Unit 3: Cellular Energetics

• ATP: (adenosine triphosphate) main energy source that cells use for most of their work
• reduction: Gain of electrons by a chemical reactant; any reduction is accompanied by an oxidation.
• oxidation: Relative loss of electrons in a chemical reaction; either outright removal to form an ion, or the sharing of electrons with substances having a greater affinity for them, such as oxygen. Most oxidations, including biological ones, are associated with the liberation of energy.
• oxidized: loses electrons
• NAD: nicotinamide adenine dinucleotide - a coenzyme that is an electron carrier; NAD+ is oxidized, NADH is reduced
• reducing agent: compound that loses electrons in a reaction.
• oxidizing agent: compound that gains electrons in a reaction
• cellular respiration: The catabolic pathways by which electrons are removed from various molecules and passed through intermediate electron carriers to O2, generating H2O and releasing energy.
• aerobic: Requiring molecular oxygen, O2
• pyruvate oxidation: pyruvate molecules are oxidized and produces acetyl-CoA, CO2, and NADH
• citric acid cycle: In cellular respiration, a set of chemical reactions whereby acetyl CoA is oxidized to carbon dioxide and hydrogen atoms are stored as NADH and FADH2. Also called the Krebs cycle.
• energy-harvesting reactions: exergonic stage of glycolysis in which G3P is converted into two molecules of pyruvate
• pyruvate: Three-carbon compound that forms as an end product of glycolysis.
• NADH: reduced electron carrier molecule formed in glycolysis
• Krebs cycle: another name for the citric acid cycle. The main source of energy for cells and an important part of aerobic respiration.
• acetyl CoA: molecule formed from the oxidation of pyruvate
• FADH2: a reduced coenzyme similar to NADH, an electron carrier
• anaerobic: Occurring without the use of molecular oxygen, O2.
• lactic acid fermentations: Anaerobic series of reactions that convert glucose to lactic acid, in some bacteria and animal cells.
• alcoholic fermentation: Anaerobic series of reactions that convert glucose to ethyl alcohol (ethanol) and carbon dioxide in some plants and yeast cells.
• photosynthesis: photosynthesis: Metabolic processes carried out by green plants and cyanobacteria, by which visible light is trapped and the energy used to convert CO2 into organic compounds.
• light reactions: The initial phase of photosynthesis, in which light energy is converted into chemical energy.
• pigment: A substance that absorbs visible light.
• chlorophyll: Any of several green pigments associated with chloroplasts or with certain bacterial membranes; responsible for trapping light energy for photosynthesis.
• absorption spectrum: A graph of light absorption versus wavelength of light; shows how much light is absorbed at each wavelength.
• action spectrum: A graph of a biological process versus light wavelength; shows which wavelengths are involved in the process.
• light-harvesting complex: in photosynthesis, a group of different molecules that cooperate to absorb light energy and transfer it to a reaction center. Also called antenna system.
• photosystem: A light-harvesting complex in the chloroplast thylakoid composed of pigments and proteins.
• cyclic electron transport: in photosynthetic light reactions, the flow of electrons that produces ATP but no NADPH or O2.
• noncyclic electron transport: In photosynthesis, the flow of electrons that forms ATP, NADPH, and O2.
• Calvin cycle: a series of enzyme-assisted chemical reactions that produces a three-carbon sugar
• autotroph: An organism that is capable of living exclusively on inorganic materials, water, and an energy source other than the chemical bonds of organic compounds.
• heterotroph: An organism that requires preformed organic molecules as sources of energy and chemical building blocks.
• metabolism: The sum of the building & breaking reactions occurring in cells
• catabolic pathways: Series of reactions that release energy by breaking down complex molecules into simpler compounds.
• anabolic pathways: Series of reactions that consume energy to build complicated molecules from simpler ones.
• bioenergenetics: The study of how organisms manage their energy resources.
• kinetic energy :Energy associated with relative motion of objects.
• thermal energy: Kinetic energy associated with the random movement of molecules or atoms.
• potential energy: Stored energy.