Must be in complete sentences Must be grammatically and factually accurate The p
ID: 141271 • Letter: M
Question
Must be in complete sentences Must be grammatically and factually accurate The physical structure of a protein often refilects and affects its function. 2. Describe THREE types of bonds/interactions found in proteins. For each type, describe a 3. Protein structure can be affected by environmental conditions. Identify TWO factors and 4. Abnormal hemoglobin is the identifying characteristic of sickle cell anemia. Explain the role in determining protein structure. explain the mechanism by which each affects protein structure. molecular basis of the abnormal hemoglobin. Explain why the sickle cell allele is selected for in certain areas of the worldExplanation / Answer
2. The main three types of chemical bonds/interactions found in proteins are:
DESCRIPTION: A peptide bond is a covalent bond found in the primary structure of a protein. The primary structure is the sequence of amino acids which is connected by the peptide bond. A peptide bond is formed between two amino acids when the carboxyl group of one amino acids reacts with the amino group of the other amino acid, releasing a molecule of water.This is the dehydration reaction and usually occurs between amino acids.Peptide bond between two amino acids form dipeptide and in this way, a long chain of protien is formed with the help of peptide bond. The formation of the peptide bond consumes energy, which, in organisms, is derived from ATP. A peptide bond can be broken by hydrolysis (the addition of water). In living organisms, the process is normally catalyzed by enzymes known as peptidases or proteases.
ROLE: The peptide bond is the bond used by amino acids in the primary sequence. The sequence of amino acids connected by the peptide bonds is called a polypeptide chain. Peptides and proteins are chains of amino acids held together by peptide bonds. These chains are then folded due to various forces in order to become proteins.
DESCRIPTION: A hydrogen bond is a weak type of chemical bond common in living organisms. This type of bond involves a hydrogen atom from a polar covalent bond of another molecule (partial positive charge) that is attracted to a strong electronegative atom that also is apart of another molecule (partial negative charge). Secondary structure is formally defined by the pattern of hydrogen bonds between the amino hydrogen and carboxyl oxygen atoms in the peptide backbone. Protein secondary structure is the three dimensional form of local segments of proteins.
ROLE: A hydrogen bond is a partially electrostatic attraction between a hydrogen (H) which is bound to a more electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F), and another adjacent atom bearing a lone pair of electrons. Hydrogen bond is present in the secondary structure of a protein. The secondary structure of a protein includes alpha-helices and B-pleated sheets that are separately held together by hydrogen bonds. Alpha-helices have a curled shape while B-pleated sheets are folded alongside each other in an antiparallel shape.
DESCRIPTION: Ionic bonds are formed between two oppositely charged ions, such as a cation and anion. The ionic bonds are formed between the ionized acidic or basic groups of amino acids. The atom who lost electrons becomes a cation, a positively charged ion and the atom who gained electrons becomes a anion, a negatively charged ion. Ionic bonds are strong interactions that will not be easily disrupted by heat. Ionic bonds are disrupted by changes in pH and by increasing the concentration of salts in the protein's environment.
ROLE: The tertiary structure of a protein is fashioned by many stabilizing proteins due to bonding interactions of side chain groups of amino acids. Ionic bonds between the positively and negatively charged sites in amino acid side chains, help stabilize the tertiary structure of protein. The chemistry of amino acid side chains is critical to protein structure because these side chains can bond with one another to hold a length of protein in a certain shape or conformation. Charged amino acid side chains can formionic bonds, and polar amino acids are capable of forming hydrogen bonds.
3.
pH - Several amino acids contain sidechains with functional groups that can readily gain or lose a proton. Changes in pH would lead to a change in the charge of the amino acids, leading to charge-charge repulsion or attraction between previously non-interacting amino acid residues. Or, such charge interactions could be removed. Changes in pH can disrupt both hydrogen bonds and ionic bonds inside of a protein.
Temperature - High temperatures can lead to protein denaturation. Heat can disrupt hydrogen bonding and hydrophobic interactions. Heating of protien can eventually cause the conversion of protien to largely unfolded state. Changes in pH instead disrupt hydrogen bonds and ionic bonds, whereas hydrophobic interactions may be disrupted by heat.
4. When oxygen tension is reduced, the deoxygenated sickle cell hemoglobin (Hb S) molecules undergo polymerization that leads to the formation of long fibers which cause the red blood cell to assume a sickle-like shape. The basic physical mechanism responsible for sickling is linear aggregation of deoxygenated molecules of sickle hemoglobin (Hb S) into long fibers within erythrocytes. The disease is caused by a change in a single amino acid difference in the beta chain of hemoglobin.
Sickle cell anemia affects approximately 70,000 Americans, almost exclusively those with African ancestry. This recessive mutation is one amino acid difference in an allele of hemoglobin. The mutation is very debilitating and eventually fatal in homozygous recessive condition. The heterozygous condition confers some advantage in malaria country, especially to the young, by crenelating a good percentage of the red blood cells which make them almost impervious to the Plasmodium protist.
The disease is caused by a change in a single amino acid difference in the beta chain of hemoglobin. Individuals with two copies of the sickle form of the gene have sickle cell anemia. Heterozygotes individuals with one normal and one mutant copy of the gene appear normal and do not manifest the disease except under very stressful conditions; however, they are carriers. If two carriers have a child, the child has a twenty-five percent probability of receiving two copies of the sickle form and having the anemia. Approximately ten percent of African Americans are carriers. In Africa itself, the frequencies of the disease and carriers are even higher. The frequency of the sickle cell allele is higher in African populations than in African Americans is due to both this selection and the genetic mixing between whites and blacks in the United States.
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