Question

is Adderall related to the citric acid cycle/Krebs cycle? if so, how so?

Answer 1

The citric acid cycle (also known as the Krebs Cycle) is actually a part of the much larger process called cellular respiration, the process where your body harvests energy from the food you eat. Yes, the citric acid cycle has the same citric acid found in oranges and other citrus fruits!

Where does the citric acid cycle fit into cellular respiration?

1. Glycolysis, where the simple sugar glucose is broken down, occurs in the cytosol.
2. Pyruvate, the product from glycolysis, is transformed into acetyl CoA in the mitochondria for the next step.
3. The citric acid cycle, where acetyl CoA is modified in the mitochondria to produce energy precursors in preparation for the next step.
4. Oxidative phosphorylation, the process where electron transport from the energy precursors from the citric acid cycle (step 3) leads to the phosphorylation of ADP, producing ATP. This also occurs in the mitochondria.

The citric acid cycle captures the energy stored in the chemical bonds of acetyl CoA (processed glucose) in a step-by-step process, trapping it in the form of high-energy intermediate molecules. The trapped energy from the citric acid cycle is then passed on to oxidative phosphorylation, where it is converted to a usable form of cellular energy, ATP (adenosine triphosphate). We can then use that energy to move, breathe, make our hearts beat, and think (among other things)

The citric acid cycle is called a cycle because the starting molecule, oxaloacetate (which has 4 carbons), is regenerated at the end of the cycle. Throughout the citric acid cycle, oxaloacetate is progressively transformed into several different molecules (as carbon atoms are added to and removed from it), but at the end of the cycle, it always turns back into oxaloacetate to be used again. Energy can be captured from this cycle because several of the steps are energetically favorable. When a step is favored, it means that the products of the reaction have lower energy than the reactants. The difference in energy between the products and the reactants is the energy that is released when the reaction takes place (see enzyme kinetics). The released energy is captured as the electron shuttles (NAD^\text{+}+start superscript, plus, end superscript, and FAD) are reduced to NADH and FADH_{2}2​start subscript, 2, e

To start the cycle, an enzyme fuses acetyl CoA and oxaloacetate together so that citric acid is formed (a 2-carbon molecule + a 4-carbon molecule = a 6-carbon molecule!). This is the first molecule that is made in the cycle and is where the cycle gets its name. Enzymes then proceed to speed up (or “catalyze”) a sequence of rearrangements that convert the newly made citric acid molecule into a series of slightly different molecules. These enzymes only change the rate that these rearrangements occur, not the outcome.

Energy shuttles:

1. NADH: An energy shuttle which delivers high energy electrons to the electron transport chain where they will eventually power the production of 2 to 3 ATP molecules. When this electron shuttle is not carrying high energy electrons, meaning it has been oxidized (lost its electrons), it is left with a positive charge and is called NAD^\text{+}+start superscript, plus, end superscript.
2. FADH_{2}2​start subscript, 2, end subscript: Another energy shuttle that carries high energy electrons to the electron transport chain, where they will ultimately drive production of 1 to 2 ATP molecules. The oxidized form of FADH_{2}2​start subscript, 2, end subscript is FAD and happens just like in NADH.

High energy molecules:

1. ATP: The basic energy currency of the cell. It’s a form of energy that cells can use right away.
2. GTP: Similar to ATP, GTP can be easily converted to ATP in the cell.