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>
Answer:
I think is D because I had this question
Answer:
d. ATP is present and the intracellular Ca2+Ca2+ concentration is high.
Explanation:
Myosins are motor proteins that plays a major role in muscle contraction. They depend on ATP and responsible for motility in actin-based substances. Skeletal muscle is composed of myosin and actin fibers. Each myosin thick filament is surrounded by actin thin filaments, and each thin filament is surrounded by thick filaments. There exists a strong attraction between the myosin head and the myosin-binding site of actin which binds them spontaneously. This bond is aided by the presence of ATP and the high concentration of intracellular Ca2+. The myosin protein undergoes a change in its shape.
Answer:
Explanation:Which of the following is true about dominant alleles?
- Dominant alleles mask the presence of recessive alleles.
- Dominant alleles are passed on more often than recessive alleles.
- Dominant alleles are more important than recessive alleles.
- Dominant alleles are more common in the population than recessive alleles.
- Dominant alleles are healthier than recessive alleles.
