proteiin

Proteiin is not a standard scientific term; in most contexts it refers to protein, a broad class of biomolecules essential to life. Proteins are polymers built from amino acids linked by peptide bonds.

Amino acids: There are 20 standard amino acids; the sequence determines structure and function. The chain folds into secondary structures like alpha helices and beta sheets; the overall 3D arrangement is the tertiary structure. Some proteins assemble into multi-subunit complexes (quaternary structure).

Synthesis: Genes encode proteins; transcription to mRNA; translation on ribosomes; tRNA delivers amino acids. After synthesis, proteins often undergo folding aided by chaperone proteins and post-translational modifications. Misfolding can cause disease; proteins are degraded by proteasomes or lysosomes when damaged or no longer needed.

Functions: Enzymes accelerate reactions, structural proteins give support (collagen, keratin), transporters move substances (hemoglobin), signaling molecules (hormones, receptors), immune molecules (antibodies). Proteins also regulate gene expression and metabolism.

Classification and examples: Fibrous proteins (keratin, collagen) are structural; globular proteins (enzymes, many transport proteins) are typically soluble. Some proteins require cofactors (heme in hemoglobin) and are called conjugated proteins.

Biological importance and diet: Proteins provide amino acids for growth and repair; the body can synthesize some but not all essential amino acids; dietary proteins vary in quality. Protein concentration and integrity are measured by assays in labs.