Lecture 13: Energy Capture and Release

Comprehensive vocabulary flashcards covering the thermodynamic principles, trophic classifications, pathways of phosphorylation, and metabolic mechanisms from Lecture 13: Energy Capture and Release by Dr Kelsey White.

Solar constant

The solar energy flux density received at the distance of Earth from the Sun ($1.5 \times 10^8\,\text{km}$), measured at approximately $1{,}360\,\text{W/m}^2$.

Metabolism

The biological process primarily defined as the capture, transformation, and distribution of solar energy.

Primary producers

Organisms, including plants and certain microorganisms, that trap the sun's energy to generate $ATP$ and drive biosynthesis.

Adenosine triphosphate (ATP)

A high-energy molecule chemically related to a $DNA$ nucleotide that has been repurposed for short-term energy storage and driving cellular tasks.

Phototroph

An organism that uses sunlight as its primary energy source.

Chemotroph

An organism that obtains energy by breaking down chemical bonds within compounds.

Oxidation

The removal or loss of electrons from a substrate when an organism breaks down its chemical bonds.

Electron donor

A substrate molecule that donates electrons during metabolic oxidation reactions; categorized as either organic (organo-) or inorganic (litho-).

Electron acceptor

A chemical entity that collects donated electrons during metabolic reactions, thereby becoming reduced.

Redox reactions

Coupled oxidation-reduction reactions involving electron flows that form the basis of cellular energy generation and $ATP$ synthesis.

Nicotinamide adenine dinucleotide (NAD)

The typical modified-nucleotide electron carrier (acceptor and donor) functioning in biochemical redox reactions.

Autotroph

An organism that uses carbon dioxide ($CO_2$) as its inorganic carbon source for biosynthesis.

Heterotroph

An organism that utilizes preformed organic molecules as its carbon source for biosynthesis.

Lithotroph

An organism that utilizes inorganic molecules as its electron donor source for redox reactions.

Organotroph

An organism that utilizes organic molecules as its electron donor source for redox reactions.

Photoorganoheterotroph

An organism that uses sunlight for energy, organic compounds as electron donors, and organic molecules as a carbon source (e.g., some bacteria such as Rhodobacter).

Photolithoautotroph

An organism that uses sunlight for energy, inorganic electron donors, and carbon dioxide ($CO_2$) for biosynthesis via photosynthesis (e.g., cyanobacteria/blue-green algae, eukaryotic algae, and land plants).

Chemoorganoheterotroph

An organism that derives energy from breaking chemical bonds, utilizes organic electron donors, and consumes organic carbon (e.g., heterotrophic protists, fungi, and animals).

Chemoorganoautotroph

An organism that obtains energy from breaking chemical compounds, uses organic electron donors, and fixes carbon dioxide ($CO_2$) via chemosynthesis (e.g., anaerobic methanotrophic archaea).

Chemolithoheterotroph

An organism that derives energy from chemical compounds, uses inorganic electron donors, and assimilates organic carbon (e.g., Oceanithermus profundus).

Chemolithoautotroph

An organism that acquires energy from chemical compounds, utilizes inorganic electron donors, and fixes carbon dioxide ($CO_2$) via chemosynthesis (e.g., Nitrobacter and Methanobacteria).

Substrate-level phosphorylation

An evolutionarily old, simple, and direct enzymatic mechanism of transferring a phosphate group to $ADP$ to form $ATP$, resulting in a low yield per mole of substrate.

Oxidative phosphorylation

A complex, highly evolved mechanism of $ATP$ generation with high yield per mole that requires an electron transport chain, a proton motive force, $ATP$ synthetase, and an external final electron acceptor.

Catabolism

The degradative phase of metabolism that breaks down energy-containing nutrients into simple end products ($CO_2$, $H_2O$, $NH_3$), releasing chemical energy captured as $ATP$, $NAD(P)H$, or $\text{FADH}_2$.

Anabolism

The biosynthetic phase of metabolism that utilizes chemical energy to assemble small precursor molecules into complex cellular macromolecules.

Entner-Doudoroff pathway

A prokaryote-specific catabolic pathway utilized for carbohydrate breakdown and $ATP$ generation.

Methanogenesis

A specialized prokaryotic pathway of $ATP$ generation that produces methane as a metabolic byproduct.