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Role and structure of enzymes
Metabolism refers to all the chemical reactions that take place inside living cells or organisms. In anabolic reactions molecules are synthesised and energy is required. An example would be photosynthesis. In catabolic reactions molecules are broken down and energy is released. An example would be cellular respiration.
Enzymes a biological catalysts:
Catalyst: Increase the rate of a chemical reaction but are unchanged at the end.
Biological: They are produced by cells and catalyse metabolic reactions inside cells or organisms.
Enzymes increase the rate of metabolic reactions by binding a specific substrate and converting it into a product. The enzyme is unchanged in the reaction and able to bind another substrate. The turnover number is the number of reactions that can be catalysed per second. Metabolic reactions are linked together to form metabolic pathways. Each step is catalysed by a different specific enzyme. The product of one enzyme is the substrate for the next.
Advantages of using enzymes over chemical catalysts:
Specific to a particular substrate/reaction so enzymes do not produce unwanted byproducts.
High turnover.
Work at lower temperatures and pressures and often at neutral pH.
Production and activity of enzyme can be regulated by cell.
Disadvantages of using enzymes over chemical catalysts:
Less stable.
May require specific cofactors to work.
Enzymes a proteins coded for by genes so mutations mat affect their tertiary structure and activity and cause a metabolic disorder.
Catalase
Catalase is an enzyme found in peroxisomes with a high turnover. It catalyses the breakdown of hydrogen peroxide to oxygen and water (2H₂O₂ → O₂ + 2H₂O). Hydrogen peroxide must be broken down quickly as it can damage DNA and cause mutations. The catalase structure consists of 4 identical polypeptide chains each with an iron containing haem prosthetic group (similar to haemoglobin). Catalase is an example of an intracellular enzyme which are enzymes that act inside cells.
Amylase
Amylase catalyses the hydrolysis of starch into maltose. It acts in the mouth if produced by the salivary glands and in the small intestines if produced by the pancreas. It is an example of an extracellular enzyme which are enzymes that act outside of cells.
Extracellular enzymes or particularly important for extracellular digestion which many organisms rely on to obtain nutrients. The enzymes digest the complex macromolecules into smaller molecules that can be absorbed and used in respiration or for synthesis of molecules for growth.
Enzyme structure
Enzymes are globular proteins. They have a tertiary structure, which gives them a specific 3D shape that is essential for their function. The substrate binds to a part of the enzyme called the active site, which has a specific shape that is complementary in shape to the substrate.
Enzymes are generally soluble in water, therefore the hydrophilic R groups will be on the outside where they can interact with water, while the hydrophobic R groups will be on the inside where they can interact with each other and exclude water.
The tertiary structure of enzymes is maintained by many weak hydrogen bonds and ionic bonds between the R groups, which can be broken by extremes of pH and high temperatures causing the enzyme to denature. Denaturation is an irreversible change in the tertiary structure of a protein. If the shape of the active site of an enzyme is changed, then it will no longer be complementary in shape to the substrate and will therefore not be able to catalyse that reaction.
Role and structure of enzymes
Metabolism refers to all the chemical reactions that take place inside living cells or organisms. In anabolic reactions molecules are synthesised and energy is required. An example would be photosynthesis. In catabolic reactions molecules are broken down and energy is released. An example would be cellular respiration.
Enzymes a biological catalysts:
Catalyst: Increase the rate of a chemical reaction but are unchanged at the end.
Biological: They are produced by cells and catalyse metabolic reactions inside cells or organisms.
Enzymes increase the rate of metabolic reactions by binding a specific substrate and converting it into a product. The enzyme is unchanged in the reaction and able to bind another substrate. The turnover number is the number of reactions that can be catalysed per second. Metabolic reactions are linked together to form metabolic pathways. Each step is catalysed by a different specific enzyme. The product of one enzyme is the substrate for the next.
Advantages of using enzymes over chemical catalysts:
Specific to a particular substrate/reaction so enzymes do not produce unwanted byproducts.
High turnover.
Work at lower temperatures and pressures and often at neutral pH.
Production and activity of enzyme can be regulated by cell.
Disadvantages of using enzymes over chemical catalysts:
Less stable.
May require specific cofactors to work.
Enzymes a proteins coded for by genes so mutations mat affect their tertiary structure and activity and cause a metabolic disorder.
Catalase
Catalase is an enzyme found in peroxisomes with a high turnover. It catalyses the breakdown of hydrogen peroxide to oxygen and water (2H₂O₂ → O₂ + 2H₂O). Hydrogen peroxide must be broken down quickly as it can damage DNA and cause mutations. The catalase structure consists of 4 identical polypeptide chains each with an iron containing haem prosthetic group (similar to haemoglobin). Catalase is an example of an intracellular enzyme which are enzymes that act inside cells.
Amylase
Amylase catalyses the hydrolysis of starch into maltose. It acts in the mouth if produced by the salivary glands and in the small intestines if produced by the pancreas. It is an example of an extracellular enzyme which are enzymes that act outside of cells.
Extracellular enzymes or particularly important for extracellular digestion which many organisms rely on to obtain nutrients. The enzymes digest the complex macromolecules into smaller molecules that can be absorbed and used in respiration or for synthesis of molecules for growth.
Enzyme structure
Enzymes are globular proteins. They have a tertiary structure, which gives them a specific 3D shape that is essential for their function. The substrate binds to a part of the enzyme called the active site, which has a specific shape that is complementary in shape to the substrate.
Enzymes are generally soluble in water, therefore the hydrophilic R groups will be on the outside where they can interact with water, while the hydrophobic R groups will be on the inside where they can interact with each other and exclude water.
The tertiary structure of enzymes is maintained by many weak hydrogen bonds and ionic bonds between the R groups, which can be broken by extremes of pH and high temperatures causing the enzyme to denature. Denaturation is an irreversible change in the tertiary structure of a protein. If the shape of the active site of an enzyme is changed, then it will no longer be complementary in shape to the substrate and will therefore not be able to catalyse that reaction.
