Online Assignment CH 18

What type of secondary structure is characteristic of (a) the α-keratins and (b) silk fibroin, an alpha-helix or a Beta-pleated sheet? Be sure to answer all parts.

(A). alpha helix (b). beta pleated sheet

Complete the general structure of an L− α −amino acid by assigning groups to the correct positions. This L-alpha amino acid should be drawn at physiological pH. Be sure to include formal charges. Use R for the side chain.

1: H3N+ 2: COO- 3. H 4: R

How do the primary structures of normal hemoglobin and sickle cell hemoglobin differ? A glutamic acid residue in normal hemoglobin is replaced by a valine residue in sickle cell hemoglobin. A valine acid residue in normal hemoglobin is replaced by a glutamic acid residue in sickle cell hemoglobin. There are four heme groups in normal hemoglobin whereas there are only three heme groups in sickle cell hemoglobin. There are three heme groups in normal hemoglobin whereas there are 4 heme groups in sickle cell hemoglobin. Both A and C are correct.

A glutamic acid residue in normal hemoglobin is replaced by a valine residue in sickle cell hemoglobin.

As you increase the temperature of an enzyme-catalyzed reaction, the rate of the reaction initially increases. It then reaches a maximum rate and finally dramatically declines. Keeping in mind that enzymes are proteins, how do you explain these changes in reaction rates? Select the single best answer. At first the rate of reaction increases because the temperature increase causes an increase in the number of collisions between the enzyme and the substrate. At some point the rate of reaction dramatically decreases because the enzyme denatures due to the high temperature. At first the rate of reaction increases because the temperature increase causes a decrease in the number of collisions between the enzyme and the substrate. At some point the rate of reaction dramatically decreases because the enzyme denatures due to the high temperature. At first the reaction rate increases because the temperature increase causes the enzyme to denature. At some point the rate of reaction dramatically decreases because the enzyme and substrate collisions increase. At first the reaction rate increases because the temperature increase causes the enzyme to coagulate. At some point the rate of reaction dramatically decreases because the enzyme and substrate collisions increase.

At first the rate of reaction increases because the temperature increase causes an increase in the number of collisions between the enzyme and the substrate. At some point the rate of reaction dramatically decreases because the enzyme denatures due to the high temperature.

Write an equation representing the binding to, and release of, oxygen from hemoglobin. Use Hb as the abbreviation for hemoglobin in your equation. Click in the answer box to activate the palette.

Hb + 4O2 <--> Hb(O2)4

Why are hydrogen bonds so important to protein structure? Select all that apply. It maintains the secondary structure of a protein. It contributes to the stability of the tertiary and quaternary levels of structure. It maintains the primary structure of a protein. It contributes to the stability of the primary and secondary levels of structure.

It maintains the secondary structure of a protein. It contribute to the stability of the tertiary and quaternary levels of structure

What allows for the transfer of oxygen from the bloodstream of a mother to the bloodstream of fetus? here is a partial pressure difference between the O2 of the mother and the O2 of the fetus. The blood vessels of the fetus are larger than that of the mother. The hemoglobin of the fetus is different than adults and has a greater affinity for oxygen than the hemoglobin of the mother. The hemoglobin of the fetus is larger than the hemoglobin of the mother.

The hemoglobin of the fetus is different than adults and has a greater affinity for oxygen than the hemoglobin of the mother.

How does the primary structure of a protein determine its three-dimensional shape? Select the single best answer The primary structure promotes covalent bonds between the thiol-containing amino acids. The primary structure determines the locations of the R groups along the protein chain. The primary structure disrupts the hydrogen bonds between the polar R groups of the polar amino acids. The primary structure causes the Van der Waals forces between the R groups of nonpolar amino acids that are hydrophobic.

The primary structure determines the locations of the R groups along the protein chain.

Coagulation occurs when a protein unfolds and becomes entangled. True of False

True

What is a transport protein? Select the single best answer. A protein that transports materials across the cell membrane or throughout the body. A protein that controls many aspects of cell function, including metabolism and reproduction. A protein that transports materials in the bloodstream. A protein that serves as a source of amino acids for embryos or infants. A protein that provides mechanical support to large animals and provides them with their outer coverings.

a protein that transports materials across the cell membrane or throughout the body.

What is a glycoprotein? Select the single best answer. a biological catalyst a specific protein molecule produced by specialized cells of the immune system in response to foreign antigens a protein that is necessary for all forms of movement a protein with sugars as prosthetic groups

a protein with sugars as prosthetic groups

What determines the primary structure of a protein? α-helix hydrogen bonding between amide hydrogens and carboxyl oxygens amino acid sequence of the chain ionic bonds between the R group of oppositely charged amino acids None of the choices are correct.

amino acid sequence of the chain

Define the term nonessential amino acid. Select the single best answer. an amino acid that is not found in the body an amino acid that is not needed by the body an amino acid that cannot be synthesized by the body an amino acid that can be synthesized by the body

an amino acid that can be synthesized by the body

Blood proteins will become denatured when they develop an overall negative charge. This would be the result of which of the following? a lowering of pH an increase in pH a lowering of the partial pressure of oxygen an increase in the partial pressure of oxygen poor circulation

an increase in pH

What two functional groups characterize the amino acids found in human proteins? carboxylate group and an amino group an amide group and an amino group a primary amine group and an aldehyde group a primary amine group and a ketone group an amino group and an aldehyde group

carboxylate group and an amino group

a fully vegetarian diet cannot provide a complete source of protein. true or false

false

Which hydrophobic amino acid contains a sulfur atom in its side chain? alanine valine phenylalanine proline methionine

methionine

What is the difference between sickle cell disease and sickle cell trait? Select all that apply. people with sickle cell trait may pass sickle cell anemia to their offspring; people with sickle cell disease cannot pass sickle cell anemia to their offspring people with sickle cell disease do not exhibit serious side effects; people with sickle cell trait exhibit all symptoms of sickle cell anemia people with sickle cell trait carry two genes for sickle cell anemia; people with sickle cell disease carry one gene for sickle cell anemia people with sickle cell trait carry one gene for sickle cell anemia; people with sickle cell disease carry two genes for sickle cell anemia people with sickle cell disease may pass sickle cell anemia to their offspring; people with sickle cell trait cannot pass sickle cell anemia to their offspring people with sickle cell trait do not exhibit serious side effects; people with sickle cell disease exhibit all symptoms of sickle cell anemia

people with sickle cell trait carry one gene for sickle cell anemia; people with sickle cell disease carry two genes for sickle cell anemia people with sickle cell trait do not exhibit serious side effects; people with sickle cell disease exhibit all symptoms of sickle cell anemia

How is the following amino acid categorized? The structure shows its form at pH = 7. hydrophobic polar, acidic polar, basic polar, neutral none of the above

polar, neutral

What is the purpose of the R groups of the amino acids? Select the single best answer. the formation and maintenance of only the quaternary structures of proteins the formation and maintenance of the tertiary and quaternary structures of proteins the formation and maintenance of only the tertiary structures of proteins the formation and maintenance of the primary and secondary structures of proteins

the formation and maintenance of the tertiary and quaternary structures of proteins

What is the function of heme in hemoglobin and myoglobin? Select the single best answer. to transport hydrogen to transport oxygen to bind protein to bind to molecular hydrogen to bind to molecular oxygen to transport protein

to bind to molecular oxygen

What is the function of hemoglobin? Select the single best answer. to carry oxygen from the lungs to tissues to carry oxygen to the lungs to store oxygen in the skeletal muscle to bind to molecular oxygen

to carry oxygen from the lungs to the tissues

Similarities and differences in the primary structures of a protein isolated from two different organisms can provide an estimate of the evolutionary relationship between the two organisms. True or False

true