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8.4 Inside the Mitochondria -- Part 2
The electron transport chain has three complexes and two carriers.
The members of the electron transport chain accept electrons, which they pass from one to the other via redox reactions.
The complexes of the electron transport chain use the energy released during reactions to pump hydrogen ion from the matrix into thechondrion.
Energy can be obtained from electron passage because H+ ion are pumped and transported.
There are already many H+ ion in the matrix, so they will be moved to the intermembrane space.
cristae and the walls of a dam hold back water, allowing it to collect.
Ten times as many H+ are found in the intermembrane space as in the matrix, as a strong electrochemical gradient develops.
The gates of a dam are similar to the ATP synthase complex.
When the gates of a hydroelectric dam are opened, water rushes through and energy is produced.
Once formed, ATP moves out of mitochondria and is used to perform cellular work, during which it breaks down to ADP and P. At any given time, the amount of ATP in a human can only last a short time.
Our body weight is produced by the mitochondria every day.
The muscles need more than less active cells to function.
When a burst of energy is required, the muscles still use fermentation.
Consider that the dark meat of chickens, the thigh meat, contains more mitochondria than the white meat of the breast.
This suggests that chickens walk or run around the barnyard.
The figure shows the theoretical yield for the complete breakdown of glucose to CO2 and H2O during cellular respiration.
The electron transport chain can produce a maximum of 32 to 34 ATP molecules.
The grand total of the total of the electron transport chain is between 36 and 38 ATP.
Other factors can affect the efficiency of cellular respiration.
The delivery of the electrons from outside the mitochondria is different for cells.
If they are delivered by a shuttle mechanism to the start of the electron transport chain, there will be six ATP results.
There is a net gain of two ATP from the process of glycolysis.
The matrix of mitochondria has the citric acid cycle in it.
A total of four ATP are formed outside of the electron transport chain.
The electron transport chain is responsible for most of the ATP.
The NADH and FADH2 take electrons to the electron transport chain.
FADH2 doesn't pump as much H+ as NADH because it doesn't deliver its electrons to the transport chain after NADH.
FADH2 can't account for the amount of production.
Each stage of cellular respiration is provided in Figure 8.9.
We know that cells rarely achieve these values.
The "shuttle" mechanism allows NADH to be delivered to the electron transport chain inside the mitochondria in some cells.
Each NADH is shuttled to the ETC at a cost to the cell.
This reduces the count of ATP produced by some cells to four instead of six.
At times, cells need to use energy to move pyruvate into the cell and to establish a nucleus in the mitochondria.
There is still a lot of research going on.
Most estimates place the actual yield at around 30.
Only between 32 and 39 percent of the available energy is usually transferred from sugar to fuel.
In the form of heat, the rest of the energy is lost.
We will look at how cellular respiration fits into metabolism as a whole in the next section.
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