4 Enzymes Flashcards
Describe “enzymes”
- biological catalysts
- made of globular proteins
- can be intracellular or extracellular
Two types of enzyme action?
Anabolic:
build complex molecules from simpler organic compounds
Catabolic:
large molecules are broken down into smaller ones
Describe “lock and key hypothesis”
- enzymes have an active site where specific substrates bind forming an enzyme-substrate complex
- the specificity of an enzyme is a result of the complementary shape of the active site to its substrate
Describe “induced-fit hypothesis”
- enzymes and substrate interact
- enzyme and it’s active site can change shape (conformational changes)
- ensures an ideal binding arrangement is achieved
- maximises the ability of the enzyme to catalyse the reaction
How do enzymes catalyse reactions?
- influence the stability of bonds in the reactants
- destabilisation of bonds in the substrate makes it more reactive
- substrate is held in a way that right atoms are close enough to react
- R-group within active site make temporary bonds with substrate
- puts a strain on the bonds with substrate and helps lower activation energy
Factors affecting enzyme activity?
- pH
- temperature
- enzymes concentration
- substrate concentration
How does temperature affect enzyme activity?
- enzymes have specific optimum temperature depending on where they are from
- enzymes catalyse a reaction at maximum rate in optimum temperature
- low temperature leads to low frequency of successful collisions and enzyme-substrate collide with less energy to break bonds
- raising the temperature leads to more successful collision to form enzyme-substrate complex and collide with more energy
What happens when enzymes are above optimum temperature?
- enzymes denature
- bonds vibrate and eventually break
- alters tertiary structure so shape of active site
- substrate cannot bind
- non-reversible
How does pH affect enzyme activity?
- slight changes in pH do not denature the enzyme
- any changes to the enzyme active site can be reversed
- large changes in pH will lead to enzymes becoming denatured by affecting and breaking hydrogen bonds
Describe “extremophiles”
- organisms adapted to live in harsh environment
- have enzymes suited to extreme temperature
- thermophiles which live in hot springs have enzymes with optimum temp of above 70 degrees Celsius
- phychrophilic organisms have adapted to live in cold environments that they have enzymes with optimum temp of 5 degrees Celsius
How are enzymes related to metabolism?
- enzymes play a key role in metabolic pathways (e.g. respiration)
- enzymatic pathways need to be regulated
- enzyme activity can be reduced or stopped temporarily by reversible inhibition
Describe “inhibitors”
Competitive inhibitors
- have a similar shape to that of the substrate
- compete with the substrate for the active site
- statins competitively inhibit enzyme used in cholesterol synthesis
Non-competitive inhibitors
- bind to the enzyme at an allosteric site
- alters the shape of the active site and prevents the substrate from binding
- proton pump inhibitors used to reduce production of acid in the stomach
What is the Vmax of an enzyme?
The maximum rate of reaction
Describe “end product inhibitors”
- metabolic reactions can be controlled by using the end-product of a metabolic reaction
- acts as non-competitive, reversible inhibitors
- as the enzyme converts substrate to product the process itself is slowed down
- end-product can then detach from the enzyme and be used elsewhere
Describe “cofactors”
- inorganic ions (minerals e.g. zinc)
- may help stabilise structure or take part in reaction
- chloride ions acts as cofactors for amylase
