The thermophilic bacteria possibly have strong cell membranes and minimal protein content to survive at high temperatures? Just guessing, please correct me if I am wrong...
Although this topic is on enzymes, why don't we take this discussion on thermophilic bacteria further to tie in what we've already learnt in Biological Molecules and Membranes?
1) Cell membrane - 'Strong' cell membrane is in layman terms. Could you improve on your answer, given your theoretical understanding of the previous topic? Let me give you a clue: How do you think the COMPOSITION of phospholipids in the membrane of the thermophilic bacteria differs from a regular bacteria's one?
2) DNA - How do you think the composition of DNA in thermophilic bacteria differs from a regular bacteria's one?
3) Proteins (including enzymes) - How do you think the composition of amino acids in thermophilic bacteria differs from a regular bacteria's one?
Perhaps these bacteria have thicker cell walls surrounding the phospholipid bilayer to survive high temperatures? And perhaps intramolecular hydrogen bonds are less common in thermophilic bacteria, and are instead replaced by stronger covalent bonds such as disulfide linkages which are less affected by temperature? And about the DNA part; reminds me of the tutorial qn on singapore soil bacteria and australian hot spring bacteria.These bacteria have a higher concentration of guanine and cytosine bases as compared to normal bacteria as they have three bonds between them which makes them much stronger than adenine-thymine pairings. This is my other prediction. Pls feel free to correct:) ~Thaheera
1) Cell membrane - Recall the topic on cell membrane. During the lecture, it was mentioned (and also in your lecture notes) that since the surrounding temperatures are high, the membrane might be overly fluid. Hence the thermophilic bacteria have evolved to have more phospholipids with saturated FA tails (than unsaturated FA tails).
2) Enzymes (proteins) - You are absolutely right! Thermophilic bacteria have many cysteine residues that are able to form strong covalent disulfide bonds in the proteins.
It is POSSIBLE, but i think it is hard to put a number to exactly how much change in pH (alot or very little) is required to cause the enzyme to denature as it depends on the extent to which ionic and hydrogen bonds (maintaining the secondary and tertiary structures of the enzyme) are disrupted. These bonds are disrupted as a change in pH from the optimum pH cause the NEUTRALISATION of the charged R groups of amino acid.
Let's use the lysosomal enzyme as an example. Recall in we learnt in Cell structure and Functions about how the contents of the cytosol are protected against the cell's own lysosomal enzymes (optimum pH is 5.0). We learnt that in the event of leakage, the enzymes are denatured by the higher cytosolic pH (7.2).
Mathematically speaking, it may seem like there hasn't been a major change as the pH has only increased by about 2.2. But what does this increase in pH mean, in terms of the CONCENTRATION OF H+ IONS present? In other words, how does [H+] change for every +1 (or -1) in pH?
The thermophilic bacteria possibly have strong cell membranes and minimal protein content to survive at high temperatures? Just guessing, please correct me if I am wrong...
ReplyDeleteGreat guess Thaheera! :)
DeleteAlthough this topic is on enzymes, why don't we take this discussion on thermophilic bacteria further to tie in what we've already learnt in Biological Molecules and Membranes?
1) Cell membrane - 'Strong' cell membrane is in layman terms. Could you improve on your answer, given your theoretical understanding of the previous topic? Let me give you a clue: How do you think the COMPOSITION of phospholipids in the membrane of the thermophilic bacteria differs from a regular bacteria's one?
2) DNA - How do you think the composition of DNA in thermophilic bacteria differs from a regular bacteria's one?
3) Proteins (including enzymes) - How do you think the composition of amino acids in thermophilic bacteria differs from a regular bacteria's one?
Feel free to answer guys!
Any takers on the pH question? :)
Perhaps these bacteria have thicker cell walls surrounding the phospholipid bilayer to survive high temperatures?
ReplyDeleteAnd perhaps intramolecular hydrogen bonds are less common in thermophilic bacteria, and are instead replaced by stronger covalent bonds such as disulfide linkages which are less affected by temperature?
And about the DNA part; reminds me of the tutorial qn on singapore soil bacteria and australian hot spring bacteria.These bacteria have a higher concentration of guanine and cytosine bases as compared to normal bacteria as they have three bonds between them which makes them much stronger than adenine-thymine pairings.
This is my other prediction. Pls feel free to correct:)
~Thaheera
Good work!
Delete1) Cell membrane - Recall the topic on cell membrane. During the lecture, it was mentioned (and also in your lecture notes) that since the surrounding temperatures are high, the membrane might be overly fluid. Hence the thermophilic bacteria have evolved to have more phospholipids with saturated FA tails (than unsaturated FA tails).
2) Enzymes (proteins) - You are absolutely right! Thermophilic bacteria have many cysteine residues that are able to form strong covalent disulfide bonds in the proteins.
3) DNA - Correct! :)
Yay!!! thanks:)
Deleteam really gonna miss u!!
About the enzymes, is it possible that they may be denatured by even slight changes in pH?
ReplyDeleteIt is POSSIBLE, but i think it is hard to put a number to exactly how much change in pH (alot or very little) is required to cause the enzyme to denature as it depends on the extent to which ionic and hydrogen bonds (maintaining the secondary and tertiary structures of the enzyme) are disrupted. These bonds are disrupted as a change in pH from the optimum pH cause the NEUTRALISATION of the charged R groups of amino acid.
ReplyDeleteLet's use the lysosomal enzyme as an example. Recall in we learnt in Cell structure and Functions about how the contents of the cytosol are protected against the cell's own lysosomal enzymes (optimum pH is 5.0). We learnt that in the event of leakage, the enzymes are denatured by the higher cytosolic pH (7.2).
Mathematically speaking, it may seem like there hasn't been a major change as the pH has only increased by about 2.2. But what does this increase in pH mean, in terms of the CONCENTRATION OF H+ IONS present? In other words, how does [H+] change for every +1 (or -1) in pH?
We have neglected the pH question for too long! Will give you guys a clue in my next post.
DeleteMiss Teong