action of enzymes Flashcards
What are enzymes? (2)
Biological catalysts that speed up chemical reactions;
Without being used up in the reaction
What types of reactions do enzymes catalyse? (2)
At a cellular level, e.g., respiration;
At the whole organism level, e.g., digestion in mammals
What are intracellular enzymes and give one example & it’s function? (2)
Enzymes that work inside cells;
Example: Catalase, which breaks down hydrogen peroxide into water and oxygen
What are extracellular enzymes and give two examples & their functions? (3)
Enzymes that work outside cells;
Example: Amylase, found in saliva, catalyses the breakdown of starch into maltose;
Example: Trypsin, secreted into the small intestine, catalyses the breakdown of polypeptides
Describe the structure of enzymes (2)
Globular proteins with an active site;
The active site has a specific shape determined by the enzyme’s tertiary structure
How are enzymes specific? (2)
Their active site only binds to substrate molecules with a complementary shape;
Forming an enzyme substrate complex
What is activation energy? (2)
The minimum energy required for a reaction to occur;
Enzymes lower the activation energy, allowing reactions to occur at lower temperatures
How do enzymes lower activation energy? (2)
By reducing repulsion between molecules, making it easier for substrates to bond (in the case of joining);
By putting strain on the bonds in substrates, making it easier for them to break apart (in breakdown reactions)
Describe the lock and key hypothesis (3)
Theory suggests:
Active site is rigid;
Only exactly complementary substrates can bind;
To form enzyme-substrate (ES) complexes
Describe the induced hypothesis (3)
The active site changes shape slightly as the substrate binds;
Providing a better fit;
After the reaction, the products are released, and the active site reverts to its original shape
