Chapter 5

Question 1

Describe a catalyst

Answer 1

a substance that increases the rate of a chemical reaction and is not changed by the reaction

Question 2

Describe enzymes

Answer 2

proteins that are involved in all metabolic reactions, where they function as biological catalysts

Question 3

Describe why enzymes are important in all living organisms

Answer 3

The speed at which they can catalyse reactions is sufficient to sustain life, otherwise the metabolic reactions would be too slow to sustain life

Question 4

Explain enzyme action

Answer 4

The substrate attaches to the active site, forming an enzyme-substrate complex where the molecules collide and are turned to products

Question 5

Explain the specificity of enzymes

Answer 5

The shape of the active site is complementary to the shape of the its specific substrate so that they can form the enzyme-substrate complex, the shape of a protein molecule is different from the shape of a starch molecule, so amylase cannot digest proteins

Question 6

Explain the effect of changes in temperature on enzyme activity

Answer 6

An increase in temperature increases the KE of molecules, so the substrate molecules collide more frequently with the active site, more products are formed, hence the increased rate. the maximum activity of an enzyme is at its optimum temperature, after which it gets too high causing permanent denaturation → shape of active site starts to change → no longer complementary to the the substrate → no formation of enzyme-substrate complex → no products form → declined rate

Question 7

Explain the effect of changes in pH on
enzyme activity

Answer 7

Extreme ph → shape of active site starts to change → no longer complementary to the the substrate → no formation of enzyme-substrate complex → no products form → declined rate