Chapter 9 Summary
Chapter 9.1
- Under normoxic condition, a cell’s oxygen supply meets its oxygen demand, and the cell can make large amounts of ATP via aerobic metabolism.
- Hypoxia occurs when a cell’s oxygen demand exceeds its oxygen supply.
- Anoxia occurs when a cell experiences a total absence of oxygen.
- Hypoxic conditions may be caused by increased metabolism activity or by decreased oxygen availability.
- When a cell is oxygen limited, anaerobic processes take over to produce ATP for essential cell function (i.e., cell maintenance).
- Anaerobic respiration is not as efficient as aerobic respiration and can only support short-term functioning.
Chapter 9.2
- To response to hypoxia, cells must be able to detect when oxygen levels are low.
- Many cells can detect hypoxic and anoxic conditions via signalling pathways that involve Hypoxia-Inducible Factors (HIF), transcription factors that become active during hypoxia.
- Low oxygen availability results in production of more reactive oxygen species (ROS) than normal by the mitochondrial electron transport system (ETS), and these ROS can stimulate additional signalling pathways.
Chapter 9.3
- After detecting hypoxia, stress-tolerant organisms can decrease their demand for oxygen, increase oxygen uptake, or a combination of those two strategies.
- Cells can decrease their demand for oxygen by downregulating cellular processes that consume ATP.
- Cells can also decrease their demand for oxygen by increasing activity of metabolic pathways that produce ATP without using oxygen (glycolysis and fermentation).
- To increase oxygen uptake, organisms (multicellular or single-celled) can move to environments (or parts of their environment) with higher oxygen, a behavioural response.
- Additionally, multicellular organisms can modify their physiology to increase oxygen delivery to the tissues that need it, like animals that adjust their circulatory system.