nitrogen cycle

what do microorganisms convert nitrogen gas into

microorganism convert nitrogen gas into nitrogen containing substances that plants and animals can absorb

role of saprobionts in recycling chemical elements

• saprobionts decompose (break down) organic compounds eg proteins/urea/dna in dead matter or organic waste

• by secreting enzymes for extracellular digestion (saprobiotic nutrition)

• absorb soluble needed nutrients and releases minerals ions eg phosphate ions

role of mycorrhizae

mycorrhizae → symbiotic association between fungi and plant roots

• fungi (hyphae) act as an extension of plant roots to increase surface area of root system

• to increase rate of uptake / absorption of water and inorganic ions

• in return, fungi receive organic compounds like carbohydrates

mutualistic relationship

which biological molecules contain hydrogen

amino acids/ protein / enzymes/ ATP or ADP/ DNA or RNA (nucleic acids)/urea / NAD or NADP

the nitrogen cycle cannot work without…

saprobiotic nutrition and microbes

steps of nitrogen cycle

nitrogen fixation

ammonification

nitrification

denitrification

nitrogen fixation

• nitrogen fixing bacteria (found in soil - free living OR found in legume root nodules -mutualistic)

• N2 (nitrogen) → [ammonia (NH3)] → ammonium ions NH4+ in soil

ammonification

• saprobionts - secrete enzymes for extracellular digestion

• nitrogen-containing compounds (eg proteins/urea) from dead organisms and waste are broken down/ decomposed

• nitrogen containing compounds → ammonia NH3 → ammonium ions NH4+ in soil

nitrification

• nitrifying bacteria - in aerobic conditions (oxygen)

• ammonium ions (NH4+) in soil converted to → NITRITES (NO2-) → then NITRATED (NO3-)

• by 2 step oxidation reaction

• nitrates - for uptake by plant root hair cells by active transport

• → nitrates used to make nitrogen containing compounds eg amino acids/ ATP/ dna

denitrification

• denitrifying bacteria - in anaerobic conditions (no oxygen) eg waterlogged soil / flooded

• nitrates in soil → converted into nitrogen gas (N2) → REDUCTION

dont want to loose nitrogen/ nitrogen contains compound from soil

examples of biological molecules that contain phosphorus

phospholipids/ DNA or RNA/ ATP or ADP/ NADP/ TP or GP/ RuBP jn

phosphorus cycle

• environmental conditions eg erosion and weathering → cause release phosphate ions in rocks into soils and bodies of water

• phosphate ions are then absorbed by producers/ plants/ algae + incorporated into their biomass → rate of absorption increased by mycorrhizae

• phosphate ions transferred through for chain (animals eg herbivores eat producers)

• some phosphate ions lost for animals as waste product (excretion)

• death of plants/ animals → saprobionts decompose organic compounds → release phosphate ions into soil/ bodies of water

some phosphate ions remain in parts of animals → transported by streams/rivers into lakes/ oceans to form sedimentary rocks