Enzymes Flashcards
What type of proteins are enzymes?
Globular proteins
What are enzymes?
Biological catalysts that speed up the ROR while remaining chemically unchanged
What does intracellular mean?
Enzymes are produced and function inside the cell
What does extracellular mean?
Secreted by cels and catalyse reactions outside cells
What is an example of extracellular enzymes?
Digestive enzymes in the gut
What happens at the active site?
The substrate binds
What type of protein are enzymes?
Globular proteins
What is an example of an intracellular enzyme?
Catalase
What does catalase do?
Converts hydrogen peroxide into water and oxygen- preventing damage to cells or tissues
What is an example of an extracellular enzyme?
Amylase
What does amylase do?
Carbohydrate digestion- hydrolyses starch into simple sugars
Why is digestion usually carried out by extracellular enzymes?
The macromolecules being digested are too large to enter the cell
Where is amylase secreted from?
The salivary glands and the pancreas for the digestion of starch in the mouth and small intestine
What is the definition of an enzyme?
Tertiary proteins that catalyse reactions by providing an alternative pathway with a lower Ea by the orientation of substrates
What is the shape of the active site determined by?
The sequence of the amino acids in the primary structure and the R groups- the folding into the secondary and tertiary structure
Lock and key theory?
Enzyme active site is a fixed shape
Random collisions between substrate and enzyme- forms ESC
Once ESC has formed, the substrate distorts in shape (lowering the Ea), the products are released and the active site is empty- can be reused again
Lock and key theory?
Enzyme active site is a fixed shape
Random collisions between substrate and enzyme- forms ESC
Once ESC has formed, the substrate distorts in shape (lowering the Ea), the products are released and the active site is empty- can be reused again
Induced fit theory?
Active site is induced (changes shape) to mould around the substrate
Puts strain on the bonds and weakens them- therefore lower Ea for the reaction to occur
Products are formed and released- the active site reverts back to its original shape
Temperature?
Too low- not enough KE for successful collisions- less ESC’s
Too high- enzyme denatures- AS changes shape- no ESC’s formed
The bonds holding the AA in the 3D tertiary structure in the AS are broken- AS changes shaped
PH?
Enzyme will denature
Too high- too many H+ ions
Too low= too many OH- ions
Fewer ESC’s- decreased ROR
Interfere with the charges on the AA in the AS— the hydrogen and ionic bonds will break
Substrate concentration?
At the low concentration, the substrate conc is the limiting factor
Fewer substrate molecules are available to collide with the enzyme- fewer ESC’s- decreased ROR
When the graph plateaus- the increased substrate concentration- the enzyme concentration is the new limiting factor- the AS becomes saturates- the reaction cannot occur any faster
Enzyme conc?
Empty AS due to insufficient substrate- more enzyme than substrate- not enough substrate to collide with the AS
Competitive- what shape is the inhibitor?
The same or very similar tothe substrate- therefore it is complementary and can bind to the AS
What does the competitive inhibitor prevent?
The substrate from binding and the reaction from occurring
What will happen if more substrate is added to a competitive inhibitor?
This will out-compete the inhibitor- knocking them out of the AS
Where do non-competitive inhibitors bind to the enzyme at?
The allosteric site
What does the non-competitive inhibitor cause to the active site?
To change shape- the substrate can no longer bind (regardless of how much substrate is added)
What do non-competitive inhibitors cause to the structure of the enzyme?
Causes the 3D (tertiary) structure of the enzyme to change shape- fewer ESC’s formed
