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Questions and Answers
What does the Henderson-Hasselbalch equation help predict?
What does the Henderson-Hasselbalch equation help predict?
Which amino acid is NOT mentioned as having potentially charged groups in its side chains?
Which amino acid is NOT mentioned as having potentially charged groups in its side chains?
What constitutes the definition of ampholytes?
What constitutes the definition of ampholytes?
Which of the following forms of a weak acid, like aspirin, can permeate through cell membranes?
Which of the following forms of a weak acid, like aspirin, can permeate through cell membranes?
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When a drug is in its protonated form (BH+), how does it behave?
When a drug is in its protonated form (BH+), how does it behave?
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How does the pKa of an ionizable group affect a drug's absorption?
How does the pKa of an ionizable group affect a drug's absorption?
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What happens to the pH of a solution when the concentration of a weak acid increases?
What happens to the pH of a solution when the concentration of a weak acid increases?
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Which factor greatly affects the effective concentration of the permeable form of a drug at its absorption site?
Which factor greatly affects the effective concentration of the permeable form of a drug at its absorption site?
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Which of the following statements about weak bases is true?
Which of the following statements about weak bases is true?
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What effect does the binding of CO2 have on hemoglobin's affinity for oxygen?
What effect does the binding of CO2 have on hemoglobin's affinity for oxygen?
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What is formed when carbon monoxide (CO) binds to hemoglobin?
What is formed when carbon monoxide (CO) binds to hemoglobin?
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How does carboxyhemoglobin affect the oxygen-dissociation curve?
How does carboxyhemoglobin affect the oxygen-dissociation curve?
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What therapy is used to treat CO poisoning?
What therapy is used to treat CO poisoning?
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What happens to the remaining heme sites of hemoglobin when CO binds to one of the four heme sites?
What happens to the remaining heme sites of hemoglobin when CO binds to one of the four heme sites?
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Which gas carried by hemoglobin is a potent vasodilator?
Which gas carried by hemoglobin is a potent vasodilator?
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What is the significance of cross-links in concept maps?
What is the significance of cross-links in concept maps?
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What occurs at physiologic pH regarding amino acids?
What occurs at physiologic pH regarding amino acids?
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Which property characterizes the α-carbon of amino acids?
Which property characterizes the α-carbon of amino acids?
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Which classification of amino acids is determined by the nature of the R group?
Which classification of amino acids is determined by the nature of the R group?
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What is the primary function of buffering in amino acids?
What is the primary function of buffering in amino acids?
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Which form of amino acids is predominantly found in proteins synthesized by the human body?
Which form of amino acids is predominantly found in proteins synthesized by the human body?
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What does the Henderson-Hasselbalch equation describe?
What does the Henderson-Hasselbalch equation describe?
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What is the role of charged amino acids in peptide chains?
What is the role of charged amino acids in peptide chains?
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Which statement about proline is correct?
Which statement about proline is correct?
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At which point on a titration curve would the net charge on an amino acid be zero for a nonpolar amino acid?
At which point on a titration curve would the net charge on an amino acid be zero for a nonpolar amino acid?
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What is the role of the steep slope in the oxygen-dissociation curve of hemoglobin?
What is the role of the steep slope in the oxygen-dissociation curve of hemoglobin?
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What effect does a lower pH have on hemoglobin's oxygen release?
What effect does a lower pH have on hemoglobin's oxygen release?
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How does an increase in pCO2 influence the oxygen-dissociation curve?
How does an increase in pCO2 influence the oxygen-dissociation curve?
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What is the Bohr effect primarily associated with?
What is the Bohr effect primarily associated with?
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What happens to CO2 in metabolically active tissues?
What happens to CO2 in metabolically active tissues?
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What physiological change occurs when the pH is raised in the lungs?
What physiological change occurs when the pH is raised in the lungs?
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Why would myoglobin not be able to deliver oxygen efficiently in the same range of pO2 as hemoglobin?
Why would myoglobin not be able to deliver oxygen efficiently in the same range of pO2 as hemoglobin?
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What is the primary function of bicarbonate in the blood?
What is the primary function of bicarbonate in the blood?
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What type of curve does hemoglobin exhibit compared to myoglobin?
What type of curve does hemoglobin exhibit compared to myoglobin?
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What effect does the presence of protons (H+) have on hemoglobin?
What effect does the presence of protons (H+) have on hemoglobin?
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What characterizes the arrangement of antiparallel β-sheets?
What characterizes the arrangement of antiparallel β-sheets?
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What types of hydrogen bonds are formed in a β-sheet created from separate polypeptide chains?
What types of hydrogen bonds are formed in a β-sheet created from separate polypeptide chains?
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Which amino acid is known to cause a kink in the polypeptide chain commonly found in β-bends?
Which amino acid is known to cause a kink in the polypeptide chain commonly found in β-bends?
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What is the typical composition of β-bends in terms of amino acids?
What is the typical composition of β-bends in terms of amino acids?
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In globular proteins, what orientation do β-sheets commonly exhibit?
In globular proteins, what orientation do β-sheets commonly exhibit?
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Approximately what fraction of an average globular protein is organized into repetitive structures?
Approximately what fraction of an average globular protein is organized into repetitive structures?
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Which term describes the less regular structure of nonrepetitive secondary structures in proteins?
Which term describes the less regular structure of nonrepetitive secondary structures in proteins?
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What stabilizes β-bends in proteins?
What stabilizes β-bends in proteins?
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Which of the following is true regarding β-sheets formed by a single polypeptide chain?
Which of the following is true regarding β-sheets formed by a single polypeptide chain?
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What role do β-bends play in the structure of proteins?
What role do β-bends play in the structure of proteins?
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Study Notes
Mobility Patterns and Diseases
- Variations in amino acid mobility patterns can indicate certain diseases.
Amino Acid Charge at Neutral pH
- At physiological pH, amino acids possess a negatively charged carboxyl group (–COO–) and a positively charged amino group (–NH3+).
- Amino acids such as glutamate, aspartate, histidine, arginine, and lysine contain additional charged groups in their side chains.
- Amino acids function as ampholytes, acting as both acids and bases.
Henderson-Hasselbalch Equation
- Used to predict pH changes based on concentrations of bicarbonate (HCO3–) and carbon dioxide (CO2).
- Calculates how pH responds to changes in concentrations of weak acids and their salt forms.
- In the bicarbonate buffer system, it illustrates the influence of HCO3– and CO2 on pH.
Drugs and Ionizable Forms
- Many drugs are weak acids or bases; their absorption depends on their charged or uncharged forms.
- Acidic drugs release protons and become negatively charged, while basic drugs lose protons and become uncharged.
- Uncharged forms of drugs permeate membranes more readily, influencing their effective concentration at absorption sites.
Cross-Links in Concept Maps
- Concept maps can include cross-links to represent complex ideas across different topics.
- Facilitates understanding of relationships in biochemistry and enhances preparation for exams like the USMLE.
Amino Acid Structure
- Each amino acid has an α-carboxyl group and a primary amino group, except proline, which has a secondary amino group.
- Physiological pH leads to dissociation of the α-carboxyl group and protonation of the α-amino group.
- Amino acids possess distinct side chains (R groups) that classify them as nonpolar, uncharged polar, acidic (polar negative), or basic (polar positive).
Buffer Systems
- Free amino acids and charged amino acids in peptide chains function as buffers.
- Buffering effectiveness is highest within ±1 pH unit of the pKa, where [A–] = [HA].
Chiral Carbon
- The α-carbon of amino acids (excluding glycine) is a chiral carbon connected to four different groups, exhibiting optical activity.
- L-forms of amino acids are incorporated into proteins in humans.
Secondary Structure of Proteins
- β-sheets can form from multiple polypeptide chains arranged parallel or antiparallel, with interchain or intrachain bonds.
- α-helices and β-sheets maximize hydrogen bonding among peptide bond components.
β-Bends and Nonrepetitive Structures
- β-Bends consist of four amino acids and help reverse polypeptide chain direction for compact shapes.
- Nonrepetitive secondary structures occupy roughly half of globular proteins, possessing less regular organization than repetitive structures.
Oxygen-Dissociation Curve
- The sigmoidal shape of the oxygen-dissociation curve in hemoglobin enables efficient oxygen transport between high and low pO2 areas.
- Myoglobin has a hyperbolic curve, which limits oxygen release efficiency.
Bohr Effect
- Oxygen release from hemoglobin increases with lower pH or higher pCO2, stabilizing the deoxygenated T state and shifting the curve to the right.
- Higher pH and lower CO2 concentration shift the curve left and stabilize the oxygenated R state.
Carbonic Acid and Bicarbonate
- Increased CO2 in active tissues leads to a lower pH as it forms carbonic acid, contributing to the unloading of oxygen from hemoglobin.
- This pH gradient favors oxygen release in tissues and uptake in lungs.
CO2 Transport and Carbaminohemoglobin
- CO2 is mainly transported as bicarbonate but also binds to hemoglobin to form carbaminohemoglobin, stabilizing the deoxygenated form and decreasing oxygen affinity.
Carbon Monoxide Binding
- CO binds tightly to hemoglobin, shifting the oxygen-dissociation curve left and impairing oxygen release due to high affinity for heme.
- CO poisoning requires treatment with high-pressure oxygen to displace CO from hemoglobin, preventing cellular damage and hypoxia.
Additional Gas Transport
- Hemoglobin also transports nitric oxide (NO), which acts as a vasodilator, contributing to its functions in the body.
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Description
Explore the variations in the mobility patterns of amino acids and their implications in different diseases. Understand the net charge of amino acids at neutral pH, including the importance of charged groups and the roles of specific amino acids like glutamate and lysine.
