protein Flashcards
What are the basic properties of amino acids?
Amino acids have an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen atom, and a unique side chain (R group) attached to a central carbon (α-carbon)
What are the main classes of amino acids?
Amino acids are classified based on the properties of their side chains into groups:
nonpolar (hydrophobic),
polar (hydrophilic),
acidic (negatively charged),
and basic (positively charged).
Examples include glycine (nonpolar), serine (polar), glutamate (acidic), and lysine (basic).
What is a peptide bond, and how is it formed?
A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another.
hydrolysis
What is the structural aspect of a peptide bond?
The peptide bond has a partial double-bond character, making it planar and rigid. This restricts rotation around the bond, which is crucial for the stable, three-dimensional structure of proteins.
What is an enantiomer in the context of amino acids?
Enantiomers are non-superimposable mirror images of chiral molecules. In amino acids, enantiomers are referred to as “L” (left-handed) and “D” (right-handed) forms. Only L-amino acids are commonly found in proteins.
How are amino acid enantiomers distinguished?
Amino acid enantiomers are distinguished based on their arrangement around the central (α) carbon. This central carbon is chiral, meaning it has four different groups attached to it. Enantiomers are identified by their optical activity; L-amino acids rotate plane-polarized light in one direction, while D-amino acids rotate it in the opposite direction.
Why is glycine not an enantiomer?
Glycine is not an enantiomer because it lacks a chiral center. Its R group is a hydrogen atom, making it symmetric around the central carbon. As a result, glycine cannot have L- or D- forms and does not display optical activity like other amino acids.
What is primary protein structure?
Primary structure is the linear sequence of amino acids in a polypeptide chain, held together by peptide bonds. The sequence determines the protein’s final shape and function. For example, insulin has a specific sequence of amino acids that allows it to regulate blood sugar.
What is secondary protein structure?
Secondary structure refers to local folded structures that form within a polypeptide due to hydrogen bonding. Common types include α-helices and β-sheets. For example, α-keratin in hair has an α-helix structure.
spontaneous
What is tertiary protein structure?
Tertiary structure is the three-dimensional shape of a protein, formed by interactions between side chains (hydrophobic interactions, hydrogen bonds, disulfide bridges). This structure is essential for protein function, such as the globular shape of enzymes.
requires accessory proteins (chaperones)
What is quaternary protein structure?
Quaternary structure occurs when multiple polypeptide chains (subunits) come together to form a functional protein. Hemoglobin, for instance, has four subunits that work together to carry oxygen in the blood.
prosthetic group added
What are protein domains?
Protein domains are specific regions within a protein that can fold independently and have unique structural or functional roles, such as binding to other molecules or carrying out enzymatic reactions.
What is the difference between functional and structural domains in proteins?
Functional domains perform specific activities like binding to DNA or enzymatic functions, while structural domains are stable regions of around 40+ amino acids that form secondary and tertiary structures.
What are the main structural classes of proteins?
globular proteins (water-soluble, compact),
fibrous proteins (elongated, low solubility, form fibers),
integral membrane proteins (span cell membranes with hydrophobic regions).
How does aspirin work at the molecular level?
Aspirin covalently binds to and inactivates cyclooxygenases, enzymes that produce prostaglandins involved in pain and inflammation, which is useful in pain management.
