Enzymes
Enzymes: are biological catalysts made of proteins formed in unique 3-dimensional shapes. They increase the rate of chemical reactions (by reducing the activation energy of reactions) without themselves being chemically changed at the end of the reactions
Lock and Key hypothesis
- Actions of enzymes are specific to the targeted substrates.
- Enzyme= “Lock”, Substrate=”Key”
- The specificity of an enzymes action is due to the shape of substrate and the enzyme active sites being complimentary to each other just like a Lock and a key.
- Enzymes only need to be present in small quantity since they are reuse after their actions.
Denaturation
Denaturation is the change in a three-dimensional structure of an enzyme or any other solution proteins, caused by heat or chemicals such as acids or alkalis.
Enzymes-catalyzed processes
Break down substances:
• Digestion of food substances by breaking down of larger food molecules into smaller water soluble molecules which are diffusible through cells membrane in order to be absorbed by the body.
• Breakdown of glucose during cells respiration.
Build up substances: synthesis of complex substances within cells
• Photosynthesis dark stage synthesis of glucose by chloroplasts.
• Building various proteins from amino acids.
• Building glycogen or starch from glucose for storage
• Digestion of food substances by breaking down of larger food molecules into smaller water soluble molecules which are diffusible through cells membrane in order to be absorbed by the body.
- Amylase: digest starch to maltose.
- Maltase: digest maltose to glucose.
- Proteases: digest proteins to amino acids
- Lipase: digest lipid to fatty acids and glycerol
• Breakdown of glucose during cells respiration.
Build up substances: synthesis of complex substances within cells
• Photosynthesis dark stage synthesis of glucose by chloroplasts.
• Building various proteins from amino acids.
• Building glycogen or starch from glucose for storage
Factors affecting enzymes
Temperature:
• Enzymes are less active at very low temperature.
• Rising temperature increases the rate of reaction by higher collision rate between enzymes and substrates. Enzymes are twice as active when temperature is raised by 10 degree C till the optimum temperature is reached.
• Beyond optimum temperature, enzymes start to denatured and lost their ability to catalyze the reaction.
pH level:
• Different Enzymes structures are specific at different pH level. Extreme deviation of pH environment denatures the enzymes.
Limiting factor (Substrate and enzyme Concentrations):
• When the limiting factor of a reaction is the enzymes concentration, increasing the enzyme concentration will increase the rate of reaction.
• Increase substrates concentration increases the rate of reaction when
enzymes concentration is not the limiting factor.
• Enzymes are less active at very low temperature.
• Rising temperature increases the rate of reaction by higher collision rate between enzymes and substrates. Enzymes are twice as active when temperature is raised by 10 degree C till the optimum temperature is reached.
• Beyond optimum temperature, enzymes start to denatured and lost their ability to catalyze the reaction.
pH level:
• Different Enzymes structures are specific at different pH level. Extreme deviation of pH environment denatures the enzymes.
Limiting factor (Substrate and enzyme Concentrations):
• When the limiting factor of a reaction is the enzymes concentration, increasing the enzyme concentration will increase the rate of reaction.
• Increase substrates concentration increases the rate of reaction when
enzymes concentration is not the limiting factor.
