Nutrient Cycles

Question 1

Describe the role of saprobionts in the nitrogen cycle.

Answer 1

• decompose proteins
• releasing ammonia

Question 2

Nitrification is…

Answer 2

• NH3 (ammonia) > NO2 (nitrites) > NO3 (nitrates)
• using nitrifying bacteria

Question 3

Denitrification is…

Answer 3

• NO3 (nitrates) > N2 (nitrogen gas)
• NO3 (nitrates) > NO2 (nitrites)
• using denitrifying bacteria

Question 4

Nitrogen fixation is…

Answer 4

• N2 (nitrogen gas) > NH3 (ammonia)
• using nitrogen fixing bacteria

Question 5

Decomposition is…

Answer 5

• nitrogen containing compounds to Ammonia (ammonification)
• using saprobionts

Question 6

Nitrogen found in…

Answer 6

• amino acids
• proteins
• nuclei acids
• ADP
• ATP
• NADP
• NAD
• FAD

Question 7

Describe how the action of microorganisms in the soil produces a source of nitrates for crop plants.

Answer 7

• proteins into ammonia
• by saprobionts
• ammonia into nitrite
• nitrite into nitrates
• by nitrifying bacteria
• nitrogen gas to ammonia
• by nitrogen fixing bacteria in soil

Question 8

Explain how carbon containing compounds are absorbed and used for growth by saprobionts in soil.

Answer 8

• extracellular digestion
• by secretion of enzymes
• absorption of digested products
• synthesis of structural compounds
• respiration provide energy for growth

Question 9

Describe why phosphates are needed by a growing plant.

Answer 9

• production of phospholipids
• in cell membranes
• synthesis of ATP
• production of DNA
• production of RNA
• production of NADP

Question 10

Describe how a lack of phosphates in the soil surrounding a plant can affect its growth.

Answer 10

• less ATP so less respiration
• less nucleotides so less DNA
• less RuBP so less CO2 fixed into sugar
• make phospholipids for membranes

Question 11

Advantages of having Mycorrhizae growth near plants.

Answer 11

• help plants defend themselves
• help plants take up nitrates

Question 12

Describe process of eutrophication.

Answer 12

• nitrates into waterway
• increased algal bloom
• light blocked out
• aquatic plants cant photosynthesise and die
• increase in saprobionts
• increased aerobic respiration
• organisms die due to lack of oxygen
• increase in anaerobic respiration
• production of toxins
  = putrid conditions

Question 13

Describe how you obtain a quantitative measurement of water cloudiness.

Answer 13

• use of colorimeter
• measure the absorbance of light
• standardisation e.g. same water volume, same light wavelength

Question 14

Environmental impact of using fertilisers.

Answer 14

• reduced species diversity / plants adapted to nitrates outcompete other
• environmental issues / less nitrate returned to soil as less decomposition
• leaching / nitrates washed into water