BIO 107 Chapter 6: An Introduction to Metabolism (Concepts 6.1–6.3)

Comprehensive vocabulary flashcards covering concepts 6.1 through 6.3 from Chapter 6 of BIO 107, focusing on thermodynamics, metabolism, free-energy changes, and the role of ATP in powering cellular work.

Metabolism

The totality of an organism's chemical reactions, representing an emergent property of organized molecular interactions within cells.

Metabolic pathway

A series of chemical reactions that begins with a specific starting molecule and proceeds through intermediate steps to a final product, with each step catalyzed by a specific enzyme.

Catabolic pathways

Metabolic pathways that break down complex molecules into simpler molecules, releasing energy in the process (e.g., cellular respiration).

Anabolic pathways

Metabolic pathways that consume energy to build complicated molecules from simpler ones (e.g., protein synthesis).

Bioenergetics

The overall study of how energy flows through living organisms.

Energy

The capacity to cause change.

Work

The movement of matter against an opposing force.

Kinetic energy

Energy associated with the relative motion of objects.

Thermal energy

Kinetic energy associated with the random motion of atoms or molecules.

Heat

Thermal energy in transfer from one body of matter to another.

Potential energy

Stored energy that matter possesses because of its location or spatial arrangement.

Chemical energy

Potential energy available for release in chemical reactions, such as the catabolism of food molecules.

Open system

A system in which energy and matter can be transferred between the system and its surroundings; living organisms are open systems.

Isolated system

A system that is completely separated from its surroundings and cannot exchange either energy or matter with them.

First law of thermodynamics

The principle of conservation of energy stating that energy can be transferred and transformed, but it cannot be created or destroyed.

Second law of thermodynamics

The principle stating that every energy transfer or transformation increases the entropy of the universe.

Entropy

A quantitative measure of molecular disorder and energy dispersal.

Spontaneous process

A process that occurs without an ongoing external input of energy, leading to an increase in entropy, which does not necessarily proceed rapidly.

Free energy ($G$)

The portion of a biological system's energy that can perform work under conditions of uniform temperature and pressure.

Free-energy change ($\Delta G$)

The difference between the free energy of the final state and the initial state, calculated as $\Delta G = G(\text{final}) - G(\text{initial})$; spontaneous processes are characterized by a negative value.

Exergonic reaction

A spontaneous chemical reaction in which there is a net release of free energy, resulting in $\Delta G < 0$ and products that contain less free energy than the reactants.

Endergonic reaction

A nonspontaneous chemical reaction that absorbs free energy from its surroundings, resulting in $\Delta G > 0$ and products that contain more free energy than the reactants.

Free-energy diagram

A graphical representation plotting free energy ($G$) against reaction progress, illustrating the downward curve of exergonic reactions ($\Delta G < 0$) and the upward curve of endergonic reactions ($\Delta G > 0$).

Chemical equilibrium

A state of balance in a reversible chemical reaction where the forward and reverse reaction rates are equal, resulting in no net change in reactant and product concentrations and no capacity to perform work.

Chemical work

One of the three major types of cellular work, which involves pushing endergonic reactions that would not occur spontaneously, such as the synthesis of polymers from monomers.

Transport work

A type of cellular work that moves substances across biological membranes against concentration or electrochemical gradients (e.g., ion pumping by the sodium-potassium pump).

Mechanical work

A type of cellular work that produces movement, such as the action of motor proteins along cytoskeleton filaments.

Energy coupling

The cellular strategy of using an exergonic process to drive an endergonic process, primarily mediated through the intermediate ATP.

ATP (Adenosine triphosphate)

A primary energy-transfer molecule in cells composed of the nitrogenous base adenine, the five-carbon sugar ribose, and three phosphate groups.

Adenosine

The structural nucleoside unit of ATP formed specifically by adenine bonded to ribose.

ATP hydrolysis

The exergonic reaction in which ATP reacts with water to yield adenosine diphosphate (ADP), inorganic phosphate ($P_i$), and free energy: $ATP + H_2O \rightarrow ADP + P_i + \text{energy}$.

Phosphorylation

The transfer of a phosphate group from a molecule like ATP to another recipient molecule, increasing the recipient's chemical reactivity or altering its structural conformation and function.

ATP cycle

The revolving cellular cycle in which ATP hydrolysis ($ATP + H_2O \rightarrow ADP + P_i$) powers cellular work and ATP is continuously regenerated from ADP and inorganic phosphate using energy supplied by catabolism ($ADP + P_i + \text{energy} \rightarrow ATP$).