In the cytosol, most protein folding _________?A. Is notB. Isspontaneous, meaning that most proteins ________ refold following denaturation.A. CannotB. Can Learn It: Explain the role of chemicalattractions in protein folding anddenaturation.Every protein is a three-dimensional molecule that has a specificshape. This shape, the structure of the protein, is essential to thefunction of that protein. For example, if a protein functions as anenzyme, catalyzing a reaction, it must have the right shape to take upthe reactants and allow them to be converted to products. The maindetermining factor of the shape of a given protein is the sequence ofamino acids that make up the polypeptide chain(s) of the proteinitself. Each of the twenty amino acids that make up a protein has aside chain, known as the R group, that gives it unique properties. Theway that these R groups interact with one another and the outsideenvironment causes the protein to fold into the specific structure thatenables its function.The amino acids are grouped into four categories based on theproperties of their side chains. The largest of these groups is thehydrophobic amino acids. The side chains of these amino acids arenonpolar and are hydrophobic, or "water-fearing." The second-largestgroup of amino acids are those that have electrically charged sideM D-Learn It: Explain the role of chemicalattractions in protein folding anddenaturation..The interactions described are all relatively weak and are vulnerableto a process called denaturation. During protein denaturation, aprotein loses its structure, and therefore cannot perform its function.Conditions such as heat disrupt interaction like hydrogen bondsbetween R groups, while high salt, acidic, or basic conditions candisrupt the formation of salt bridges. These forces are usually notstrong enough to break the covalent bonds that join the amino acidstogether. Denatured proteins are often marked for destruction sothat the amino acids can be recycled into new proteins.One amino acid, cysteine, foims very strong, covalent bonds withother cysteines. This is due to the presence of a sulfur atom in theside chain of this amino acid. These sulfur groups are capable offorming covalent bonds, known as disulfide bonds, with other sulfur"groups. These bonds are very difficult to break and are often found inhigh numbers in proteins from organisms that live in hightemperatures because they are more resistant to denaturation in thepresence of high heat.You may be wondering why proteins cannot just refold afterLearn It: Explain the role of chemicalattractions in protein folding anddenaturation.group of amino acids are those that have electrically charged sidechairis at physiological pH. Some of these amino acids have a positivecharge, while others have a negative charge. The third group ofamino acids includes those whose side chains are polar, but notelectrically charged. Finally, there is a group of "special case" aminoacids, whose side groups have properties that don't fit into the othergroups. One of these amino acids, cysteine, plays a special role inprotein structure, and we will come back to it later.The R groups of the polypeptide interact with one another accordingto the rules of chemical bonding that you've already learned. 4Opposite charges attract one another, so positive and negative sidechains may move toward each other, forming what are known as saltbridges. Polar side chains tend to interact with water. Remember thatthe cytosol is made of mostly water, so you will often find theseamino acids on the outside of a protein. Hydrophobic nonpolar sidechains tend to fold away from the cytosol, toward the inside of theprotein. Some side groups are also able to form hydrogen bonds withother side groups, while others interact via Van der Waals attractions.MOLearn It: Explain the role of chemicalattractions in protein folding anddenaturation..Cother cysteines. This is due to the presence of a sulfur atom in theside chain of this amino acid. These sulfur groups are capable offorming covalent bonds, known as disulfide bonds, with other sulfurgroups. These bonds are very difficult to break and are often found inhigh numbers in proteins from organisms that live in hightemperatures because they are more resistant to denaturation in thepresence of high heat.'You may be wondering why proteins cannot just refold after.denaturation because the amino acid sequence remains intact. This isbecause proteins do not usually fold on their own in the cytosol,During protein synthesis, specialized proteins, known as chaperones,protect the protein and provide an environment that is conducive toprotein folding. Once the protein is in the cytosol, or whatever cellularcompartment that it is targeted to, the environment is no longerfolding-friendly, so once the protein loses its shape it is difficult, oftenimpossible, to refold.

In the cytosol, most protein folding is spontaneous, meaning that most proteins can refold following…

Answered: In the cytosol, most protein folding…

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...