a series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule into simpler compounds (catabolic pathway).
a metabolic pathway that releases energy by breaking down complex molecules to simpler compounds.
the energy of motion, which is directly related to the speed of that motion. Moving matter does work by imparting motion to other matter.
(1) the study of energy transformations that occur in a collection of matter (2) a phenomenon in which external DNA is taken up by a cell and functions here.
first law of thermodynamics
the principle of conservation of energy. energy can be transferred and transformed, but it cannot be created or destroyed.
second law of thermodynamics
the principle whereby every energy transfer or transformation increases the entropy of the universe. Ordered forms of energy are at least partly converted to heat, and in spontaneous reactions, the free energy of the system also decreases.
the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system. The change in free energy of a system is calculated by the equation ΔG=ΔH-TΔS, where T is absolute temperature.
a non-spontaneous chemical reaction, in which free energy is absorbed from the surroundings.
in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.
adenosine triphosphate (ATP)
an adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
a chemical agent that changes the rate of a reaction without being consumed by the reaction.
a protein serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction.
the amount of energy that reactants must absorb before a chemical reaction will start.
a temporary complex formed when an enzyme binds to its substrate molecule(s).
the specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.
the change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate.
any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely with the substrate during catalysis.
an organic molecule serving as a cofactor. Most vitamins function as coenzymes in important metabolic reactions.
a substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.
a substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.
the binding of a molecule to a protein that affects the function of the protein at a different site.
an interaction of the constituent subunits of a protein whereby a conformational change in one subunit is transmitted to all the others.
a method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.
a catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.
the most prevalent and efficient catabolic pathway for the production of ATP, in which oxygen is consumed as a reactant along with the organic fuel.
a chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction.
nicotinamide adenine dinucleotide, a coenzyme present in all cells that helps enzymes transfer electrons during the redox reactions of metabolism.
electron transport chain
a sequence of electron carrier molecules (membrance proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.
the splitting of glucose into pyruvate. Glycolysis is the one metabolic pathway that occurs in all living cells, serving as the starting point for fermentation or aerobic respiration.
citric acid cycle
a chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the mitochondrion; the second major stage in cell respiration.
the production of ATP using energy derived from the redox reactions of an electron transport chain.
the formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism.
acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme.
an iron-containing protein, a component of electron transport chains in mitochondria and chloroplasts.
a cluster of several membrane proteins found in the mitochondrial crista (and bacterial plasma membrane) that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentration gradient to make ATP. ATP synthases provide a port through which hydrogen ions diffuse into the matric of a mitrochondrion.
an energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cells occurs by chemiosmosis.
the potential energy stored in the form of an electrochemical gradient, generated by the pumping of hydrogen ions across biological membranes during chemiosmosis.
containing oxygen; referring to an organism, environment, or cellular process that requires oxygen.
lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen and may be poisoned by it.
a metabolic sequence of that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA.
the conersion of light energy to chemical energy that is stored in gluose or other organic compounds; occurs in plants, algae, and certain prokaryotes.
an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones.
an organism that obtains organic food molecules by eating other organisms or their by-products.
a green pigment located within the chloroplasts of plants. Chlorophyll a can participate directly in the light reactions, which convert solar energy to chemical energy.
the ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.
a microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant.
the second of two major stages in photosynthetsis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate.
nicotinamide adenine dinucleotide phosphate, an acceptor that temporarily stores energized electrons produced during the light reactions.
the process of generating ATP from ADP and phosphate by means of a proton-motive force generated by the thylakoid membrane of the chloroplast during the light reactions of photosynthesis.
the incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic prokaryote).
a type of blue-green photosynthetic pigment that participates directly in the light reactions.
a graph that depicts the relative effectiveness of different wavelengths of radiation in driving a particular process.
a type of yellow-green accessory photosynthetic pigment that transfers energy to chlorophyll a.
A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate.
a plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. Carbon dioxide entering open stomata during the night is converted into organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed.