Biochemistry Protein Structure Overview

Secondary structure refers to localized regions of protein where amino acids fold into regular structures, such as alpha helix and beta sheets. These structures are stabilized by hydrogen bonds.

False (B)

<p>In a parallel beta-pleated sheet, all the strands run in the same direction (N-terminus to C-terminus). In an antiparallel beta-pleated sheet, the strands run in opposite directions.</p> Signup and view all the answers

<p>Beta turns are short, sharp turns in the polypeptide chain that connect adjacent segments of beta sheets. They are crucial for forming compact globular structures and changing the direction of the polypeptide chain.</p> Signup and view all the answers

<p>Loops are irregular, non-repetitive stretches of amino acids that connect secondary structural elements in proteins. They are often located on the surface of the protein and contribute to flexibility and specificity in protein-protein interactions.</p> Signup and view all the answers

<p>Tertiary structure refers to the overall three-dimensional shape of a protein, resulting from interactions between side chains of amino acids. It is maintained by various bonds and interactions, including disulfide bonds, hydrogen bonds, hydrophobic interactions, and electrostatic interactions.</p> Signup and view all the answers

<p>Disulfide bonds are covalent bonds formed between cysteine residues in proteins. They contribute significantly to the stability of tertiary structure by holding the polypeptide chain in a specific shape.</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>Quaternary structure refers to the arrangement and interaction of multiple polypeptide chains (subunits) within a protein complex. It is present only in proteins that have more than one polypeptide chain.</p> Signup and view all the answers

<p>Monomer, dimer, trimer, tetramer (C)</p> Signup and view all the answers

<p>Homooligomers are protein complexes composed of identical subunits, while heterooligomers are made up of different subunits.</p> Signup and view all the answers

<p>The interactions that stabilize quaternary protein structure are primarily noncovalent bonds, including hydrogen bonds, electrostatic interactions, and hydrophobic interactions. Disulfide bonds can also play a role in some cases.</p> Signup and view all the answers

<p>Denaturation refers to the loss of a protein's native three-dimensional structure, leading to a loss of its biological function. It can be caused by various factors, including heat, extreme pH, chemical denaturants, mechanical stress, and the presence of certain organic compounds.</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

It is a localized region within a protein where the polypeptide chain folds into regular, repeating structures, such as alpha helices and beta sheets.

A helical shape that is a type of secondary protein structure. It is stabilized by hydrogen bonds between the backbone of the polypeptide chain.

A hydrogen bond formed between the amino group of one amino acid and the carboxyl group of another amino acid in the alpha helix structure.

Amino acids that disrupt the formation of alpha helices.

A sheet-like structure consisting of two or more straight chains (called β strands) that are hydrogen-bonded side by side.

The type of beta sheet where the β strands run in opposite directions.

The type of beta sheet where the β strands run in the same direction.

A compact, U-shaped structure that connects beta sheets.

A diverse group of secondary structures that connect main secondary structures, often found on the surface of the protein.

The three-dimensional arrangement of all amino acid residues in a protein.

A very strong covalent bond formed between the sulfur atoms in the thiol groups of two cysteine amino acids, stabilizing the tertiary structure.

Interactions involving non-covalent bonds that stabilize the tertiary structure, including hydrogen bonds, hydrophobic interactions, and electrostatic interactions.

Weak interactions between nonpolar side chains of amino acids that cluster together in the protein interior, away from the water.

A protein composed of more than one polypeptide chain.

The arrangement of subunits in a protein with more than one polypeptide chain and the interactions between them.

A protein composed of a single polypeptide chain.

An oligomeric protein with two identical subunits.

An oligomeric proteins consisting of different subunits.

The process of breaking down proteins into amino acids.

The process of disrupting the native structure of a protein, leading to unfolding and loss of function.

The ability of a protein to dissolve in water.

The process of applying heat to a protein, which can disrupt the weak bonds holding the protein together and lead to denaturation.

The process of mechanically disrupting a protein's structure, for example, by shaking or stirring.

Extremes of pH can disrupt the electrostatic interactions between amino acids, leading to denaturation.

Organic compounds such as acetone and ethanol can disrupt hydrophobic interactions, leading to denaturation.

Detergents can disrupt hydrophobic interactions and electrostatic interactions, leading to denaturation.

Urea and guanidine hydrochloride can disrupt hydrogen bonding and hydrophobic interactions, leading to denaturation.

Reducing agents such as β-mercaptoethanol and dithiothreitol break disulfide bonds, leading to denaturation.

This refers to the specific three-dimensional structure that is required for a protein to perform its biological function. This shape is determined by the protein's amino acid sequence and various interactions within the protein.