The cell membrane is an extremely pliable structure composed primarily of back-to-back phospholipids (a “bilayer”). Cholesterol is also present, which contributes to the fluidity of the membrane, and there are various proteins embedded within the membrane that have a variety of functions.
A single phospholipid molecule has a phosphate group on one end, called the “head,” and two side-by-side chains of fatty acids that make up the lipid tails (Figure 1). The phosphate group is negatively charged, making the head polar and hydrophilic—or “water loving.” A hydrophilicmolecule (or region of a molecule) is one that is attracted to water. The phosphate heads are thus attracted to the water molecules of both the extracellular and intracellular environments. The lipid tails, on the other hand, are uncharged, or nonpolar, and are hydrophobic—or “water fearing.” A hydrophobic molecule (or region of a molecule) repels and is repelled by water. Some lipid tails consist of saturated fatty acids and some contain unsaturated fatty acids. This combination adds to the fluidity of the tails that are constantly in motion. Phospholipids are thus amphipathic molecules. An amphipathic molecule is one that contains both a hydrophilic and a hydrophobic region. In fact, soap works to remove oil and grease stains because it has amphipathic properties. The hydrophilic portion can dissolve in water while the hydrophobic portion can trap grease in micelles that then can be washed away.
A crystals shape is determined by the arrangement of the atoms or molecules inside the crystal.
Answer:
apidly reversible active-inactive transition
Explanation:
"Two haploid cells are formed" happens in meiosis during telophase I.
<u>Answer:</u> Option C
<u>Explanation:</u>
The chromosomes are inserted into nuclei during telophase I. The cell now needs to undergo a cytokinesis cycle, which separates the initial cell's cytoplasm into two daughter cells. One set of chromosomes are contained in each daughter cell and called as haploid or half the original cell's overall chromosomes number.
The parent cell has two poles, each with a full haploid set of chromosomes (consisting sister chromatids) when the meiotic process hits Telophase I. A cleavage furrow is formed at this point, splitting the cytoplasm of the cell into a half (cytokinesis). Once the cytoplasm is completely separated, the two originating daughter cells start planning for the second meiotic division.
