Various living creatures, simple or complex, from animals and plants to bacteria, are physiologically, behaviorally and molecularly adapted to their surroundings. An example of physiological adaptation is a thick layer of fat, which provides thermal insulation, and an example of behavioral adaptation is nocturnal activity in warm habitats.
- Give one example of molecular level adaptation of living creatures to their surroundings
- Organisms living in habitats with temperatures below zero degrees Celsius (00c) are at risk of freezing. What is the risk, at the cellular level, to an organism exposed to temperatures below zero degrees Celsius?
A. DNA breaks
B. The formation of ice crystals, which may pierce the cell membrane
C. Increased cellular respiration and waste of energy
D. Increased breakdown of proteins
The correct answer is: B. The formation of ice crystals in the cells may cause ruptures in the cell membrane and the content of the cell to leak out.
One of the biochemical adaptations of organisms in such a cold environment is the production of Anti Freezing Proteins (AFPs). Thanks to their chemical and spatial structure, they have a tendency to bind the nuclei of the ice crystals to their surface in a way that inhibits the crystallization process of the ice, thus protecting the cell from harm.
The existence of large molecules that inhibit ice crystallization – such as antifreeze proteins or small molecules, which increase the concentration of solutes and in this way decrease freezing temperature – are examples of molecular level adaptations to a living environment with low temperatures.
Deciphering the spatial structure of the antifreeze proteins (AFPs) may aid in understanding the function of these proteins. So far scientists have succeeded in determining the amino acid sequence of only a few antifreeze proteins. It was found that AFPs are very long and contain hydrophilic amino acids as well as hydrophobic amino acids.
However, it is still unclear what the spatial structure of the AFPs is, and how this structure is related to their role in inhibiting the ice crystallization process.
A team of scientists from Queen’s University in Canada raised the following research questions:
- What is the spatial structure of the antifreeze proteins (AFPs), and how is the structure stabilized?
- Which amino acids in the protein are vital for binding ice molecules, and how do they prevent ice crystallization?
In order to answer the research questions, the scientists must first determine the spatial structure of the AFPs using experiments. First, they grew bacteria originating in the north pole called Marinomonas primoryenis, and produced from them the antifreeze protein MpAFP. The scientists created a crystal comprised of many MpAFP molecules and determined the spatial structure of the protein using a method called X-ray diffraction. The findings, like all protein structures determined until now, are compiled in a database called RCSB-Protein Data Bank or abbreviated to PDB-RCSB.
In the next stage, the scientists should analyze the spatial structure and address the different levels of the protein structure, starting with the amino acid sequence, through the secondary structures, and up to the three dimensional structure and binding to other molecules, including ice. This way they will be able to learn about the connection between the protein sequence, its structure and function.