AP BIOLOGY - Cellular Respiration and Photosynthesis
Terms
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- Fermentation
- partial degradation of sugars that occurs without the help of oxygen
- cellular respiration
- the most prevalent and efficient catabolic pathway in which oxygen is consumed as a reactant along with the organic fuel (mitochondria)
- redox reactions
- a transfer of one or more electrons from one reactant to another - the long name for this is oxidation- reduction reactions
- oxidation
- in a redox reaction, the loss of electrons from one substance
- reduction
- the addition of electrons to another substance
- reducing agent
- the electron donor in a redox reaction
- oxidizing agent
- the electorn acceptor in a redox rxn
- NAD+ (nictotinamide adenine dinucleotide)
- A coenzyme present in all cells that helps enzymes transfer electrons during the redox rxns of metabolism
- electron transport chain
- used by respiration to break the fall of electrons to oxygen into several energy-releasing steps instead of one explosive reaction; Consists of a number of molecules built into the inner membrane or a mitochondrian
- Glycolysis
- the spliting of glucose into pyruvate. Gylcolysis is the one metabolic pathway that occurs in all living cells, serving as the starting point for fermentation or aerobic respiration
- The Krebs Cycle
- takes place within the mitochondrial matrix, completes the job (of glycolysis) by decomposing a derivetive of pyruvate to CO2
- oxidative phosphorylation
- Energy released at each step of the chain is stored in a form the mitochondrian can use to make ATP. This mode of ATP synthesis is called oxidative phosphorylation becasue it is powered by the redox reactions that transfer electrons from food to oxygen
- substrate-level phosphorylation
- a mechanism in which a smaller amount of ATP is formed directly in a few reactions of glycolysis and the Krebs cycle
- acetyl CoA
- upon entering the mitochondrian, pyruvate is first converted to a compound acytyl CoA
- cytochromes (cyt)
- An iron-containing protien, a component of electon transport chains in mitochondria and chloroplasts
- ATP synthase
- the enzyme that makes ATP
- chemiosmosis
- coupling mechanism for oxidative phosphorylation
- proton-motive force
- the potentail energy stored in the form of an electochemical gradient, generated by the pumping of H ions across biological membranes during chemiosmosis
- aerobic
- with air
- anaerobic
- without air
- alcohol fermentation
- The conversion of pyruvate to carbon dioxide and ethyl alcohol.
- lactic acid fermentation
- The conversion of pyruvate to lactate with no release of carbon dioxide.
- facultative anaerobes
- An organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions.
- beta oxidation
- A metabolic sequence that breaks fatty acids down to two-carbon fragments which enter the Krebs cycle as acetyl CoA.
- 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.
- heterotroph
- An organism that obtains organic food molecules by eating other organisms or their by-products
- 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
- mesophyll
- The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.
- stomata
- A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange.
- 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.
- 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.
- 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.
- NADP+
- An acceptor that temporarily stores energized electrons produced during the light reactions.
- 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.
- carbon fixation
- The incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic bacterium).
- wavelength
- The distance between crests of waves, such as those of the electromagnetic spectrum.
- electromagnetic spectrum
- The entire spectrum of radiation ranging in wavelength from less than a nanometer to more than a kilometer
- 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.
- photons
- A quantum, or discrete amount, of light energy.
- spectrophotometer
- An instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution.
- absorption spectrum.
- The range of a pigment's ability to absorb various wavelengths of light.
- action spectrum
- A profile of the relative performance of different wavelengths of light.
- carotenoids
- 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
- photosystems
- The light-harvesting unit in photosynthesis, located on the thylakoid membrane of the chloroplast and consisting of the antenna complex, the reaction-center chlorophyll a, and the primary electron acceptor. There are two types of photosystems, I and II; they absorb light best at different wavelengths.
- reaction center
- The chlorophyll a molecule and the primary electron acceptor in a photosystem; they trigger the light reactions of photosynthesis. The chlorophyll donates an electron, excited by light energy, to the primary electron acceptor, which passes an electron to an electron transport chain.
- primary electron acceptor
- A specialized molecule sharing the reaction center with the chlorophyll a molecule; it accepts an electron from the chlorophyll a molecule.
- photosystem I
- One of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P700 reaction-center chlorophyll.
- photosystem II
- One of two light-harvesting units of a chloroplast's thylakoid membrane; it uses the P680 reaction-center chlorophyll.
- 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+.
- 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
- cyclic photophosphorylation
- The generation of ATP by cyclic electron flow
- glyceraldehyde-3-phosphate (G3P)
- The carbohydrate produced directly from the Calvin cycle
- rubisco.
- Ribulose carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP, or ribulose bisphosphate).
- C3 plants
- 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.
- 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.
- C4 plants
- A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin cycle.
- Bundle-sheath cells
- A type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf.
- mesophyll cells
- A loosely arranged photosynthetic cell located between the bundle sheath and the leaf surface.
- PEP carboxylase
- PEP carboxylase An enzyme that adds carbon dioxide to phosphoenolpyruvate (PEP) to form oxaloacetate
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CAM and CAM Plants
(crassulacean acid metabolism) - 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.