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Questions and Answers
What is the primary function of Crassulacean acid metabolism (CAM) in plants?
What is the primary function of Crassulacean acid metabolism (CAM) in plants?
Which compound acts as a substrate for malate movement in chloroplasts?
Which compound acts as a substrate for malate movement in chloroplasts?
Which of the following processes is characteristic of C3 plants regarding PEP carboxylase activation?
Which of the following processes is characteristic of C3 plants regarding PEP carboxylase activation?
What is the role of physiological acclimation in plants?
What is the role of physiological acclimation in plants?
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Which metabolic product supports the synthesis of NADH in plants?
Which metabolic product supports the synthesis of NADH in plants?
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What is required for starch elongation to begin?
What is required for starch elongation to begin?
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Which type of bonds must be broken to yield glucose from branched starch?
Which type of bonds must be broken to yield glucose from branched starch?
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What role does ferredoxin play in starch metabolism?
What role does ferredoxin play in starch metabolism?
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How do hemicelluloses differ from celluloses in terms of structure?
How do hemicelluloses differ from celluloses in terms of structure?
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What component is essential for the formation of secondary plant cell walls?
What component is essential for the formation of secondary plant cell walls?
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What characterizes the primary cell wall compared to the secondary cell wall?
What characterizes the primary cell wall compared to the secondary cell wall?
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Which component makes up approximately 50% of plant cell walls?
Which component makes up approximately 50% of plant cell walls?
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What is one function of pectins in plant cell walls?
What is one function of pectins in plant cell walls?
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What physiological condition causes a plant cell to shrink significantly when placed in a sucrose solution?
What physiological condition causes a plant cell to shrink significantly when placed in a sucrose solution?
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In order for water to move from the soil into the plant through the Soil Plant Atmosphere Continuum, what must be true about the water potential in the soil compared to that in the plant?
In order for water to move from the soil into the plant through the Soil Plant Atmosphere Continuum, what must be true about the water potential in the soil compared to that in the plant?
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Given that the water potential (Ψw) of the ocean is -3.02 MPa and the pressure potential (Ψp) of kelp is 1.0 MPa, what is the solute potential (Ψs) of kelp?
Given that the water potential (Ψw) of the ocean is -3.02 MPa and the pressure potential (Ψp) of kelp is 1.0 MPa, what is the solute potential (Ψs) of kelp?
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How does relative humidity affect the water potential in the air surrounding the plant?
How does relative humidity affect the water potential in the air surrounding the plant?
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What is the main reason that pressure potential (Ψp) becomes significant in a plant's water transport mechanism?
What is the main reason that pressure potential (Ψp) becomes significant in a plant's water transport mechanism?
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What occurs to the osmotic potential (Ψs) in a pond of freshwater where Ψw is assumed to be close to zero?
What occurs to the osmotic potential (Ψs) in a pond of freshwater where Ψw is assumed to be close to zero?
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What drives the process of water entering the roots from the soil in plants?
What drives the process of water entering the roots from the soil in plants?
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What role does matric potential play in the relationship between soil and plant water uptake?
What role does matric potential play in the relationship between soil and plant water uptake?
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Study Notes
CAM Plants
- CAM plants have Crassulacean acid metabolism, a second strategy to minimize photorespiration similar to C4 plants.
- They thrive in environments with low temperatures at night and high humidity.
- During the night, CAM plants fix CO₂ into organic acids within their mesophyll cells.
- During the day, light provides ATP and NADPH for the Calvin cycle, while water from the organic acids is used.
- CAM plants must have a PEP carboxylase that is active in the dark, unlike C3 plants, which only activate PEP in the light.
- Carbonic anhydrase is pH activated.
Dark
- Carbonic anhydrase is activated by H⁺ ions, pyruvate from starch, and PEP carboxylase.
- Oxaloacetate is formed from PEP carboxylase and CO₂.
- NAD⁺ malic dehydrogenase converts oxaloacetate to malate.
- The resulting malate is stored as starch.
Light
- CO₂ is released from the malate stored during the night.
- Malic acid is converted to pyruvate, which is used as a substrate to move malic acid within the chloroplasts
- Starch is broken down into glucose, and glucose is used to synthesize sucrose.
- Malic acid is sequestered to prevent the cytosol from becoming too acidic, which would drive HCO₃ back to CO₂.
C3 Intermediates
- Triose phosphates are produced in the Calvin cycle.
- RuBP, Erythrose-4-Phosphate, Ribose-5-Phosphate, and 5-C intermediates are also present in the Calvin cycle.
Pathways
- Starch, sucrose, and cellulose synthesis are key metabolic pathways in plants.
- Glycolysis, the Krebs Cycle, and the Pentose Phosphate pathway are also vital for energy production and biosynthesis.
- The Shikimic acid pathway produces lignin and aromatic amino acids.
Products
- Starch is a storage carbohydrate.
- Sucrose is a transportable sugar.
- Cellulose is a structural component of plant cell walls.
- CO₂ and organic and amino acids support NADH synthesis.
- CO₂ supports NADPH synthesis.
- Lignin and aromatic amino acids contribute to structural integrity and defense mechanisms.
- RNA and ATP are essential for protein synthesis and energy metabolism.
- Hemicelluloses are structural polysaccharides that help reinforce plant cell walls.
Physiological Acclimation
- Plants can adapt to environmental stressors, such as changes in CO₂ levels, through physiological acclimation.
- This adaptation involves fine-tuning plant processes to optimize resource utilization and survival.
- Understanding how to acclimate plants can be crucial for maximizing crop yields in the future.
Starch Physiology
- Starch synthesis requires a primer to initiate the process, followed by the addition of ADP-glucose.
- The starch synthesis pathway is the same in all plants.
- Starch initially forms a linear polymer that is then branched by a branching enzyme.
- When starch is broken down, it is cleaved into maltose and glucose within the chloroplast, and then into sucrose in the cytosol.
Control of Transitory/ Storage Starch
- A tetramer of proteins, held together by disulfide bridges, regulates starch synthesis.
- The activity of this tetramer, known as AGP-ase, is influenced by:
- Protein phosphorylation
- Redox modulation
- Allosteric regulation
- Transcriptional regulation
- Ferrodoxin plays a role in regulating the tetramer by cleaving disulfide bonds.
- The expression of genes for the four subunits of the tetramer is spatially regulated.
Hemicellulose
- Hemicellulose is a complex carbohydrate that helps reinforce plant cell walls.
- Its structure is similar to cellulose, but with added sugars on the side chains.
- Hemicellulose hydrogen bonds to cellulose, regulating cell enlargement.
Pectins
- Pectins are a diverse group of polysaccharides with varying structures.
- They can be simple or highly branched.
- Pectins have a high affinity for water, giving them a gelatinous texture.
Membrane-Associated Proteins
- These proteins are involved in cell signaling pathways.
Plant Cell Walls: Synthesis
- The complex structure of plant cell walls contributes to the diverse shapes of plant cells.
Callose
- Callose is a beta 1,3 linked glucose polymer.
- It is found in cell walls, particularly during cell plate formation and primary wall development.
- The role of callose during secondary wall formation remains unknown.
Cell Wall Components
- Mannose is a component of mannan, a structural polysaccharide in cell walls.
- All sugars in cell walls are derived from triose phosphates.
- Cellulose, the primary structural component of plant cell walls, accounts for 50% of the wall composition.
- Pectins, another important component of cell walls, are composed of sugars and homogalacturonan, a type of pectin chain.
- Lignin, structural proteins, and other compounds contribute to the remaining 25-30% of the cell wall.
Primary vs. Secondary Walls
- Primary walls are flexible and allow for cell expansion.
- Secondary walls are rigid and form after cell expansion is complete.
- Callose is present in both primary and secondary walls.
Boron Importance
- Boron is required for the synthesis of secondary cell walls.
- Secondary walls can have elaborate ingrowths, which are structures that increase their surface area.
Defining a Plant
- Lignin is a unique characteristic of plants.
- Lignin is highly ignited and is only found in secondary walls.
- While other organisms have primary cell walls, only plants have secondary cell walls with lignin.
Plant Water Potential
- Water potential (Ψw) is the potential energy of water in a system.
- Plant water potential is represented by the equation: Ψw = Ψe - Ψp + Ψm
- The components include:
- Ψe: osmotic potential
- Ψp: pressure potential
- Ψm: matric potential
Soil Water Potential
- Soil water potential can be estimated using the equation: Ψw = Ψs - Ψp + Ψm
- In soil, matric potential (Ψm) is significant and should not be ignored.
- Gravity's impact on soil water potential is usually negligible and ignored.
Water Movement:
- Water moves from a region of higher water potential to a region of lower water potential.
- Water moves from an area of lower solute concentration to higher solute concentration.
- Water moves from higher pressure to lower pressure.
- Water movement within plants occurs via diffusion and bulk flow.
Soil Plant Atmosphere Continuum (SPAC)
- For water to move from soil to the atmosphere through a plant, the water potential must decrease in each successive compartment: Soil > Root > Plant > Air.
- Water movement from soil to xylem is influenced by the matrix potential and Casparian strip in the root.
Plant Water Potential
- Plants must maintain a lower water potential than the surrounding soil to draw water into their roots.
Plant Water Potential vs Air Water Potential
- Air water potential (Ψair) is influenced by relative humidity.
- Ψair can be calculated using the formula: Ψair = 0.4619 * T * ln(1% RH/100%)
- At 100% relative humidity, Ψair is 0 because no more water can be added to the air.
- As relative humidity decreases, Ψair becomes more negative.
- The negative Ψair draws water from the soil up into the plant.
- The lower Ψair of the atmosphere is the driving force for water movement through the SPAC.
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Description
Test your knowledge on CAM plants and their unique metabolic processes. This quiz covers topics including Crassulacean acid metabolism, the role of carbonic anhydrase, and the intricacies of photosynthesis in varying light conditions. Perfect for biology students studying plant physiology.
