IGCSE Nitrogen Cycle

What is the element required to make proteins that is not found in carbohydrates and fats?

• Hydrogen

• Carbon

• Nitrogen

• Oxygen

How do nitrogen fixing bacteria help in converting N2 gas into nitrates?

• By absorbing N2 gas directly

• By changing N2 gas into nitrates in the soil

• By releasing N2 gas into the air

• By converting N2 gas into nitrous oxides

What is the process called when lightning splits the bond between nitrogen atoms in N2 gas?

• Nitrogen Fixation

• Nitrogenation

• Nitrification

• Denitrification

How do plants absorb nitrogen from the soil?

• Through their flowers

• Through their leaves

• Through their stems

• Through their roots

What happens to the nitrogen in plants when animals eat them?

• It gets converted into proteins in animals

• It gets converted into carbohydrates in animals

• It gets released into the air

• It gets stored in the animals' bodies

What type of bacteria convert ammonium compounds to nitrites and then to nitrates in the soil?

• Decomposers

• Nitrogen fixing bacteria

• Nitrifying bacteria

• Denitrifying bacteria

What is the process of converting ammonium compounds to nitrites and then nitrates known as?

• Denitrification

• Nitrification

• Nitrogen Fixation

• Nitrogenation

How do denitrifying bacteria affect the nitrogen cycle?

• They convert nitrates into ammonium compounds

• They convert nitrates back into N2 gas

• They convert nitrates into nitrites

• They convert nitrates into proteins

What can farmers do to reduce the amount of denitrifying bacteria in the soil?

• Use more fertilizers

• Increase soil aeration

• Reduce ploughing

• Add more water to the soil

Where are nitrogen fixing bacteria found in addition to soil?

• In the water

• In the root nodules of certain plants

• In the leaves of plants

• In the air