Chapter 13 Summary

Chapter 13.1

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Chapter 13.2

• Low temperature stress occurs before, during, and after the freeze-thaw process.
• Low temperatures decrease membrane fluidity and protein flexibility, with implications for membrane and protein function.
• To combat low temperature stress, cells must protect their macromolecules either by modifying their composition or accumulating protective substances like cryoprotectants and chaperones.

Chapter 13.3

• Most mechanical stress occurs during freezing, and the severity of stress depends on where ice forms and how fast it propagates.
• Both intracellular and extracellular ice can damage cellular membranes, although intracellular ice tends to cause much more damage.
• To combat mechanical stress during freezing, cells must control ice formation and decrease overall ice content in or around their cells.

Chapter 13.4

• Osmotic stress occurs during freezing (decrease in water availability) and thawing (increase in water availability)
• Osmotic stress creates many challenges for the cell such as macromolecule crowding, protein denaturation, disruption in ion balance, and structural damage to the cell membrane.
• To combat osmotic stress induced by freezing a cell can decrease ice content, stabilize macromolecules, and coordinate repair/recovery.

Chapter 13.5

• Hypoxia occurs when organisms are frozen, as ice surrounds the cell, decreasing cellular access to oxygen.
• Hypoxia reduces the cell’s ability to produce ATP via aerobic respiration, resulting in a reduced ability to perform normal cellular processes that require ATP.
• To combat hypoxia stress, the cell can alter metabolism by using anaerobic respiration and/or decreasing the activity of cellular processes that require ATP.

Chapter 13.6

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Chapter 13.7

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