PMB Quiz 2 PDF

Have a general understanding of how electrons are used in PSII and I to produce ATP and NADPH, how oxygen is generated, the difference between reduction and oxidation PSI: reduces NADP+ into NADPH in the stroma via the action of ferredoxin (Fd). PSII: Water is oxidized and protons are released in th...

Have a general understanding of how electrons are used in PSII and I to produce ATP and NADPH, how oxygen is generated, the difference between reduction and oxidation PSI: reduces NADP+ into NADPH in the stroma via the action of ferredoxin (Fd). PSII: Water is oxidized and protons are released in the lumen by PSII to make ATP. In PSII, water molecules are split into oxygen, protons (H⁺ ions), and electrons. How DCIP works. Strong absorbance at 600 nm DCIP is blue (oxidized form) and reduces to DICPH2 is clear (reduced form). Role: accept and donate electrons. Know where in the chloroplast light reactions and carbon fixation take place. The light reaction takes place in thylakoid membranes The carbon-fixing reaction takes place in the chloroplast stroma. What is DCMU and how does it act in the plant? DCMU is a very specific and sensitive inhibitor of photosynthesis Role: The herbicide DCMU blocks e-flow from PSII. DCMU interferes with Plastoquinone-Protein interactions blocking reduction of plastoquinone and subsequent redox reactions. photosynthetic rate increases proportionally to the light intensity and reaches a maximum. However, as light intensity is increased further, chlorophyll can get damaged and as a result the rate of photosynthesis decreases. What influences photosynthetic efficiency and how can we measure it? At low light intensities, photosynthesis is light-limited, so as more photons are absorbed more CO2 is fixed. Plants have mitochondria and respire, consuming O2 and producing CO2. In the light, they are net CO2 consumers, but in the dark, production is greater than consumption. As light intensity increases above the light saturation point, the photosynthetic reaction rate is determined by nonlight-dependent reactions. The light compensation point: The amount of light needed to balance photosynthetic CO2 consumption to respiratoryCO2 production Quantum efficiency measures the energetic efficiency of photosynthesis and is a good indicator of stress. (Fluorescence) What is abiotic stress and what examples of natural adaptations to abiotic stress? Abiotic stress is the negative impact of non-living factors on living organisms in a specific environment. Examples: drought, salinity, and extreme temperatures, 1. Know how domestication has influenced abiotic stress tolerance, plant responses to stress, and ways of improving stress tolerance. how domestication has influenced abiotic stress tolerance: Plant responses to stress: Non-adaptive lead to damage or death and chemical kinetics. Adaptive by Altered membrane composition, Stomatal closure/opening, Plant architecture, Metabolite synthesis Ways of improving stress tolerance: Management practices Timing of planting/harvest Sprays Reduce stress Irrigation Add fertilizer Use high tunnel or greenhouse Plant breeding for tolerance Conventional Genetic engineering/gene editing Experiment: Plant responses to cold stress: SPAD unit and biomass decrease. Leaf area and leaf thickness increased. Other responses to cold stress: 1. Certain proteins accumulate that help to stabilize cell membranes and prevent ice crystal growth. b. Increase in osmoprotectants such as soluble sugars, and proline. c. Reactive Oxygen Species (ROS) accumulate which signals the plant to activate stress responses = gene expression and ROS scavenging d. Ca2+ accumulates and is thought to be an early signal in cold sensing that may trigger the early changes in gene expression. e. Reduction in photosynthesis. Understand how to use a standard curve to estimate sample concentrations. Knowledge of what alpha-amylase is, how it is affected by GA, and what role they play in the Barley seed. Alpha-amylase is enzyme that hydrolyses α bonds of large, α-linked polysaccharides, such as starch and glycogen, yielding shorter chains thereof, dextrins, and maltose Gibberellic acid (GA) is a plant hormone that regulates various aspects of plant growth and development, including seed germination. Gibberellic acid enhances the synthesis of α-amylase in isolated aleurone layers of barley-seeds. During germination, GA induces the expression of amylase. GA breakdown of starch in the endosperm is initiated by GA produced by the embryo or added during the malting process. Understand how GA affects plant growth and how the GA signaling pathway works, including the role of PIF4/5 in stem elongation. Effect of GA on Plant Growth: promote stem prolongation and seed germination. In some plants, they promote flowering and fruit development. how the GA signaling pathway works: GA binds to the receptor GID1 facilitating the binding to DELLA proteins. DELLAs complexed with GID1 are recognized by an F-box protein. DELLA proteins are negative regulators of GA signaling. The role of PIF4/5 in stem elongation: PIF3 and PIF4 activate the transcription of growth-promoting genes, leading to elongation of the hypocotyl in the dark. DELLA proteins bind PIF3 and PIF4 and interfere with their action. GA promotes DELLA degradation, allowing PIF3 and PIF4 to act. DELLAs can affect growth through their actions on other proteins. Mutants and overexpressors of PIFs support a role for PIFs in GA-dependent elongation. PIF4 – a transcription factor that promotes stem elongation. In the light – phy B destabilizes PIF4. GA triggers the degradation of DELLA repressors in the dark What cycloheximide and Actinomycin D are used for. Actinomycin D inhibits transcription. Cycloheximide inhibits translation **** Know how to use sterile technique and why it is important. Prevent infection.