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BIOL Exam II - Ex. 8
Plant Physiology and Metabolic Reactions
|the process by which plants, some bacteria, and some protists convert carbon dioxide into organic compounds, especially sugars, using the energy from sunlight
|overall reaction of photosynthesis
|Solar E + 6H2O + 6CO2 --> C6H12O6 + 6O2
|In eukaryotic photosynthetic organisms, photosynthesis is a two-stage process that occurs in the ___.
|Photosynthetic organisms convert ___ to ___.
|- light/solar energy - chemical energy
|Give examples of photosynthetic organisms.
|- plants - multicellular alga - unicellular protists - cyanobacteria - purple sulfur bacteria
|Where are chloroplasts found?
|mainly in the mesophyll of plant leaves; in plant cells
|Photosynthesis is a two-step redox process in which H2O is ___ and CO2 is ___.
|- oxidized - reduced
|During the light reactions, enzymes located in thylakoid membrane ___.
|split H2O into hydrogen and oxygen (removing electrons)
|During the calvin cycle, enzymes located in thylakoid membrane ___.
|incorporate the electrons from hydrogen into sugar molecules
|“splits” (oxidizes) water to generate electrons and in the process produces oxygen
|Using algal cells, you examined the effect of light on dissolved oxygen concentration. You used a handheld D.O. meter to determine the conc. of O in the light and then in the dark. How did the conc. of O change after a light source was turned off?
|an herbicide that inhibits photosynthesis (blocks the electron flow from photosystem II to pq)
|As the plant took in water, the pressure of the air pocket inside the tube ___. This change in pressure was measured by the ___.
|- decreased - gas pressure sensor
|In plants, gas exchange occurs at the ___.
|When a leaf’s CO2 concentration is low during photosynthesis, stomata ___. A strong concentration gradient favoring entry of CO2 is maintained by ___.
|- open to allow atmospheric CO2 to diffuse into the leaf and its cells’ chloroplasts - the Calvin cycle, which constantly uses up the CO2 in chloroplasts
|The Vernier Gas Pressure Sensor is used to monitor ___.
|pressure changes (in kPa's)
|What is the effect of transpiration on pressure?
|there is a decrease in pressure over time
|a plant hormone that causes the guard cells to shrink and the stomata to close
|What is the effect of abscisic acid on transpiration?
|it decreases the rate of transpiration
|What is the predicted effect of abscisic acid on pressure?
|there will be no change in pressure over time (because no water is leaving the plant)
|The rate of evaporation of water from the air spaces of the leaf to the outside air depends on the water potential gradient between ___.
|the leaf and the outside air
|Various environmental factors will affect a plant’s transpiration rate. What conditions might increase/decrease the rate of transpiration? Explain.
|- relative humidity (more humid outside = lower rate) - temperature (more hot outside = higher rate) - soil water (more water in soil = higher rate) - light (stomata triggered by light = higher rate) - wind (more wind = higher rate)
|Explain the relationship between the photosynthetic activity of algae and dissolved oxygen levels.
|as algae undergo photosynthesis, the dissolved oxygen level in a solution will increase
|Scientists interested in measuring water quality use dissolved oxygen meters to measure DO. Research the relationship between dissolved oxygen and aquatic life. What is the effect of temperature and nutrient enrichment on dissolved oxygen?
|- aquatic life use DO to carry out respiration - as temp. increases, levels of DO decreases (b/c O solubility decreasing) - water becomes nutrient rich (pollution) -> algae bloom -> DO used for respiration-> algae die -> bodies decomposed -> uses DO
|Why is transpiration necessary for plant growth and survival?
|- it drives the transport of water and minerals from roots to shoots via the xylem - without water, photosynthesis cannot occur; if photosynthesis is not occurring, the plant will eventually run out of food and die
|Explain why a plant that closes its stomata on a hot, dry day both benefits and is harmed by the closing of the stomatal pore. Be sure to think about the movement of materials through the pore and the movement of materials from the soil into the plant.
|- helps the plant conserve water, BUT then CO2 cannot enter; so, photosynthesis cannot occur - transpiration cannot occur if closed; the loss of negative pressure would stop the upward flow of water and minerals - harmful O buildup if closed
|How did you use the Gas Pressure Sensor and Logger Pro to determine the rate of transpiration? What does a negative slope tell us about the rate of transpiration? What does a negative slope tell us about activity at the cellular level?
|- measured pressure changes from transpiration; closed system; water pulled in plant, sensor membrane flexes down; linear reg. performed - negative slope = pressure decreasing; transpiration creates - pressure; only when guard cells turgid n form stomata
|What are the main physiologically relevant gases that move through plant stomata?
|water vapor, molecular oxygen, and carbon dioxide
|What is transpiration in a plant?
|loss of water vapor through stomata
|Abscisic acid (ABA) is a plant hormone made in response to water stress. What physiological condition does one attempt simulate with application of abscisic acid to a plants’ leaves?
|induced stomatal closure as a result of water stress
|How should abscisic acid affect pressure readings?
|pressure readings should not change because abscisic acid will inhibit transpiration
|Molecular oxygen is given off as a by-product of photosynthesis. The oxygen atom comes from ___.
|You used algae to examine the relationship between photosynthetic activity and oxygen production. What resulted in a DECREASE in oxygen production?
|- placing the algae in the dark - blocking their electron transport system - disrupting their cell membranes (like the thylakoid membrane) - denaturing their proteins (such as those found in Photosystem II)
|What’s the difference between photosystem II and I?
|- P II: inner surface of thylakoid membrane; oxidation of water (for e); ATP production - P I: outer thylakoid membrane; NADPH production
|How can you measure photosynthetic activity?
|- water intake - carbon dioxide intake - oxygen production - sugar production
|How could you decrease or inhibit photosynthetic activity?
|- herbicides (interrupt e flow during light reactions) - decrease exposure to light/water/CO2
|Describe the flow of water through a plant.
|in through roots/root hairs and out through stomata
|What part of the cell deals with cohesion and adhesion of water?
|What is the phloem?
|where nutrients are transported throughout the plant
|What type of pressure does water move through the cells with?
|- negative pressure in xylem - positive pressure in phloem