Chapter 6 Vocab: Pathways that Harvest and Store Chemical Energy
Absorption Spectrum- a graph of light absorption vs. wavelength of light; shows how much light is
absorbed at each wavelength
Action Spectrum- graph of a biological process vs. light wavelength; shows which wavelengths are
involved in the process
Aerobic- requires 02
Anaerobic- doesn’t require 02
Autotrophs- organism that is capable of living exclusively on inorganic materials, water, and some energy
source (sunlight- photoautotrophs, chemically reduced matter- chemoautotrophs)
Calvin cycle- stage of photosynthesis when CO2 rx with RuBP to form 3PG, then 3PG is reduced to a sugar,
and RuBP is regenerated, while other products are released to the rest of the plant
Carbon-fixation reaction- phase of photosynthesis in which chemical energy captured in light rx is used to
drive the reduction of CO2 to form carbohydrates
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
Chemiosmosis- formation of ATP in mitochondria and chloroplasts, resulting from a pumping of protons
across a membrane (against a gradient of electrical charge and of pH), followed by the return of
the protons through a protein channel with ATP synthase activity
Chlorophyll A- complex ring structure with magnesium ion in center and long hydrocarbon tail that
anchors the chlorophyll to the integral proteins in the thylakoid membrane of the chloroplast
Chlorophyll B- differs from A only with the replacement of a methyl group (--CH3) with an aldehyde
group (--CHO)
Citric acid cycle/Krebs cycle- in cellular respiration, a set of chemical rx whereby acetyl CoA is oxidized to
CO2 and hydrogen atoms are stored as NADH and FADH2
Coenzyme A (CoA)- used in various biochemical rx as a carrier of acyl groups
Cyclic electron transport- in photosynthetic light rx, the flow of e- that produces ATP but no NADPH or O2
(anaerobic cycle)
Electromagnetic radiation- a self-propagating wave that travels through space and has both electrical and
magnetic properties
Electron transport- passage of e- through a series of proteins with a release of energy which may be
captured in a concentration gradient or in chemical form such as NADH or ATP
Fermentation-anaerobic degradation of a substance such as glucose to smaller molecules such as lactic
acid or alcohol with the extraction of energy
Gluconeogenesis- biochemical synthesis of glucose from other substances, such as aa, lactate, and glycerol
Glyceraldehyde 3-Phosphate (G3P)- phosphorylated three carbon sugar; intermediate in glycolysis and
photosynthetic carbon fixation
Glycolysis- enzymatic breakdown of glucose to pyruvic acid
Heterotrophs- an organism that requires preformed organic molecules as food (depends on autotrophs)
Light reactions- initial phase of photosynthesis, in which light energy is converted to chemical energy
Light-harvesting complexes- in photosynthesis, a group of different molecules that cooperate to absorb
light energy and transfer it to a rx center
Oxidation- relative loss of electrons in a chemical rx; either outright removal to form an ion, or the
sharing of electrons with substances having a greater affinity for them, such as O2; include
liberation of energy
Oxidative phosphorylation- ATP formation in the mitochondria associated with the flow of e- through the
respiratory chain
Photons- quantum of visible radiation; a “packet” of light energy
Photosynthesis- metablolic process carried out by green plants, by which visible light is trapped and the
energy used to convert CO2 into organic compounds
Photosystem- a light-harvesting complex in the chloroplast thylakoid composed of pigments and proteins
Photosystem I- complex that absorbs light at 700nm, passing electrons to ferrodoxin and then to NADPH
Photosystem II- absorbs light at 680nm, passing e- to the electron transport chain in the chloroplast
Pigments- substances that absorb visible light
Pyruvate oxidation- conversion of pyruvate to acetyl CoA and CO2 that occurs in the mitochondrial
matrix in the presence of O2 (aerobic rx)
Reaction center- group of e- transfer proteins that receive energy from light-absorbing pigments and
convert it to chemical energy by redox reactions
Redox (reduction-oxidation) reaction- chemical reaction in which one reactant becomes oxidized and the
other becomes reduced
Reduction- gain of e- by a chemical reactant; any reduction is accompanied by oxidation
Ribulose bisphosphate carboxylase/oxygenase- see rubisco
Rubisco- the enzyme that combines CO2 or O2 with ribulose bisphosphate to catalyze the first step of
photosynthetic carbon fixation or photorespiration
Wavelength- distance between successive peaks of a wave train, such as electromagnetic radiation