Download Glycolysis and Anaerobic Respiration Lecture Notes

Glycolysis and Anaerobic
Respiration
Biology Exploring Life section 7.5-7.6
Modern Biology section 7-1
Glycolysis and Anaerobic Respiration
• Objectives:
• Describe the process of glycolysis in
terms of its products and energy yield.
• Explain why a fermentation pathway
must be included with glycolysis in order
for anaerobic respiration to occur.
• Compare and contrast the fermentation
pathways used by animal cells and
yeasts.
• Give examples of how both types of
fermentation are used in industry.
Anaerobic Respiration
• What is
anaerobic
respiration?
• Cellular respiration is the process by which living
cells release the energy contained in food
molecules.
• Most of the ATP produced by cells uses a complex
electron transport chain in which oxygen is the
final electron acceptor. Because the process uses
oxygen, it is called aerobic respiration.
• When cells are forced to work without enough
oxygen they can produce ATP and continue
working for short periods by using other
biochemical pathways (fermentation).
• Some organisms (yeasts and some bacteria) can
provide all their ATP requirements without the
use of oxygen.
• Biochemical pathways that release energy
without the use of oxygen are collectively called
anaerobic respiration.
Anaerobic Respiration
•
How does
anaerobic
respiration
produce ATP?
• Anaerobic respiration uses glycolysis, the
splitting of sugar molecules, to produce a
small amount of ATP.
– Glycolysis only extracts about 3.5% of the
total energy available in a molecule of sugar.
• This process is accomplished by various
enzymes in the cytoplasm of the cell and
does not require mitochondria or other
cellular organelles.
• Glycolysis is also the first stage of aerobic
respiration so the products of the
reaction can be further broken down by
mitochondria to release more energy in
aerobic respiration.
Anaerobic Respiration
• How does
anaerobic
respiration
produce
ATP?
1
1. Using two ATP molecules as
activation energy, the cell splits a sixcarbon glucose molecule in half. The
result is two three-carbon molecules of
PGAL, each with one phosphate group.
Anaerobic Respiration
•
2
How does
anaerobic
respiration
produce ATP?
1
3
2. Each three-carbon PGAL molecule then transfers
electrons and hydrogen ions to a carrier molecule called
NAD+.(very similar to NADP+ found in the light reactions
of photosynthesis).
 Accepting two electrons and one hydrogen ion
converts the NAD+ to a compound called NADH.
3. A second phosphate group is now added to each
molecule of PGAL.
Anaerobic Respiration
•
2
How does
anaerobic
respiration
produce ATP?
1
3
4
4. Both phosphate groups added to each 3-carbon
molecules are now removed and used to convert
2 ADP molecules to ATP. The resulting 3-carbon
molecule is pyruvic acid.
 The end result is that four new ATP molecules
are produced, a net gain of two ATP molecules.
Fermentation Pathways
•
What is
fermentation?
• The products of glycolysis can be further
broken down without the use of oxygen
through additional biochemical pathways
that occur in the cytosol.
• The combination of glycolysis pulse these
additional pathways is called fermentation.
• Fermentation does not produce any
additional ATP but it does regenerate
NAD+ which is used to keep glycolysis
going.
 NAD+ is the final electron acceptor for
glycolysis. Without a constant supply, the
process would stop.
Fermentation Pathways
• Lactic acid
fermentation:
• This is a fermentation pathway that occurs in
the cells of animals and some microorganisms.
• In this process two hydrogen atoms provided
by NADH and H+ ions are transferred to
pyruvic acid converting it to lactic acid.
• The NADH is oxidized (loses an electron) to
become NAD+ which is used to power
glycolysis.
Fermentation Pathways
•
Alcoholic
Fermentation:
•
•
•
•
This is a fermentation pathway that occurs in the
cells of yeasts and some microorganisms.
In this process, a CO2 molecule is removed from
each pyruvic acid molecule and released as a gas.
Two hydrogen atoms provided by NADH and H+
ions are transferred to the two carbon molecule
converting it to ethyl alcohol.
The NADH is oxidized (loses an electron) to become
NAD+ which is used to power glycolysis.
Fermentation Pathways
• Industrial
uses of
fermentation
pathways:
• Fermentation carried out by
microorganisms is a part of many
modern manufacturing processes.
• Lactic acid fermentation:
– Microbes to transform milk into cheese
and yogurt.
– The sharpness or sour flavor of yogurt and
some cheeses is mainly due to lactic acid.
– Microbial fermentation turn soybeans into
soy sauce and cabbage into sauerkraut.
– Microbial fermentation is used in the
treatment of waste water to help break
down solid waste into sludge which is used
for fertilizer.
Fermentation Pathways
• Industrial
uses of
fermentatio
n pathways:
• Fermentation carried out by
microorganisms is a part of many
modern manufacturing processes.
• Lactic acid fermentation:
Fermentation Pathways
• Industrial
uses of
fermentati
on
pathways:
Barley Malt
(sprouted grain)
• Fermentation carried out by
microorganisms is a part of many
modern manufacturing processes.
• Alcoholic fermentation:
– Used to make alcoholic beverages such as
beer and wine.
– The carbon dioxide is what makes
champagne and beer bubbly. Copper “Pot Still”
Barley Malt
and Grist
Mash
(fermentation)
Fermentation Pathways
• Industrial
uses of
fermentati
on
pathways:
• Fermentation carried out by
microorganisms is a part of many
modern manufacturing processes.
• Alcoholic fermentation:
– Carbon dioxide bubbles from baker's
yeast make bread rise.
Fermentation Pathways
• Fermentation carried out by microorganisms is a part of
many modern manufacturing processes.
• Alcoholic fermentation:
– Alcoholic fermentation of bio-matter such as corn stalks and
processed sugar cane is used to make ethanol which is fuel for
cars.
Video Resources
• Bozeman Science
– Anaerobic respiration
• Brightstorm! Science Help
– Anaerobic respiration
• Khan Academy
– Anaerobic respiration