y3.1: enzymes 🔐 Flashcards
catabolic vs anabolic reactions
- catabolic: break up complex molecules into simpler molecules (eg hydrolysis)
- anabolic: build up simpler molecules intro complex molecules (eg condensation reactions)
what is the mode of action of enzymes?
- effective collision between specific substrates and the enzyme in the correct orientation
- substrate molecules bind to the active site of the enzyme to form a enzyme-substrate complex
- this lowers the activation energy and chemical reaction occurs
- products are released into surrounding medium
lock and key vs induced fit model
lock and key:
- substrate is a “key” whose shape is complementary to the active site of the enzyme, the “lock”
- substrate fits exactly into the active site of the enzyme
VS
induced fit model:
- active site of enzymes is complementary not an exact fit to the substrate
- when substrate binds to the active site of the enzyme, it induces a change in the shape of the active site, allowing the substrate to fit more tightly into the active site
both:
- substrate binds to the active site of the enzyme, forming an enzyme-substrate complex
- chemical reaction occurs and products are released into the surrounding medium
what are the characteristics of enzymes?
1) enzymes speed up the rate of chemical reactions by lowering the activation energy
2) enzymes are required in minute amounts because they remain unchanged at the end of chemicaal reactions
3) enzymes are specific in nature due to their unique 3d shape
effect of temperature on enzymatic reaction (low temperature)
- enzymes are inactive (reversible)
- chance of effective collision is low; less enzyme-substrate complexes are formed
- rate of reaction decreases
effect of temperature on enzymatic reaction (temperature increasing up to optimum temperature)
- as temperature increases, kinetic energy of enzyme and substrate increases
- increases the chance of effective collision; more enzyme substrate complexes are formed
- rate of reaction increases
- rate of reaction is at its maximum at optimum temperature
effect of temperature on enzymatic reaction (beyond optimum temperature)
- enzymes become denatured, enzyme loses its 3d shape and active site is unable to bind to the substrate (irreversible)
- less enzyme-substrate complexes are formed, rate of reaction decreases
effect of pH on rate of enzymatic reaction
- enzymes have an optimum pH at which enzyme activity is at the maximum
- any pH that deviates from the optimum pH causes enzymes to denature
- lose the 3d shape, active site is unable to bind to the substrate, less enzyme-substrate complexes are formed and rate of reaction decreases (irreversible)
effect of enzyme concentration on enzymatic reaction
increasing gradient of graph:
- enzyme concentration is the limiting factor
- when enzyme concentration increases, more effective collision occurs, more enzyme-substrate complexes are formed, rate of reaction increases
at plateau:
- substrate concentration is the limiting factor
- not enough substrate molecules to occupy all active sites of the enzymes
- rate of reaction remains constant
effect of substrate concentration on enzymatic reaction
increasing gradient of graph:
- substrate concentration is the limiting factor
- when substrate concentration increases, more effective collision, more enzyme-substrate complexes formed, rate of reaction increases
at plateau:
- enzyme concentration is the limiting factor
- all enzyme active sites are occupied, enzymes are saturated, no further increase in rate possible
- rate of reaction remains constant
what is a limiting factor?
a factor that directly affects the rate of chemical reaction if its quantity is changed. the value of this factor has to be increased in order to increase the rate of the process
enzymes
enzymes are biological catalysts which speed up the rate of chemical reactions without themselves being chemically changed at the end of the reactions
