L2 - factors affecting enzyme function

• Factors which affect the rate of reaction of enzymes:

  -pH

  -temperature

  -enzyme concentration

  -substrate concentration
• How pH affects enzyme reaction rate:

  -a change of pH results in changes to H+ concentration

  -a pH either side of the enzyme’s optimum pH will affects bonds that hold the enzyme structure together

  -3D enzyme structure is denatured

  -successful collision number is reduced so fewer enzyme substrate complexes are formed
• How temperature affects enzyme reaction rate:

  -temperature increase means kinetic energy increase

  -more kinetic energy means more frequent successful collisions

  -rate of reaction doubles every 10*C increase

  -too high a temperature and enzymes denature

  -most bodily enzymes have a 40*C optimum but others have evolved to work at much higher temperatures
• Temperature coefficient or Q10 value shows how much the rate of reaction changes when the temperature is raised by 10*C

  
• Tyrosinase is an enzyme that makes melanin pigment (dark colour). Mutant tyrosinase is denatured at body temperature. Extremities are colder so it is not denatured on ears, feet, and face
• How enzyme concentration affects enzyme reaction rate:

  -an increase means more active sites are available so more enzyme substrates complexes can be made each second

  -the rate of reaction increases until it reaches its maximum (Vmax). at this point all the substrate molecules are in active sites so the rate cannot increase unless more substrate is added
• How substrate concentration affects enzyme reaction rate:

  -an increase means more collisions so move complexes are formed

  -at high substrate concentrations, the enzyme is saturated with substrate (adding more will not speed up the reaction)

  -only was to increase rate is to increase enzyme concentration or temperature
• Catalase enzyme:

  -organisms produce hydrogen peroxide naturally as its a waste product of metabolism

  -hydrogen peroxide is often used as bleach and also a propellant in rockets

  -means it’s very dangerous to cells

  -because of this, nearly all living things have an enzyme (called catalase) that decomposes low concentrations of hydrogen peroxide to water and oxygen