2.1.4 - Enzymes Flashcards
What is an enzyme ?
A biological catalyst that increase the rate of chemical reactions without being used up
Define the term ‘Metabolism’ ?
Metabolism - All the chemical reactions that occur within a living organism
Define the term ‘Anabolic reaction’ ?
Anabolic reactions - The building of large molecules from smaller molecules
Name an example of enzymes being involved in anabolic reactions ?
The synthesis of large polymer-based components in cells
Define the term ‘Catabolic reactions’ ?
Catabolic reactions - The breakdown of larger molecules into smaller molecules
Name an example of enzymes being involved in catabolic reactions ?
The breakdown of glucose to release energy
Define the term ‘intercellular enzymes’ ?
Intercellular enzymes - Enzymes that catalyse reactions inside the ell that produced them
Name an example of an intercellular enzyme ?
Catalase - An intercellular enzyme that catalyses the breakdown of hydrogen peroxide into oxygen and water. Hydrogen peroxide is a toxic product of many metabolic pathways therefore preventing its accumulation.
Define the term ‘Extracellular enzymes’ ?
Extracellular enzyme - Enzymes that catalyse reactions outside the cell that produced them
What is the role of extracellular enzymes ?
- Nutrients are often in the form of polymers and therefore too large to enter cell via the cell surface membrane
- Extracellular enzymes are used to break down the large nutrient molecules into smaller molecules so they can be absorbed by the cell
Name examples of an extracellular enzymes ?
- Amylase
- Trypsin
Explain how amylase acts as an extracellular enzyme ?
Amylase - It is an extracurricular enzyme that breakdown of starch to maltose.
- Maltase catalyses breakdown of maltose to glucose which os then small enough to be absorbed by cells lining the digestive system and into the bloodstream
Explain how trypsin acts as an extracellular enzyme ?
- Trypsin is a protease that catalyses the digestion of proteins into smaller peptides which can then be broken down into amino acids by other proteases
- Amino acids are then absorbed by cells lining digestive system and then absorbed into bloodstream
Define the term ‘Activation energy’ ?
Activation energy - The minimum amount of energy required for a chemical reaction to occur
How do enzymes function ?
- Many different enzymes are produced by organisms, each enzyme catalysing one biological reaction making them specific ( specificity of enzyme )
- Enzymes help the molecules collide, lowering the activation energy required by the reaction and producing an alternative reaction pathway
Define the term ‘Turnover number’ ?
Turnover number : The number of reactions that an enzyme molecule can catalyse per second
What are the two models for how enzymes function ?
- Lock and key hypothesis
- Induced-fit hypothesis
Explain the lock and key hypothesis ?
- The tertiary structure of the enzyme determines the enzyme’s and enzyme’s active site’s shape which is complementary to a specific substrate molecule
- Lock and key hypothesis says that like only a specific key will fit into a lock / only a specific substrate will ‘fit’ in active site of enzyme
- When the substrate binds to the active site of an enzyme, an enzyme-substrate complex forms. Substrate then react leading to formation of product in enzyme-product complex which are then released leaving the enzyme to react is subsequent reactions
Explain the induced-fit hypothesis ?
- The induced-fit hypothesis suggests the enzyme’s active site changes shape slightly when reacting with substrate to accommodate for the substrate
- When a substrate binds with active site of an enzyme, this induces a change in the enzymes tertiary structure so it becomes complementary to substrate
- This can put strain on substrate and weaken bonds in substrate lowering the activation energy of the reaction
What are the factors affecting enzyme activity ?
- Temperature
- pH
- Substance concentration
- Inhibitors