12. Energy & Respiration Flashcards
Respiratory Quotient (RQ)
The volume of carbon dioxide produced divided by the volume of oxygen taken in per unit time
Suggest why mitochondrial membranes in cells lose their normal structure when the water potential is low. [3m]
- water molecules leave mitochondrion
- down water potential gradient by osmosis
- there will be a mechanical disruption to membranes, which are made of phospholipid bilayer
- this may reduce stability/fluidity of membrane
- as hydrophilic heads form fewer hydrogen bonds with water
Describe how you would carry out an investigation to determine the RQ of germinating barley seeds. [9m]
- by using a respirometer, the volume of CO2 released and the volume of O2 taken in can be measured
- the germinating barley seeds are placed on a mesh in the respirometer
- KOH is used to absorb the CO2
- temperature and air pressure have to be kept constant during the investigation
- the movement of the manometer fluid in 5 minutes indicates the volume of O2 absorbed in 5 minutes
- repeat the experiment again with the similar setup, except the KOH is replaced by water to measure the volume of CO2 released in 5 minutes
- the difference in manometer readings is due to the CO2 released
Describe the circumstances in which alanine (an amino acid) and lactate are used as respiratory substrates. [2m]
alanine: starvation / lack of fat or carbohydrate
lactate: after anaerobic respiration
Describe how ATP is made by substrate-linked reactions. [2m]
Inorganic phosphate group from a PHOSPHORYLATED compound is added to ADP / ADP + Pi
After anaerobic respiration, breathing is faster and deeper than normal. Explain why. [3m]
- requiring additional O2 than normal
- oxygen debt
- lactate build up
- convert lactate to pyruvate in liver cells
- reoxygenate myoglobin
