzyme, called
_______________, that’s attached to
the inner membrane.
The Electron Transport Chain !!
4) The movement of the H+
molecules through ATPsynthase
makes it spin! With each rotation,
a phosphate is attached to an ADP
molecule, forming __________!
The Electron Transport Chain !!
5) Inside the mitochondrial matrix,
these H+ ions (a.k.a. protons), O2
molecule and free-flowing
electrons (e-) combine to form
water.
The formation of water is
an_____________ reaction,
meaning it produces energy!
_____________ is so important for
cellular respiration because it’s the
final electron acceptor in the
E.T.C.!! Without it, the E.T.C.
wouldn’t function.
The Electron Transport Chain !!
6) This chain continues all along the inner
mitochondrial membrane, with H+ moving in
and out the whole way… and in total, from 1
glucose molecule _______ ATP are produced!
(the multi-step chain has some sections that
produce more or less ATP than others!)
Electron Transport Chain Summary
32-34 ATP Produced
~6 H2O Produced
NAD+ and FAD+ are regenerated for use in the
Krebs Cycle and glycolysis!!
CLARIFICATION!! -- There are two
types of Lactic Acid Fermentation…
Homolactic and Heterolactic Fermentation
In Homolactic Acid Fermentation (like in
humans), all of the pyruvic acid is converted to
lactic acid, and no CO2 is produced.
In heterolactic acid fermentation, some of the
pyruvic acid isn’t fully converted to pyruvic acid,
and CO2 is produced as a byproduct.
Overall Equation for Cellular
Respiration
YIELDS
C6H12O6 + 6O2
6CO2 + 6H20 +
34-36ATP
Structure of ATP
The ADP-ATP Cycle
ATP
Synthetase
ATP-ase
Copyright Cmassengale