Chm 124 (Owl) - Proteins Quiz

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Questions and Answers

Which amino acids have side-chain groups that can form salt bridges?

Glutamate (correct)

Histidine (correct)

Aspartate (correct)

Arginine (correct)

Lysine (correct)

What are salt bridges?

The result of ionic bonds that form between the ionized side chain of an acidic amino acid (COOH-) and the side chain of a basic amino acid (NH3+).

What are disulfide bridges?

A disulfide linkage can form between two cysteine residues that are close to each other in the same chain or between cysteine residues in different chains.

How do hydrogen bonds form in proteins?

Between side chains that possess amino, hydroxyl, and amide functional groups. Signup and view all the answers

What are hydrophobic interactions?

Interactions that result when nonpolar groups are either attracted to one another or forced together by their mutual repulsion of aqueous solvent. Signup and view all the answers

What do glycine, alanine, valine, leucine, isoleucine, phenylalanine, proline, and methionine have in common?

They have nonpolar side chains. Signup and view all the answers

Which of the following amino acids have side chains that could participate in hydrogen bonding?

Histidine Signup and view all the answers

What determines the globular shape of proteins in aqueous solutions?

Polar groups are pointed outward toward the aqueous solvent, and nonpolar groups are pointed inward away from the water. Signup and view all the answers

What influences the quaternary structure in proteins?

Hydrogen bonding, hydrophobic interactions, ionic attraction, and disulfide bridges. Signup and view all the answers

What is a subunit in the context of proteins?

A polypeptide chain that has its own primary, secondary, and tertiary structure. Signup and view all the answers

What is the primary structure of proteins?

The order in which amino acid residues are linked together. Signup and view all the answers

What happens when a proton is added to an amino acid?

It forms a conjugate acid. Signup and view all the answers

What happens when a proton is removed from an amino acid?

It forms a conjugate base. Signup and view all the answers

What is a zwitterion?

An amino acid that has an equal number of positive and negative charges, resulting in no net charge. Signup and view all the answers

When pH is less than the pI for an amino acid, what is the net charge of the amino acid?

Positive Signup and view all the answers

When pH is greater than the pI for an amino acid, what is the net charge of the amino acid?

Negative Signup and view all the answers

How are amino acids linked together?

By covalent bonds to form larger molecules called polypeptides. Signup and view all the answers

What describes the secondary structure of proteins?

The folding pattern of an amino acid chain. Signup and view all the answers

What type of bonding holds the secondary structure of a protein together?

Hydrogen bonds. Signup and view all the answers

Which amino acid can form covalent disulfide bridges?

Cysteine. Signup and view all the answers

What type of interaction do salt bridges refer to?

Ionic bonds. Signup and view all the answers

Salt bridges occur between which types of amino acids?

Two amino acids with ionized side chains (an acidic and a basic amino acid). Signup and view all the answers

Study Notes

Amino Acids and Interactions

Aspartate, arginine, lysine, glutamate, and histidine can form salt bridges due to their charged side-chain groups.
Salt bridges result from ionic bonds between acidic (ionized COOH-) and basic (ionized NH3+) amino acid side chains.
Disulfide bridges are formed by covalent linkages between two cysteine residues within or between polypeptide chains.
Hydrogen bonds can occur between side chains with amino, hydroxyl, and amide functional groups, stabilizing protein structures.
Hydrophobic interactions arise when nonpolar groups are drawn together in an aqueous environment, common in phenylalanine residues.

Amino Acids Properties

Glycine, alanine, valine, leucine, isoleucine, phenylalanine, proline, and methionine have nonpolar side chains.
Glutamate, histidine, aspartate, lysine, and arginine possess side chains capable of hydrogen bonding.
Polar groups in a protein's structure typically orient outward, while nonpolar groups direct inward to minimize water exposure.

Protein Structures

Quaternary structure stability is influenced by hydrogen bonding, hydrophobic interactions, ionic attractions, and disulfide bridges.
A subunit of a protein refers to a polypeptide chain with its distinct conformation that contributes to the overall protein structure.
The primary structure of a protein remains unchanged during cooking, as it refers to the sequence of amino acids linked in a chain.

Amino Acid Ionization

Adding a proton to an amino acid creates a conjugate acid, while removing a proton generates a conjugate base.
In acidic conditions (pH < pI), amino acids bear a positive net charge; in basic conditions (pH > pI), they have a negative charge.
The ionized form of amino acids exists as zwitterions, featuring both positive and negative charges balanced within the molecule.

Structural Characteristics

Each amino acid contains an amino group (-NH2), a carboxyl group (-COOH), and a variable R group or side chain.
Secondary structure patterns of amino acid chains, such as alpha helices and beta-pleated sheets, are stabilized by hydrogen bonding.
Cysteine is the only amino acid that can form covalent disulfide bridges with itself, important for protein stability.

Additional Notes

Salt bridges are specific types of ionic interactions occurring between two amino acids with ionized side chains, enhancing protein structure.
Understanding these interactions is crucial for comprehending protein folding, stability, and function within biological systems.

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Description

Test your knowledge on proteins in this Chm 124 flashcard quiz. Explore key concepts such as salt bridges and the amino acids involved in their formation. Enhance your understanding of protein structure and interactions.