Biological Adaptations: Lipid Saturation, Starch Gelatinization, and Protein Structures

1. Cell Membrane Fatty Acids in Reindeer Legs

In plants, unsaturated fatty acids predominate in homeotherms. The temperatures at which lipids solidify depend on their degree of unsaturation. Highly saturated lipids solidify at higher temperatures than less saturated fats with equivalent chain lengths.

Adaptation to Low Temperatures

Many groups of animals, bacteria, and plants that live at low temperatures deposit lipids with lower saturation levels than those living at higher temperatures. This is an adaptation to avoid the deleterious hardening of lipids. A hardening of cell membranes and intracellular components may adversely affect vital biophysical properties. Many enzymes are bound to membranes, and the solidification of the lipid membrane can negatively impact the function of these enzymes.

2. Starch Granule Properties and Gelatinization

Starch is unique among carbohydrates as it occurs in nature as complex, discrete particles. Starch granules are relatively dense, insoluble, and poorly hydrated in cold water.

The Gelatinization Process

While insoluble in cold water, starch granules absorb water as temperatures increase, undergoing a process called gelatinization. This involves the leaching of amylose. Total gelatinization typically occurs over a broad temperature range, with larger granules gelatinizing first.

Stages of Gelatinization

• Temperature of initiation
• Average temperature
• Final temperature of the loss of birefringence
• Gelatinization temperature range

At the end of this phenomenon, a paste is created containing highly hydrated, low-molecular-weight amylose chains surrounding hydrated granule aggregates.

3. Alpha Keratin Protein Structure

Alpha keratin is a protein characterized by the distortion of alpha helices, which consist of groupings of coiled pairs. Interchain crosslinks appear via disulfide bridges, which render them insoluble. Hard keratins (found in hair and nails) contain more disulfide bonds than soft keratins (found in skin).

4. Food Preservation via Salting

Salting is a traditional food preservation system explained by the effect of osmotic pressure. Organisms must maintain osmotic balance with their environment to prevent dehydration (in concentrated media) or cell rupture (in diluted media). These pressure changes are utilized in salted food preservation to control microbial development through osmotic shock.