Enzymes Flashcards
What are enzymes
biological catalysts and globular proteins
What are the two forms of enzyme
Intracellular or Extracellular
What is an extracellular enzyme
enzymes active outside of the cell
What is an intracellular enzyme
enzymes active inside of the cell
Give an example of an intracellular enzyme
Catalase
Give an example of an extracellular enzyme
Amylase
What does catalase do
Converts hydrogen peroxide, which is harmful to cells and a by product of many processes, into water and oxygen - preventing damage to cells and tissues.
What does Amylase do
Hydrolyses starch into simple sugars. Digestion is usually carried out by extracellular enzymes, as macromolecules are too large to enter the cell.
What forms when an enzyme and substrate combine
An enzyme-substrate complex
What can denature enzymes
Heat and pH
What is the shape of the active site determined by
The complex tertiary structure of the protein that makes up the enzyme.
What determines the shape of an enzyme
the order of amino acids (if altered the 3D shape changes)
Is enzyme substrate complex temporary or fixed
Temporary
What two types of enzyme reactions are there
Catabolic or Anabolic
What is a catabolic reaction
When a single substrate is drawn into the active site and broken apart into two or more distinct molecules. E.g. Cellular respiration and hydrolysis
What is an anabolic reaction
When two or more substrates are drawn into the active site, forming bonds between them and releasing a single product. E.g. Protein synthesis and photosynthesis
What do enzymes do to activation energy
Lower it
What is activation energy
Amount of energy needed for a substrate to be unstable enough for a reaction to occur and products form
How do enzymes speed up chemical reactions
They influence the stability of bonds in reactants.
What does lock and key model suggest
Enzyme and substrates are a rigid shape that locked in together.
What does induced fit model suggest
Prior to binding substrate and active site aren’t completely complementary in shape. When substrate binds the active site alters shape and moulds around substrate.
What evidence is there to support induced fit model
X-ray diffraction techniques allow for 3D pictures of molecules to be formed. Can take pictures of enzyme before and after bond to see if it changes shape.
What are changes in shape known as
Conformational changes
How does a conformational change support the enzyme
It maximises the ability of the enzyme to catalyse the reaction