Nitrogen 1
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What do amino acids and nucleotides contain that carbohydrates and fats don’t?
Nitrogen
Where does the nitrogen in our bodies come from?
Our diet
How do the plants/animals we eat get their nitrogen?
From nitrogen fixing bacteria known as diazotrophs
What are the 3 stages called in the nitrogen cycle?
Fixation Assimilation Degreadation
What is the structure of nitrogen?
2 nitrogen atoms are held together by triple bond making it very unreactive
How can nitrogen be captured?
Adding oxygen using lightening to form NO or NO Adding hydrogen using the Haber process to form NH3
What are 2 examples of nitrogen-fixing bacteria?
• Cyanobacteria found in Lake Atitlan - Rhizobium bacteria found on root nodules of legumes
What do bacteria require for nitrogen fixation?
Energy Nitrogenase enzymes
What does the fixation of nitrogen produce?
Un-ionised ammonia (NH3) which in water will exist in equilibrium with ionised ammonium (NH4+)
What inactivates nitrogenase?
Oxygen
How do nitrogen fixing bacteria get around the abundance of oxygen?
They live anaerobically Some uncouple mitochondria which increases electron flow and ‘burns’ off oxygen in the cell
How do cyanobacteria prevent O2 entry?
They form heterocysts whose cell wall prevents oxygen entry
How do leguminous plants allow nitrogenase to work?
They produce leghaemoglobin which binds oxygen and keeps the concentration low enough to allow nitrogenase to remain activated and work
What happens after nitrogen is fixed?
Soil bacteria convert ammonia to nitrite and then to nitrate (nitrification). Nitrate is then taken up by plants and microbes. Once the nitrate has been taken up, it is then converted back to ammonia via nitrite
What is the only amino acid that can obtain its nitrogen directly from NH4 and the only one which can give it up directly?
Glutamate
What are the 4 amino acids which are found in higher concentration in cells compared to other amino acids
• Alanine • Glutamine • Glutamate • Aspartate
What are the roles of glutamate?
• Excitatory neurotransmitters • Important in taste • Amino acid breakdown
What is transamination?
Conservation of nitrogen by transferring amino groups between different molecules
What are the general principles of transamination?
• No loss or gain of nitrogen • Readily reversible • One of the 2 substrate pairs is often glutamate • Amino acid 1+ Keto acid 2= Keto acid 1+ Amino acid 2
What is the difference between an amino acid and a a-keto acid?
• Amino acid has an NH3 group attached to a carbon which is attached to a COOH group • a-Keto acid has a C double bond O attached to the acidic group
What does the reversible nature of transamination allow it to do?
Participate in amino acid synthesis and degradation
What do all aminotransferases rely on?
Pyridoxal phosphate cofactor
What typically accepts amino groups?
a-ketoglutarate
What acts as a temporary storage of nitrogen?
L-glutamine