Questions and Answers
What characterizes free amino acids at physiologic pH of 7.4 in solution?
How does glycine's side chain affect its function in proteins?
What is true about the carboxyl and amino groups in peptide linkages?
Which classification describes amino acids based on their side chains?
Signup and view all the answers
What role does glycine primarily play in protein structures?
Signup and view all the answers
Which statement about amino acids is incorrect?
Signup and view all the answers
What is a major feature of zwitterionic amino acids?
Signup and view all the answers
Which of the following statements is accurate regarding the amino acids' side chains?
Signup and view all the answers
What is the importance of amino acid classification?
Signup and view all the answers
At which pH value does alanine predominantly exist as form II, with a net charge of zero?
Signup and view all the answers
What happens when the pH equals pK2 for alanine?
Signup and view all the answers
Which pairs act as buffers in the titration of alanine?
Signup and view all the answers
Which group in amino acids has a dissociable proton at the carboxyl terminal?
Signup and view all the answers
What characteristic of amino acids is described as amphoteric substances?
Signup and view all the answers
Which of the following does not participate in the titration of alanine?
Signup and view all the answers
Which amino acid has a side chain that contains a hydroxyl group allowing it to engage in hydrogen bonds?
Signup and view all the answers
Which of the following amino acids is characterized by a nonpolar hydrophobic side chain that lacks substituents?
Signup and view all the answers
What characteristic makes tryptophan more polar than phenylalanine?
Signup and view all the answers
Which amino acid serves as a site for attachment of oligosaccharide chains in glycoproteins?
Signup and view all the answers
Which of the following amino acids is least likely to have its side chain located on the surface of water-soluble globular proteins?
Signup and view all the answers
What common feature do serine and threonine share that allows them to serve as sites of attachment?
Signup and view all the answers
When at alkaline pH, which property is true of tyrosine?
Signup and view all the answers
Which amino acids fall into the category of aliphatic, polar, and uncharged amino acids?
Signup and view all the answers
Which property of serine makes it an important component in enzyme active sites?
Signup and view all the answers
Which of the following correctly describes the properties of hydroxyl and amide groups in amino acids?
Signup and view all the answers
Which statement about histidine's side chain is correct?
Signup and view all the answers
What is the primary amino group location in lysine?
Signup and view all the answers
How does the side chain of arginine contribute to protein interactions?
Signup and view all the answers
Which basic amino acid is recognized for its ability to form ionic bonds effectively?
Signup and view all the answers
What role do the positive charges of basic amino acids play in proteins?
Signup and view all the answers
At physiological pH, how are the side chains of lysine and arginine characterized?
Signup and view all the answers
Which of the following statements regarding hydrogen bonding in amino acids is true?
Signup and view all the answers
What characteristic of histidine allows it to serve different roles in protein function?
Signup and view all the answers
Which amino acids primarily form ionic bonds and salt bridges with negatively charged groups?
Signup and view all the answers
The charges on amino acid side chains at physiological pH depend on what property?
Signup and view all the answers
Which of the following statements accurately describes the characteristics of branched chain amino acids?
Signup and view all the answers
What structural feature of proline contributes to its unique behavior in protein structures?
Signup and view all the answers
How do hydrophobic amino acids primarily promote their association within proteins?
Signup and view all the answers
What is the significance of the electron sharing in the side chains of nonpolar amino acids?
Signup and view all the answers
What type of interaction is primarily responsible for the association of branched chain amino acid side chains?
Signup and view all the answers
Which of the following properties do aromatic amino acids share due to their structure?
Signup and view all the answers
What role does proline play in the structure of collagen?
Signup and view all the answers
Why are branched chain amino acids considered oily or lipid-like?
Signup and view all the answers
What structural characteristic distinguishes aromatic amino acids from other amino acids?
Signup and view all the answers
How do branched chain amino acids enhance protein stability?
Signup and view all the answers
Study Notes
Immunoglobulins and Their Function
- Immunoglobulins, also known as antibodies, play a critical role in the immune system by targeting and neutralizing infectious bacteria and viruses.
Structure of Amino Acids
- There are 20 amino acids that are the building blocks of proteins.
- At physiological pH (7.4), free amino acids exist as zwitterions, with a dissociated carboxyl group (-COO-) and a protonated amino group (-NH3+).
- Peptide linkages typically involve the amino and carboxyl groups, making them unavailable for other chemical reactions, except for hydrogen bonds.
- The role of an amino acid in proteins is primarily determined by the characteristics of its side chain.
Classification of Amino Acid Side Chains
- Amino acids are classified based on polarity and structural features, aiding in the understanding of their functional roles and metabolic pathways.
Nonpolar, Aliphatic Amino Acids
- Glycine: Simplest amino acid with a hydrogen side chain; causes minimal steric hindrance, often found in bends or compact chains.
- Alanine and Branched Chain Amino Acids: Valine, Leucine, Isoleucine; their bulky nonpolar side chains cluster to form hydrophobic cores in proteins.
- Proline: Features a rigid ring structure that induces kinks in peptide backbones, affecting the formation of collagen and interrupting alpha-helices.
Aromatic Amino Acids
- Side chains contain aromatic ring structures, contributing to variable polarity based on substituents.
- Phenylalanine: Hydrophobic structure with a nonpolar ring; stacks on itself.
- Tyrosine: Contains a hydroxyl group, making it polar and hydrophilic, allowing for hydrogen bonding and modifications.
- Tryptophan: Complex indole ring that can engage in hydrogen bonding, making it more polar than phenylalanine.
Aliphatic, Polar, Uncharged Amino Acids
- Asparagine and Glutamine: Have carbonyl and amide groups, engaging in hydrogen bonding.
- Serine and Threonine: Contain polar hydroxyl groups for hydrogen bonding and attachment sites.
- Frequent components on water-soluble globular proteins due to their hydrophilic nature.
Basic Amino Acids
- Histidine: Weakly basic with an imidazole ring; can be positively charged or neutral depending on pH.
- Lysine: Contains a primary amino group, contributing to its basic nature.
- Arginine: Contains a guanidinium group; both lysine and arginine form ionic bonds with negatively charged residues.
Interactions and Charges of Amino Acids
- Basic amino acids can form ionic bonds with negatively charged groups (e.g., phosphate groups in ATP).
- They can also participate in hydrogen bonding and form salt bridges with inorganic ions.
Titration and Charge States
- Titration curves illustrate how the charges of amino acids change with pH.
- The isoelectric point occurs when an amino acid has a net charge of zero, common in neutral pH.
- Amino acids are amphoteric; they can act as acids or bases, a property of importance in biochemical reactions.
Titrable Groups in Proteins
- Only the side chains of specific amino acids, as well as the amino- and carboxyl-termini groups, have dissociable protons, affecting their behavior in different environments.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the roles of immunoglobulins in defending against infectious bacteria and viruses, alongside a detailed exploration of amino acids, their structure, and behavior in physiological pH. Understanding zwitterions and the peptide linkage of amino acids is essential for deeper insights into biochemistry.