Functions of Proteins
- Living organisms synthesize many different proteins with a wide range of functions
- Proteins are so versatile that they have many different roles in cells, tissues and organs
- All of the following functions are performed by proteins:
- Speeding up cellular reactions, or catalysis, is performed by enzymes
- Blood clotting, where blood proteins interact with oxygen to form a gel-like scab across a wound
- Strengthening fibres in skin, hair, tendons, blood vessels eg. collagen, keratin
- Transport of vital metabolites eg. oxygen which is carried by haemoglobin
- Formation of the cytoskeleton, a network of tubules within a cell that cause chromosomes to move during the cell cycle
- Cell adhesion, where cells in the same tissue stick together
- Hormones, chemical messengers that are secreted in one part of the body to have an effect elsewhere
- Compaction of DNA in chromosomes for storage, caused by histone proteins
- The immune response produces antibodies, the most diverse group of proteins
- Membrane transport channel and carrier proteins that determine which substances can pass across a membrane
- Cell receptors, which are binding sites for hormones, chemical stimuli such as tastes, and for other stimuli such as light and sound
Examiner Tip
Many exam questions focus on enzymes but don't forget all the other types of protein when discussing protein functions.