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Questions and Answers
A carboxyl group is deprotonated when it receives a hydrogen ion.
A carboxyl group is deprotonated when it receives a hydrogen ion.
False
Amino acids have a three-letter abbreviation.
Amino acids have a three-letter abbreviation.
True
The structure of R influences the solubility of an amino acid in non-polar solvents.
The structure of R influences the solubility of an amino acid in non-polar solvents.
False
Amino acids are soluble in non-polar solvents due to their ionic character.
Amino acids are soluble in non-polar solvents due to their ionic character.
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The COO- group is a feature of amino acids.
The COO- group is a feature of amino acids.
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A carboxyl group is basic when it receives a hydrogen ion.
A carboxyl group is basic when it receives a hydrogen ion.
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Amino acids have only one type of abbreviation.
Amino acids have only one type of abbreviation.
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The R group of an amino acid influences its solubility.
The R group of an amino acid influences its solubility.
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Non-polar amino acids have hydrocarbon chains.
Non-polar amino acids have hydrocarbon chains.
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Polar amino acids are soluble in water.
Polar amino acids are soluble in water.
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Aromatic amino acids are bulky and have a negative charge.
Aromatic amino acids are bulky and have a negative charge.
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Proline is an example of a polar amino acid.
Proline is an example of a polar amino acid.
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Non-polar amino acids are usually found in the kinks of proteins.
Non-polar amino acids are usually found in the kinks of proteins.
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Amino acids with an R-group containing sulfur are always charged.
Amino acids with an R-group containing sulfur are always charged.
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Hydrophobic amino acids are capable of forming hydrogen bonds.
Hydrophobic amino acids are capable of forming hydrogen bonds.
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Hydrophilic amino acids are insoluble in water.
Hydrophilic amino acids are insoluble in water.
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All non-polar amino acids have aliphatic R-groups.
All non-polar amino acids have aliphatic R-groups.
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Polar amino acids are always hydrophilic.
Polar amino acids are always hydrophilic.
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Glycine has a polar R-group.
Glycine has a polar R-group.
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Proline is likely to be found in kinks of a protein structure.
Proline is likely to be found in kinks of a protein structure.
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The pH of a solution is equal to 2.
The pH of a solution is equal to 2.
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The pH of a solution is directly proportional to the hydrogen ion concentration.
The pH of a solution is directly proportional to the hydrogen ion concentration.
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Cysteine's R-group is a hydrocarbon.
Cysteine's R-group is a hydrocarbon.
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The R-group of methionine is easily polar.
The R-group of methionine is easily polar.
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A solution with a pH of 2 is basic.
A solution with a pH of 2 is basic.
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Serine and threonine have similar R-groups.
Serine and threonine have similar R-groups.
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The pH of a solution can be calculated as the square of the hydrogen ion concentration.
The pH of a solution can be calculated as the square of the hydrogen ion concentration.
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A solution with a pH of 11 is neutral.
A solution with a pH of 11 is neutral.
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Valine's R-group is small and non-polar.
Valine's R-group is small and non-polar.
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Alanine is a polar amino acid.
Alanine is a polar amino acid.
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The pH of a solution is a linear function of the hydrogen ion concentration.
The pH of a solution is a linear function of the hydrogen ion concentration.
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A solution with a pH of 2 has a higher hydrogen ion concentration than a solution with a pH of 11.
A solution with a pH of 2 has a higher hydrogen ion concentration than a solution with a pH of 11.
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Two cysteine molecules can form a disulfide bond.
Two cysteine molecules can form a disulfide bond.
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The pH of a solution is always a whole number.
The pH of a solution is always a whole number.
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Isoleucine has a large R-group.
Isoleucine has a large R-group.
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Phenylalanine's R-group contains oxygen.
Phenylalanine's R-group contains oxygen.
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The pH of a solution can be calculated using the formula pH = log[H+]
The pH of a solution can be calculated using the formula pH = log[H+]
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Weak acids and weak bases dissociate completely in water
Weak acids and weak bases dissociate completely in water
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The carboxyl group (-COOH) is basic
The carboxyl group (-COOH) is basic
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The pK1 of glycine is 9.6
The pK1 of glycine is 9.6
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The amino group (-NH3+) is acidic
The amino group (-NH3+) is acidic
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At pH < 2.2, the carboxyl group (-COOH) is fully deprotonated
At pH < 2.2, the carboxyl group (-COOH) is fully deprotonated
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The reaction between an acid and its conjugate base is reversible
The reaction between an acid and its conjugate base is reversible
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The pKR of an acid is equal to the pH at which the acid is fully dissociated
The pKR of an acid is equal to the pH at which the acid is fully dissociated
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At pH > 9.4, the amino group (-NH3+) is fully protonated
At pH > 9.4, the amino group (-NH3+) is fully protonated
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The pH of a solution can be calculated using the formula pH = [OH-]
The pH of a solution can be calculated using the formula pH = [OH-]
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Study Notes
Amino Acids
- Carboxyl group is deprotonated, making it acidic, and receives an H+ to become basic
- Amino acids are soluble in polar solvents due to their ionic character, exemplified by the COO- and +NH3 groups
- Solubility is influenced by the structure of the R group
Types of Amino Acids
- Non-Polar Amino Acids: have hydrocarbon chains, are hydrophobic, neutral, and aliphatic
- Polar Amino Acids: dissolve in water, are hydrophilic, neutral, and form H-Bonds
- Aromatic Amino Acids: contain oxygen, are bulky, and have polarity dependent on the R group
Characteristics of Amino Acids
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Some amino acids are found inside the protein, usually in the kinks of the protein
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The R group has a charge, which affects solubility
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Hydrogen bonds are not formed when the R group has no charge### Amino Acids
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There are 20 standard amino acids, each with a unique R-group
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Glycine (Gly) and Alanine (Ala) have small R-groups
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Serine (Ser) and Threonine (Thr) have R-groups with a hydroxyl (-OH) group
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Cysteine (Cys) has an R-group with a sulfur atom, which can form a disulfide bridge with another Cysteine
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Tyrosine (Tyr) and Tryptophan (Trp) have large, rigid R-groups
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Proline (Pro) has a unique, rigid structure that can cause kinks in protein chains
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Valine (Val) and Isoleucine (Ile) have non-polar, hydrophobic R-groups
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Asparagine (Asn) and Glutamine (Gln) have R-groups with an amide group
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Methionine (Met) has a sulfide group in its R-group, making it easily soluble in water
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Leucine (Leu) has a non-polar, hydrophobic R-group
Polarity of Amino Acids
- Amino acids can be classified as polar or non-polar based on their R-group
- Polar amino acids have R-groups with a hydroxyl (-OH) or amide group
- Non-polar amino acids have R-groups with hydrocarbon chains or sulfur atoms
- Glycine (Gly) and Serine (Ser) are polar amino acids
- Alanine (Ala) and Valine (Val) are non-polar amino acids
- Proline (Pro) is a non-polar amino acid, but its rigid structure makes it unique
Protein Structure
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Disulfide bridges can form between two Cysteine (Cys) residues, stabilizing protein structure
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Hydrogen bonds and weak interactions between amino acids help stabilize protein structure
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Proline (Pro) can cause kinks in protein chains due to its rigid structure### pH Scale and Acid-Base Properties
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pH is a measure of the concentration of hydrogen ions (H+) in a solution, calculated as pH = -log[H+].
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pH scale ranges from 0 to 14, with a pH below 7 being acidic, pH 7 being neutral, and pH above 7 being basic.
Weak Acids and Bases
- A weak acid is a molecule that partly dissociates in water, releasing H+ ions.
- Weak acids have a higher pKa (acid dissociation constant) than strong acids, indicating a lower tendency to donate a proton (H+).
- A weak base is a molecule that accepts H+ ions to form a conjugate acid.
Acid-Base Properties of Amino Acids
- Amino acids have both an acidic carboxyl (-COOH) and a basic amino (-NH2) group.
- The carboxyl group is protonated (acidic) at low pH and deprotonated (basic) at high pH.
- The amino group is deprotonated (basic) at low pH and protonated (acidic) at high pH.
Titration of Glycine
- Glycine, an amino acid, has two pKa values: pK1 (COOH) = 2.34 and pK2 (NH3+) = 9.6.
- At pH < 2.34, glycine is fully protonated (acidic).
- At pH > 9.6, glycine is fully deprotonated (basic).
- The zwitterion form of glycine, where the carboxyl group is deprotonated and the amino group is protonated, is most prevalent at pH around 6-7.
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Description
This quiz explores the acidic properties of carboxyl groups, including their deprotonation and acidic behaviors. Test your knowledge of carboxyl groups and their chemical properties.
