Chapter 10: Photosynthesis Flashcards
Photosynthesis
- Conversion of light energy to chemical energy that is stored in sugars or other organic compounds
- Occurs in plants, algae, and certain prokaryotes
Autotroph
- Organism that obtains organic food molecules without eating other organisms or substances derived from other organisms
- Use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones
Heterotroph
Organism that obtains organic food molecules by eating other organisms or substances derived from them
Mesophyll
- Leaf cells specialized for photosynthesis
- In C3 and CAM plants, located between the upper and lower epidermis
- In C4 plants, they are located between the bundle-sheath cells and the epidermis
Stomata
- Microscopic pores surrounded by guard cells
- In the epidermis of leaves and stems that allow gas exchange between the environment and the interior of the plant
Stroma
- Dense fluid within the chloroplast surrounding the thylakoid membrane
- Contains ribosomes and DNA
- Involved in the synthesis of organic molecules from carbon dioxide and water
Thylakoid
- Flattened membrane sac inside the chloroplast
- Used to convert light energy into chemical energy
Chlorophyll
Green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes
Light Reactions
- First of two major stages in photosynthesis
- Comes before the Calvin Cycle
- Occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes
- Convert solar energy into the chemical energy of ATP and NADPH
- Releases oxygen
Calvin Cycle
- Second of two major stages in photosynthesis
- Involves the fixation of atmospheric carbon dioxide and the reduction of fixed carbon into carbohydrate
NADP+
- Nicotinamide adenine dinucleotide phosphate
- Electron acceptor
- As NADPH, temporarily stores energized electrons produced during the light reactions
Photophosphorylation
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
Initial incorporation of carbon from carbon dioxide into an organic compound by an autotrophic organism (i.e. plant, other photosynthetic organism, chemoautotrophic prokaryote)
Wavelength
DIstance between crests of waves, such as those of the electromagnetic spectrum
Electromagnetic Spectrum
- Entire spectrum of electromagnetic radiation
- Ranges in wavelength from less than a nanometer to more than a kilometer
Visible Light
- Portion of the electromagnetic spectrum that can be detected as various colors by the human eye
- Ranges in wavelength from about 380 nm to about 750 nm
Photon
Quantum/ discrete quantity of light energy that behaves as if it were a particle
Spectrophotometer
Instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution
Absorption Spectrum
- Range of a pigment’s ability to absorb various wavelengths of light
- Also a graph of such a range
Chlorophyll a
Photosynthetic pigment that participates directly in the light reactions
Chlorophyll b
Accessory photosynthetic pigment that transfers energy to chlorophyll a
Carotenoid
- Accessory pigment in the chloroplasts of plants
- Either yellow or orange
- Absorbs wavelengths of light that chlorophyll cannot
- Broaden the spectrum of colors that can drive photosynthesis
Photosystem
- A light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes
- Consists of a reaction-center complex surrounded by numerous light-harvesting complexes
- Two types: I and II
- Absorb light best at different wavelengths
Reaction-Center Complex
- Complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor
- Located centrally in a photosystem
- Triggers the light reactions of photosynthesis
- Excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain
Light-Harvesting Complex
- Complex of proteins associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids)
- Captures light energy and transfers it to reaction-center pigments in a photosystem
Primary Electron Acceptor
In the thylakoid membrane of a chloroplast or in the membrane of some prokaryotes, a specialized molecules that shares the reaction-center complex with a pair of chlorophyll a molecules and accepts an electron from them
Photosystem II (PS II)
- One of two light-capturing units in a chloroplast’s thylakoid membrane or in the membrane of some prokaryotes
- Occurs first
- Has two molecules of P680 chlorophyll a at its reaction center
Photosystem I (PS I)
- Light capturing unit in a chloroplast’s thylakoid membrane or in the membrane of some prokaryotes
- Happens second
- Has two molecules of P700 chlorophyll a at its reaction center
Linear Electron Flow
- Route of electron flow during the light reactions of photosynthesis –Involves both photosystems (I and II)
- Produces ATP, NADPH, and O2
- Net electron flow from H2O to NADP+
Cyclic Electron Flow
- Route of electron flow during the light reactions of photosynthesis
- Involves only photosystem I
- Produces ATP but not NADPH or oxygen
Glyceraldehyde 3-phosphate (G3P)
- Three-carbon carbohydrate
- Direct product of the Calvin Cycle
- An intermediate in glycolysis
Rubisco
- Ribulose carboxylase
- Enzyme that catalyzes the 1st step of the Calvin cycle (addition of CO2 to RuBP, or ribulose bisphosphate)
- Can bind to oxygen when excess oxygen is present or carbon dioxide levels are low
C3 Plant
- Plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material
- Form a three-carbon compound as the first stable intermediate
Photorespiration
- Metabolic pathway
- Consumes oxygen
- Releases carbon dioxide
- Doesn’t generate ATP
- Decreases photosynthetic output
- Generally on hot, dry, and bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide
C4 Plant
Plant in which the Calvin cycle comes after reactions that incorporate CO2 into a four-carbon compound, the end product supplying CO2 for Calvin cycle
Bundle-Sheath Cell
In C4 plants, a type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf
PEP Carboxylase
- Enzyme that adds CO2 to phosphoenolpyruvate (PEP) to form oxaloacetate in C4 plants
- Acts prior to photosynthesis
Crassulacean Acid Metabolism (CAM)
- Adaptation for photosynthesis in arid conditions
- First discovered in the family Crassulaceae
- Plant takes up CO2 and incorporates it into a variety of organic acids at night when stomata are open
- During the day, CO2 is released from organic acids for use in the Calvin cycle while stomata are closed
CAM Plant
-Plant that uses crassulacean acid metabolism (adaptation for photosynthesis in arid conditions)
