Transcript Unit Two “Energy Acquisition”

Unit Two
“Energy Acquisition”
“How Cells Harvest Energy from
Food”
Energy in Food
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Energy is obtained from Glucose for use in
building ATP via the removal of electrons
from the Glucose molecule
“Cellular Respiration” is defined as the
oxidation (loss of electrons) of food to obtain
energy
Cellular Respiration is quite different from
“Respiration” (breathing), however, the two
are related in that “Respiration” supplies
Oxygen to the cells so they can carry out
“Cellular Respiration”
Energy in Food
It is important to note that both plants and
animals participate in Cellular Respiration, and
therefore, both have Mitochondria, the organelle
where ATP production occurs
 The main difference between plants and animals
is that plants synthesize Glucose from smaller
molecules ,whereas animals need to consume
food matter in order to obtain Glucose
 The above is why plants are called “Producers”
and animals are called “Consumers”
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Cellular Respiration and its
Stages
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Cellular Respiration is accomplished in three stages:
– A) Glycolysis: production of ATP that takes place in
the cytoplasm of cells, and does not require Oxygen
(occurs in the Cytoplasm)
– B) Acetyl-CoA formation and Krebs Cycle: production
of large amounts of ATP that takes place in the
Mitochondria, and does require Oxygen (occurs in the
Mitochondria)
– C) Electron Transport Chain: NADH and FADH2 release
electrons that fuel the movement of protons across
inner mitochondrial membrane; result in the addition
of phosphate to ADP to generate lots of ATP (occurs
in the Mitochondria)
Chemical Reaction for Cellular
Respiration
 Glucose
+ Oxygen  Carbon Dioxide
+ Water + Energy
 C6H12O6
energy
+ 6O2  6CO2 + 6H2O +
Stage 1 of Cellular Respiration
– A) Glycolysis: production of ATP that takes place in
the cytoplasm of cells, and does not require Oxygen
1. 2 Phosphates from 2 ATP’s are added to
Glucose
2. The “Phosphorylated” Glucose is split in two,
forming 2 three-carbon sugar phosphates
3. In a series of reactions, both three-carbon
sugars phosphate groups are converted to
“Pyruvate”
4. The above Pyruvate forming process liberates
Hydrogen so it can bond with NAD+ to form
NADH, and 2 ATP’s are formed from each
Pyruvate
Glycolysis
Stage 2 of Cellular Respiration
– B) Acetyl-CoA formation and Krebs Cycle:
production of approximately 4 ATP’s that occurs
in the Mitochondria and does require Oxygen
1. A Carbon is removed from Pyruvate and
departs as a carbon dioxide molecule
2. The 2 carbon fragment that remains after the
removal of one Carbon joins to a structure called
“Coenzyme A” (CoA) forming a compound known
as “Acetyl-CoA”
Stage 2 of Cellular Respiration
3. If the cell has ample amounts of ATP, then
Acetyl-CoA is funneled into fat synthesis; if the
cell does not have ample amounts of ATP, then
Acetyl-CoA is directed toward ATP production
via the Krebs Cycle
4. The Krebs Cycle begins when a 2 Carbon
fragment is transferred from Acetyl-CoA to a 4
Carbon molecule to form a 6 Carbon molecule
5. The 6 carbon molecule has Carbon and
Hydrogen removed twice to form NADH from
NAD+, while the removed Carbons bond with
Oxygen to form Carbon Dioxide (byproduct)
Stage 2 of Cellular Respiration
6. Finally, the resulting 4 Carbon molecule
loses more Hydrogens via oxidation to form
FADH2 and NADH
7. This final 4 Carbon molecule is the starting
material needed to begin Cellular
Respiration again
Krebs Cycle
Step 3 of Cellular Respiration
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C) Electron Transport Chain: formation of approximately
30 ATP’s that occurs in the Mitochondria in the presence
of oxygen
1. NADH and FADH2 transfer high energy
electrons to molecules embedded in inner
mitochondrial membrane
2. Once they’ve donated electrons, NAD+ and FAD
move back to Krebs Cycle
3. Electrons fuel a proton pump that results in the
addition of a phosphate group to an ADP to form
ATP; this happens approximately 30 times!
Electron Transport Chain
Cellular Respiration Summary
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3 Main stages
– Glycolysis: occurs in Cytoplasm, can be
aerobic or anaerobic and generates a net of 2
ATP’s
– Formation of Acetyl-CoA and Krebs(Citric
Acid) Cycle: occurs in Mitochondria, must be
aerobic and generates approximately 4 ATP’s
– Electron Transport Chain: occurs in
Mitochondria, must be aerobic and generates
approximately 30 ATP’s
Other Cellular Food
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The focus to now has been the conversion of
Carbohydrates (Glucose) into other molecules
thereby liberating energy for use by cells
There are other categories of
macromolecules that can serve as the “Raw
Materials” for subsequent energy production
(Chapter 4)
Proteins (Amino Acids) and Lipids (Fatty
Acids) undergo chemical changes to convert
them into molecules that can be inserted into
either stage of Cellular Respiration
Cellular Respiration Overview
http://www.phschool.com/science/biology
_place/biocoach/cellresp/intro.html
 https://www.youtube.com/watch?v=00jbG
_cfGuQ
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