Biology Chapters 9 and 10 Glossary

Tejank

Chapter 9	Chapter 9
acetyl CoA	Acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme.
aerobic	Containing oxygen; referring to an organism, environment, or cellular process that requires oxygen.
alcohol fermentation	The conversion of pyruvate to carbon dioxide and ethyl alcohol.
anaerobic	Lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen and may be poisoned by it.
ATP synthase	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 matrix of a mitrochondrion.
beta oxidation	A metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA.
cellular respiration	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.
chemiosmosis	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.
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 cellular respiration.
cytochrome	An iron-containing protein, a component of electron transport chains in mitochondria and chloroplasts.
electron transport chain	A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.
facultative anaerobe	An organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions.
fermentation	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.
glycolysis	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.
lactic acid fermentation	The conversion of pyruvate to lactate with no release of carbon dioxide.
NAD+	Nicotinamide adenine dinucleotide, a coenzyme present in all cells that helps enzymes transfer electrons during the redox reactions of metabolism.
oxidation	The loss of electrons from a substance involved in a redox reaction.
oxidative phosphorylation	The production of ATP using energy derived from the redox reactions of an electron transport chain.
oxidizing agent	The electron acceptor in a redox reaction.
proton-motive force	The potential energy stored in the form of an electrochemical gradient, generated by the pumping of hydrogen ions across biological membranes during chemiosmosis.
redox reaction	A chemical reaction involving the transfer of one or more electrons from one reactant to another; also called oxidation-reduction reaction.
reducing agent	The electron donor in a redox reaction.
reduction	The addition of electrons to a substance involved in a redox reaction.
substrate-level phosphorylation	The formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism.
Chapter 10	Chapter 10
absorption spectrum	The range of a pigment’s ability to absorb various wavelengths of light.
action spectrum	A graph that depicts the relative effectiveness of different wavelengths of radiation in driving a particular process.
autotroph	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.
bundle-sheath cell	A type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf.
C3 plant	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.
C4 plant	A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle.
Calvin cycle	The second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate.
CAM plant	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.
carbon fixation	The incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic prokaryote).
carotenoid	An accessory pigment, either yellow or orange, in the chloroplasts of plants. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis.
chlorophyll	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.
chlorophyll a	A type of blue-green photosynthetic pigment that participates directly in the light reactions.
chlorophyll b	A type of yellow-green accessory photosynthetic pigment that transfers energy to chlorophyll a.
crassulacean acid metabolism (CAM)	A type of metabolism in which carbon dioxide is taken in at night and incorporated into a variety of organic acids.
cyclic electron flow	A route of electron flow during the light reactions of photosynthesis that involves only photosystem I and that produces ATP but not NADPH or oxygen.
electromagnetic spectrum	The entire spectrum of radiation ranging in wavelength from less than a nanometer to more than a kilometer.
glyceraldehyde-3-phosphate (G3P)	The carbohydrate produced directly from the Calvin cycle.
heterotroph	An organism that obtains organic food molecules by eating other organisms or their by-products.
light reactions	The steps in photosynthesis that occur on the thylakoid membranes of the chloroplast and that convert solar energy to the chemical energy of ATP and NADPH, evolving oxygen in the process.
light-harvesting complex	Complex of proteins associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem.
mesophyll	The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.
mesophyll cell	A loosely arranged photosynthetic cell located between the bundle sheath and the leaf surface.
NADP+	Nicotinamide adenine dinucleotide phosphate, an acceptor that temporarily stores energized electrons produced during the light reactions.
noncyclic electron flow	A route of electron flow during the light reactions of photosynthesis that involves both photosystems and produces ATP, NADPH, and oxygen. The net electron flow is from water to NADP+.
PEP carboxylase	An enzyme that adds carbon dioxide to phosphoenolpyruvate (PEP) to form oxaloacetate.
photon	A quantum, or discrete amount, of light energy.
photophosphorylation	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.
photorespiration	A metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide.
photosynthesis	The conversion of light energy to chemical energy that is stored in glucose or other organic compounds; occurs in plants, algae, and certain prokaryotes.
photosystem	Light-capturing unit located in the thylakoid membrane of the chloroplast, consisting of a reaction center surrounded by numerous light-harvesting complexes. There are two types of photosystems, I and II; they absorb light best at different wavelengths.
photosystem I	One of two light-capturing units in a chloroplast’s thylakoid membrane; it has two molecules of P700 chlorophyll a at its reaction center.
photosystem II	One of two light-capturing units in a chloroplast’s thylakoid membrane; it has two molecules of P680 chlorophyll a at its reaction center.
primary electron acceptor	A specialized molecule sharing the reaction center with the pair of reaction-center chlorophyll a molecules; it accepts an electron from one of these two chlorophylls.
reaction center	Complex of proteins associated with two special chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. Excited by light energy, one of the chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain.
rubisco	Ribulose carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP, or ribulose bisphosphate).
spectrophotometer	An instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution.
stoma	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.
stroma	The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
thylakoid	A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
visible light	That portion of the electromagnetic spectrum detected as various colors by the human eye, ranging in wavelength from about 380 nm to about 750 nm.
wavelength	The distance between crests of waves, such as those of the electromagnetic spectrum.