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Module 12 in the Syllabus

Photosynthesis Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Photosynthesis
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Though it may be useful, detailed knowledge of photosynthesis is not required for the MCAT
Basic Terms

PhotosynthesisPhotosynthesis is the conversion of light energy into chemical energy by living organisms.
ChlorophyllChlorophyll is a green pigment found in most plants, algae, and cyanobacteria which absorbs light to begin the energy transduction processes of photosynthesis.
ChloroplastChloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis.
Light-dependent reactionIn photosynthesis the light dependent reaction produces oxygen gas and converts ADP and NADP+ into the energy carriers ATP and NADPH.
PhotoautotrophPhotoautotrophs are organisms that carry out photosynthesis.
PhotosystemPhotosystems, or reaction centers, are protein complexes involved in photosynthesis which use light to reduce molecules.
ThylakoidA thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria which are the site of the light-dependent reactions of photosynthesis.
Light-harvesting complexA light-harvesting complex is one or more polypeptide chains containing photosynthetic pigments, which surrounds a photosynthetic reaction centre and focuses light inward toward its core.
Antenna complexThe antenna complex is an array of chlorophyll molecules embedded in the thylakoid membrane which transfer light energy to one chlorophyll A molecule at the reaction center of a photosystem.
PhotophosphorylationThe production of ATP using the energy of sunlight is called photophosphorylation.
Accessory pigmentAccessory pigments are light-absorbing compounds, found in photosynthetic organisms, that work in conjuction with chlorophyll A.
P700P700 is the reaction-center chlorophyll A molecule in association with photosystem I.
P680P680 is the reaction-center associated with photosystem II and consists of 2 chlorophyll A molecules that are not bound to proteins unlike the other chlorophyll molecules in photosystem II.
Photosynthetic reaction centerA photosynthetic reaction center is a protein that is the site of the light reactions of photosynthesis.
CarotenoidIn photosynthetic organisms, the accessory pigments carotenoids play a vital role in the photosynthetic reaction center, either participating in the energy-transfer process or protecting the reaction center from auto-oxidation.
Carbon fixationCarbon fixation is a process found in autotrophs, usually driven by photosynthesis, whereby carbon dioxide is changed into organic materials.
C3 carbon fixationC3 carbon fixation is a metabolic pathway that uses the Calvin Cycle for the initial steps of carbon fixation in photosynthesis converting carbon dioxide and ribulose bisphosphate into 3-phosphoglycerate.
C4 carbon fixationWith C4 carbon fixation, a plant prefaces the Calvin Cycle with reactions that incorporate carbon dioxide into 4-carbon organic acid which has the ability to regenerate carbon dioxide in the chloroplasts of bundle sheath cells.
Fluorescence resonance energy transferFluorescence resonance energy transfer describes an energy transfer mechanism between two chromophores.
Cytochrome b6f complexThe cytochrome b6f complex of chloroplasts and cyanobacteria transfers electrons between the two reaction center complexes of oxygenic photosynthetic membranes, photosystem I and photosystem II, and also participates in formation of the transmembrane electrochemical proton gradient.
Nicotinamide adenine dinucleotide phosphateNicotinamide adenine dinucleotide phosphate is reduced in chloroplasts by means of the light reactions of photosynthesis.
Oxygen evolving complexThe oxygen evolving complex is a water oxidizing enzyme involved in the photooxidation of water during the light reactions of photosynthesis.

Intermediate Terms

Ribulose-1,5-bisphosphateRibulose-1,5-bisphosphate is an important 5-carbon intermediate serving as the substrate for carbon fixation in the Calvin cycle of photosynthesis.
Crassulacean acid metabolismCrassulacean acid metabolism, also known as CAM photosynthesis, is an elaborate carbon fixation pathway in some photosynthetic plants.
RuBisCORibulose-1,5-bisphosphate carboxylase/oxygenase, most commonly known by the shorter name RuBisCO, is an enzyme that is used in the Calvin cycle to catalyze the first major step of carbon fixation.
Bundle-sheathBundle-sheath cells are photosynthetic cells arranged into tightly packed sheaths around the veins of a leaf in certain C4 plants.
ChromophoreA chromophore is a region in a molecule where the energy difference between two different molecular orbitals falls within the range of the visible spectrum.
PhotorespirationPhotorespiration is the wasteful, alternate pathway for production of glyceraldehyde 3-phosphate by rubisco in which oxygenation of rubisco occurs producing a glycolate and a glycerate.
ChlorinA chlorin is the name for the large heterocyclic aromatic ring structure within chlorophyll having a core of 3 pyrroles and one reduced pyrrole. In chlorophyll, this structure contains coordinated magnesium.
PlastoquinonePlastoquinone is a quinone molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis.
PhotoinhibitionPhotoinhibition is a reduction in a plant's capacity for photosynthesis caused by exposure to strong light above the saturation point.
BacteriochlorophyllBacteriochlorophylls are photosynthetic pigments related to chlorophylls that occur in various phototrophic bacteria.

Advanced Terminology

Green sulfur bacteriaThe green sulfur bacteria are a family of obligately anaerobic photoautotrophic bacteria. They use sulfide ions, hydrogen or ferrous iron as an electron donor.
FerredoxinFerredoxins are iron-sulfur proteins that mediate electron transfer in a range of metabolic reactions.
Reverse Krebs cycleThe reverse Krebs cycle is a sequence of chemical reactions that are used by some bacteria to produce carbon compounds from carbon dioxide and water.
Fenna-Matthews-Olson complexThe Fenna-Matthews-Olson complex appears in green sulfur bacteria and mediates the excitation energy transfer from the light-harvesting chlorosomes to the membrane embedded bacterial reaction center.
EtioplastEtioplasts are chloroplasts that have not been exposed to light.
PhytolPhytol is a natural linear diterpene alcohol which is a decomposition product of chlorophyll.
PhaeophytinPhaeophytin is a grey pigment that appears in chromatographs of photosynthetic pigments which has the same structure as chlorophyll; excluding the central magnesium ion, which is replaced by two protons.
Rieske proteinRieske protein is the iron-sulfur protein (ISP) component of cytochrome bc1 complex.
PhycobilinPhycobilins, not found in green algae or higher plants, are unique among the photosynthetic pigments in that they are bonded to certain water-soluble proteins, known as phycobiliproteins.
PhycobiliproteinPhycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae that capture light energy which is then passed on to chlorophylls during photosynthesis.
Reductive acetyl CoA PathwayThe reductive acetyl CoA Pathway is a method of fixing organic carbon from carbon dioxide used by some bacteria and archaea.
Red edgeRed edge refers to the region of rapid change in reflectance of chlorophyll in the near infrared range.

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