Investigate the effect of temperature on the activity of trypsin, using a suspension of casein as the substrate.
Aim:
The aim of the experiment is to investigate the effect of temperature on the activity of trypsin, using a suspension of casein as the substrate.
Hypothesis:
Enzymes are substances that act as catalysts, in other words they increase the rate of chemical reactions.
In biological system, this reaction might occur very slowly, or not at all, in the absence of an enzyme. Enzymes will greatly increase the rate of formation of the product. Enzymes can increase the rate of reaction by a factor of at least one million.
Most enzymes are large protein molecules, with complex three-dimensional shapes.
This diagram shows the complex 3D-structure of trypsin.
Trypsin is an enzyme that acts to degrade protein; it is often referred to as a proteolytic enzyme, or proteinase. Trypsin is one of the three principal digestive proteinases, the other two being pepsin and chymotrypsin . In the digestive process, trypsin acts with the other proteinases to break down dietary protein molecules to their component peptides and amino acids. Trypsin continues the process of digestion (begun in the stomach) in the small intestine where a slightly alkaline environment (about pH 8) promotes its maximal enzymatic activity. Trypsin, produced in an inactive form by the pancreas, is remarkably similar in chemical composition and in structure to the other chief pancreatic proteinase, chymotrypsin.
Unlike chemical catalysts, enzymes are specific. This means that each enzyme will normally catalyse one reaction. The substances with which the enzyme combines with is know is the substrate, which combines with the enzyme at a particular place on the enzyme's surface called the active site. Enzyme molecules are usually very much larger than their substrate and their active site is only relatively small part of the enzyme.
The precise shape of the active site is important because it is complementary to the shape of the substrate molecule, which fits into the active site by what is often known as the 'lock-and-key' mechanism.
In living cells, most chemical reactions require an input of energy before the molecules will react together. This is referred to as the activation energy.
Enzymes increase the rates of reaction by reducing the free energy of activations, so that the barrier to a reaction occurring is lower in the presence of an enzyme. The combination of enzyme and substrate crease a new energy profile, for the reaction.
Activation Energy Without Enzyme
Energy
Level
Activation Energy With Enzyme.
Progress of Reaction
This graph illustrates how addition of an enzyme lowers the amount of activation energy required to initiate the reaction.
One the products have been formed; they leave the active site of the enzyme, which is left free to combine with a new substrate molecule. Enzymes, like chemical catalysts, are not used up in the reaction they catalyse so they can be used over and over again. The active site of an enzyme is the region that binds the substrate and contributes the amino acid residues that directly participate in the making and breaking of chemical bonds. The amino acid residues are called the catalytic groups. Enzymes differ widely in structure, function & mode of catalysis so active sites vary, but possible to make some generalizations. Enzymes are usually very large in comparison with substrate, so only small portion of amino acid residues are near or in direct contact with substrate in enzyme-substrate complex. Most of the enzyme involved in control and maintaining correct structural configuration of enzyme i.e. structural backbone. Active site is a 3-dimensional entity. Not a point or a plane usually an intricate pocket or cleft structurally designed to accept the structure of the substrate in 3-D terms. Substrate is bound by relatively weak forces. The free energy of interaction between enzyme and substrate ranges -12 to -36 kJ/mole compare this with the strength of a covalent bond up to -450 kJ/mole. Most are clefts or crevices designed to exclude water from the active site and are surrounded with non-polar amino acid residues, which give the active site a non-polar environment. This appears essential for both binding and catalysis. Essential to exclude water (unless water involved in the reaction) because water disrupts bond breaking and making processes. Specificity, active site provides specificity for its particular substrate, which is a characteristic feature of enzymes. The overall reaction between the enzyme and substrate can be represented by the following equation:
The aim of the experiment is to investigate the effect of temperature on the activity of trypsin, using a suspension of casein as the substrate.
Hypothesis:
Enzymes are substances that act as catalysts, in other words they increase the rate of chemical reactions.
In biological system, this reaction might occur very slowly, or not at all, in the absence of an enzyme. Enzymes will greatly increase the rate of formation of the product. Enzymes can increase the rate of reaction by a factor of at least one million.
Most enzymes are large protein molecules, with complex three-dimensional shapes.
This diagram shows the complex 3D-structure of trypsin.
Trypsin is an enzyme that acts to degrade protein; it is often referred to as a proteolytic enzyme, or proteinase. Trypsin is one of the three principal digestive proteinases, the other two being pepsin and chymotrypsin . In the digestive process, trypsin acts with the other proteinases to break down dietary protein molecules to their component peptides and amino acids. Trypsin continues the process of digestion (begun in the stomach) in the small intestine where a slightly alkaline environment (about pH 8) promotes its maximal enzymatic activity. Trypsin, produced in an inactive form by the pancreas, is remarkably similar in chemical composition and in structure to the other chief pancreatic proteinase, chymotrypsin.
Unlike chemical catalysts, enzymes are specific. This means that each enzyme will normally catalyse one reaction. The substances with which the enzyme combines with is know is the substrate, which combines with the enzyme at a particular place on the enzyme's surface called the active site. Enzyme molecules are usually very much larger than their substrate and their active site is only relatively small part of the enzyme.
The precise shape of the active site is important because it is complementary to the shape of the substrate molecule, which fits into the active site by what is often known as the 'lock-and-key' mechanism.
In living cells, most chemical reactions require an input of energy before the molecules will react together. This is referred to as the activation energy.
Enzymes increase the rates of reaction by reducing the free energy of activations, so that the barrier to a reaction occurring is lower in the presence of an enzyme. The combination of enzyme and substrate crease a new energy profile, for the reaction.
Activation Energy Without Enzyme
Energy
Level
Activation Energy With Enzyme.
Progress of Reaction
This graph illustrates how addition of an enzyme lowers the amount of activation energy required to initiate the reaction.
One the products have been formed; they leave the active site of the enzyme, which is left free to combine with a new substrate molecule. Enzymes, like chemical catalysts, are not used up in the reaction they catalyse so they can be used over and over again. The active site of an enzyme is the region that binds the substrate and contributes the amino acid residues that directly participate in the making and breaking of chemical bonds. The amino acid residues are called the catalytic groups. Enzymes differ widely in structure, function & mode of catalysis so active sites vary, but possible to make some generalizations. Enzymes are usually very large in comparison with substrate, so only small portion of amino acid residues are near or in direct contact with substrate in enzyme-substrate complex. Most of the enzyme involved in control and maintaining correct structural configuration of enzyme i.e. structural backbone. Active site is a 3-dimensional entity. Not a point or a plane usually an intricate pocket or cleft structurally designed to accept the structure of the substrate in 3-D terms. Substrate is bound by relatively weak forces. The free energy of interaction between enzyme and substrate ranges -12 to -36 kJ/mole compare this with the strength of a covalent bond up to -450 kJ/mole. Most are clefts or crevices designed to exclude water from the active site and are surrounded with non-polar amino acid residues, which give the active site a non-polar environment. This appears essential for both binding and catalysis. Essential to exclude water (unless water involved in the reaction) because water disrupts bond breaking and making processes. Specificity, active site provides specificity for its particular substrate, which is a characteristic feature of enzymes. The overall reaction between the enzyme and substrate can be represented by the following equation:
