Enzymes - the Catalysts of Life 1-2 Flashcards
Discuss the ways in which enzymes catalyse reactions.
Enzymes bind to substrates and catalyze reactions in four different ways: bringing substrates together in an optimal orientation, compromising the bond structures of substrates so that bonds can be more easily broken, providing optimal environmental conditions for a reaction to occur, or participating directly in their chemical reaction by forming transient covalent bonds with the substrates.
Describe the ways in which the rate of an enzyme-catalysed reaction may vary with changes in the concentration of the enzyme and of the substrate.
As the enzyme molecules become saturated with substrate, this increase in reaction rate levels off. The rate of an enzyme-catalyzed reaction increases with an increase in the concentration of an enzyme. At low temperatures, an increase in temperature increases the rate of an enzyme-catalyzed reaction
Describe the molecular nature of competitive and non-competitive inhibition of enzyme-catalysed reactions.
Inhibitors can bind to the active site of an enzyme which stops it being able to bind to the substrate. This is known as competitive inhibition as both the inhibitor and the substrate are competing for the active site of the enzyme. Alternatively, enzymes can bind allosterically at another site to the active one and change the shape of the active site, this is non competitive.
Define the term ‘Michaelis constant’, describe how it may be experimentally estimated
and describe what a knowledge of the constant may allow to be deduced about the nature of the catalysed reaction.
The Michaelis constant Km is equal to the reactant concentration at which rA=vmax/2. Km is independent of enzyme concentration but varies from one enzyme to another and with different substrates for the same enzyme. Values of. Km and other enzyme properties depend on the source of the enzyme.
Understand why enzyme activity is measured in a clinical setting.
Enzymes of the liver, kidney, skeletal muscle, heart, etc. leak into blood during related disorders. Measuring the amount of the corresponding protein for his or her presence in high or low levels in blood indicates the particular disorder. This is why it is important to have enzymes in medicine.
Understand what factors can influence enzyme activity in samples.
Several factors affect the rate at which enzymatic reactions proceed - temperature, pH, enzyme concentration, substrate concentration, and the presence of any inhibitors or activators.
Discuss the use of enzyme assays in clinical diagnosis.
Enzyme assays are mainly used for determination of body status of vitamins. As vitamins usually function either as coenzymes or building blocks of coenzymes, the activity of the vitamin-dependent enzymes is a measure of vitamin status. Usually, the assay is carried out by determining the enzyme activity with and without activation by added coenzyme. The activity can be monitored by measuring changes in concentration of substrates or products during the reaction.
