Enzymes Flashcards
Enzymes are …
Biological catalysts
What do biological catalysts do?
Speed up the rate of (chemical) reactions without changing themselves at the end of the reaction
Why are enzymes biological?
Involved in catalysing metabolic reactions
Enzymes speed up ROR due to …
Reduced activation energy
Why is it important to reduce activation energy?
So that reactions in the body can take place rapidly at lower temperatures (37˚c and below)
Why can’t body temperatures be raised more than 40˚C?
Proteins in the body will be denatured
What is activation energy?
Energy needed to change substrates into products
Structure of enzymes
- globular proteins
- coiled into precise 3D shapes
Where are hydrophilic R groups located?
On the outside of the molecule so the enzymes are soluble
The active site has what type of shape?
Specific shape
The enzymes are … to the substrate?
Specific
The ‘lock and key’ hypothesis allows the enzyme to …
Catalyse the breakdown of a substrate molecule to 2 product molecules
Lock and key hypothesis
- specific shape of active site allows the substrate with a complimentary shape to active site, fit perfectly
- combined structure = enzyme-substrate complex
- substrate held by temporary bonds, formed between…
- bonds in substrate molecule are broken to produce 2 products
- products leave the AS as they are not complimentary in shape to AS
- enzyme left unchanged at end of reaction - can be reused and is available to receive another substrate mol.
When the substrate binds with the active site, how is it held in place?
With temporary bonds, (e.g. hydrogen) - formed between substrate molecule and some of the R groups of the amino acids in the active site
Induced fit hypothesis
- enzyme’s active site is flexible (sometimes substrate) so changes shape as substrate molecule enters the enzyme
- allows for a conformational change
- able to be held close to active site for temporary bonds to be formed between the R groups of amino acids and the substrate molecule (substrate binds to active site)
- enzyme-substrate complex formed
- products are produced
How many active sites can an enzyme have?
Intracellular enzymes
Enzymes that function inside cells
Extracellular enzymes
Enzymes that are secreted by cells and catalyse reactions outside the cell
Example of extracellular enzyme
Digestive enzymes
Activation energy
The minimum amount of energy required for a collision between two particles to result in a reaction
