Enzymes Flashcards
Where do reactions in the body occur?
Sequences called metabolic pathways
What happens in catabolic reactions with an example?
Building up molecules
E.g. protein synthesis
What happens in anabolic reactions with an example?
Breaking down molecules
E.g. digestion
What do metabolic pathways consist of?
A sequence of enzyme controlled reactions in which a product of one reaction becomes the reaction of the next
What type of proteins are enzymes?
Globular proteins
Why are enzymes called biological catalysts?
Biological because they’re made by living cells
Catalysts because they speed up reactions but remain unchanged at the end
What does metabolism refer to?
All the reactions in the body
What 4 things do enzymes share with chemical catalysts?
Speed up reactions
Not used up
Not changed
Have high turn over number (catalyse many reactions per second)
How are enzymes structured?
Tertiary structure proteins with specific 3d globular shape
Why are enzymes water soluble?
Protein chain folds so hydrophilic R groups are on the outside of the molecule
What three sites of a cell can enzymes act at?
Extracellular
Intracellular
Membrane bound, intracellular
What happens with extracellular with an example?
Some enzymes are secreted by exocystosis and catalyse extracellular reactions.
E.g amylase is secreted by saprotrophic fungi to digest food prior to absorption.
What happens with intracellular with an example?
Act in solution inside cells
E.g enzymes in solution in chloroplast stroma catalyse glucose synthesis
What happens with intracellular membrane-bound with an example?
Intra may be attached to membranes
E.g. Mitochondria cristae and chloroplast grana- transfer electrons and hydrogen ions in ATP formation
What is an active site?
Site on the enzyme with a particular 3d structure that permits bonding with a substrate
What happens when an enzyme and substrate successfully collide?
Temporary bonds are made at active site, forming a substrate-enzyme complex
When the reaction is complete, products are released, leaving the enzyme unchanged and the active site ready to receive another substrate molecule
What is the lock and key theory?
Active site has unique shape that means only a fully complimentary substrate shape will bind and form e-s complex.
What is the induced fit theory?
Active site is not fully complimentary to the substrate. As substrate binds, active site slightly changes shape to accomodate.
Example for induced fit:-
Lysozyme (antibac in saliva, mucus, tears)
Active site is a grove, sugars on bac cell wall fit into it. Grove closes over sugars and lysozyme changes shape around them and hydrolyses bonds holding them together.
Cell wall is weakened, bacteria absorb water by osmosis and burst.