BIOLOGY SAC 1B: ENZYME ACTIVITY

How does concentration affect enzyme activity?

(enzyme) because there are more enzymes to react with the substrate, the enzyme activity will be higher (assuming excess substrate) (substrate) increase initially and then level off because all enzymes are constantly occupied (rate then depends on how quickly catalysis occurs)

How do enzymes affect activation energy

Enzymes catalyse (speed up) chemical reactions by lowering the activation energy

Explain Lock and Key model and Induced fit model of enzyme action

LOCK AND KEY MODEL: the active site is a specially shaped area of the enzyme that fits around the substrate. the active site is the keyhole of the lock. INDUCED FIT MODEL: the shape of the enzyme changes when the substrate attaches to the active site. as with the lock and key method, the enzyme returns to its original shape after releasing the products and can be used again.

What is meant by activation activity?

The amount of energy required to start a reaction

How does temperature affect enzyme activity?

a. as temperature increases, so does the rate of reaction because the molecules are moving faster and have a higher chance of hitting eachother b. at extremely high temperatures, the enzyme is denatured due to disruption of noncovalent bonds c. lower temperatures the substrate molecules do not have enough kinetic energy for the reaction to take place even in the presence of the enzyme (An increase in temperature results in more kinetic energy of the enzyme and the substrate. More kinetic energy results in more collisions between the enzyme and the substrate. In turn, the number of successful collisions increases and more enzyme-substrate complexes form. Therefore an increase in temperature increases the rate at which enzyme substrate complexes form. However, all enzymes have an optimum temperature at which it will work best and favour the activity)

How does pH affect enzyme activity?

a. changes shape of enzyme by interacting with noncovalent bonds b. also changes shape or charge properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis c. As pH increases, enzyme activity increases until it reaches an optimal point in which enzymes denatures and as pH increases, enzyme activity decreases. (Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either the substrate connot bind to the active site or it cannot undergo catalysis. Extremes in pH can denature enzymes. In geneal enzyme have a pH optimum. However the optimum is not the same for each enzyme. for example: pepsin is 2.0 trypsin is 9.5)

How do enzymes catalyse reactions?

by lowering the activation energy required for the reaction to occur (Chemical reactions generally require energy called "activation energy" to get them started. Enzymes lower the activation energy required for a reaction to proceed. Many reactions that go on in cells might have to be heated or shaken or stirred in order for them to "go." The presence of enzymes makes the heating or shaking unnecessary. Enzymes speed up the rate of chemical reactions because they lower the energy of activation, the energy that must be supplied in order for molecules to react with one another. Enzymes lower the energy of activation by forming an enzyme-substrate complex allowing products of the enzyme reaction to be formed and released. Enzyme catalysed reactions occur at a particular place on the surface of the large enzyme molecule called the active site (as in heterogeneous catalysts). The reactant molecule, often called the substrate, is able to form relatively weak, temporary bonds to the enzyme at the active site.)

Endergonic/ Exergonic Reactions

endergonic: energy absorbing reactions e.g. anabolism (complex chemicals are formed from simpler units, requiring energy to occur) exergonic: energy releasing reactions e.g. catabolism (complex chemicals are broken down into simpler ones to release energy)