D. Polarity and size.
<span>The size, polarity, and charge of a substance will determine whether or not the substance can cross the cell membrane by diffusion. The cholesterol was an example of a lipid, and is highly soluble in the nonpolar environment of the lipid bilayer. You saw, in the animation above, the cholesterol freely passing into the hydrophobic environment of the membrane. Cholesterol distributes freely in the membrane and then some fraction will dissolve in the aqueous environment of the cytoplasm. Water, on the other hand, while polar, is small enough to cross the membrane at a slow rate. Note that specialized transport proteins in certain cell membranes can provide a channel for the water, greatly increasing its rate of crossing the membrane. The lipid bilayer is much less permeable to the ion, because of its charge and larger size. As a general rule, charged molecules are much less permeable to the lipid bilayer.</span>
Index fossils (also known as guide
fossils, indicator fossils or zone
fossils) are fossils used to define
and identify geologic periods (or
faunal stages).
Answer:
Main function of phloem Transportation of food particles.
Explanation:
Phloem is the living vascular tissue in plants. Phloem is also known as bast. Phloem is responsible for transporting food to parts of the plant where needed. It's mainly transport sugar sucrose which is made by photosynthesis. This transport process is called translocation. In trees the phloem is the innermost layer of the bark.
<span>If the density of ice were greater than water, ice would sink to the bottom of oceans/seas/lakes etc. This ice would cool the water so much that more water would freeze, and the entire body of water would soon be a giant block of ice! You can imagine how this would affect aquatic life</span>
