Enzymes Flashcards
Define enzymes
Biological catalysts which speed up the rate of chemical reaction s without themselves being chemically changed at the end of chemical reactions. They can be reused and effective in small concentrations
Define catabolic reactions
Reactions that break up complex molecules into simpler molecules
Define anabolic reactions
Consist of chemical reactions which build up simpler molecules into complex molecules
Define activation energy
The energy that must be supplied to reactant molecules for them to react
Why is heating inappropriate for a biological system
High temperatures denature proteins and kills cells. Heating will also speed up all chemical reactions and not just the intended ones
Describe the lock and key hypothesis
Substrate is “key” and enzyme is “lock”. Substrate whose shape is complementary to shape of active site of enzyme. Active site of enzyme has specific shape into which substrate fits exactly. Substrate binds to active site of enzyme, forming enzyme-substrate complex. Once products are formed, they no longer fit into active site of enzyme and are released into surrounding medium
Describe the induced fit model
Active site of enzyme is complementary in shape but not perfect fit to substrates it catalyses. When substrate binds to the active site of the enzyme, it incudes a change in the shape of the active site. This allows the substrate to fit more tightly into the active site. Binding of substrate to active site of enzyme occur, enzyme-substrate complex is formed. Chemical reaction occurs and formed products are released into surrounding medium as they no longer fit into active site of enzyme
What are the characteristics of enzymes
They speed up chemical reactions by lowering activation energy. Enzymes are extremely efficient. They remain chemically unchanged after the reactions and can be used repeatedly, hence required in small concentration. Enzymes are specific in action due to its 3D shape
Define optimum temperature of enzymes
The temperature at which the rate of enzyme activity is at its maximum. Different enzymes have different optimum temperatures
What happens when temperature of enzymes is low
Rate of enzymes is low at low temperatures and are inactive. This is a reversible condition where enzymes increase in activity when temperature increases
What happens when temperature of enzyme increases towards optimum temperature
As temperature increase, kinetic of substrate and enzyme molecules increases. Enzymes are more active. Substrate and enzyme molecules collide more often, increases number of effective collisions and formation of enzyme-substrate complex and rate of reaction. Rate of reaction maximum at optimum temperature
What happens when temperature increases beyond optimum temperature
Rate of reaction starts to decrease. Enzyme is denatured, loses 3D shape and active site is unable to bind to the substrate. Once enzyme is denatured, it is irreversible and cannot regain function. As temperature continues to rise, more enzyme molecules are denatured which causes rate of reaction to decrease further
Define optimum pH
The pH at which enzymes activity is at its maximum. Different enzymes have different optimum pH
Describe the effect of pH on enzymes
Any pH that deviates from the optimum pH will cause rate of reaction to decrease. At extreme pH, enzyme loses 3D shape and active site is unable to bind to the substrate. When enzyme is denatured, it is irreversible and cannot regain its function
Define limiting factor
A factor that directly affects the rate of chemical reaction if quantity is changed. The value of factor has to be increased in order to increase the rate of process
