They are like that because they can't always be faulty and may have at least some spark of truth to this theory also as stated earlier a theory in scientific terms is just an observation so it can't really be turned down hence theory.
Purebred is another word for homozygous
Answer:
c. a high percentage of very long chain saturated fatty acids
Explanation:
Saturated fatty acids do not have double bonds (they are saturated with hydrogens), so their tails are relatively straight. Unsaturated fatty acids, on the other hand, contain one or more double bonds, which often produces an elbow or bend. (You can see an example of an unsaturated bent tail in the phospholipid structure diagram that appears at the beginning of this article.) Saturated and unsaturated phospholipid fatty acid tails behave differently when the temperature drops:
- At colder temperatures, the straight tails of saturated fatty acids can be tightly bound, producing a dense and quite rigid membrane.
- Phospholipids with unsaturated fatty acid tails cannot bind so closely due to the bent structure of their tails. For this reason, an unsaturated phospholipid membrane remains fluid at lower temperatures than a saturated phospholipid membrane.
Most cell membranes contain a mixture of phospholipids, some with two saturated (straight) tails and others with a saturated tail and an unsaturated (folded) tail. <u>Many organisms — fish, for example — can adapt physiologically to cold environments by changing the proportion of unsaturated fatty acids in their membranes, that is, increasing the proportion of saturated long-chain fatty acids.</u>
In addition to phospholipids, animals have an additional component in their membrane that helps them maintain fluidity. Cholesterol, another type of lipid that is embedded between the membrane phospholipids, helps decrease the effects of temperature on fluidity.
<span>Mucous membranes provide a mechanical barrier at body openings. They also line the respiratory, GI, urinary, and reproductive tracts. Mucous membranes secrete mucus, a slimy substance that traps pathogens. The membranes also have hair-like cilia.</span>
