Chapter 10 Flashcards
Define Autotroph.
Autotrophs have the ability to make their own food via photosynthesis.
How do plants take in atmospheric CO2? How do plants absorb water?
Plants take in CO2 by the openings under their leaves called stomata. They absorb water through the roots.
Define transpiration.
When water evaporates and as it exits through the leaves, it sucks up more water into its roots.
During transpiration, how does water travel through plants?
Water travels through plants vascular cells.
Not a question just information.
Photosynthetic organisms use sunlight to oxidize water
into oxygen, and reduce carbon dioxide into glucose. This is the opposite as cellular
respiration, where oxygen is reduced into water, and glucose is oxidized to form carbon
dioxide!
Define the five characteristics and attributes of a chloroplast: chlorophyll, stroma, thylakoids, grana, and mesophyll cells.
Chlorophyll are light absorbing pigments which helps convert solar energy into chemical energy.
Stroma is a viscous liquid inside chloroplasts.
Thylakoids are folded interconnected membranous sacs.
Grana are stacks of thylakoids.
Mesophyll cells are what chloroplasts are found in (high concentrations of chloroplasts.
Chloroplasts can be found in multiple types of plant tissues. Where are they most abundantly found?
They are mostly found in the leaves of plants.
Name the type of cell that regulate the opening of the leaves’ stomata.
The cell that regulates the opening of the leaves’ stomata are called guard cells
Summarize what occurs during the light reactions of photosynthesis.
Energy from light splits water and drives the synthesis of ATP and NADPH
Summarize what occurs during dark reactions of photosynthesis.
ATP is energy required to synthesize sugar, NADPH provides electrons to reduce CO2 into glucose. This occurs in the stroma.
Light consists of high-speed particles called ____? These high-speed particles are packets of what type of energy?
Called photons. Photons are packets of electromagnetic energy.
What are the three pigments found in chloroplasts that absorb different wavelengths? Describe which colors each pigment absorbs and reflects.
Chloroplasts contain chlorophyll a, chlorophyll b, and carotenoids. Chlorophyll absorbs violet, blue and yellow, orange, red, and they reflect green light. Carotenoids absorb violet, blue, green and reflect yellow, orange, and red light.
Write out the chemical equation for the splitting of water.
2H2O —> 4H+ + 4e- + O2
(Not a question, just information!) Electrons move from a ground state (low energy) to an excited state (high energy). These electrons are harnessed in a network of pigments, referred to as a photosystem
Define photosystem. What is a pigment’s role in a photosystem, and how does it relate to an electron’s energy state?
Photosystem is a molecular light-capture device. A pigment receives an energy boost by the impact of photons. This energy is used to excite electron to a higher energy state (resonance)
Explain how energy is transferred through photosystem II, including the role of electrons.
Sunlight striking the chlorophyll molecules in photosystem II transfers energy, which eventually is used to excite the electron. This is known as resonance.
When is the potential energy of the excited electron converted to kinetic energy? What is this kinetic energy used for?
The potential energy of the excited electron is converted to kinetic energy as it “falls” down the chain. This kinetic energy is used to pump hydrogen ions (H+) across the thylakoid membrane against their concentration gradient.
Define proton motive force.
The proton motive force is the large concentration gradient of the H+ on one side of the membrane results in high potential energy.
In which membrane of the chloroplasts is ATP synthase found?
Thylakoid
(Not a question, just information!) The way ATP is created through chemiosmosis with ATP synthase is very, very similar to the way it works in cellular respiration. Hydrogen ions are
used by moving down a concentration gradient, through ATP synthase, synthesizing ATP by oxidative phosphorylation. Other than location, the main difference is then where the ATP goes.
Explain the electron’s travel and role in Photosystem I.
Sunlight is absorbed by chlorophyll molecules in photosystem I, and its excites electrons to a higher energy state (Resonance). When the electron at the reaction is energized at center chlorophylls called P700 in Photosystem I. It is transferred to the primary electron acceptor and “trapped” in its high energy state.
What is the P number for the center chorophylls in photosystem I and II? (Hint: An example would be P320, replacing 320 with the correct number for each system.)
P700
What specifically carries the high-energy electron from the end of photosystem I to the Calvin cycle?
NADPH
Explain the roles of the two electron transport chains working during the light reactions.
One provides a link between the two photosystem during which ATP is made. The second one produced NADPH, an energized molecule (carrying electron) used in the dark reactions (Calvin Cycle).
What products from the light reactions are utilized in the Calvin cycle (dark reactions)?
ATP and electrons from NADPH
Where are the enzymes that participate in the Calvin cycle located within the chloroplast?
The stroma of the chloroplast.
What is the main goal of the Calvin cycle? (Hint: What is the main goal of photosynthesis?)
To reduce CO2 to make sugars.
Explain the three phases of the Calvin Cycle.
1) Carbon Fixation: an enzyme rubisco, fixes CO2 with a 5-carbon molecule called ribulose biphosphate (RuBP)
2) Reduction: The 3-Phosphoglycerate molecules are phosporylated by atp then reduced by NADPH to produce glyceraldehyde 3-phosphate (G3P). One G3P leaves the Calvin cycle and addition G3P molecules remain in the Calvin Cycle.
3) Regeneration: The remaining G3P is used to generate more RuBP.
Define water use efficiency (WUE). What does it mean to have high WUE?
A plants Water use efficiency relates the amount of CO2 entering the plant to the amount of water lost from the plant.
High WUE means more CO2 is taken in with minimal H2O lost.
Explain the inefficiency of rubisco within the Calvin cycle, and how this affects WUE.
Rubisco is the enzyme that first binds to CO2, binging it into the Calvin Cycle. It is no very efficient, as it will bind to and bring O2 into the Calvin cycle. O2 interferes with efficiency.
Define photorespiration. Is photorespiration a positive or negative?
when it appears that oxygen is being used during photosynthesis. It is negative because phosphorespiration declines photosynthesis drastically.
Carbon fixation is favored over photorespiration when two conditions are met, list the conditions
When CO2 concentration is high, and when O2 concentration is low.
What are the two alternate “pathways” plants in very hot, dry environments use to increase WUE (thereby avoiding photorespiration)?
The two pathways are called: C4 pathway, and CAM pathway
Explain the C4 pathway, specifically how it differs from the regular photosynthetic pathway to increase WUE.
CO 2 is fixed to a 4-carbon molecule byPEP carboxylase (PEP case), an enzyme that has no affinity for O2. The bound CO2 is transported to the bundle sheets cells, the only cells in which the Calvin Cycle occurs. CO2 is unloaded in the bundle sheath cells and undergoes the Calvin cycle like normal but it is so concentrated that any effect of CO2 is “Swamped out”
Minimizes Photorespiration
Explain the CAM pathway, specifically how it differs from the regular photosynthetic pathway to increase WUE.
Crassulacean acid metabolism. CAM plants open up their stomata at night when there is less loss of water. Increases WUE by minimizing the amount os water lost from the plant.
Summarize the way C4 and CAM plants increase WUE in reference to either CO2 or H2O.
C4- CO2 enters fixed to a 4C molecule, stored in the bundle sheath cells
CAM- CO2 enters at night, fixed to a 4C molecule, stored in vacuole.
Why are most plants C3 (regular photosynthesis) plants?
More energy is require for these pathways,, so there is a trade off involved. The benefits outweigh the costs for plants in hot dry environments.
