Proteins are the work horses of cells. This is a review from last lecture. You should be able to show the peptide bond formation as depicted above. The primary structure of proteins consists of all covalent interactions, ie.
Secondary structure is stabilized by hydrogen bonds formed between components of the peptide bonds.
Parts of the structure that are not highly stable adopt a random coil formation. Figure 4.07 from the textbook. H-N Figure 4.09 from the textbook. Amino acids which are very distant in the primary structure might be close in the tertiary one because of the folding of the chain. Sometimes the function of proteins can only be understood in the context of the whole structure of proteins.