Chapter 7 Part 2

How many antigen-binding sites are present on an IgM molecule? 2 4 10 16 25

10

IgG is the most common immunoglobulin in the circulatory system and in the extravascular fluid. It is composed of two light chains and two heavy chains. What is the approximate molecular mass of an IgG molecule? 23 kDa 75 kDa 150 kDa 360 kDa 950 kDa

150 kDa

How many antigen-binding sites are present on an IgG molecule? 1 2 3 4 5

2

IgG is one of five classes of antibodies that can be produced by our immune system. IgGs have a molecular mass of approximately 150 kDa, what is their subunit composition? 2 light chains and 2 heavy chains 2 light chains, 2 heavy chains, and a J chain 4 light chains, 4 heavy chains, and a J chain 6 light chains, 6 heavy chains, and a J chain 10 light chains, 10 heavy chains , and a J chain.

2 light chains and 2 heavy chains

Humoral immunity refers to that part of the immune response that is mediated by T lymphocytes. antibodies. antigens. the thymus. the skin.

antibodies.

How many different classes of antibodies are produced by the human immune system? 1 2 3 4 5

5

Which of the following statements about actin is not true? Actin is the most abundant cytoplasmic protein in many cell types. Actin forms microfilaments in many cell types. Actin plays an important role in endocytosis. Actin is present only as monomers in nonmuscle cells. Actin filaments are dynamic, they grow at one end and they lose subunits at the other end.

Actin is present only as monomers in nonmuscle cells.

Which statement about actin is correct? Actin is expressed only in muscle. Actin is expressed at low levels in most cells. No known function has been described for actin in nonmuscle cells. Nonmuscle cells only contain G actin. Actin is the most abundant cytoplasmic protein in many cell types.

Actin is the most abundant cytoplasmic protein in many cell types.

Which of the statements about muscle contraction is correct? During muscle contraction the sarcomere becomes shorter. During muscle contraction the I band becomes shorter. During muscle contraction the H zone becomes shorter. During muscle contraction the distance between the Z disk and the M disk becomes shorter. All of the answers above are correct.

All of the answers above are correct.

Which statement about myosin is not true? Myosin is a heterohexamer. Myosin contains two globular heads. Myosin contains six different polypeptides Myosin aggregates to form thick filaments All of the answers above are true of myosin

All of the answers above are true of myosin

Select the statement that best matches the following: Monoclonal antibodies Fragments of proteolyzed IgG that have antigen-binding sites. Cells that mediate humoral immunity. Antibodies produced by hybridoma cells. Diverse group of proteins also known as antibodies. Cells that mediate cellular immunity.

Antibodies produced by hybridoma cells.

Which statement about antigen-binding sites in antibodies is false? An antigen-binding site on an IgG is formed by the amino-terminal ~110 amino acids of a light chain and the amino terminal ~110 amino acids of a heavy chain. An antigen-binding site on an IgG is formed by the variable region of a light chain and the variable region of a heavy chain. The antigen-binding site is composed of two Ig folds. Antigen-binding specificity is determined by the sequences of the hypervariable sequences in both the light chain and the heavy chain. Antigen binding specificity is determined exclusively by the sequences in the carboxy-terminal ~110 amino acids in the light chain and the heavy chain

Antigen binding specificity is determined exclusively by the sequences in the carboxy-terminal ~110 amino acids in the light chain and the heavy chain

Humoral immunity is mediated by soluble molecules. Which cell type produces the soluble molecules that carry out the humoral immunity? T cells B cells macrophages neutrophils monocytes

B cells

How are IgG molecules able to recognize a wide variety of different antigens? Both light and heavy chains have hypervariable sequences that form the antigen binding site. Each light chain has hypervariable sequences that form the antigen binding site, while the heavy chains do not vary. Each heavy chain has hypervariable sequences that form the antigen binding site, while the light chains do not vary. The Fc portion has hypervariable sequences that form the antigen binding site.

Both light and heavy chains have hypervariable sequences that form the antigen binding site.

Select the statement that best matches the following: Troponin C Calcium binding protein. Functional unit of the myofibril. Chemical energy source for muscle contraction. Major component of the thick filament of the myofibril. Major component of the thin filament of the myofibril.

Calcium binding protein.

How is muscle contraction stimulated by calcium ions? Calcium ions are released from the sarcoplasmic reticulum and bind to actin, promoting its binding to myosin. Calcium ions are released from the sarcoplasmic reticulum and bind to tropomyosin, stimulating its ATPase activity. Calcium ions are released from the sarcoplasmic reticulum and bind to myosin, stimulating ATPase activity. Calcium ions are released from the sarcoplasmic reticulum and bind to troponin C, promoting the binding of myosin to actin

Calcium ions are released from the sarcoplasmic reticulum and bind to troponin C, promoting the binding of myosin to actin

Select the statement that best matches the following: T lymphocytes, or T cells Fragments of proteolyzed IgG that have antigen-binding sites. Cells that mediate cellular immunity. Antibodies produced by hybridoma cells. Cells that mediate humoral immunity. Diverse group of proteins also known as antibodies.

Cells that mediate cellular immunity.

Select the statement that best matches the following: B lymphocytes, or B cells Cells that mediate humoral immunity. Fragments of proteolyzed IgG that have antigen-binding sites. Cells that mediate cellular immunity. Antibodies produced by hybridoma cells. Diverse group of proteins also known as antibodie

Cells that mediate humoral immunity.

Select the statement the best matches that following: ATP Major component of the thick filament of the myofibril. Major component of the thin filament of the myofibril. Calcium binding protein. Chemical energy source for muscle contraction. Functional unit of the myofibril.

Chemical energy source for muscle contraction.

Select the statement that best matches the following: Immunoglobulins Fragments of proteolyzed IgG that have antigen-binding sites. Antibodies produced by hybridoma cells. Cells that mediate humoral immunity. Cells that mediate cellular immunity. Diverse group of proteins also known as antibodies.

Diverse group of proteins also known as antibodies.

Which of the statements about muscle contraction is not true? During muscle contraction the sarcomere becomes shorter. During muscle contraction the I band becomes shorter. During muscle contraction the H zone becomes shorter. During muscle contraction the A band becomes shorter. During muscle contraction the distance between the Z disk and the M disk becomes shorter.

During muscle contraction the A band becomes shorter.

Select the statement that best matches the following: Fab fragments Antibodies produced by hybridoma cells. Diverse group of proteins also known as antibodies. Fragments of proteolyzed IgG that have antigen-binding sites. Cells that mediate cellular immunity. Cells that mediate humoral immunity.

Fragments of proteolyzed IgG that have antigen-binding sites.

Select the statement that best matches the following: Sarcomere Functional unit of the myofibril. Major component of the thick filament of the myofibril. Major component of the thin filament of the myofibril. Calcium binding protein. Chemical energy source for muscle contraction.

Functional unit of the myofibril.

Which of the following statements is not true about IgG? The antigen-binding site is located at the tip of each Fab fragment in a crevice between its VL and VH domains Has a Y-shaped general structure. The heavy chain of an IgG molecule is composed of four similar domains made of beta sheets. Has two antigen binding sites that can recognize and bind different antigens. The antigen binding sites have an immunoglobulin fold motif (a sandwich composed of three- and four-stranded antiparallel sheets that are linked by a disulfide bond).

Has two antigen binding sites that can recognize and bind different antigens.

Which class of antibodies has been implicated in allergic reactions? IgA IgD IgE IgG IgM

IgE

How does the sliding filament model explain the shortening of the sarcomere during muscle contraction? Interdigitating thin filaments slide past each other. Interdigitating thick and thin filaments compress by forming coiled coils. Interdigitating thick filaments slide past each other. Interdigitating thick and thin filaments slide past each other.

Interdigitating thick and thin filaments slide past each other. This accounts for the shortening of the sarcomere during muscle contraction

Select the statement that best matches the following: Myosin Functional unit of the myofibril. Major component of the thick filament of the myofibril. Major component of the thin filament of the myofibril. Calcium binding protein. Chemical energy source for muscle contraction.

Major component of the thick filament of the myofibril.

Select the statement that best matches the following: Actin Functional unit of the myofibril. Chemical energy source for muscle contraction. Major component of the thick filament of the myofibril. Major component of the thin filament of the myofibril. Calcium binding protein.

Major component of the thin filament of the myofibril.

What distinguishes monoclonal antibodies from the antibodies produced in a typical immune response. Monoclonal antibodies have somewhat lower affinity for their antigens. Monoclonal antibodies come from a clonal line of immortalized lymphocytes, and so they form an identical population. Monoclonal antibodies come from memory B cells. Monoclonal antibodies have much higher affinity for their antigens.

Monoclonal antibodies come from a clonal line of immortalized lymphocytes, and so they form an identical population.

Which statement about actin is not true? Actin can bind ATP. Actin filaments are polar (the ends can be distinguished). Actin is a common protein in nonmuscle cells. There are two actin genes, one for F-actin and one for G-actin. Monomeric G-actin polymerizes to form F-actin.

There are two actin genes, one for F-actin and one for G-actin.

Where are disulfide bonds found in immunoglobulins? They are found between the beta sheets in many of the domains. They link the light chains to the heavy chains. They link the heavy chains to each other. They are found in all of the places listed above.

They are found in all of the places listed above.

What is the primary role of nonmuscle actin in eukaryotic cells? They form microfilaments that are part of the cytoskeleton. They form a protective barrier on the surface of the cell. They are stored to provide a source of energy. They are stored in organelles, for future use in muscle function.

They form microfilaments that are part of the cytoskeleton.

What is the basic subunit structure of immunoglobulins? Two identical light chains and two identical heavy chains. Two identical light chains. Two identical heavy chains. One light chain and one heavy chain.

Two identical light chains and two identical heavy chains.

The Ig fold can be described as a globular fold composed of helices. a globular fold composed of a four helix bundle. a globular fold composed of a sandwich. a globular fold composed of barrel. a coiled-coil.

a globular fold composed of a sandwich.

Treadmilling refers to myosin heads walking along actin microfilaments. actin and myosin filaments sliding along each other. actin monomers moving through a microfilament from the (+) end to the (-) end. synthesis and degradation of actin monomers. the interactions between actin and tropomyosin

actin monomers moving through a microfilament from the (+) end to the (-) end.

What are the main bonds or forces that stabilize the dimer formed by two myosin heavy chains? hydrophobic interactions hydrogen-bonds ionic interactions disulfide bonds isopeptide bonds

hydrophobic interactions

Muscle contraction is triggered in response to an increase in the cytoplasmic Ca2+ concentration. in response to a decrease in the cytoplasmic Ca2+ concentration. in response to an increase in the cytoplasmic cAMP concentration. in response to a decrease in the cytoplasmic cAMP concentration. in response to an increase in the cytoplasmic titin concentration.

in response to an increase in the cytoplasmic Ca2+ concentration.

Fab fragments can be generated by reduction of IgG molecules. oxidation of IgG molecules. limited digestion of IgG molecules with papain. combining two light chains. combining two heavy chains.

limited digestion of IgG molecules with papain.

The energy needed to drive muscle contraction comes from ATP hydrolysis that is carried out by G-actin. F-actin. myosin heads. myosin tails. tropomyosin.

myosin heads.

During muscle contraction myosin pulls actin filaments toward the M disk. myosin pushes actin filaments toward the Z disk. actin pulls myosin toward the Z disk. actin pushes myosin toward the M disk. All of the answers above are correct.

myosin pulls actin filaments toward the M disk.

The repeating functional unit in a myofibril is called the A band. the I band. the sarcomere. the H zone. the M disk.

the sarcomere.

Muscle contraction is directly caused by structural changes in actin. structural changes in myosin. thick and thin filaments sliding past each other. structural changes in the Z disk. None of the above is correct.

thick and thin filaments sliding past each other.

During muscle contraction myosin heads walk along thick filaments toward the M disk. walk along thick filaments toward the Z disk. walk along thin filaments toward the M disk. walk along the thin filaments toward the H zone. walk along the thin filaments toward the Z disk.

walk along the thin filaments toward the Z disk.