One of the most abundant organic molecules in living systems with the most diverse range of functions of all macromolecules
Functions of proteins
Structural
Regulatory
Contractile
Protective
Transport
Storage
Membrane
Toxins
Enzymes
Each cell in a living system may contain thousands of different proteins, each with a unique function
Amino acids
The monomers that make up proteins
There are 20 different chemically distinct amino acids that form long chains, and the amino acids can be in any order
Enzymes
Catalysts in biochemical reactions (like digestion) that are usually proteins, each specific for the substrate upon which it acts
Hormones
Chemical signaling molecules, usually proteins or steroids, secreted by an endocrine gland or group of endocrine cells that act to control or regulate specific physiological processes
Protein shape
Critical to its function
Changes in temperature, pH, and exposure to chemicals may lead to permanent changes in the shape of the protein, leading to a loss of function or denaturation
All proteins are made up of different arrangements of the same 20 kinds of amino acids
Amino acid
The monomers that make up proteins, each with a central carbon atom bonded to an amino group, a carboxyl group, and a variable R group
Peptide bond
The covalent bond formed between the carboxyl group of one amino acid and the amino group of a second amino acid, releasing a water molecule
Polypeptide
A polymer of amino acids
Protein
A polypeptide or polypeptides that have combined together, have a distinct shape, and have a unique function
The sequence and number of amino acids ultimately determine a protein's shape, size, and function
Cytochrome c is an important component of the molecular machinery that harvests energy from glucose, and has changed very little over millions of years
Protein sequencing has shown that there is a considerable amount of sequence similarity among cytochrome c molecules of different species, allowing evolutionary relationships to be assessed
In sickle cell anemia, the hemoglobin β chain has a single amino acid substitution, causing a change in both the structure and function of the protein
Primary structure
The unique sequence and number of amino acids in a polypeptide chain
Secondary structure
Folding patterns resulting from interactions between the non-R group portions of amino acids, including alpha-helix and beta-pleated sheet structures
Tertiary structure
The unique three-dimensional structure of a polypeptide, caused by chemical interactions between various amino acids and regions of the polypeptide
Quaternary structure
The interaction of multiple polypeptide subunits to form a complete protein
Denaturation is the loss of a protein's shape, often reversible if the denaturing agent is removed, but sometimes irreversible
Nucleic acids are key macromolecules in the continuity of life, carrying the genetic blueprint and instructions for cell functioning
DNA
The genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals
RNA
Mostly involved in protein synthesis, communicating genetic information from the nucleus to the rest of the cell
Nucleotide
The monomers that make up DNA and RNA, consisting of a nitrogenous base, a pentose sugar, and a phosphate group
DNA has a double-helical structure composed of two strands of nucleotides bonded at the bases with hydrogen bonds