18) The \"Holy Grail\" for biofuels is conversion of ligno-cellulosie biomass in

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18) The "Holy Grail" for biofuels is conversion of ligno-cellulosie biomass into a liquid petroleum substitute. The objective is to liberate the glucose from the cellulose and make it available for fermentation to ethanol (or other high-energy liquid). The cellulose is hard enough to break down because the individual strands H-bond to each other and exclude H 0 needed for hydrolysis. Lignin complicates the problem because it forms covalent bonds with other cell wall components and is also hard to breakdown. Describe the structure and synthesis of lignin with specific reference to why it is difficult to breakdown (2) It is proposed that modern coal deposits mostly derive from the Carboniferous period because A) Algae in ocean surrounding the Pangea supercontinent settled to the oxygen-poor depths, where it 19) became petrified as coal B) Plant cell walls in the extensive forests became petrified because of sudden cooling and drying of the environment C) Plants evolved lignocellulosic cells walls-80 million before white rot fungus evolved the ability to efficiently degrade these structures D) The warm wet climate supported the most prolific forests the world has ever had E) Ca" was more prevalent because of extensive weathering of rock and volcano action, making plant cell walls stronger and more resistant to degradation. 20) In the context of plant cell walls, explain what is happening when making homemade jam Gi.e heating fruit in a jar to convert intact fruit to a gelled matrix) (1 pt). 21) Explain why adding caleium (Ca?, from Tums, etc.) while making homemade jam would help make the jam thicker and stiffer (1 pts) In a signal transduction cascade, the receptor is usually located A) In the nucleus 22) B) on the plasma membrane C) Anywhere the signal can reach D) In the cytoplasm E) On the leaf surface Which statement is most FALSE regarding signal transduction cascades in plants A) Signal transduction cascades interact with each other B) Signal transduction cascades can work over very short or very long distances C) Plant cascades are usually a series of positive activation steps D) Plant cascades usually involve the inactivation of a repressor E) The receptor for a hormone may be part of the ubiquitination process targeting a repressor for 23) degradation 24) The expression "one bad apple ruins the bunch" can be applied figuratively to a disruptive student in a lecture hall, but in literal, botanical terms, this expression refers to the action of A) Ethylene B) Auxin C) Cytokinin D) Gibberellic acid E) Abscisic acid

Explanation / Answer

Ans18

It is difficult to break down lignin because it's structure is very strong and rigid. Individual units are joined by strong ether and carbon - carbon covalent bond.

During the synthesis of lignin, certain radicals are formed. Covalent bonding between these radicals makes lignin harder and difficult to break down.

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