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Questions and Answers
Which amino acid is neutral but contains a hydroxyl group?
Which amino acid is neutral but contains a hydroxyl group?
Cysteine contains a hydroxyl group in its side chain.
Cysteine contains a hydroxyl group in its side chain.
False
Name one positively charged amino acid.
Name one positively charged amino acid.
Lysine
Aspartic acid and glutamic acid have __________ side chains.
Aspartic acid and glutamic acid have __________ side chains.
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Match the amino acids with their characteristics:
Match the amino acids with their characteristics:
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Which of the following amino acids is classified as hydrophobic?
Which of the following amino acids is classified as hydrophobic?
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All polar amino acids are hydrophilic.
All polar amino acids are hydrophilic.
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What type of functional group do asparagine and glutamine contain?
What type of functional group do asparagine and glutamine contain?
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The amino acid __________ contains a phenyl ring replacing one of the methyl hydrogen atoms of alanine.
The amino acid __________ contains a phenyl ring replacing one of the methyl hydrogen atoms of alanine.
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Which amino acid has an indole ring in its side chain?
Which amino acid has an indole ring in its side chain?
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What is the central carbon atom in an amino acid called?
What is the central carbon atom in an amino acid called?
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Essential amino acids cannot be synthesized by the body and must be obtained from the diet.
Essential amino acids cannot be synthesized by the body and must be obtained from the diet.
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Name one amino acid that has an ionizable side chain.
Name one amino acid that has an ionizable side chain.
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Amino acids with R groups that have a positive charge at physiological pH are classified as __________ amino acids.
Amino acids with R groups that have a positive charge at physiological pH are classified as __________ amino acids.
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Match the following functional groups with their corresponding amino acid categories:
Match the following functional groups with their corresponding amino acid categories:
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Which of the following groups classifies amino acids with nonpolar R groups?
Which of the following groups classifies amino acids with nonpolar R groups?
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R groups of amino acids are always the same across different amino acids.
R groups of amino acids are always the same across different amino acids.
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How many total amino acids are there in the standard set?
How many total amino acids are there in the standard set?
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At acidic pH, the carboxyl group of an amino acid is __________.
At acidic pH, the carboxyl group of an amino acid is __________.
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Which structure does an amino acid contain?
Which structure does an amino acid contain?
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Study Notes
Chapter 3: Amino Acids
- Amino acids are the building blocks of proteins.
- Amino acids have a central carbon atom bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and an R group (side chain).
- The R group varies among different amino acids, giving each its unique properties.
- At neutral pH, amino acids exist as zwitterions (dipolar ions), with the amino group protonated (-NH₃⁺) and the carboxyl group deprotonated (-COO⁻).
- Changes in pH affect the charged groups on amino acids. In acidic conditions, the amino group retains its proton while in basic conditions, the carboxyl group loses its proton.
- There are 20 common amino acids, each with a specific letter abbreviation.
- Amino acids are classified based on the properties of their side chains.
- The seven amino acids with ionizable side chains are: tyrosine, cysteine, arginine, lysine, histidine, aspartic acid, and glutamic acid. These can bind and release protons during chemical reactions and thus enhance reactivity.
- There are essential and nonessential amino acids.
- Essential amino acids cannot be synthesized by the body and must be obtained from the diet.
- Nonessential amino acids can be produced by the body.
- R groups determine the hydrophobic character and affect hydrogen bonding.
- Functional groups such as alcohols, thiols, thioethers, carboxylic acids, carboxamides, and various basic groups are found in amino acid side chains.
- The structure of R groups causes the varying properties of amino acids. These properties affect their classification.
Amino Acid Classification
- Hydrophobic amino acids have nonpolar R groups.
- Polar amino acids have neutral R groups, but charge is not evenly distributed.
- Positively charged amino acids exhibit a positive charge at physiological pH (7.4).
- Negatively charged amino acids exhibit a negative charge at physiological pH.
Specific Examples of Amino Acids.
- Hydrophobic: glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptophan
- Polar, neutral: serine, threonine, tyrosine, cysteine, asparagine, glutamine
- Positively charged: lysine, arginine, histidine
- Negatively charged: aspartic acid, glutamic acid
Essential Amino Acids
- histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine
Nonessential Amino Acids
- alanine, arginine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, tyrosine
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Description
This quiz covers the essential aspects of amino acids, the fundamental building blocks of proteins. You will learn about their structure, classification, and how their properties change under different pH conditions. Test your knowledge on the 20 common amino acids and their unique characteristics.
