Energy, ATP, and Cellular Respiration Flashcards

A set of vocabulary flashcards covering the basics of bioenergetics, ATP structure, metabolic pathways, enzyme function, and the stages of cellular respiration based on lecture notes.

ATP (Adenosine Triphosphate)

A molecule composed of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups that stores chemical potential energy.

ADP (Adenosine Diphosphate)

The molecule formed when the terminal phosphate group "pops off" of ATP, a process that releases energy.

ATP Cycle

The process where cells use energy to drive chemical reactions and recycle ATP thousands of times by attaching a phosphate group ($Pi$) back to ADP using energy from food breakdown.

Exergonic reactions

Chemical reactions that release energy; they are characterized by a negative $\Delta G$ because the reactants have more free energy than the products.

Endergonic reactions

Chemical reactions that require or absorb energy; they are characterized by a positive $\Delta G$ because the products have more free energy than the reactants.

Gibbs Free Energy ($G$)

The energy available to do useful work within a system.

$$\Delta G$$

The change in free energy, calculated as the energy ($G$) of products minus the energy ($G$) of reactants.

Catabolic pathways

Metabolic pathways that release energy by breaking down complex molecules into simpler compounds, such as Cellular Respiration.

Anabolic pathways

Metabolic pathways that consume energy to build complex molecules from simpler ones, such as Photosynthesis.

Activation Energy ($E_A$)

The initial energy barrier required to start a chemical reaction.

Enzymes

Biological catalysts that speed up reactions by lowering the activation energy ($E_A$) barrier, while leaving the $\Delta G$ of the reaction unaffected.

Glycolysis

The first stage of cellular respiration occurring in the cytosol where a $6$-carbon glucose is split into two $3$-carbon molecules of pyruvate, yielding a net of $2\,ATP$ and $NADH$.

Conversion of pyruvate to acetyl-CoA

A stage in the mitochondrial matrix where pyruvate is converted into acetyl-CoA, producing $NADH$ and releasing $CO_2$ as a byproduct.

Citric Acid (Krebs) Cycle

A stage in the mitochondrial matrix where acetyl-CoA is broken down to $CO_2$, generating $2\,ATP$ through substrate-level phosphorylation and transferring electrons to $NADH$ and $FADH_2$.

Electron Transport Chain

A series of complexes in the inner mitochondrial membrane where high energy electrons from $NADH$ and $FADH_2$ move to better electron acceptors until they reach $O_2$, releasing energy to pump $H^+$ ions.

ATP Synthase

An enzyme complex that catalyzes the addition of $P$ to $ADP$ to form $ATP$ using the power generated by the movement of $H^+$ ions through its rotor.

Chemiosmosis

The process where $H^+$ ions move down their concentration gradient from the intermembrane space into the mitochondrial matrix through ATP Synthase.

Oxidative Phosphorylation

The combination of the electron transport chain and chemiosmosis which generates approximately $28\,ATP$ through the use of high energy electrons and an oxygen acceptor.

Photosynthesis Inputs and Outputs

Inputs include sunlight energy, $CO_2$ and $H_2O$; outputs include $C_6H_{12}O_6$ and $O_2$.