Based on the formProteins were classified into 2, namely:a. Protein fibersCharacteristics:1. long fibers2. are not soluble in water3. has a structural function or protectiveexample:- Collagen: type of protein found in the connective tissue- Keratin: type of protein found in wool, natural silk, hair, nails, skin- Actin (muscle interaction)- Fibrin: blood clotting.
b. Globular proteinsCharacteristics:1. a very large protein2. soluble in water and easily diffusesexample:- Albumin found in blood serum and egg white- Globulin: found in blood serum, muscle and other tissues in the body- Histones: present in pancreatic tissue- Protamine: found in fish sperm cells- Enzymes, antibodies, hemoglobin, casein, and others.
Based on the biological functionProteins were classified into 7 categories:a. Protein structureFunction: giving strength or protection of biological structuresExample: collagen, keratin, fibroin
b. Protein and nutrient storageFunction: food reservesExample: ovalbumin in egg, casein in milk
c. AntibodiesFunction: immuneExample: imunoglobin, fibrinogen, and thrombin
d. EnzymeFunction: biocatalystExample: fibrinogen, amylase
e. Regulatory proteinsFunction: regulating cellular activityExample: hormone
f. Protein transportFunction: bind and remove specific molecules or ionsExample: Hb
g. Contractile proteinsFunction: provides the ability to move living thingsExample: actin, myosin.
Based on the combination with other compoundsa. Face protein: protein combined with carbohydrate groupsb. Lipoprotein: protein combined with fatc. Nucleoprotein: a combination of proteins with nucleic acids.