C4: Enzymes

Question 1

In living organisms, the catalysts are called ____

Answer 1

enzymes

Question 2

what is a catalyst

Answer 2

A substance that can speed up a chemical reaction without itself being chemically changed at the end of the reaction.

Question 3

what is activation energy

Answer 3

For a chemical reaction to be activated, energy is needed. energy is called activation energy

Question 4

how do catalysts speed up chemcial reactions

Answer 4

they lower the activation energy

Question 5

definition of enzymes

Answer 5

Enzymes are proteins that function as biological catalysts. They catalyse or speed up the rate of chemical reactions. They remain chemically unchanged at the end of the reaction.

Question 6

what reactions do enzymes catalyse

Answer 6

• Reactions that build up complex substances
• Reactions that break down complex substances

Question 7

examples of enzyme-catalysed chemical reactions

Answer 7

digestion:
as some food molecules are large and insoluble in water, they have to be broken down.
eg, amylase: starch to maltose
maltase: maltose to glucose
protease: protein to amino acids
lipase: fats to fatty acids and glycerol

complex substances:
Building up complex substances (condensation reactions):
– Protein synthesis (building proteins from amino acids)
– Photosynthesis
Breaking down complex substances (hydrolysis reactions):
– Respiration
– Decomposition of hydrogen peroxide

more info of ghe complex substances in tb

if it ends with -lase it is an enzyme

Question 8

what is the lock and key hypothesis

Answer 8

The lock-and-key hypothesis is used to describe how an enzyme will only act on a specific substance called the substrate.

Question 9

explain lock and key hypothesis

Answer 9

There are depressions on the enzyme molecule that form the active site.The specific substrate binds with the enzymes active site as it has a shape complementary to the active site.When the substrate and enzyme are bound together, they form the enzyme-substrate complex. A chemical reaction occurs on the substrate molecule. Chemical reactions will then occur and the substrate is converted into products. The products then detach from the active site. The enzyme remains chemically unchanged. The active site is available for another substrate molecule to bind to it.

Question 10

characteristics of enzymes

Answer 10

1. Enzymes speed up chemical reactions by lowering activation energy.
2. Enzymes are required in minute amounts and remain chemically unchanged
   * Once the products leave, the enzyme’s active site is free to bind to another substrate molecule.
   * This means that enzymes can be reused and hence are required only in minute quantities.
   at the end of the reaction.

3.Enzymes are highly specific in action.
* An enzyme molecule has a specific 3D shape.
* Only a substrate that has a shape complementary to the enzyme’s active site will be able to bind with the enzyme and cause a chemical reaction
* This means that enzymes are specific in action.

4.Enzymes are affected by temperature and pH. ( check notes for more details)