Biology · MU Pleven

2. Biological macromolecules. Proteins – structure and function.

Explains proteins as chains of amino acid residues whose sequence, set by genes, folds into a functional three-dimensional shape. Covers the four structural levels in turn: primary sequence and amino acid structure, secondary alpha helices and beta sheets, tertiary folding forces such as hydrophobic interactions and disulphide bridges, and quaternary assembly, illustrated with haemoglobin. Closes with protein synthesis from DNA and the main biological functions.

Inside: 8 sections · 2 labelled pictures · 20 flashcards · 6 min

Topic 2 of 63 in the MU Pleven syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 8 sections, about 905 words (6 min of reading), with 20 flashcards.

In this note

  1. Biological macromolecules. Proteins – structure and function.
  2. Structure:
  3. Primary:
  4. Secondary Structure:
  5. Tertiary Structure:
  6. Quaternary Structure:
  7. Protein Structure Determination
  8. Functions:

Biological macromolecules. Proteins – structure and function.

Proteins are large biological molecules, or macromolecules, consisting of one or more long chains of amino acid residues.

Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in folding of the protein into a specific threedimensional structure that determines its activity.

Structure:

The four levels of protein structure are distinguished from one another by the degree of complexity in the polypeptide chain. A single protein molecule may contain one or more of the protein structure types.

Primary:

  • Describes the unique order in which amino acids are linked together to form a protein.
  • Proteins are constructed from a set of 20 amino acids. Generally, amino acids have the following structural properties.
  • A carbon (the alpha carbon) bonded to the four groups below:

A hydrogen atom (H), A Carboxyl group (-COOH), An Amino group (-NH2), A "variable" group or "R" group All amino acids have the alpha carbon bonded to a hydrogen atom, carboxyl group, and amino group. The "R" group varies among amino acids and determines the differences between these protein monomers. The amino acid sequence of a protein is determined by the information found in the cellular genetic code.

The order of amino acids in a polypeptide chain is unique and specific to a particular protein. Altering a single amino acid causes a gene mutation, which most often results in a non-functioning protein.

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