proteins- david klein

An amino acid contains two key functional groups: Amino group (–NH₂) Carboxylic acid group (–COOH) These two groups can be separated by various numbers of carbon atoms, but the most biologically important amino acids are those where: The amino group is attached to the α-carbon, which is the carbon adjacent to the carboxyl group. ➤ α-Amino Acids: Defined by the structure: H 2 N – C H ( R ) – C O O H H 2 ​ N–CH(R)–COOH The α-carbon: Is bonded to: An amino group (–NH₂) A hydrogen (H) A carboxyl group (–COOH) A side chain group (R) Becomes a chiral center if R ≠ H.

Amino acids join to form peptides or proteins through amide bonds called peptide bonds. This occurs via a condensation reaction: The –NH₂ group of one amino acid reacts with the –COOH group of another. A molecule of water (H₂O) is eliminated. A peptide bond is formed: – C O – N H – –CO–NH– This reaction links amino acids into long chains (polypeptides).

A peptide is a short chain of amino acids linked by peptide bonds (amide linkages). Naming is based on the number of amino acids: Dipeptide: 2 amino acids Tripeptide: 3 amino acids Tetrapeptide: 4 amino acids And so on…

Chains with fewer than 40–50 amino acids are typically called polypeptides. Chains with more than 50 amino acids are usually considered proteins.

They perform a variety of structural, regulatory, transport, and catalytic functions. Enzymes are a class of proteins that: Act as biological catalysts Speed up chemical reactions in cells Are crucial for metabolism and life processes 🧠 It is estimated that the human body uses more than 50,000 enzymes to carry out life functions efficiently.

A: A short chain of amino acids linked by peptide (amide) bonds.

A: 2

A: 3

A: A peptide bond (–CO–NH–)

A: A polypeptide has fewer than 40–50 amino acids, while a protein is a longer chain (usually >50 amino acids).

A: Proteins that function as biological catalysts to speed up chemical reactions in cells.

A: When it has more than 50 amino acids.

to be needed by the human body? A: Over 50,000

A: Catalysis (enzymes), structure (e.g., collagen), transport (e.g., hemoglobin), signaling (e.g., hormones).

While 20 standard amino acids are commonly found in proteins, other amino acids exist in the body that: Are biologically important Do not get incorporated into proteins Serve specific physiological roles

Structure: NH₂–CH₂–CH₂–CH₂–COOH Classification: γ-amino acid (amino group is on the γ-carbon—3 carbons away from the carboxyl group) Function: Acts as a neurotransmitter Found in the brain Inhibitory — reduces neuronal excitability Not used in proteins

Structure: A complex derivative of tyrosine with iodine atoms Classification: A modified amino acid Function: A hormone secreted by the thyroid gland Regulates metabolism, growth, and development Not incorporated into proteins directly

A A: No, some amino acids (like GABA and thyroxine) are not found in proteins but still serve important functions in the body.

A: γ-Aminobutyric acid

A: It acts as an inhibitory neurotransmitter in the brain.

A: Because the amino group is on the γ-carbon (3 carbons away from the carboxyl group).

A: No

A: A hormone derived from tyrosine, produced by the thyroid gland.

A: It regulates metabolism, growth, and development.