test123 -BC 1 correct

The immunoglobulin fold motif in antibodies is composed primarily of which type(s) of secondary structure?

strands

Neuroglobin is a member of the globin family found in neurons. It is a monomeric protein that helps protect the brain from hypoxia (low O2). Identify the CORRECT statement(s) about neuroglobin below. i) It binds O2 with a hyperbolic binding curve. ii) It binds O2 with a sigmoidal binding curve. iii) It binds O2 with higher affinity than hemoglobin. iv) It binds O2 with lower affinity than hemoglobin. ------ A) i and iii B) i and iv C) ii and iii D) ii and iv E) None of the statements is correct.

A) I and iii

Myosin moves relative to actin filaments by using energy derived from the hydrolysis of which molecule?

ATP

2,3-bisphosphoglycerate (BPG) is an _____?____ modulator.

Allosteric

Myosin obtains its high tensile strength due to its composition of_____?____.

Alpha helices supercoiled around each other in a left-handed coiled coil.

Which part of the IgG molecule is NOT involved in binding to an antigen?

Fc

Two proteins bind to the same ligand, and protein A has half of its binding sites occupied when the ligand concentration is 5 mM, while protein B has half of its binding sites occupied when the ligand concentration is at 3 mM. Which protein binds the ligand more strongly, and what is the dissociation constant for that protein-ligand interaction?

Protein B binds more strongly, and Kd = 3 mM.

The binding of oxygen to hemoglobin stabilizes the __?___ of the protein due to interactions between __?___ residues in the center of the multisubunit complex.

R state; His

8b. CO binding to hemoglobin is (reversible or irreversible?).

Reversible

The energy that is released by the hydrolysis of ATP by actin is used for_____?____.

actin filament assembly.

Cooperative binding of a ligand to a protein is usually a form of _____?____.

allosteric interactionMMM

0c. Hemoglobin and myoglobin are both primarily composed of __?___.

alpha helices

The Fab regions of an antibody are made of which protein chain?

both a light chain and a heavy chain containing variable and constant regions

Antigens typically bind to antibodies via which type of interactions?

both hydrophobic interactions and hydrogen bonding

Muscle fibers are made up of which protein(s)?

both myosin and actin

You are attempting to crystallize the head group of a myosin-like muscle protein from a newly discovered vertebrate organism. Assuming that the protein structure is similar to other vertebrate myosins, which enzymes should you use to remove the myosin-like head group from the rest of the myosin-like protein?

both trypsin and papain

Conversion of CO2 in the blood into the more soluble form of HCO3ñ is catalyzed by which enzyme?

carbonic anhydrase

The coordinated nitrogen atoms in the heme prosthetic group have _____ character, which prevents conversion of the heme iron from the _____ state to the _____ state.

electron-donating; Fe2+; Fe3+

An individual molecular structure within an antigen to which an individual antibody binds is as a(n)_____?____.

epitope.

Antibodies bind to antigens via ____?___.

induced fit.

The binding site of a protein is complementary to a specific ligand due to which characteristics of the binding site? (4)

its size, its shape, its charge, its hydrophobicity

0c. Cooperative binding of a ligand to a protein results in a _____?____ curve.

sigmoidal binding

8c. The binding of one CO molecule to hemoglobin makes __?___.

the binding of other CO molecules more efficient.

8d. More than ____?___ different antibodies can be produced in humans.

00 million

Which statement about antigen-antibody interactions is CORRECT?

Antigens bind to antibodies through induced fit.

Which immune-system cells are responsible for producing antibodies?

B cells

The change in hemoglobin-binding affinity for oxygen due to changing pH and CO2 concentration in the blood is known as the_____?____.

Bohr effect.

8c. Antibodies can be soluble, membrane-bound, or both?

Both soluble and membrane bound

38a. __?___ binds to hemoglobin better than O2 does.

CO

Which molecule binds MOST strongly to the heme iron?

CO

CO binds more strongly to the heme iron than O2 does due to which reason?

CO binds to the heme iron perpendicular to the porphyrin ring, allowing maximum electron orbital overlap between CO and Fe2+.

Hemoglobin is involved in the transport of which ion and/or molecule through the blood?

CO2, O2, and H+

Nerve impulses control muscle contractions by releasing which ion?

Ca2+

Hemoglobin binds to O2 __?___; myoglobin __?___.

Cooperatively; does not bind cooperatively

The covalent bonds that hold antibody structures together are formed from which amino acid side chains?

Cys

A test where antibodies are used to quantitatively detect the presence of antiviral antibodies in human blood samples is referred to as_____?____.

ELISA.

Macrophages bind to the __?___ region of IgG antibodies, thereby triggering phagocytosis of antibody-antigen complexes.

Fc

A significant contribution to the change in hemoglobin affinity for oxygen from pH 2 to pH 6 is due to a change in the protonation state of which amino acid side chain?

His

Which amino acid in hemoglobin is involved in coordinating iron in addition to the heme prosthetic group?

His

During muscle contraction, the _____ of myofibrils contract and the _____ move closer together due to the movement of myosin thick filaments along actin thin filaments.

I bands; Z disks

Which antibody is principally found in saliva, tears, and breast milk?

IgA

Which type of antibody interacts with basophils and plays a role in the allergic response?

IgE

You are working as a scientist in an antibody-design group at a biologics company. Based on your knowledge of antibodies, which region(s) on which antibody type should you target for your design efforts to develop new antigen-binding capabilities in soluble antibodies?

IgG antibodies, variable light and variable heavy chain regions

Which antibody is secreted as a cross-linked pentamer?

IgM

Sickle cell anemia is often lethal in childhood, yet the gene for sickle cell hemoglobin persists in the human population. Why this is the case?

Individuals with sickle cell trait are protected from malaria infection, while normal individuals are not.

Antibodies against a specific antigen can be injected into a person to provide passive immunity. For which reason is this NOT as effective as the process of vaccination with that antigen?

Injection of antibodies does not provide long-lasting immunity, and vaccination with antigens triggers a clonal selection of B cells and cytotoxic T cells.

0b. Hemoglobin is a __?___ protein; myoglobin __?___.

Multisubunit; is not a multisubunit protein

You are studying a muscle disorder where an individual's muscles have a higher tendency to be overextended due to a protein mutation. This mutation is likely to be in which protein?

Nebulin

If a developing fetus made beta hemoglobin subunits instead of gamma hemoglobin subunits, what would be MOST likely to occur?

The fetus would not be able to extract O2 from its mother's blood as effectively.

You are examining the effects of a mutation in the proximal histidine of a heme-containing protein. This mutation has changed the histidine into an alanine. Based on your knowledge of the role of heme in hemoglobin and how it is coordinated in the protein, what is the MOST likely effect of the mutation?

The iron in heme will have two uncoordinated bonds.

. The larger the Ka, _____?____.

The larger the Ka, the smaller the Kd (dissociation constant).

Which generalization concerning motor proteins convert _____?____ into _____?____.

They convert chemical energy into kinetic energy

0b. Cooperative binding of a ligand to a protein results in _____?____ plot.

a nonlinear Hill Plot

The predominant structural feature in myosin molecules is_____?____.

an alpha helix.

A monoclonal antibody differs from a polyclonal antibody in that monoclonal antibodies_____?____.

are synthesized by a population of identical, or "cloned", cells.

The interactions of ligands with proteins _____?____.

are usually transient.

. An allosteric interaction between a ligand and a protein is one in which_____?____.

binding of a molecule to a binding site affects binding properties of another site on the protein.

Carbon monoxide (CO) is toxic to humans because it_____?____.

binds to the Fe in hemoglobin and prevents the binding of O

Tropomyosin and troponin prevent muscle contractions in the absence of Ca2+ because they_____?____.

block the myosin head binding sites on actin filaments.

During muscle contraction, hydrolysis of ATP results in a change in the_____?____.

conformation of myosin.

2,3-bisphosphoglycerate (BPG) _____?____the affinity of hemoglobin for oxygen.

decreases

Which types of covalent bonds hold antibody structures together?

disulfide bonds

Sickle cell anemia is caused by a single mutation in the hemoglobin protein from a Glu to a Val, which results in what alteration in the hemoglobin subunits?

fewer negative charges and formation of a hydrophobic contact point

4 Small molecules attached to larger protein structures that elicit an immune response are referred to as_____?____.

haptens

A person who is HIV-positive asks you why they have reduced immune system function. You tell them that the most likely reason is due to a deficiency of which cells that are targets of HIV viral infections?

helper T cells

The fundamental cause of sickle-cell disease is a change in the structure of_____?____.

hemoglobin.

The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein because of _____ interactions between molecules.

hydrophobic

You want to purify a specific soluble protein from a solution of lysed cells so that you can conduct biochemical tests of the protein's function. To best achieve this, which type of antibody would be MOST effective to use in your affinity purification?

monoclonal IgG

8d. The binding of one CO molecule to hemoglobin makes the binding of O2 molecules __?___.

more efficient.

58b. Antibodies typically bind to antigens ____?___ than enzymes ____?___.

more strongly; bind to substrates

Cooperative binding of a ligand to a protein _____?____ occurs in enzymes..

often

. When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are occupied by.... _____?____.

one O2 molecule and one heme atom.

. In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by_____?____.

oxygen binding.

Patients with chronic hypoxia (low O2 levels) due to decreased lung function may adapt by increasing their circulating BPG levels. Predict which outcome will be TRUE for such a patient.

p50 for O2 will be increased.

. A prosthetic group of a protein is a nonprotein structure that is _____?____.

permanently associated with the protein.

0a. Cooperative binding of a ligand to a protein is usually associated with _____?____.

proteins with multiple subunits.

Which event triggers a "power stroke" in myosin?

release of Pi (phosphate)

If myosin head groups were unable to hydrolyze ATP due to an alteration in the protein structure but could still bind and release ADP and inorganic phosphate (Pi), which step in the actin-myosin cycle would NOT take place?

repositioning of the myosin head group on the actin filament

Individual contractile units in muscle fibers are called_____?____.

sarcomeres.

. 2,3-bisphosphoglycerate (BPG) binds at a distance from _____?____.

the heme groups of hemoglobin

0d. Hemoglobin and myoglobin both contain __?___.

the heme prosthetic group

A Hill coefficient (nH) of 2 indicates that_____?____.

there is positive cooperativity in ligand binding.

Which class of proteins includes the LARGEST polypeptide chains discovered to date in humans?

titins

Which protein undergoes a conformational change upon interacting with Ca2+, leading to stimulation of muscle contraction?

troponin

IgG antibodies have __?___ binding site(s) that is/are made up of the __?___ regions of the light and heavy chains.

two; variable

. Myoglobin and the subunits of hemoglobin have_____?____.

very similar tertiary structures, but different primary structures.

2,3-bisphosphoglycerate (BPG) binds with lower affinity to _____?____ than to _____?____.

with lower affinity to fetal hemoglobin than to adult hemoglobin

2,3-bisphosphoglycerate (BPG) is normally found associated with _____?____.

with the hemoglobin extracted from red blood cells