Topic 5: Nutrient Cycles Flashcards
Which biological molecules contain Nitrogen?
-Proteins (Amino acids)
-Nucleic Acids
-ATP
What are the two ways of nitrogen fixation?
- Nitrogen-fixing bacteria
- Lightning
What does Nitrogen-fixing bacteria do?
Convert Nitrogen gas into nitrogen-containing compounds (Ammonia)
Where are Nitrogen-fixing bacteria also found in?
Found in the soil and root nodules of leguminous plants.
Why does the leguminous plant and nitrogen-fixing bacteria have a symbiotic relationship?
The bacteria provide the plant with nitrogen compounds; and the plants provide the bacteria with carbohydrates
How does lightning causes nitrogen-fixation?
Lightning causes nitrogen to be oxidised forming nitrates.
What’s the role of nitrifying bacteria?
Converts ammonium ions (NH4) in the soil into nitrite ions (NO2) and nitrate ions (NO3)
How do plants absorb nitrogen-containing compounds by?
Active Transport
What are saprobiotic nutrition?
Remains of dead plants/animals and their waste
What are saprobionts?
Group of microorganisms which feed on saprobiotic nutrient
Describe the process of ammonification.
Saprobionts break down amino acids in organic matter and convert them into Ammonia, which forms ammonium ions in the soil
What is extracellular digestion?
Saprobionts secrete enzymes which break down organic matter which they absorb from the outside of the organism
What does denitrifying bacteria do?
Convert nitrates in the soil back into nitrogen gas
What does denitrification cause?
Reduces the availability of nitrogen-containing compounds for plants.
What conditions are needed for denitrifying bacteria to grow?
-Anaerobic
(They break down nitrates to absorb the O2, whilst releasing nitrogen as a gas in the process).
How do farmers avoid growing denitrifying bacteria?
-Ploughing
-Aerating the soil
(Increases the amount of oxygen in the soil).
What is the Haber process?
It’s used to convert nitrogen by adding hydrogen gas to form ammonia which is used in fertilisers.
Which biological molecules contain phosphorous?
-ATP
-Nucleic Acids
Phospholipid Bilayer
What is phosphorus found as?
Phosphate ions (mineral form) in sedimentary rock.
What is mycorrhizae?
Fungal associations between plant roots and beneficial fungi.
Why is mycorrhizae beneficial for plant growth?
-Hyphae of the fungus increase S.A for water + mineral absorption.
-Acts like a sponge: hold water + minerals around the roots.
-Makes plants more drought resistant
What is the general role of mycorrhizae in the phosphorus cycle?
-Improving the uptake of relatively scarce ions
(phosphate ions)
Describe the phosphorus cycle. (4 marks)
-Phosphate ions in rocks released by erosion/weathering
-Phosphate ions taken up by plants and incorporated into their biomass
-Phosphate ions transferred through the food chains
-Phosphate ions lost from animals in excretion as waste products.
-Saprobionts decompose organic compounds
What is guano?
Waste coming from sea birds which is a major source of phosphate ions
