Michael Slemp
Review of Cellular Respiration
1. Where does glycolysis happen? Is it aerobic or anaerobic
process? Cytoplasm, anaerobic process
2. What is the final product of glycolysis?
Two 3-carbon molecules (pyruvate), 2 ATP
3. Where does cellular respiration happens? Is it aerobic or
anaerobic process? Mitochondria, aerobic process
4. Name the 2 steps of cellular respiration? Where does each
step happen? 1. Krebs cycle – matrix of mitochondria. 2- electron
transport – inner membrane of mitochondria
5. What are the final products of each step?
1- small amounts of ATP, other energy-carrying molecules, co2
2-large number of ATP, water, heat
Oxygen present
Cellular Respiration
Large amount of ATP
produced.
Glycolysis
aerobic
glucose
Oxygen NOT present
anaerobic
2 ATP
molecules
Two 3-carbon
molecules
Fermentation
In order to understand fermentation we need to
look at glycolysis a little bit closer
We said that the final product of glycolysis are two 3-carbon molecules
and 2 molecules of ATP
During the splitting of glucose more energy is
released that 2 molecules of ATP can capture
Remember ?
ATP = $1.00 bill
This extra energy is captured into other energy-carrying
molecule (NAD+)
Remember ?
During Krebs cycle, energy-carrying molecules were also formed. These
were our $20.00 bills which entered electron transport for creation of ATP?
Glycolysis
+ 2 ATP + extra energy
glucose
Two 3-carbon
molecules
(2 pyruvates)
Packed into NAD+
molecule
NAD+ + extra energy = NADH
Energy-poor
molecule (pennies)
Energy-rich molecule ($20.00),
too large for cell use
Cellular respiration only happens during the presence of
oxygen.
So what would happen in anaerobic conditions, when
products of glycolysis cannot enter process of cellular
respiration?
Finally, all NAD+ would be used up, cell could not
produce no more ATP in glycolysis and would die.
That is why, in anaerobic conditions,
cell enters process of fermentation!
FERMENTATION
•
•
•
•
Anaerobic process
Does not produce more ATP
Recycles NAD+ (which makes possible for glycolysis to continue)
Without fermentation, glycolysis would stop
Different cells (like yeast, plants) use different type s of fermentations.
Why is this important?
Think of cheese, bread,
yogurt, wine, alcohol…
The taste and texture of
fermented food is based on
the final product of
fermentation. E.g. alcohol
fermentation = alcohol
For example: Lactic acid fermentation
Glucose
Two 3-carbon
molecules
(pyruvates)
energy
2 lactic acid
molecules
NADH = energy + NAD+
Glycolysis
2 ATP
NAD+ + energy = NADH
Waste product = lactic acid
(sour taste in milk and yogurt)
Fermentation
This process is used by our
muscle cell during strenuous
exercise (when not enough O2).
Lactic acid causes muscle
burning.
Another example: Alcoholic fermentation
Glycolysis
Pyruvate
Yeast use alcoholic
fermentation during the
production of bread.
CO2 causes the dough to
puff up and rise. During
baking, CO2 evaporates
into air and yeast is killed
by heat of baking.
2 alcohol
molecules
+ 2 CO2
(carbon dioxide)
Fermentation
Waste product: alcohol and
carbon dioxide