A family of proteins is a group of homologous proteins, often with the same or similar functions. Examples are haemoglobin and myoglobin, and the cytochroms c from various species. A disulfide bond is a covalent bond formed between the sulfur atoms of two cysteine side chains. They may be interchain or intrachain. See diagram top left page 60.
Globular proteins are less regular with an overall roughly spherical shape.
It would be a good idea to draw simple diagrams. In Silk fibres polypeptide chains are fully extended and arranged antiparrallel. To extend a silk fibre would involve breaking of many covalent bonds. Meanwhile keratin molecules in hair are a -helical. To stretch a hair requires only the breakage of hydrogen bonds.