Chapter 10 Flashcards
Photosynthesis
Heterotrophs
Unable to make their own food. Live on compounds produced by other organisms. Consumers. Eating others or the remains of others. Decomposers = heterotrophs.
Autotrophs
Producers. Self-feeders. Produce their organic molecules from CO2 and other inorganic raw materials. Plants and some bacteria.
Photoautotrophs
Autotrophs that specifically use light energy to drive the synthesis of organic molecules from CO2 and (in most cases) water. Plants, algae, non-algal unicellular protists, prokaryotes called cyanobacteria and other photosynthetic prokaryotes.
Chloroplast
Eukaryotic organelle that absorbs energy from sunlight and uses it. EUKARYOTIC ONLY, there are prokaryotes who can do photosynthesis, but they don’t use the chloroplast.
Chlorophyll
A fat-soluble pigment found naturally in plants. It is the substance that gives plants their green color and helps them create energy via photosynthesis.
Green pigment gives leaves color, resides in the thylakoid membranes of the chloroplast. Absorbs light energy.
Mesophyll
Tissues in the interior of a leaf, where chloroplasts are mainly found. Typically has about 30-40 chloroplast.
Stomata
Microscopic pores (mostly on the bottom of leaves) that O2 exits by.
Stroma
A dense fluid in the two membranes of the chloroplast. Space inside the chloroplast.
Thylakoids
Sacs suspended in the stroma. Inside thylakoids is thylakoid space. Stacked in columns called grana (singular, granum). Light reactions take place here.
Split Water
6CO2 + 6H2O + LE -> C6H12O6 + 6O2
Simplest form: CO2 + H2O -> [CH2O] + O2 (O2 comes from water, not CO2).
2 stages of photosynthesis
- Light reactions
- Calvin cycle
Calvin Cycle (Dark cycle)
Named for Melvin Calvin. Takes place in the Stroma.
1. Incorporates CO2 from the air. This initial incorporation of carbon into organic compounds is known as carbon fixation.
2. Reduces the fixed carbon to carbohydrate via the addition of electrons. (provided by NADPH and ATP from the light reactions).
3. Produces [CH2O] per cycle, usually written in sets of 3, producing G3P.
4. Requires 3 ATP and 2 NADPH per cycle. To make 1 glucose molecule, you need 6 cycles = 18 ATP and 12 NADPH.
Light reactions
Convert solar energy to chem. energy.
1. Water is split -> H+ and O2 ions.
2. Light absorbed by chlorophyll drives a transfer of electrons and H+ ions to an acceptor called NADP+. Creates NADPH.
3. Photophosphorylation via light reactions creates ATP.
Gets the NADP+ and ADP + Pi from the Calvin cycle.
Light + Water -> NADPH + ATP
Photophosphorylation
A process in which light reactions generate ATP using chemiosmosis to power the addition of a phosphate group to an ADP.
Adding a phosphate group to sumthin
Visible light
Wavelength (distance between crests of electromagnetic waves) of 380 nm to 740 nm. Can be detected as various colors by the human eye.
Photons
Not tangible objects, but they act like objects in that each of them has a fixed quantity of energy. Shorter wavelength = greater energy of each photon of that light.
A particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has zero rest mass.
Spectrophotometer
Pigments can be absorbed, reflected or transmitted.
Device that measures the ability of a pigment to absorb various wavelengths of light.
Absorption Spectrum
A graph plotting a pigment’s light absorption versus wavelength.
Chlorophyll molecules absorb every color but green, so green reflect, that why it look green.
Chlorophyll a, b and carotenoids
- Chlorophyll a: Key light-capturing pigment that participates directly in the light reactions (purple)
- Chlorophyll b: Accessory pigment (purplish blue)
- Carotenoids: A separate group of accessory pigments (blue and purple)
Carotenoids
Tetraterpene pigments, which exhibit yellow, orange, red and purple colors
Are the most widely distributed pigments in nature and are present in photosynthetic bacteria, some species of archaea and fungi, algae, plants, and animals
Hydrocarbons that are various shades of yellow and orange because they absorb violet/blue-green light. May broaden the spectrum of colors that can drive photosynthesis. Some seem to be photoprotection: compounds absorb and dissipate excessive light energy that would otherwise damage chlorophyll.
Action Spectrum
Profiles the relative effectiveness of different wavelengths of radiation in driving processes.
Excitation of Chlorophyll
Increases electron to an orbital of higher energy = pigment molecule is in an excited state. Electron cannot stay excited long.
The only photons absorbed are those whose energy is exactly equal to the energy difference between the ground state and an excited state
Fluorescence
An afterglow given off as electrons fall back to the ground state by photons that’re given off.
Reaction-Center Complex
An organized association of proteins holding a special pair chlorophyll a molecules and a primary electron acceptor.
Photosystems
Composed of a reaction-center complex surrounded by several light-harvesting complexes
Light-harvesting Complex
Consists of various pigment molecules bound to proteins. Number and variety of pigment molecules enable a photosystem to harvest light over a larger surface area and a larger portion of the spectrum.
Primary electron acceptor
A molecule capable of accepting electrons and becoming reduced. In a photosystem.
Photosystem II (PS II)
Discovered second, but functions first in light reactions. Has a characteristic reaction-center complex-a particular kind of primary electron acceptor next to a special pair of chlorophyll a molecules associated with specific proteins. The reaction-center chlorophyll a of PS II is known as P680 (absorbs 680nm WL). Nearly identical to P700.
Photosystem I (PS I)
Discovered first, but function second in light reactions. Has a characteristic reaction-center complex-a particular kind of primary electron acceptor next to a special pair of chlorophyll a molecules associated with specific proteins. The reaction-center complex of PS I is called P700 (absorbs 700nm WL). Nearly identical to P680.
Electron Flow - Linear
Occurs during the light reactions of photosynthesis. A flow of electrons through the photosystems and other molecular components built into the thylakoid membrane. Produces ATP and NADPH.
Electron Flow - Noncyclic
Electron flow linear.
1. Light
2. PS II -> Primary Electron Acceptor
3. Pq -> Cytochrome Complex (produces ATP into the stroma) -> Pc }(ETC)
4. PS I -> Primary Electron Acceptor
5. Fd -> NADP+ reductase -> NADPH
Electron Flow - Cyclic
An alternative path to electron flow. Uses PS I, but not PS II. No O2 (no water used) or NADPH made, but ATP is made.
Chloroplasts vs Mitochondria
Chloroplasts: Do not need molecules from food. Produce ATP into the stroma. Gets e- from water.
Mitochondria: Produce ATP into the mito. matrix. Gets e- from organic molecules.
Plastoquinone
PQ in the ETC during Light Reactions, next to the PS II and cytochrome complex.
Plastocyanin
PC in the ETC during Light Reactions, next to the cytochrome complex and PS I.
Ferrodoxin
Fd in the ETC during Light Reactions, next to the PS I and NAD+ reductase.
C4 Photosynthesis
Involves Mesophyll cell + Bundle-sheath cell + vascular tissue. CO2 fixed into oxaloacetate (an organic acid) when added to PEP (pyruvate + phosphate group (ATP)). Oxaloacetate turns into malate, and then drops off a CO2 into a normal Calvin cycle in the bundle-sheath cell. Leaves a pyruvate which goes back into the mesophyll cell, grabbing a phosphate group from ATP restarting the process.
Photorespiration
A repiratory process in many higher plants by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general patter of photosynthesis.
CAM plants
Crassulacean Acid Metabolism. During the night, stomata is open and take up CO2 and incorporste it into a variety into a organic acids (first part of C4 photosynthesis).
RuBisCo
Ribulose-1,5-Biphosphate Carboxylase/oxygenase.
RuBP
Ribulose-1,5-Biphosphate. 5 carbon compound, main acceptor of CO2 in plants.
