Questions

Deeper questions

The following questions require some thought and reaching the answer may require you to think beyond the contents of this TLP.

1. Crystallization is usually fatal to cells because:

   Yes	No	a	Crystals can puncture cell walls
   Yes	No	b	The formation of crystals changes the ionic ratios in the cytosol
   Yes	No	c	Crystallization speeds up the cell reactions
   Yes	No	d	Ice formation causes water to be drawn into the cell by osmosis causing the cell to swell and burst
   Yes	No	e	Nucleation of the crystals requires large amounts of energy

2. Ice formation in cells can be limited by:

   Yes	No	a	The presence of antifreeze proteins
   Yes	No	b	The dispersion of water in the cellular structure, which limits heterogeneous nucleation
   Yes	No	c	The formation of starch from sugar
   Yes	No	d	The introduction of Ice Nucleating Agents (INAs) into the cells
   Yes	No	e	The freezing of extracellular water

3. Crystallization of minerals in the cells can be limited by:

   Yes	No	a	The presence of anti-freeze proteins
   Yes	No	b	The hydrolysis of starch to sugar
   Yes	No	c	The preferential formation of a glass
   Yes	No	d	The increased activity of the Golgi Apparatus

4. In some alpine plants, extracellular ice formation occurs at around –2°C. What is the critical radius for ice nucleation at this temperature?

   In these plants, the extracellular ice forms on ice nucleating agents. If an ice nucleating agent is a circular disc and is a perfect template for ice, what size must it be for nucleation to occur at –2°C?

   (For the ice-water interface, the interfacial energy γ = 0.028 J m^-2; the latent heat of freezing of ice is ΔH_v = -3.34 x 10⁸ J m^-3.)