c04 enzymes Flashcards
(10 cards)
What is a catalyst?
A substance that can speed up a chemical reaction, remaining chemically unchanged at the end of a reaction.
What is an enzyme?
Enzymes are proteins that function as biological catalysts. They catalyse (speed up) the rate of the chemical reaction, and remain chemically unchanged at the end of the reaction.
what are enzymes made up of
Made up of protein molecules folded to a three-dimensional globular shape
How do enzymes catalyse a chemical reaction?
Enzymes catalyse chemical reactions by lowering the activation energy.
What is activation energy?
Activation energy is the energy needed to start a chemical reaction.
WHAT REACTIONS DO ENZYMES CATALYSE?
Enzymes are required to break down large molecules into smaller molecules so that they are soluble in water and small enough to diffuse through the cell surface membrane.
what is the ‘LOCK’ AND ‘KEY’ HYPOTHESIS
Enzymes have a unique shape of the active site, where only the substrate with the complementary shape can fit.
The substrate binds to the active site of the enzyme, forming an enzyme-substrate complex. Chemical reactions then occur, to produce products. The products leave the active site and enzyme remains chemically unchanged at the end of the reaction. These products are able to combine to substrate molecules.
CHARACTERISTICS OF ENYMES
Speed up chemical reactions
By lowering the activation energy in a chemical reaction needed to start a reaction.
Specific in action
Unique shape of the active site where only substrate with complementary shape can
fit, binding to form enzyme-substrate complex.
Required in minute amounts (little) and remain chemically unchanged at the end of a reaction
The same enzyme molecules can be used repeatedly, so only small amount of enzyme is required to catalyse reactions.
Affected by temperature
Affected by pH
how are enzymes affected by temperature
DESCRIBE: enzyme is less active at low temperatures. Enzyme activity is low, rate of reaction is slow.
EXPLAIN: kinetic energy of enzyme and substrate molecules is low. The rate os substrate molecules colliding with enzyme is very low.
DESCRIBE: as temperature increases, enzyme activity increases as indicated by the increase in the rate of reaction it catalyses.
EXPLAIN: increasing temperature increases the kinetic energy of molecules. The rate of substrates colliding and fitting into the active site is increased, increasing the rate of formation of enzyme-substrate complex.
DESCRIBE: this is the optimum temperature. Enzyme is the most active. Rate of reaction is the fastest.
EXPLAIN: molecules have the highest kinetic energy, the highest rate of collision and formation of enzyme-substrate complex. (Human enzymes optimum temperature is 36-37degrees celcius)
DESCRIBE: above optimum temperature, enzyme activity decreases rapidly
EXPLAIN: enzymes are made of proteins. The enzyme loses its shape and active site, less substrate can fit into the active site and less enzyme-substrate complex is formed. The enzyme is denatured. The higher the temperature, the faster the rate of denaturation.
DESCRIBE: there is no enzyme activity, enzyme activity stops, there is no reaction.
EXPLAIN: enzyme is completely denatured, enzyme lost its three-dimensional shape and active site completely. The substrate can no longer fit into the active site. No enzyme-substrate complex is formed.
how are enzymes affected by pH
as pH decreases from (start from optimum pH then to extreme pH) , activity decreases.
As pH increases from (start from optimum pH then to extreme pH) , activity decreases.
There is no activity at pH (extreme pH) is fully denatured and lost its three-dimensional shape and active site. Substrate cannot bind to the active site, enzyme-substrate complex is not formed and cannot catalyse the reaction.
activity is the highest at pH (optimum pH)
