Jeffery Arnett is a physiologist who coined the term "emerging adulthood." This has previously been known as; delayed adulthood, transition age youth, youthhood, and the twixter years. He believes that the period between adolescence and adulthood is when the person reaches adulthood but doesn't have children, have sufficient funds, or have their own home. He believes it starts at 18 and ends around 25 years of age. He thinks this is when people are still looking for love, make money to spend on recreational activities, and trying to develop their own identities. This theory is highly controversial and has been contested by developmental psychologists.
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.
Answer: All of the statements are true.
Explanation:
Purines are biologically synthesized as nucleotides and in particular as ribotides, that is, bases attached to ribose 5-phosphate. Adenine and guanine are both derived from the nucleotide inosine monophosphate (IMP), which is the first compound in the pathway to have a completely formed purine ring system.
Purine nucleotides can be synthesized in two distinct pathways. First, purines are synthesized de novo, starting with simple starting materials such as amino acids and bicarbonate. the purine bases are assembled already attached to the ribose ring. Alternatively, purine bases, released by the hydrolytic degradation of nucleic acids and nucleotides, can be salvaged and recycled. Purine salvage pathways are mostly noted for the energy that they save and the remarkable effects of their absence.
All statements are correct because the organization of purine synthetic enzymes involves multifunctional enzymes, reversible enzyme formations, through out the sequence there is maintenance of high local concentration and the ten steps requires only six enzymes.
