Understanding the Kreb Cycle and ATP

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In summary, the Krebs cycle is an exergonic process that releases ATP. This is because carbon-oxygen bonds are more stable than carbon-hydrogen or carbon-carbon bonds. Additionally, the Krebs cycle increases the entropy of the system.
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tica86
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Having some trouble understanding if the Kreb cycle is exergonic or endergonic?
I know it has to be exergonic because it's releasing ATP?
 
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tica86 said:
Having some trouble understanding if the Kreb cycle is exergonic or endergonic?
I know it has to be exergonic because it's releasing ATP?

GTP is actually is released, which from a potential chemical energy perspective, is equivalent to ATP. The Krebs cycle reduces the electron carrier NAD+ to NADH, which is used in the electron transport chain after the Krebs cycle to create ATP. The overall process must be exergonic, or else we would not have made far past being protoplasm. Individual endergonic reactions in the overall process are generally overcome through the use of highly energetic phophate-containing compounds; glycolysis is the best example of this, where 2 ATPs are consumed but 4 are gained, with a net of two ATP out.
 
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What makes a process exergonic? Well, it is helpful to consider the equation for Gibbs free energy: ΔG = ΔH - TΔS. Since exergonic processes bring your system to a state of lower free energy (i.e. ΔG < 0), processes that lower the potential energy of your system (ΔH < 0) or increase its disorder (ΔS > 0) will help a process be more exergonic.

How does one lower the potential energy of the system? Well, for carbon-based compounds, the answer is basically by increasing the number of bonds carbon has to oxygen. This is true because carbon-oxygen bonds are much more stable (i.e. have a lower potential energy) than carbon-hydrogen or carbon-carbon bonds.

What about the disorder of the system? One easy way to increase the disorder of a system is to break large molecules into smaller molecules.

Now, consider the Krebs cycle. The cell feeds acetyl-CoA into the Krebs cycle and it releases two molecules of carbon dioxide and regenerates free coenzyme A (CoA). Does this process create products that have a lower potential energy than the reactants? Does the process increase the entropy of the system?
 

1. What is the Kreb Cycle and how does it work?

The Kreb Cycle, also known as the citric acid cycle, is a series of biochemical reactions that take place in the mitochondria of cells. It is responsible for producing energy in the form of ATP (adenosine triphosphate) through the breakdown of glucose and other molecules. The cycle involves a series of chemical reactions that produce NADH and FADH2, which are then used in the electron transport chain to produce ATP.

2. What is the role of ATP in the Kreb Cycle?

ATP is the main energy currency of the cell, and it plays a crucial role in the Kreb Cycle. In the cycle, ATP is produced through a process called substrate-level phosphorylation, where a phosphate group is added to ADP (adenosine diphosphate) to form ATP. This ATP is then used as a source of energy for cellular processes.

3. How is the Kreb Cycle regulated?

The Kreb Cycle is regulated through a process called feedback inhibition. This means that the products of the cycle, such as ATP and NADH, can inhibit the enzymes responsible for the reactions in the cycle. This helps to maintain a balance of energy production in the cell and prevents an excessive buildup of ATP.

4. How does the Kreb Cycle contribute to cellular respiration?

The Kreb Cycle is the second stage of cellular respiration, following glycolysis. It is responsible for producing the majority of the ATP in aerobic respiration. The NADH and FADH2 produced in the Kreb Cycle are then used in the electron transport chain to generate even more ATP. Therefore, the Kreb Cycle is essential for the efficient production of energy in cells.

5. How does the Kreb Cycle differ in aerobic and anaerobic respiration?

The Kreb Cycle is only present in aerobic respiration, as it requires oxygen to function. In anaerobic respiration, the Kreb Cycle is not used, and ATP is produced through other processes such as fermentation. Additionally, the end products of the Kreb Cycle may differ in anaerobic respiration, depending on the type of molecule being broken down.

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