Unit 5

Question 1

What is a catalyst?

Answer 1

A catalyst is a substance that increases the rate of a chemical reaction by lowering the activation energy, the catalyst is not changed by the chemical reaction.

Question 2

What is an enzyme?

Answer 2

An enzyme is a protein which functions as a biological catalyst.

Question 3

Where are enzymes made?

Answer 3

Enzymes are made in all living cells.

Question 4

In what way are enzymes and their substrates complementary?

Answer 4

Enzymes and substrates have complementary shapes, this means that they fit together and that other substrate molecules could not fit in the enzyme.

Question 5

Can enzymes work with more than one type of substrate?

Answer 5

Yes, but the substrates would have to be very similar.

Question 6

What will a rise in temperature do to the rate of a chemical reaction?

Answer 6

It will speed it up.

Question 7

What happens to enzymes when the temperature becomes very high?

Answer 7

At above around 50°C enzymes will permanently lose their shape and be unable to combine with substrates. In other words, they are denatured.

Question 8

What is the temperature or pH that an enzyme works best at called?

Answer 8

It is called the optimum temperature or pH.

Question 9

Are the effects of a change in pH for a cell reversible?

Answer 9

Yes, although a change in pH may affect the activity of an enzyme, these effects are typically reversible. The enzyme will usually resume it’s normal activity when it’s optimum pH is restored.

Question 10

What are intracellular enzymes?

Answer 10

Intracellular enzymes are enzymes which are found in cells and speed up reactions in the nucleus and cytoplasm.

Question 11

Where are all enzymes made?

Answer 11

All enzymes are made inside cells.

Question 12

What are extracellular enzymes?

Answer 12

Extracellular enzymes are enzymes which work outside of cells.

Question 13

How are extracellular enzymes used?

Answer 13

Fungi and bacteria release extracellular enzymes in order to digest their food. For example, mould growing on bread may release extracellular enzymes which will digest starch, the cell then absorbs the soluble sugar that the enzyme produces from the starch. In animals extracellular enzymes digest food in the stomach and intestines.

Question 14

What is the substance on which an enzyme acts called?

Answer 14

The substrate.

Question 15

What is an anabolic reaction?

Answer 15

An anabolic reaction is where large molecules are built up from smaller molecules.

Question 16

What is temporarily formed when an enzyme combines with a substrate?

Answer 16

An enzyme-substrate complex.

Question 17

What is a catabolic reaction?

Answer 17

A catabolic reaction is where enzymes break large molecules into smaller molecules. Ex. Amylase break starch down into maltose.

Question 18

What is the active site?

Answer 18

Enzymes have active sites, complementary substrates fit into these active sites in enzymes.

Question 19

What is it meant by enzymes being specific?

Answer 19

Enzymes are specific because an enzyme that acts on one substance will usually never act on another substance.

Question 20

What does it mean by enzymes and substates being complementary?

Answer 20

The shape of the active site and the shape of the substrate must fit in each other, this makes them complementary.

Question 21

What do enzymes usually end with?

Answer 21

-ase.

Question 22

How is an enzyme typically named?

Answer 22

An enzyme is typically named after the substance on which it acts. Ex. Dehydrogenase removes hydrogen from the body.

Question 23

Why does an increase in temperature typically cause the rate of reactions between enzymes and substrates to speed up?

Answer 23

As temperature is increased, the enzyme and substrate molecules gain more kinetic energy, this causes them to move faster and for more collisions to occur. This should increase the rate of reaction.

Question 24

Why does the rate of reaction slow down above an enzymes optimum temperature?

Answer 24

Because the proteins become denatured (lose their shape) at higher temperatures, thus, the active site is deformed. This means that the enzyme will no longer be able to combine with substrates, even after the optimum temperature is restored.

Question 25

Can changes pH denature enzymes?

Answer 25

Usually a small change in pH will only cause an enzyme to temporarily stop working, once optimum pH is restored it should return to normal. However, extreme changes in pH can permanently denature an enzymes and deform it’s active site.

Question 26

What happens in an anabolic reaction?

Answer 26

Two molecules are joined together by an enzyme to form a more complicated substance called the product.

Question 27

Why are enzymes important to life?

Answer 27

They speed up chemical reactions, without enzymes these chemical reactions would take place too slowly and life would not be able to be sustained.