Protein Functions


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•  Living organisms synthesise many different proteins with a wide range of functions

Proteins are a very diverse class of compounds and may serve a number of different roles within a cell, including:

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  • Structure – e.g. collagen, spider silk
  • Hormones – e.g. insulin, glucagon
  • Immunity – e.g. immunoglobulins
  • Transport – e.g. haemoglobin
  • Sensation – e.g. rhodopsin
  • Movement – e.g. actin, myosin
  • Enzymes – e.g. Rubisco, catalase

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•  Rubisco, insulin, immunoglobulins, rhodopsin, collagen and spider silk as examples of the range of 

   protein functions

The following are specific examples of the different functions of proteins:


  • Collagen: A component of the connective tissue of animals (most abundant protein in mammals)
  • Spider silk: A fiber spun by spiders and used to make webs (by weight, is stronger than kevlar and steel)


  • Insulin: Protein produced by the pancreas and triggers a reduction in blood glucose levels
  • Glucagon: Protein produced by the pancreas that triggers an increase in blood glucose levels


  • Immunoglobulins: Antibodies produced by plasma cells that are capable of targeting specific antigens


  • Haemoglobin: A protein found in red blood cells that is responsible for the transport of oxygen
  • Cytochrome: A group of proteins located in the mitochondria and involved in the electron transport chain


  • Rhodopsin: A pigment in the photoreceptor cells of the retina that is responsible for the detection of light


  • Actin: Thin filaments involved in the contraction of muscle fibres
  • Myosin: Thick filaments involved in the contraction of muscle fibres


  • Rubisco: An enzyme involved in the light independent stage of photosynthesis