Cell Respiration
Process by which cells harvest the energy stored in food molecules; usually accompanied by the uptake to O2 and the release of CO2.
Oxidative Phosphorylation
Process in bacteria and mitochondria in which ATP formation is driven by the transfer of electrons from food molecules to molecular oxygen.
Electron-Transport Chain (respiratory chain)
A series of membrane-embedded electron carrier molecules that facilitate the movement of electrons from a higher to a lower energy level, as in oxidative phosphorylation and photosynthesis.
ATP Synthase
Membrane-associated enzyme complex that catalyzes the formation of ATP from ADP and inorganic phosphate during oxidative phosphorylation and photosynthesis.
Chemiosmotic Hypothesis
The mechanism for generating energy that was first propose din 1961. It linked the chemical bond-forming reactions that synthesize ATP with the membrane transport processes that pump protons.
Chemiosmotic Coupling
Mechanism that uses the energy stored in a transmembrane proton gradient to drive the energy-requiring process, such as the synthesis of ATP or the transport of a molecule across a membrane.
Mitochondria
Membrane-enclosed organelle, about the size of a bacterium, that carries out oxidative phosphorylation and produces most of the ATP in eukaryotic cells.
Matrix
Large internal compartment within a mitochondrion.
Outer Membrane
Contains many molecules of a transport protein called porin, which, forms wide aqueous channels through the lipid bilayer. It is permeable to molecules (less than 5000 daltons) and small proteins.
Inner Membrane
Impermeable to the passage of ions and most small molecules, except where a path is provided by specific membrane transport proteins. It is the site of oxidative phosphorylation and contains the proteins of the ETC, proton pumps, and ATP synthase required
Cristae
A series of infoldings that make up the inner mitochondrial membrane. These worlds greatly increase the surface area of the membrane.
Chlorophyll
Light-absorbing green pigment that plays a central part in photosynthesis.
Respiratory Enzyme Complex
Set of proteins in the inner mitochondrial membrane that facilitates that transfer of high-energy electrons from NADH to water while pumping protons into the inter membrane space.
NADH Dehydrogenase Complex
The first respiratory complex in the ETC that accepts electrons from NADH in the form of a hydride ion which is then converted into a proton and two high-energy electrons.
Cytochrome c Reductase
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Cytochrome c Oxidase
Protein complex that serves as the final electron carrier in the respiratory chain; removes electrons from cytochrome c and passes them to O2 to produce H2O.
Electrochemical Gradient
Driving force that determines which way an ion will move across a membrane; consists of a combined influence of the ion's concentration gradient and the membrane potential.
Redox Reaction
A reaction in which electrons are transferred from one chemical species to another. An oxidation-reduction reaction.
Redox Pair
Two molecules that can be interconverted by the gain or loss of an electron; for example, NADH and NAD+.
Redox Potential
A measure of the tendency of a given redox pair to donate or accept electrons.
Quinone
Small, lipid-soluble, mobile electron carrier molecules found in the respiratory and photosynthetic electron-transport chains.
Iron-Sulfur Center
Metal complex found in electron carriers that operate early in the electron-transport chain; has a relatively weak affinity for electrons.
Cytochrome
Membrane-bound, colored, heme-containing protein that transfers electrons during cellular respiration and photosynthesis.
Cytochrome c
A small protein that accepts electrons from the cytochrome c reductase complex and transfers them to the cytochrome c oxidase complex, has a redox potential of +230 mV.
Photosynthesis
The process by which plants, algae and some bacteria use the energy of sunlight to drive the synthesis of organic molecules from carbon dioxide and water.
Chloroplast
Specialized organelle in algae and plats that contains chlorophyll and serves as the site in which photosynthesis takes place.
Carbon Fixation
Process by which green plants and other photosynthetic organisms incorporate carbon atoms from atmospheric carbon dioxide into sugars. The second stage of photosynthesis.
Stroma
In a chloroplast, the large interior space that contains the enzymes needed to incorporate CO2 into sugars during the carbon-fixation stage of photosynthesis; equivalent to the matrix of mitochondria.
Thylakoid
In a chloroplast, the flattened dislike sac whose membranes contain the proteins and pigments that convert light energy into chemical energy during photosynthesis. They are arranged in stacks called grana.
Thylakoid Space
The space inside each thylakoid that is connected with that of other thylakoids.
Light Reactions
In photosynthesis, the set of reactions that converts the energy of sunlight into chemical energy in the form of ATP and NADPH.
Dark Reactions
In photosynthesis, the set of reactions that produce sugars from CO2; these reactions, also called carbon fixation, can occur in the absence of sunlight.
Glyceraldehyde 3-Phosphate
A three carbon sugar that is exported to the cytosol where it is then used to produce sucrose and a large number of other organic molecules in the leaves of a plant.
Photosystem
Large multi protein complex containing chlorophyll that captures light energy and converts it into chemical energy; consists of a set of antenna complexes and a reaction center.
Antenna Complex
In chloroplasts and photosynthetic bacteria, the part of the membrane-bound photosystem that captures energy from sunlight; contains an array of proteins that bind hundreds of chlorophyll molecules and other photosensitive pigments.
Special Pair
A chlorophyll dimer which holds its electrons at a lower energy than do the other chlorophyll molecules.
Reaction Center
In photosynthetic membranes, a protein complex that contains a specialized pair or chlorophyll molecules that performs photochemical reactions to convert the energy of photons (light) into high-energy electrons for transport down the photosynthetic ETC.
Plastoquinone
A mobile electron carrier that is part of the photosynthetic ETC that transfers the high-energy electrons to the proton pump, which uses the movement of electrons to generate an electrochemical proton gradient.
Nitrogen Fixation
Conversion of nitrogen gas from the atmosphere into nitrogen-containing molecules by soil bacteria and cyanobacteria.
NADH
Activated carrier widely used in the energy-producing breakdown of sugar molecules.
NAD+
Activated carrier that accepts a hydride ion from a donor molecule, thereby producing NADH. Widely used in the energy-producing breakdown of sugar molecule.