Cellular Respiration: Krebs Cycle and ETC

Vocabulary practice flashcards focusing on the steps, coenzymes, carbon accounting, and ATP yield of the linked reaction, Krebs cycle, and electron transport chain (ETC).

Linked reaction process

The reaction in which two molecules of pyruvate from the cytosol combine with two molecules of coenzyme A in the presence of oxygen to form Acetyl CoA, changing the molecule from a 3-carbon to a 2-carbon pyruvate and releasing the lost carbon as carbon dioxide.

Acetyl CoA

A 2-carbon molecule formed during the linked reaction that serves as the actual input for the Krebs cycle.

Mitochondrial matrix

The internal compartment of the mitochondrion where Acetyl CoA enters to be fully processed during the Krebs cycle.

Krebs cycle products

The processing of Acetyl CoA in the mitochondrial matrix results in $2\text{ ATP'S}$, $8\text{ NADH}$, and $2\text{ molecules of } FADH_2$.

$$FADH_2$$

A coenzyme that performs the exact same function as NADH; its primary job is to store energy by being "loaded" with hydrogens to be "cashed in" later at the electron transport chain.

Total Carbon Accounting

The complete breakdown of the 6 carbons from the original glucose molecule: glycolysis yields two 3-carbon pyruvates; the transition/link reaction releases $2\text{ molecules of } CO_2$ (2 carbons); and the Krebs cycle releases the remaining $4\text{ molecules of } CO_2$ (4 carbons), totaling $2 + 4 = 6\text{ carbon dioxides}$.

Purpose of the ETC

To spend the energy stored in coenzyme batteries (NADH and $FADH_2$) to move hydrogen ions ($H^+$) into a specific location.

Intermembrane space

The area between the inner and outer mitochondrial membranes where protons are pumped during the ETC, creating a hypertonic environment on one side and a hypotonic environment on the other to form a steep concentration gradient.

ATP synthase

An enzyme that provides a pathway for protons to flow back into the mitochondrial matrix to relieve hypertonic pressure, utilizing the kinetic/movement energy of the protons to power its mechanical rotation.

ATP formation (ETC Step 3)

The process where movement energy generated by rotating ATP synthase is used to attach an inorganic phosphate (Pi) to adenosine diphosphate (ADP) to synthesize adenosine triphosphate (ATP).

Total ATP production

The overall yield of cellular respiration, consisting of a net of $2\text{ ATP}$ from glycolysis, a net of $2\text{ ATP}$ from the Krebs cycle, and $26\text{ to } 28\text{ ATP}$ net from the ETC, resulting in an overall total of $30\text{ to } 32\text{ ATP}$.