BIOL 1070 Lecture Notes - Ice, Supercooling, Body Fluid

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blueelephant164

29 Nov 2011

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I clicker: normally, body fluids of fish in temperate waters have a freezing point somewhere between -0. 6 and -1. 1 c whereas seawater freezes at -1. 9 c. A. due to the noncolligative properties of the body fluid. Colligative: antifreezers lower freezing point of body fluids by increasing concentration of solutes. (ex. glycerol, propaline glycol) Noncolligative antifreezes lower the freezing point of body fluids because of specialized chemical properties. What strategies do arc ectotherms use to survive. Strategies freeze tolerance freeze intolerance: behavioural avoidance. X: production of antifreeze x x compounds, synthesis of ice x nucleating agents, supercooling (temperate. Hypothesis: in cold water marine fish, the trigger for synthesis of antifreeze protein is temperature. Prediction: if so, then if we lower the external temp and sample blood should be an increase in antifreeze protein. (decreasing water temp will increase [afp]). Experimental group: 20 fish, decrease temp to -1. 51 degrees(c) Observation: antifreeze proteins increase in fall and decrease in spring in arctic marine fishes.

Related Questions

Many polar-dwelling fishes have "antifreeze proteins" that prevent their bodies from freezing solid even at very low temperatures. Briefly describe how these proteins function.

Briefly describe the four emergent properties of water that contribute to earth's suitability for life.

1. Cohesion of water molecules

2. Moderation of temperatue by water

3. Expansion upon freezing

4. Versatility as a solvent

Q: "Here we show that freezing stimulates the self-ligation (circularization) of linear forms of the hairpin ribozyme (HPR) containing 2',3'-cyclic phosphate and 5'-OH termini. Divalent metal ions (M2+) are not required, but monovalent cations and anions at millimolar concentrations can have various effects on this reaction depending on the specific ion. Under optimal conditions, the observed rate of M2+-independent self-ligation reaches a peak (0.04 min(-1)) at -10 degrees C with a yield of -60% after 1 h. In contrast, no ligation occurs either at above 0 degrees C or in solutions that remain unfrozen when supercooled to subzero temperatures. Under freezing conditions, the cleavage-ligation equilibrium strongly favors ligation. Besides freezing, evaporation of the aqueous solvent as well as the presence of ethanol at levels of 40% or above can also induce M2+-independent HPR ligation at 25 degrees C. We argue that partial RNA dehydration, which is a common feature of freezing, evaporation, and the presence of ethanol, is a key factor supporting HPR ligation activity at both above- and below-freezing temperatures. In the context of the RNA world hypothesis, freezing-induced ligation is an attractive mechanism by which complex RNAs could have evolved under conditions in which RNA was relatively protected against degradation."
--Kasakov et al. (2006) RNA 12(3):446-456.
1. The authors suggest that by changing the solvent, the RNA enzyme function changes to favor the ligation (joining) reaction. Give an example of how the DNA structure can change in different solvents that might support that model for RNA.
2. The solvent is important in determining the native state (lowest energy/most stable) 3-D structure of a protein. In a sentence or two, explain why the way an RNA finds its native state in a particular environment is different from the way a protein finds its native state (hint: Chargaff's rules do not apply to single-stranded RNA, but are more relevant in RNA than in protein).
3. What is the RNA world hypothesis? Briefly explain why you agree or disagree with the statement made by the authors that their findings support the RNA world hypothesis.

BIOL 1070 Lecture Notes - Ice, Supercooling, Body Fluid

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