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Ch.10 AP Bio
Terms in this set (13)
identify the two broad stages of photosynthesis.
The two stages of photosynthesis are light reactions and the Calvin Cycle. Light reactions occur within the thylakoids and the Calvin Cycle takes place in the stroma. The light reactions create ATP and NADPH, which are used by the Calvin Cycle which also brings in carbon to produce sugar.
What is carbon fixation?
Carbon fixation is the initial incorporation of carbon into organic compounds *It occurs during Photosynthesis, while The Calvin Cycle also uses carbon fixation. Occurs in the chloroplast
What is a photon?
Particles making up light. They aren't tangible but act like objects in that each has a fixed quantity of energy.
Why are leaves green?
The reason why we see leaves as green is because when we look at a leaf, the chlorophyll (the pigment found in leaves/plants) absorbs violet, blue, and red lights. However, the chlorophyll reflects the color green. This causes us to see leaves as green in our eyes
What is the difference between an absorption spectra and action spectrum?
The absorption spectra are the range of a pigment's ability to absorb various wavelengths of light. The action spectrum is a graph that depicts the relative effectiveness of different wavelengths of radiation in driving a particular process.
What happens to chlorophyll when it is hit by light? How does this relate to potential energy
The colors responding to the absorbed wavelengths disapear but energy can't, when the light hits the chlorophyll. One of the electrons has more energy when a molecule absorbs a photon of lights.
Identify the following parts of a photosystem:
a. Photosystem - composed of a reaction center surrounded by a anumber of light-harvsting complexes.
b. Light harvesting complex - consists of pigment molecules bound to particular proteins.
- The number and variety of pigment molecules enable light to be harvested over a larger portion of the spectrum.
c. Reaction center - a protein complex that includes two special chlorophyll a molecules.
d. Primary electron acceptor- a specialized molecule sharing the reaction center with the pair of reaction-center chlorophyll
enables use of energy from light to boost an electron to a higher level
What are the steps in noncyclic electron flow in photosynthesis?
1. Photon of light strikes a pigment molecule until it reaches the chlorophyll and exicites one of the electrons to a higher energy state.
2. This electron is captured by the primary electron acceptor.
3. An enzyme comes along and spits a water molecule into two electrons, two hydrogen ions, and an oxygen atom. The electrons are supplied to the chlorophyll molecules, which replaces an electron lost to the primary electron acceptor. The oxygen atom combines with another oxygen atom, creating oxygen gas.
4. Each electron passes from photosystem II to phosystem I via the electron transport chain. The chain is made up of an electron carrier, a cytochrome complex, and a protein called plastocyanin.
5. The fall of electrons to a lower energy level provides energy for the synthesis of ATP.
6. Light energy was transferred to photosystem I, which excites an electron of one of the two chlorophyll molecules there.
7. The photoexcited electrons are passed from photosystem I's primary electron acceptor down another electron transport chain through a carrier protein.
8. The enzyme NADP reductase transfers electrons from the carrier protein to NADP. Two electrons are required for its reduction to NADPH.
What is cyclic electron flow
Cyclic electron flow is the path that electrons may take, under certain conditions, that consists of only photosystem I, not photosystem II. This flow does generate ATP but there is no production of NADPH and no release of oxygen. The cyclic electron flow makes up the difference of ATP that the Calvin cycle uses.
Describe and explain the overall purpose of the Calvin cycle and each phase listed below:
a. Calvin cycle - Consumes ATP as energy to consume NADPH as reducing power for adding high energy electrons to make sugar from simpler molecules
b. Carbon fixation uses CO2 molecules one at a time. Enzyme catalyzing this step is rubisco, adds a five carbon sugar which then splits in half later
c. Reduction each molecule of the carbon receives a phjosphate group from ATP
d. Regeneration carbon skeletons of five molecules of G3P are rearranged into three molecules of RuBP and uses three more molecules to do so which allows it to be ready for CO2 again
What is a plant's most valuable resource and why did plants need to evolve adaptations for hot, arid climates?
the plants most valuable resource is water, they don't want to dehydrate. the CO2 required for photosynthesis enters a leaf via the stoma which is the main avenue for transpiration of the evaporation of water. on dry days plants close their stomas to stop the water from escaping, they don't want to loss water.
Why is photorespiration such a "waste"?
Photorespiration-- A metabolic pathway that on hot and sunny days. The stomata close and the oxygen concentration in the leaf exceeds the carbon dioxide concentration.
· Consumes oxygen gas
· Releases Carbon dioxide
· It generates no ATP
· It decreases photosynthetic output
F Oxygen substitutes for carbon dioxide in the active site of the enzyme Rubisco and the photosynthesis rate is decreased.
The greatest rate of photosynthesis occurs when CO2 is present at
high concentration and high irradiance levels
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