AP Biology Unit 3: Cellular Energetics Flashcards

Vocabulary practice flashcards covering AP Biology Unit 3: Cellular Energetics, including enzyme structure and regulation, thermodynamics, cellular energy, and the biochemical stages of photosynthesis.

Metabolism

The sum of all chemical reactions occurring in an organism or cell.

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 the synthesis of proteins from amino acids.

Bioenergetics

The study of how organisms manage and transform their energy resources.

Catalyst

A chemical agent that speeds up a chemical reaction without being consumed by the reaction.

Enzyme

A catalytic protein that accelerates biological reactions by lowering the activation energy barrier.

Substrate

The specific reactant molecule upon which an enzyme acts.

Active Site

The specific region of an enzyme molecule where the substrate binds and where the chemical reaction is catalyzed.

Induced Fit

The conformational adjustment of an enzyme's active site upon substrate binding that positions chemical groups to enhance catalytic ability.

Activation Energy ($E_A$)

The initial amount of energy needed to start a chemical reaction, often supplied as thermal energy.

Exergonic Reaction

A spontaneous chemical reaction that involves a net release of free energy ($\Delta G < 0$).

Endergonic Reaction

A non-spontaneous chemical reaction that requires a net input of free energy ($\Delta G > 0$).

Denaturation

The disruption of a protein's secondary and tertiary structure caused by environmental extremes such as changes in temperature or pH, rendering it biologically inactive.

Competitive Inhibitor

A substance that reduces enzyme activity by binding reversibly to the enzyme's active site, competing directly with the substrate.

Noncompetitive Inhibitor

A substance that impedes enzyme activity by binding to an allosteric site, altering the enzyme's conformation and reducing active site efficiency.

Allosteric Regulation

The process by which a regulatory molecule binds to a protein at one site and modifies the protein's shape and function at a distinct active site.

Feedback Inhibition

A negative feedback mechanism in which the end product of a metabolic pathway inhibits an enzyme operating earlier in the pathway to avoid resource depletion.

First Law of Thermodynamics

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

Second Law of Thermodynamics

The principle stating that every energy transfer or transformation increases the entropy of the universe, typically releasing unusable energy as heat.

Energy Coupling

The cellular strategy of using an exergonic process (such as ATP hydrolysis) to drive an endergonic process.

Adenosine Triphosphate (ATP)

The primary cellular energy shuttle, composed of the nitrogenous base adenine, the five-carbon sugar ribose, and three phosphate groups.

Autotroph

An organism that sustains itself without consuming organic material from other organisms by producing organic molecules from $CO_2$ and other inorganic compounds.

Heterotroph

An organism that obtains organic materials by consuming other organisms or their organic by-products.

Stomata

Microscopic pores on leaf surfaces that regulate gas exchange, allowing $CO_2$ to enter and $O_2$ to exit.

Thylakoids

Flattened, interconnected sacs inside chloroplasts containing chlorophyll pigments, photosystems, and electron transport proteins.

Grana

Columns or stacks of thylakoids inside the chloroplast where the light-dependent reactions of photosynthesis take place.

Stroma

The fluid-filled space within the inner chloroplast membrane surrounding the thylakoids where the Calvin cycle occurs.

Photolysis

The light-driven splitting of water molecules ($H_2O$) in Photosystem II that supplies replacement electrons and releases protons ($H^+$) and molecular oxygen ($O_2$).

Absorption Spectrum

A graph plotting the amount of light absorbed by a purified pigment across various wavelengths of the light spectrum.

Action Spectrum

A graph depicting the relative biological effectiveness of different wavelengths of light in driving a process such as photosynthesis.

Photosystem

A light-harvesting complex in the thylakoid membrane consisting of pigment molecules surrounding a reaction-center complex with a primary electron acceptor.

Chemiosmosis

An energy-coupling mechanism where a proton ($H^+$) gradient across a membrane drives cellular work, such as the synthesis of ATP by ATP synthase.

Photophosphorylation

The light-driven generation of ATP from ADP and inorganic phosphate ($P_i$) utilizing chemiosmosis across the thylakoid membrane.

Calvin Cycle

The light-independent phase of photosynthesis occurring in the stroma that utilizes ATP and NADPH to fix $CO_2$ into carbohydrates.

Carbon Fixation

The incorporation of inorganic carbon from $CO_2$ into an organic compound, catalyzed by the enzyme rubisco in the Calvin cycle.

Glyceraldehyde 3-phosphate (G3P)

The three-carbon carbohydrate directly produced as the net output of the Calvin cycle.