1.4 Biological Reactions and Enzymes Flashcards
What are enzymes?
Globular proteins that, under certain conditions, lower the activation energy of a reaction.
What part of the enzyme does the substrate bind to in a reaction?
The active site
What is the lock and key theory?
Enzymes’ active sites are shaped specifically for a certain substrate. Active sites are fixed in shape and size. Substrates are fixed in shape and size.
What is induced fit theory?
Enzymes are not rigid. Substrates are fixed in shape and size. Only a specific substrate can get an enzyme to change shape. This is due to chemical reactions that cause bonds to lengthen and shorten.
Where are enzymes made?
Inside living cells.
Where can enzymes act?
Inside cells - intercellular Outside cells - extracellular
How does temperature affect the rate of enzyme catalysed reactions?
As temperature increases, so does rate (there are more successful collisions due to increased kinetic energy) until the optimum temperature. As the temperature increases after this point, the rate decreases as the enzymes are denatured,
What do buffers do?
Maintain a constant pH in a reaction.
What is meant when an enzyme is said to have been denatured?
Environmental conditions (extreme change in pH, high temp etc) cause bonds to break in the enzyme’s tertiary structure and its active site’s shape changes so it no longer fits with the substrate.
What is inactivation?
When an enzyme becomes temporarily inactive Can be caused by small changes in pH
What is inhibition?
When enzyme action is slowed or stopped by another substance (an inhibitor).
How do competitive inhibitors work?
The inhibitor is structurally similar to the substrate so associates with the active site. If the substrate concentration increases in the presence of competitive inhibitors, the rate of reaction will increase.
How do non-competitive inhibitors work?
They associate with a part of the enzyme that is not the active site. Causes the enzyme’s shape to change slightly Rate of reaction is unaffected by substrate concentration increasing in the presence of non-competitive inhibitors.
Draw a graph showing how pH varies rate of an enzyme catalysed reaction,
Draw a graph showing how enzyme concentration varies rate of an enzyme catalysed reaction,
Draw a graph showing how substrate concentration varies rate of an enzyme catalysed reaction,
