And: Facilitated diffusion is a type of passive transport that allows substances to cross membranes with the assistance of special transport proteins. Some molecules and ions such as glucose, sodium ions, and chloride ions are unable to pass through the phospholipid bilayer of cell membranes.
Answer: C) Apical
Explanation: An epithelium has a free surface, the apical surface, exposed to the outside, and an attached surface, the basal surface, resting on the underlying connective tissue.
Scientists
can also glimpse the awful effects of Alzheimer's disease when they look at
brain tissue beneath the microscope:
Alzheimer's tissue has numerous fewer nerve
cells and synapses than a well brain.
<span>
<span>Plaques, unusual
clusters of protein particle, which are construct up between nerve cells.</span>
</span>
<span>
<span><span>Dead and dying nerve cells contain tangles,</span> which
are produce of twisted strands of a further protein.</span>
</span>
<span>Scientists
are not absolutely sure what causes cell death and tissue deficiency in the
Alzheimer's brain, but plaques and tangles are key suspects.</span>
