Proteins (IB Topic B1.2) | Quizlet

Amino acid

Organic molecules that serve as the building blocks of proteins, consisting of a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and an R-group (side chain).

Polypeptide

A chain of amino acids linked together by peptide bonds, which folds into a specific three-dimensional structure to form a protein.

Protein

Large biomolecules composed of one or more polypeptides that perform various functions in the body, including enzymatic, structural, transport, and signaling roles.

Peptide bond

A covalent bond formed between the amino group of one amino acid and the carboxyl group of another through a condensation reaction.

Condensation reaction

A chemical reaction in which two molecules combine to form a larger molecule, releasing a molecule of water in the process.

Dipeptide

A molecule consisting of two amino acids joined by a single peptide bond.

Oligopeptide

A short chain of amino acids, typically consisting of 2-20 residues.

Essential amino acids

Amino acids that cannot be synthesized by the human body and must be obtained from the diet.

Non-essential amino acids

Amino acids that can be synthesized by the human body and do not need to be consumed through diet.

Zwitterion

A molecule with both positive and negative charges, such as an amino acid at its isoelectric point, where the amino group is protonated, and the carboxyl group is deprotonated.

R-group (side chain)

The variable group attached to the central carbon of an amino acid that determines its chemical properties and role in protein structure.

Primary structure

The linear sequence of amino acids in a polypeptide chain, held together by peptide bonds.

Secondary structure

The local folding of a polypeptide into regular structures such as alpha-helices and beta-pleated sheets, stabilized by hydrogen bonds.

Tertiary structure

The overall three-dimensional shape of a polypeptide, determined by interactions among R-groups, including hydrogen bonds, ionic bonds, disulfide bonds, and hydrophobic interactions.

Quaternary structure

The arrangement of multiple polypeptide chains in a protein, often including interactions between subunits and sometimes involving prosthetic groups.

Alpha-helix

A coiled secondary structure of proteins stabilized by hydrogen bonds between every fourth amino acid.

Beta-pleated sheet

A sheet-like secondary structure of proteins formed by hydrogen bonds between strands of a polypeptide chain.

Hydrogen bond

A weak interaction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Disulfide bond

A covalent bond between sulfur atoms in the R-groups of two cysteine residues, contributing to protein stability.

Ionic interactions

Attractions between oppositely charged R-groups in a protein that help stabilize its tertiary structure.

Hydrophobic interactions

The tendency of nonpolar R-groups to cluster together in the interior of a protein, avoiding contact with water.

Globular protein

Proteins with compact, spherical shapes that are typically soluble in water and involved in dynamic functions like catalysis and transport.

Fibrous protein

Proteins with elongated, fibrous shapes that provide structural support and strength, such as collagen and keratin.

Denaturation

The loss of a protein's native structure and function due to environmental changes like pH or temperature.

pH

A measure of the acidity or basicity of a solution, influencing protein stability and interactions.

Temperature

A physical factor affecting protein stability, where extreme heat can disrupt non-covalent interactions, leading to denaturation.

Integral proteins

Membrane proteins embedded in the lipid bilayer, often exhibiting polar and non-polar regions aligned with their environment.

Conjugated protein

A protein that contains a non-protein prosthetic group covalently or non-covalently bound to its structure.

Non-conjugated protein

A protein that consists solely of amino acids and lacks any prosthetic groups.

Prosthetic group

A non-protein component tightly bound to a protein that is essential for its biological activity.

Form and function

A concept in biology where the shape and structure of a molecule, such as a protein, determines its function.

Polarity

The distribution of electrical charge across a molecule or its regions, influencing interactions and solubility.

Cysteine

An amino acid with a thiol (-SH) group in its R-group, capable of forming disulfide bonds that stabilize protein structures.

Acid-base properties

The ability of amino acids to act as acids or bases, depending on the pH of their environment, due to their ionizable groups.

Protein conformation

The three-dimensional shape of a protein, essential for its biological function.