2.1.4 - Enzymes Flashcards
What are enzymes ?
Enzymes are biological catalysts that increase the rate of a chemical reaction, but are not consumed by that reaction
What type of proteins are enzymes ?
Globular proteins
What is meant by enzymes being specific ?
- Each enzyme is very selective, it catalyses specific reactions
- Each enzyme recognises a specific substrate, the active site fits to the substrate
What is the shape of the active site determined by ?
It is determined by the tertiary structure of the protein
What does an enzyme catalyst do ?
- Lowers the activation energy
- It is not used up during the reaction
- After the reaction, the enzyme is free to bind to a new substrate molecule.
What is activation energy ?
- It is the energy that must must be overcome in order for a reaction to occur
- The minimum amount of energy require for the reaction to begin
What are anabolic reactions ?
Chemical reactions required for growth
What catalyses anabolic reactions ?
Enzymes
What are catabolic reactions ?
Chemical reactions that break things down
What catalyses catabolic reactions ?
Enzymes
Define metabolism
Metabolism is all of the reactions happening in a cell or an organism at a given time
Define Vmax
- Vmax is the maximum possible rate of reaction
- Enzymes can only increase the rate of reaction until this point
Briefly explain how temperature increases the rate of reaction
When high temperatures and pressures are applied, the speed of the molecules will increase, therefore so will the number of successful collisions and the overall rate of reaction
What are the two hypothesis for enzymes ?
- Lock and key hypothesis
- Induced fit hypothesis
What is the lock and key hypothesis ?
- Only a specific substrate will fit the active site of an enzyme
- When the substrate is bound to the active site, an enzyme-substrate complex is formed
- The substrate then reacts and the products are formed in an enzyme product complex
What is the induced fit hypothesis ?
- The initial interaction between the enzyme and substrate is relatively weak
- These weak interactions rapidly induce changes in the enzymes tertiary structure which then strengthens the binding, putting strain on the substrate molecule
What are intracellular enzymes ?
Enzymes that act within cells
Give an example of an intracellular enzyme
Catalase breaks down hydrogen peroxide because it is a toxic product of many metabolic pathways
What are extracellular enzymes ?
Enzymes that are released from cells to break down large molecules into smaller molecules, done outside of the cell
Explain extracellular enzymes in single celled organisms
Single celled organisms, such as bacteria and yeast, release enzymes into their environment. The enzymes break down large molecules, which are then absorbed by the cells.
Explain extracellular enzymes in multicellular organisms
Large molecules are digested so smaller molecules can be absorbed into the bloodstream. They are then transported around the body to be used as substrates.
Explain the digestion of starch
- Starch is broken down into maltose, which is a disaccharide. The enzyme involved in this is called amylase
- Maltose then broken into glucose, which is a monosaccharide, the enzyme involved in this is maltase.
What is amylase ?
- Enzyme involved in the breakdown of starch into maltose
- It is present in the salivary glands and the pancreas.
- It is released in saliva into the mouth and in pancreatic juice into the small intestine
What is maltase ?
- Involved in the breakdown of maltose into glucose
- Present in the small intestine
What is trypsin ?
- Trypsin is a protease enzyme, an enzyme that catalyses the digestion of proteins
- It is produced in the pancreas and released with the pancreatic juice into the small intestine, where it acts on proteins
What is trypsin involved in ?
It is involved in the digestion of proteins into smaller peptides, which can then be broken into amino acids by other proteases
How are amino acids reabsorbed ?
They are absorbed by living cells of the digestive system and then absorbed into the bloodstream
What are the factors that affect enzyme activity ?
- Temperature
- pH
- Enzyme concentration
- Substrate concentration
What factors affect the structure of the enzyme ?
- Temperature
- pH
How can these factors be investigated ?
They can be investigated by measuring the rate of the reactions they catalyse
What does an increase in temperature do ?
Increased temperature increases the kinetic energy of the particles. As temperature increases, the particles move faster and collide more frequently
How does temperature affect an enzyme controlled reaction ?
An increase in temperature will result in more frequent successful collisions which would lead to an increase in the rate of reaction
What is the temperature coefficient ?
Q10, is a measure of how much the rate of reaction increases with a 10 degree increase in temperature
What is the temperature coefficient in enzyme controlled reactions ?
In enzyme controlled reactions, Q10 is 2
What does Q10 having a value of 2 mean ?
This means that the rate of reaction doubles with a 10 degree rise in temperature
What happens at extremely high temperatures ?
The bonds holding the protein together vibrate more until the bonds strain and then break
What does the breaking of bonds result in the structure of a protein ?
The breaking of bonds results in a change in the tertiary structure of the protein
What is the process where the temperature gets too high for the enzyme ?
Denaturing
What is optimum temperature ?
The temperature at which the enzyme has the highest rate of activity