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adell [148]
3 years ago
6

irvinase is an enzyme that has 4 cys residues tied up in 2 disulfide bonds. you denature irvinase with 8m urea in the presence o

f mercaptoethanol to break all the s-s bonds. the percent activity of irvinase recovered i
Chemistry
1 answer:
Elena L [17]3 years ago
8 0

Answer:

1. Quaternary structure of proteins relates to the interactions between separate polypeptide chains within the protein. The word polypeptide refers to a polymer of amino acids. A protein may contain one or more polypeptides and is folded and may be covalently modified.

2. Hemoglobin (and many other proteins) have multiple polypeptide subunits. Interactions between the subunits include ionic interactions, hydrogen bonds, and hydrophobic interactions. Modification of the quaternary structure of a protein may have the same effects as modification of its tertiary structure - alteration of its function/activity.

3. The enzyme ribonuclease (RNase) is interesting in being very stable to heat and other things that denature/inactivate other proteins. (By the way, denaturation is a word that means the tertiary and/or quaternary structure of a protein is disrupted.). RNase has disulfide bonds that help it to remain resistant to denaturation. Heating it to 100 Celsius, which denatures most proteins does not denature RNase. Breaking the disulfide bonds of RNAse with a reagent like mercaptoethanol followed by heating to 100 Celsius to destroy hydrogen bonds (or treatment with urea) causes loss of activity. If one allows the hydrogen bonds to reform slowly, some of the enzyme's activity reappears, which indicates that the information necessary for proper folding is contained in the primary structure (amino acid sequence).

4. Disulfide bonds are important structural components of proteins. They form when the sulfhydryls of two cysteines are brought together in close proximity. Some chemicals, such as mercaptoethanol, can reduce the disulfides (between cysteine residues) in proteins to sulfhydryls. In the process of transferring electrons to the cysteines, the sulfhydryls of mercaptoethanol become converted to disulfides. Treatment of RNase with mercaptoethanol reduces RNAse's disulfides to sulfhydryls. Subsequent treatment of RNase with urea disrupts hydrogen bonds and allows the protein to be denatured.

5. Interestingly, removal of the mercaptoethanol and urea from the solution allows RNase to refold, reestablish the correct disulfide bonds, and regain activity. Clearly, the primary sequence of this protein is sufficient for it to be able to refold itself to the proper configuration.

6. Other forces besides disulfide bonds that help to stabilize tertiary structure of proteins include hydrogen bonds, metallic bonds, ionic bonds, and hydrophobic bonds.

7. Chemicals that can disrupt some of these forces include urea or guanidinium chloride (disrupts hydrogen bonds), protons (ionic bonds), and detergents (hydrophobic bonds). In addition, dithiothreitol (DTT) can break disulfide bonds and make sulfhydryls.

8. Proteins sometimes have amino acids in them that are chemically modified. Chemical modification of amino acids in proteins almost always occurs AFTER the protein is synthesized (also described as post-translational modification). Examples include hydroxyproline and hydroxylysine in collagen, gamma carboxyglutamate, and phosphoserine. Modification of the collagen residues allows for the triple helical structure of the protein and for the strands to be cross-linked (an important structural consideration).

9. Hemoglobin (and many other proteins) have multiple polypeptide subunits. Interactions between the subunits include disulfide bonds, ionic interactions, hydrogen bonds, hydrophilic, and hydrophobic interactions. Modification of the quaternary structure of a protein may have the same effects as modification of its tertiary structure - alteration of its function/activity.

10. Folding is necessary for proteins to assume their proper shape and function. The instructions for folding are all contained in the sequence of amino acids, but we do not yet understand how those instructions are carried out rapidly and efficiently. Levinthal's paradox illustrates the fact that folding is not a random event, but rather based on an ordered sequence of events arising from the chemistry of each group.

11. Proper folding of a protein is essential. Cells have complexes called Chaperonins that help some proteins to fold properly. Misfolding of proteins is implicated in diseases such as mad cow disease and Creutzfeld-Jacob disease in humans. The causative agent in these diseases is a "contagious" protein that is coded by the genome of each organism. When it doesn't fold properly, it helps induce other copies of the same protein to misfold as well, resulting in plaque-like structures that destroy nerve cells.

Explanation:

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Select the correct answer.
konstantin123 [22]

Answer:

A.  not wearing goggles when breaking a rock with a hammer

Explanation:

You could get extremely hurt if you are not wearing goggles while doing lab work.

6 0
3 years ago
Can someone please help me with this!!!<br><br> ( I chose to stop using water bottles )
Dafna1 [17]

Answer:

Flushing goldfish down the toliet

Explanation:

This would help the planet because goldfish are a very evasive species that has been harming our natural enviroments lakes and rivers. Ever since people have been flushing them down the toliet including me since I've had over six they have been finding their ways into our ecosytem and damaging nature. You may think that goldfish are a cute and small pet species to keep in a fish tank but the fish can grow in the right conditons up to 16.1 inches long and can top over five pounds in the wild. Unfortunately most goldfish never thrive like this in fish tanks due to nasty inadequate housing and feeding conditions. And most do not live up to their expected life span in the wild of 15 to even thirty years due to their living conditons. Did you know, goldfish will actually jump out of their tank in a final desperate search for better living conditions and enviroment to live in to meet their physiological needs. But lets get back to the problem so don't be to quick to feel sorry for them, when people flush them down the toliet they repopulate somehow in our lakes and rivers. Even through, it is not clear how they got there, which the suspected culprit is the sewer system. They threaten the natural enviroment tho because they are obnivores and they eat a mixtures of plants and animal specimen. You are probrably thinking why is this a problem, well its because goldfish are particullary greedy eaters and will eat, eat, and feast on the natural envrioment they infestated. And the waste they leave on the enviroment will promote the growth of algae which could cause an extent of enviromental damage. Of course goldfish are not impacted by this algae growth for adaptation reasons which shield them. This is not the main problem tho the main problem of this is that female goldfish can produce up to 1000 eggs at a time. And to make things worse unlike other fish species where the parents of the eggs leave the eggs for predaetors and well the elements of nature the goldfish instead guard their nest foriciously from predaetors that eat fish eggs in which effectively shields the populations young from danger. And to just add to the chaos the goldfish sadly have no real natural predaetor in the unitedstates which just causes more problems since they have no one killing them. And did I mention that they could live up to a real possibility of thirty years. And that they are forocious eaters that could eat a variety of types of foods. All of these facts in the end lead to two things first stop flushing your pet goldfish down the toliet and secondly now you know how golfish impact our planet.

Give brainliest please it took me over thirty minutes of thinking!

4 0
3 years ago
How many atoms are in 0.650 mole of zinc?<br> NEED TO KNOW ASAP PLEASE
ryzh [129]
There are
4.517
⋅
10
23
atoms of Zn in 0.750 mols of Zn.
5 0
3 years ago
По сссстото пъпси и спп.<br> a. 120 mm =<br> What is 120 milliters to meters
Vera_Pavlovna [14]
120mm is equal to 0.12 meters
3 0
3 years ago
A chemical equation frequently indicates all of the following except the...
dalvyx [7]

Answer:

i think the answer is D.

Explanation:

for the chemical equation in all the other answers are true so therefor d is not.

4 0
2 years ago
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