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Lec 6

Fermentation and Cellular Respiration
◦ Fermentation
 the degradation of a sugar that occurs without the
help of oxygen

What type of Metabolic pathway is
fermentation is it Catabolic or is it
Anabolic?
◦ Catabolic

Two types of Fermentation
◦ Alcohol fermentation
◦ Lactic acid fermentation
Fermentation

Pyruvate converted to ethanol
◦ 2 Steps
 1st step releases CO2 from pyruvate
 2nd step acetaldehyde reduced by NADH to
ethanol
Alcohol Fermentation
LE 9-17a
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 Ethanol
Alcohol fermentation
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde

Pyruvate is reduced directly by NADH,
◦ Forms lactate as an end product
◦ no release of CO2

Lactic acid fermentation
◦ fungi and bacteria to make cheese and yogurt

Human muscle cells use lactic acid
fermentation
◦ to generate ATP when O2 is scarce
Lactic acid Fermentation
LE 9-17b
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Lactate
Lactic acid fermentation
2 Pyruvate

The ATP made during fermentation is
generated by what?
◦ Substrate-level phosphorylation

What is substrate-level phosphorylation?
- Production of ATP from
ADP by direct transfer of
a high-energy phosphate
group from a
phosphorylated
intermediate
Fermentation

What type of Metabolic pathway is substratelevel phosphorylation? (Catabolic or Anabolic)
◦ Catabolic pathway (Release energy)

What type of reaction is substrate-level
phosphorylation? (exergonic or endergonic?)
◦ Exergoinic (energy outward)

So ∆G would be?
◦ negative
Fermentation

Cellular Respiration
◦ Oxygen is consumed as a reactant along with
the organic fuel

What type of Metabolic pathway is Cellular
Respiration?

In Eukaryotic cells what is the main
area/compartment of cellular respiration?

What is the “Fuel” for cellular respiration?

Oxidation-reduction reactions
◦ A transfer of one or more electrons from one
reactant to another

Oxidation
◦ the loss of electrons from one substance

Reduction
◦ the addition of electrons to another substance
Redox Reactions
Where does the Oxidation and
Reduction Occur?
Redox Reactions
Na – is oxidized the loss of
electrons
Cl – is reduced the gain of
electrons
Redox
What is the Reducing
Agent and what does it
reduce?
What is the Oxidizing
agent and what does it
Reactions oxidize?
What is the Reducing Agent and what does it
reduce?
Na – is the Reducing agent (electron donor)
Cl – is Reduced
What is the Oxidizing agent and what does it
oxidize?
Cl – is the Oxidizing agent (electron
acceptor)
Na – is Oxidized
Redox Reactions
Where does the Oxidation and
Reduction Occur?
Redox Reactions
Redox Reactions
Cellular Respiration

During cellular respiration, the fuel (such as glucose) is
oxidized and oxygen is reduced:
becomes oxidized
C6H12O6 + 6O2
6CO2 + 6H2O + Energy
becomes reduced
Some redox reactions do not transfer electrons but change the
electron sharing in covalent bonds
This is what occurs here the IMPORTANT point is that
the change in the covalent status of electrons as hydrogen is
transferred to oxygen is what liberates energy

Is a series of steps
◦ Cellular respiration DOES NOT oxidize glucose in a
single step that would transfer all the hydrogen
from the fuel to the oxygen at one time.
◦ Fuel, glucose is broken down in steps
◦ Each step is catalyzed by an enzyme.

Hydrogens are stripped from glucose then
usually passed first to the coenzyme NAD+
◦ NAD+ functions as an Oxidizing agent
◦ NAD+ + H  NADH
Cellular Respiration

Krebs Cycle

Glycolysis
◦ http://www.youtube.com/watch?v=WcRm3MB3OKw
◦ http://www.youtube.com/watch?v=nKgUBsC
4Oyo
◦ http://www.youtube.com/watch?v=ub1zTkZL5sE

Making ATP (make it rain remix) Kreb
Cycle
◦ http://www.youtube.com/watch?v=YyN0wx2AHfE&f
eature=related
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