Download Cell Energy

Anaerobic Respiration
and Alternative
Pathways for fuel
Cellular Energy

Animal (and fungi and protist) cells need to
access the energy stored by photosynthesis.

They release the energy stored in sugars in a
process that is the reverse of photosynthesis

C6H12O6 + 6O2 -------- 6H2O + 6CO2
Different Pathways after Glycolysis
There are two main pathways to release
energy from glucose
 The amount of oxygen available controls
the pathway

 Plenty
of Oxygen = Cellular Respiration
 Not much Oxygen = Fermentation
Two types of Fermentation

Lactic Acid Fermentation: Our muscles
carry this out when they run low on
oxygen, producing ATP and Lactic Acid

Alcoholic Fermentation: Yeast cells carry
this out, producing ATP and Alcohol.
Picture of Pathway
Glycolysis
Cellular Respiration
Alcoholic
Fermentation
Lactic Acid
Fermentation
Cellular Respiration
Oxygen is required
 Takes place in the mitochondria
 Produces 32-34 ATP and releases CO2
and H2O as byproducts
 Muscles will do this as long as they don’t
run out of oxygen

Lactic Acid Fermentation

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Takes place when there’s not
enough oxygen for cellular
respiration
Produces ATP, but also Lactic
Acid
Also regenerates the NAD+
required to continue with
glycolysis.
Muscles do this when they run
low on oxygen
Lactic Acid causes the burning
sensation
Alcoholic Fermentation

Occurs in organisms
that do not carry out
cellular respiration or
lactic acid fermentation

Produces ATP, but also
ethanol and CO2 as
byproducts.

Yeast cells do this—we
use them to make beer,
wine, and bread.
Our Cells

Will either do:
 Cellular
respiration: During slow, steady
exercise
 Lactic Acid
Fermentation: During strenuous
exercise like sprinting, or lifting heavy
weights.

Do not carry out alcoholic fermentation—it
would kill your cells
Related Pathways to
Energy Production
Carbohydrates
 broken into monosaccharide, then broken down
for energy
 avg. yield of 16 kJ/g of energy
Proteins
 broken down into amino acids to be used to
produce cell’s proteins
 amino groups removed in deamination and
converted into ammonia (wastes)
 rest of a.a. continue through glycolysis or Kreb’s
cycle (depending on composition)
Lipids

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triglycerides broken into glycerol and fatty acids
glycerol can be converted to glucose (by
gluconeogenesis) or to DHAP or G3P (which
enter glycolysis).
fatty acids go to the matrix of mitochandria and
undergo β-oxidation – 2 carbons at a time are
chopped off into acetyl groups which combine
with co-enzyme A to produce acteyl-coA (used in
Kreb’s cycle)
much more ATP formed than from carbs. ex
lauric acid (12 C fatty acid) – produces 92 ATP
average yield is 38kJ/g of energy