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Question No. 1 of 10
Instruction: (1) Read the problem statement and answer choices carefully (2) Work the problems on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #1
1. Which of the following statements about amino acids is correct?
(A) The Amino group is the only part that differs between the 20 different amino acids.
(B) The R group is the only part that differs between the 20 different amino acids.
(C) All amino acids can be classified into 1 group: (A) Polar.
(D) All amino acids can be classified into 3 groups: (A) Polar, (B) Negatively charged and (C) Aliphatic.
Feedback
A. Incorrect!
The R group is the only part that differs between the 20 different amino acids.
B. Correct!
The R group is the only part that differs between the 20 different amino acids.
C. Incorrect!
All amino acids can be classified into many groups including: (A) Polar, (B)
Negatively charged, (C) Positively charged, (D) Hydrophobic, (E) Aromatic and (F) Aliphatic.
D. Incorrect!
All amino acids can be classified into many groups including: (A) Polar, (B)
Negatively charged, (C) Positively charged, (D) Hydrophobic, (E) Aromatic and (F) Aliphatic.
Solution
The structural formula of an amino acid is shown at the end of the animation below.
The R group is the only part that differs between the 20 amino acids. All amino acids can be classified into many groups including: (A) Polar, (B) Negatively charged, (C) Positively charged, (D) Hydrophobic, (E) Aromatic and (F) Aliphatic.
on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #2
2. Protein folding ___________.
(A) Is due to the formation of: Disulfide bonds, Hydrogen bonds, and Electrostatic attractions.
(B) Is due to the formation of: Disulfide bonds, Electrostatic attractions, and Van der Waals forces.
(C) Is due to the interaction of the protein with its surrounding lipids.
(D) Is due to the availability of surrounding lipids for stabilization.
Feedback
A. Incorrect!
Is due to the formation of: Disulfide bonds, Hydrogen bonds, Electrostatic attractions, Hydrophobic forces and Van der Waals forces.
B. Incorrect!
Is due to the formation of: Disulfide bonds, Hydrogen bonds, Electrostatic attractions, Hydrophobic forces and Van der Waals forces.
C. Correct!
Is due to the formation of: Disulfide bonds, Hydrogen bonds, Electrostatic attractions, Hydrophobic forces and Van der Waals forces.
D. Incorrect!
Is due to the formation of: Disulfide bonds, Hydrogen bonds, Electrostatic attractions, Hydrophobic forces and Van der Waals forces.
Solution
Protein folding is due to the formation of: Disulfide bonds, Hydrogen bonds, Electrostatic attractions, Hydrophobic forces and Van der Waals forces. Protein folding results in the 3D conformation of the protein which facilitates its function.
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on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #3
3. Which of the following statements about the pKa of an amino acid is correct?
(A) Amino acids in solution at acidic pH exist predominantly as dipolar ions (also called zwitterions).
(B) Amino acids in solution at neutral pH exist predominantly as dipolar ions (also called zwitterions).
(C) In high (basic) pH, the amino group is protonated (-NH3+) and the carboxyl group is not dissociated (-COOH).
(D) In low (acidic) pH, the amino group is protonated (-NH3+) and the carboxyl group is dissociated (-COO-).
Feedback
A. Incorrect!
Amino acids in solution at neutral pH exist predominantly as dipolar ions (also called zwitterions).
B. Correct!
Amino acids in solution at neutral pH exist predominantly as dipolar ions (also called zwitterions).
C. Incorrect!
In low pH, the amino group is protonated (-NH3+) and the carboxyl group is not dissociated (-COOH).
D. Incorrect!
In low pH, the amino group is protonated (-NH3+) and the carboxyl group is not dissociated (-COOH).
Solution
Amino acids in solution at neutral pH exist predominantly as dipolar ions (also called zwitterions). In the dipolar form, the amino group is protonated (-NH3+) and the carboxyl group is deprotonated (-COO-). The ionization state of an amino acid varies with pH.
In low pH, the amino group is protonated (-NH3+) and the carboxyl group is not dissociated (-COOH). As the pH is raised, the carboxylic acid is the first group to give up a proton, inasmuch as its pKa is near 2. The dipolar form persists until the pH approaches 9, when the protonated amino group loses a proton.
on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #4
4. Which of the following statements about the hierarchical structure of proteins is correct?
(A) The Primary structure is the amino acid sequence.
(B) The Primary structure involves helices and strand formation.
(C) The Tertiary structure refers to the formation of tetramers.
(D) The Tertiary structure involves helices and strand formation.
Feedback
A. Correct!
The Primary structure is the amino acid sequence.
B. Incorrect!
The Primary structure is the amino acid sequence.
C. Incorrect!
The Tertiary structure refers to how the protein is folded.
D. Incorrect!
The Tertiary structure refers to how the protein is folded.
Solution
The hierarchical structure of proteins includes:
(A) Primary structure is the amino acid sequence.
(B) Secondary structure involves helices and strand formation.
(C) Tertiary structure refers to how the protein is folded.
(D) Quaternary structure refers to the formation of tetramers.
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on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #5
5. Which of the following statements about polypeptide formation is correct?
(A) The formation of amino acids involves a condensation reaction.
(B) The formation of polypeptide involves hydrolysis and GTP.
(C) Amino acids join together and form a peptide bond.
(D) Amino acids join together and form a Van der Waals interaction.
Feedback
A. Incorrect!
The formation of polypeptide involves a condensation reaction.
B. Incorrect!
The formation of polypeptide involves a condensation reaction.
C. Correct!
Amino acids join together and form a peptide bond.
D. Incorrect!
Amino acids join together and form a peptide bond.
Solution
The formation of polypeptide involves a condensation reaction, in which amino acids join together and form a peptide bond. The polypeptide will eventually fold into its final functional form.
on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #6
6. Which of the following statements about the significance of a proteins amino acid sequence is correct?
(A) The primary structure of a protein i.e., the amino acid sequence plays no role in its function.
(B) Defects in primary structure may arise due to incorrect lipid formation.
(C) In Sickle cell anemia there is a defect in the amino acid sequence of the hemoglobin (Hb) protein and this causes changes in the folding and function of this protein.
(D) In Sickle cell anemia there is a defect in the amino acid sequence of the hemoglobin (Hb) protein and this does not causes any changes in the folding and function of this protein.
Feedback
A. Incorrect!
The primary structure of a protein i.e., the amino acid sequence is critical to its structure and function.
B. Incorrect!
Defects in primary structure may arise due to “mutations”.
C. Correct!
In Sickle cell anemia there is a defect in the amino acid sequence of the
hemoglobin (Hb) protein and this causes changes in the folding and function of this protein.
D. Incorrect!
In Sickle cell anemia there is a defect in the amino acid sequence of the
hemoglobin (Hb) protein and this causes changes in the folding and function of this protein.
Solution
Amino acids that were distant in the primary structure may now become very close to each other after the folding has taken place and therefore the primary structure of a protein i.e., the amino acid sequence is critical to its structure and function.
Mutation is a process by which a single or a few nucleotides in a DNA sequence is changed due to any mutation-causing agent like chemicals, UV rays etc. as a result of mutation the codon is changed resulting in a different amino acid. In sickle cell anemia, a single amino acid change results in defective hemoglobin and the patient suffers from severe anemia.
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on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #7
7. Which of the following statements about protein functional classes is correct?
(A) The functional classes of proteins includes: (1) Structural, (2) Receptors, (3) Channels.
(B) The functional classes of proteins includes: (1) Structural, (2) Receptors, (3) Channels, (4) Transport, (5) Storage, (6) Cell function and (7) Immune response.
(C) Structural proteins such as collagen are involved in immune responses.
(D) Structural proteins such as collagen transport oxygen in the blood.
Feedback
A. Incorrect!
The functional classes of proteins includes: (1) Structural, (2) Receptors, (3) Channels, (4) Transport, (5) Storage, (6) Cell function and (7) Immune response.
B. Correct!
The functional classes of proteins includes: (1) Structural, (2) Receptors, (3) Channels, (4) Transport, (5) Storage, (6) Cell function and (7) Immune response.
C. Incorrect!
Structural proteins such as collagen make up a major portion of tendons, bones and skin.
D. Incorrect!
Structural proteins such as collagen make up a major portion of tendons, bones and skin.
Solution
The functional classes of proteins includes: (1) Structural, (2) Receptors, (3) Channels, (4) Transport, (5) Storage, (6) Cell function and (7) Immune response.
Structural proteins such as collagen make up a major portion of tendons, bones and skin. Collagen is a fibrous protein made up of a triple helix with stabilizing Inter- strand H-bonds.
on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #8
8. Which of the following statements about membrane proteins is correct?
(A) Membrane proteins can function as receptors and channels and can be integral (embedded or buried) in the membrane, or peripheral (attached more loosely, by interactions with either lipid or integral membrane proteins).
(B) Membrane proteins can function as receptors and channels and are always found as integral (embedded or buried) in the membrane.
(C) Membrane proteins function in cell communication (e.g. cell signaling), and have a single domain spanning the membrane.
(D) Membrane proteins function in cell communication (e.g. cell signaling), and have multiple domains spanning the membrane.
Feedback
A. Correct!
Membrane proteins can function as receptors and channels and can be integral (embedded or buried) in the membrane, or peripheral (attached more loosely, by interactions with either lipid or integral membrane proteins).
B. Incorrect!
Membrane proteins can function as receptors and channels and can be integral (embedded or buried) in the membrane, or peripheral (attached more loosely, by interactions with either lipid or integral membrane proteins).
C. Incorrect!
Membrane proteins function in cell communication (e.g. cell signaling), and can have a single or have multiple domains spanning the membrane.
D. Incorrect!
Membrane proteins function in cell communication (e.g. cell signaling), and can have a single or have multiple domains spanning the membrane.
Solution
A membrane protein is a protein that is associated with a membrane, rather than found free in the cell. A membrane protein may be integral (embedded or buried) in the membrane, or peripheral (attached more loosely, by interactions with either lipid or integral membrane proteins). Membrane proteins function in cell
communication (e.g. cell signaling), and can have a single or have multiple domains spanning the membrane.
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on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #9
9. Which of the following statements about hemoglobin is correct?
(A) Hemoglobin has a tetrameric quaternary structure of four monomers, each containing one heme group βα 4 subunits 1, ß1, 2, ß2.
(B) Hemoglobin has a tetrameric secondary structure of four monomers, each containing one heme group βα 4 subunits 1, ß1, 2, ß2.
(C) Hemoglobin is present in muscle and Myoglobin is present in red blood cells.
(D) Hemoglobin transports and interacts with oxygen and Myoglobin transports and interacts with nitrogen.
Feedback
A. Correct!
Hemoglobin has a tetrameric quaternary structure of four monomers, each containing one heme group βα 4 subunits 1, ß1, 2, ß2.
B. Incorrect!
Hemoglobin has a tetrameric quaternary structure of four monomers, each containing one heme group βα 4 subunits 1, ß1, 2, ß2.
C. Incorrect!
Myoglobin is present in muscle and Hemoglobin is present in RBC.
D. Incorrect!
Hemoglobin and Myoglobin transport and interact with oxygen.
Solution
Hemoglobin has a tetrameric quaternary structure of four monomers, each containing one heme group βα 4 subunits 1, ß1, 2, ß2. Myoglobin is present in muscle and Hemoglobin is present in RBC. Hemoglobin and Myoglobin transport and interact with oxygen.
on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
Question #10
10. Which of the following statements about actin and myosin is correct?
(A) Actin and Hemoglobin filaments interact to produce muscle contraction.
(B) Actin binds to the myosin binding site and myosin utilizes energy to produce movement.
(C) Myosin binds to the lipid binding site and actin utilizes energy to produce movement.
(D) Actin binds to the myosin binding site and myosin passively (no energy required) produces movement.
Feedback
A. Incorrect!
Actin and Myosin filaments interact to produce muscle contraction.
B. Correct!
Actin binds to the myosin binding site and myosin utilizes energy to produce movement.
C. Incorrect!
Actin binds to the myosin binding site and myosin utilizes energy to produce movement.
D. Incorrect!
Actin binds to the myosin binding site and myosin utilizes energy to produce movement.
Solution
Proteins can link together to form filaments that make movement possible. Myosin and actin filaments produce muscle contraction. Actin binds to the myosin binding site (groove in myosin protein). Add energy and myosin moves, moving actin with it.
