Part 2 - Degradation Of Organic Matter Flashcards
Which compounds can and can’t diffuse through the cell membrane?
Can: gases and hydrophobic compounds like fatty acids.
Can’t: hydrophilic compounds like sugar and amino acids.
What two coupling transport methods can be used to uptake solutes into the cell?
1) An exergonic chemical reaction (primary reaction) e.g. ATP hydrolysis for sugar uptake
2) Co-transport (secondary transport) e.g. sulphate uptake with H+ or Na+ which have lower concentrations in the cell.
What are the three steps in microbial degradation of organic matter?
1) extra cellular hydrolysis of polymeric compounds.
2) uptake of dissolved molecules (monomers).
3) Metabolism in the cell.
Why is sulphate uptake into cells easier in the marine environment than in freshwater environments?
In marine environments, sulphate is abundant in water, and so a smaller concentration gradient exists (requires 2H+ for uptake). The opposite is true in freshwater environments (requires 3H+ for uptake).
What happens to organic matter and electrons in a redox reaction?
Organic matter is oxidised and the electrons are transferred to an external electron acceptor.
What compounds represent carbon’s most oxidised and reduced states, and what are the oxidation states of these compounds?
Most oxidised = Carbon Dioxide (+IV)
Most reduces = Methane (-IV)
What is the chemical formula and oxidation state of glucose?
C6H1206 (0)
What is an “osmotrophic” cell?
Osmotrophic cells can only tale up monomeric molecules.
What do cells use to break down microbial matter outside the cell?
Extracellular enzymes - some cells can anchor these to prevent losing them in the environment.
How is molecular oxygen used in aerobic degradation of organics?
Molecular oxygen is a terminal electron acceptor for aerobic respiration.
What is the approximate energy yield of aerobic respiration, and this considered to be high or low?
Aerobic respiration yield is 30-50% of the substrate - very high.
Why must high energy reactions be avoided, and give an example of a high energy reaction?
High energy reactions release too much waste heat which can damage the cell. Direct reaction of oxygen and glucose is an example.
How do cells avoid high-energy reactions by storing energy?
Cells compartmentalise oxidation and reduction reactions and produce intermediate compounds like ATP to store chemical energy.
What are the 4 stages of the respiratory chain?
1) A chain of proteins are in place with different energetic levels.
2) Electrons are allowed to travel along the chain, losing a small amount of energy at each energetic level.
3) The energy released allows transfer of protons across the cell membrane (from the cell to the environment).
4) Protons are then allowed to pass back across the cell membrane causing energy to be regained for formation of ATP to store energy.
What compounds is used as an electron carrier in organotrophic organisms below -320 mV?
NADH
