Enzymes Flashcards
What are enzymes
Biological catalysts that speed up the rate of chemical reactions without being used up
What can enzymes catalyse
Catalyse metabolic reactions - both at a cellular level (respiration) and for the organism as a whole (digestion in mammals)
Catalyse a wide range of intracellular and extracellular reactions that determine structures and functions from cellular to whole organism level - within cells or outside cells
What structures can enzymes effect
Can effect structures in an organism (eg enzymes are involved in the production of collagen, an important protein in the connective tissues of animals) as well as functions (like respiration ).
What are enzymes and what do they have
Proteins they have an active site which has a specific shape. The active site is the part of the enzyme where the substrate molecules ( the substance that the enzyme interacts with) bind to.
Why are enzymes highly specific
Due to their tertiary structure
What is activation energy
Certain amount of energy or minimum amount of energy supplied to the chemicals before the reaction will start . Often provided as heat
What do enzymes do to the activation energy
Enzymes lower the amount of activation energy needed , often making reactions happen at a lower temperature than they could without an enzyme. This speeds up the rate of reaction.
What is it called when a substrate fits into the enzymes active site
Forms an enzyme substrate complex
What does the enzyme substrate complex do
Lowers the activation energy why because if two substrate molecules need to be joined being attached to the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily
If the enzyme is catalysing a breakdown reaction , fitting into the active site puts a strain on bonds in the substrate, so the substrate molecule breaks up more easily.
What is the lock and key model
Only work with substrates that fit their active site
This is where the substrate fits into the enzyme in the same way that a key fits into a lock- the active site and the substrate have a complementary shape.
The active site and the substrate have a complementary shape.
The substrate fits into the active site , forming enzyme substrate complex, the enzyme is unchanged after the reaction and releases the products.
What did scientists then realise was wrong with the lock and key theory
The enzyme and substrate have to fit together in the first place but new evidence showed that the enzyme- substrate changed shape slightly to complete the fit.
This locks the substrate even more tightly to the enzyme scientists came up with the induced fit model
What is the induced fit model
Explains why some enzymes are so specific and only bind to one particular substrate. The substrate doesn’t only have to be the right shape to fit the active site , it has to make the active site change shape in the right way as well.
The substrate fits into the active site it forms an enzyme substrate complex and as the substrate binds the active site changes shape slightly
What do enzymes do
Break substrates down eg one substrate molecule goes into the active site and two products come out. Enzymes can also catalyse synthesis reactions eg two substrate molecules go into the active site , bind together and one product comes out
What happens after the products are released
The active site returns to its original shape and can bind to the next substrate molecule
How do the properties of an enzyme relate to the tertiary structure of its active site and its ability to combine with complementary substrates to form an enzyme substrate complex
Enzyme properties are related to their tertiary structure. Enzymes are very specific - they usually only catalyse one reaction eg Maltase only breaks down maltose sucrase only breaks down sucrose. This is because only one complementary substrate will fit into the active site.
The active site’s shape is determined by the enzymes tertiary structure ( which is determined by the enzyme’s primary structure) . Each different enzyme has a different tertiary structure and so a different shaped active site.
