Chapter 6: Bioenergetics, Enzymes, and Cellular Energetics

Vocabulary flashcards covering bioenergetics, thermodynamic laws, ATP mechanics, enzyme action, redox energetics, cellular respiration, and photosynthesis.

Kinetic Energy

Energy associated with motion.

Metabolic Pathway

A group of enzymes that can work together. Each enzyme accelerates a specific reaction and a metabolic pathway requires a unique and specific enzyme. Otherwise, the end product will not appear unless all enzymes present and functional

How to regulate metabolic pathway

A metabolic pathway breaks chemical processes into step-by-step reactions to efficiently transfer energy. Enzymes regulate it using feedback inhibition (where the end product shuts down early steps), allosteric regulation, and compartmentalization.

Enzymes influence activation energy

Enzymes lower the activation energy barrier to speed up reactions by straining bonds and orienting substrates in their active site without changing the overall energy.

ATP unfavorable reactions

Cells use energy coupling to link an unfavorable endergonic reaction to the highly favorable exergonic hydrolysis of ATP. By transferring a phosphate group to a reactant, ATP forms a high-energy phosphorylated intermediate, making the net free energy change negative so the reaction can proceed.

Potential Energy

Stored energy based on location or structural capacity.

Chemical Energy

Potential energy stored in molecular bonds.

Conservation of Energy

The First Law of Thermodynamics, which states that energy cannot be created or destroyed, only transformed.

Law of Entropy

The Second Law of Thermodynamics. When energy is changed from one form to another, there is a loss of usable energy

Synthesis

2 substrate molecules combined into a single product

Structure of a more oraganized Organism Related to Entropy

A more organized structure is less stable and yields a higher energy state

Structure of a less organized Organism Related to Entropy

A less organized structure is more stable and yields a lower energy

Metabolism

How we use energy and the sum of energy

Substrate

Reactants that bind to the enzymes

Exergonic Reaction

A spontaneous, energy-releasing process characterized by a negative change in free energy ($-\Delta G$).

Endergonic Reaction

A non-spontaneous process that consumes energy and requires an energy input, characterized by a positive change in free energy ($+\Delta G$).

Coupled Reactions

Two reactions that happen simultaneously and are linked together. This relates to ATP because as it is released (exergonic), that energy is used to drive the endergonic reactions

ATP Hyrdrolysis

When the ATP breaks, it is an excergonic reaction, which creates ADP + P. The energy created is a endergonic reaction, which makes ATP.

Phosphoanhydride Bond

These bonds store high potential energy because they link three negatively charged phosphate groups that strongly repel one another. When released, the energy creates ADP and an inorganic phosphate (P) molecule

Affecting Enzymes: PH

The pH level can influence enzyme activity by altering the enzyme's structure and the charge of its active site. Each enzyme has an optimal pH range where it functions most effectively.

Altering Enzymes: Temperature

This can change it by increasing enzyme activity, but if it gets too hot, then the proteins denature

Catabolic Pathway

A metabolic pathway that breaks down molecules and releases energy.

Anabolic Pathway

A metabolic pathway that builds complex molecules and consumes energy.

Activation Energy ($E_a$)

The initial energy barrier required to initiate a chemical reaction, which enzymes lower to accelerate reaction rates.

Denaturation

The structural breakdown of an enzyme's active site due to extreme shifts in environment, leading to a loss of catalytic function.

Cofactor

An inorganic mineral activator, such as metal ions like Iron and Zinc that assists in enzyme catalysis.

Coenzyme

An organic non-protein helper, often a vitamin derivative like $\text{NAD}^+$, that assists in enzyme catalysis.

Active Site

The specific region on an enzyme where substrate molecules bind.

Allosteric Site

An alternate regulatory site on an enzyme distinct from the active site.

Competitive Inhibitor

An inhibitor that binds directly to the active site of an enzyme to physically block the substrate.

Noncompetitive Inhibitor

An inhibitor that binds to an allosteric site, altering the shape of the active site so the substrate cannot bind efficiently.

Oxidation

The loss of electrons ($e^-$) during a reaction, which releases energy (exergonic).

ATP for energetically unfavorable reactions

Cells use energy coupling to link an unfavorable endergonic reaction to the highly favorable exergonic hydrolysis of ATP. By transferring a phosphate group to a reactant, ATP forms a high-energy phosphorylated intermediate, making the net free energy change ($\Delta G$) negative so the reaction can proceed.

Degradation

The breakdown of larger molecules into smaller ones, often releasing energy in the process.

Proton Gradient

An electrochemical difference in $\text{H}^+$ ion concentration established across a membrane.

Chemiosmosis

The movement of $\text{H}^+$ ions down their electrochemical gradient to drive ATP synthesis.

Photosynthesis

An endergonic synthesis process represented by the equation $6\,\text{CO}_2+6\,\text{H}_2\text{O}\rightarrow\text{C}_6\text{H}_{12}\text{O}_6+6\,\text{O}_2$ .

Cellular Respiration

An exergonic catabolic pathway represented by the equation $\text{C}_6\text{H}_{12}\text{O}_6 + 6\,\text{O}_2 \rightarrow 6\,\text{CO}_2 + 6\,\text{H}_2\text{O} + \text{ATP}$.

Relationship between Photosynthesis and Cellular Respiration

The products of photosynthesis are the reactants for cellular respiration, and the products of cellular respiration are the reactants for photosynthesis.

Why Both Ender/Exergonic and Oxidation/Reduction are coupled reaction

Both of these reactions happen at the same time and can’t work without the other. Energy is released/used with Ender/Exer and electrons are being released/gained with Oxi/Red

Electron Transport Chain

Series of membrane-bound carrier proteins that pass electrons to each other, resulting in energy being released as electrons are passed to make ATP