Proteins (Section 1.2: pp. 41-48)
Structure relates to function, so proper folding is vital. New properties emerge at higher orders of structure (Fig. 31)
Every protein has three orders of structure
1. Primary - this is the linear sequence of amino acids (Fig 31a; p 45)
2. Secondary- involves the backbone only (never any R-groups). Hydrogen bonds form between the carboxyl and amino groups to build alpha helices and beta pleated sheets (Fig 31b; p45)
3. Tertiary- involves R-groups. Includes H-bonding, ionic bonding, disulphide bridges (covalent bonding), and hydrophobic interactions (non-polar R-groups) (Fig 31c; p 46)
If the protein consists of two or more subunits,
4. Quaternary - involves R-groups of two or more polypeptide chains
(Fig 31d; p 46)
The structure of a protein can be disrupted (denatured) by organic solvents, heat, changes in pH, and chemical agents. Renaturation may occur under certain conditions. (see Fig 41; p 47)
Folding is accomplished with the help of chaperone proteins (p 48)
Nucleic Acids (section 1.2; pp 52-54; Fig 42)
-DNA and RNA
-made of nucleotides that are in turn made of a 5-carbon sugar (ribose in RNA; deoxyribose in DNA), one or more phosphate groups, and a nitrogenous base
There are 5 nitrogenous bases. Two purines include adenine (A) and guanine (G). Three pyrimidines include cytosine (C), thymine (T), and uracil (U). DNA contains CGAT, RNA contains CGAU.
DNA is the hereditary material of the cell and is replicated before cell division. RNA functions in protein synthesis, taking the message from DNA and bringing the amino acids to the ribosomes (so much more on this later!)
Each polymer is made by linking nucleotides by phosphodiester bonds on the sugar-phosphate backbone. RNA is a linear molecule that may show regions of H-bonding. DNA is a double helix with the bases inside held together by H-bonds. In each nucleus of our cells we have 3 billion base pairs in our DNA!
SUMMARY
see pp. 54-55
see also graphics gallery
lipids
and chemistry of life
monomers and polymers
lipids and polysaccharides
proteins
polynucleotides
NOTE: lipids are NOT polymers!!