Cellular Respiration
Harvesting Energy From Food
Chapter 7
ATP provides the energy for cellular work
ATP: (adenosine triphosphate) main energy source that cells use for most
of their work
An ATP molecule contains potential energy, much like a compressed
spring. When a phosphate group is pulled away during a chemical
reaction, energy is released.
The ATP Cycle
ATP is constantly recycled in your cells. A working muscle cell recycles all
of its ATP molecules about once each minute. That's 10 million ATP
molecules spent and regenerated per second!
Overall Equation for Cellular Respiration
In cellular respiration, the atoms in glucose and oxygen are rearranged,
forming carbon dioxide and water. The cell uses the energy released to
produce ATP.
Cellular respiration breaks down organic molecules to yield
energy.
Energy stored in organic compounds is released in a series of
enzymes controlled reactions. Similar to burning but…
In Eukaryotic Cells, the reaction of Aerobic Respiration occur
Inside MITOCHONDRIA.
Structure of Mitochondria
Mitochondria are found in almost all eukaryotic cells. Its structure is key to its
role in cellular respiration.
Its complex folding pattern of membranes and spaces allows for many sites
where reactions can occur.
Respiration involves glycolysis, the Krebs cycle, and
electron transport
Step 1
2
Step 2
2
Step 3
32- 34
GLYCOLYSIS
• The first stage in breaking down a glucose
molecule, called glycolysis (splitting
sugar), takes place outside the
mitochondria in the cytoplasm of the cell.
• releases a small amount of energy.
• It is the first step in cellular respiration.
• If oxygen isn’t present a different pathway
is followed
Stage I: Glycolysis
The first stage in breaking down a glucose molecule, called glycolysis (splitting
sugar), takes place outside the mitochondria in the cytoplasm of the cell.
Stage 2: The Krebs Cycle
The Krebs cycle finishes the breakdown of pyruvic acid molecules to carbon
dioxide, releasing more energy in the process. The enzymes for the Krebs cycle
are dissolved in the fluid matrix within a mitchondrion's inner membrane.
Kreb’s Cycle:
Where does this occur?
Identify the products.
Kreb’s Cycle movie
Stage 3: Electron Transport Chain and ATP Synthase Action
The final stage occurs in the inner membranes of mitochondria. This stage has
two parts: an electron transport chain and ATP production by ATP synthase
The inner mitochondrial membrane couples electron transport
to ATP synthesis.
The Pathway of Electron
Transport
This energy change is used
to “pump” hydrogen to the
inner membrane space
creating a gradient which
can power cell processes.
.
Chemiosmosis couples the electron transport chain to ATP
synthesis
Chemiosmosis: The Energy-Coupling Mechanism
ATP synthase protein complex
functions as a mill, powered by
the flow of hydrogen ions.
This complex resides in
mitochondrial and chloroplast
membranes of eukaryotes and
in the plasma membranes of
prokaryotes..
The gradient of hydrogen ions
“pushes” the ATP synthesis.
Animation of ATP synthesis in Mitochondria
Copyright 1997. Thomas M.
Terry, The University of
Connecticut
Cellular respiration generates many ATP molecules for each sugar
molecule it oxidizes
During respiration, most energy flows in this sequence:
Glucose NADH  electron transport chain  protonmotive force  ATP
Harvesting Energy without Oxygen
Fermentation in Human Muscle Cells
When your lungs and bloodstream can't supply oxygen fast enough to meet
your muscles' need for ATP. Your muscle cells use fermentation, to make ATP
without using oxygen.
How does the energy production of Lactic Acid fermentation compare to
aerobic respiration?
Lactic Acid fermentation occurs in animal cells deficient in oxygen
Lactic Acid Fermentation movie
Fermentation in Microorganisms
Yeast (a microscopic fungus) is capable of both cellular respiration and
fermentation.
Fermentation in yeast produces ethyl alcohol. The carbon dioxide that is
released during fermentation creates bubbles and pockets that make bread
rise. The alcohol evaporates during baking.
Fermentation enables some cells to produce ATP without the
help of oxygen. Alcoholic fermentation occurs in yeast.
Alcoholic Fermentation movie
Pyruvate as a key juncture in catabolism. Glycolysis is common to
fermentation and respiration.
How does the net gain of
ATP compare in aerobic vs.
fermentation?
The catabolism of various
food molecules.
Carbohydrates, fats, and
proteins can all be used as
fuel for cellular respiration.
WITH OXYGEN
• Cellular respiration is the process
__________________________________
__________________________________
_____________
• It is composed of
– Glycolysis
– _______________________
– _______________________