Vitamin D3 is synthesized in keratinocytes of the two epidarmal layers namely <u>stratum basale </u>(bottom layer) and <u>stratum spinosum</u>.
Explanation:
In the two epidermal layers of the skin namely <u>stratum basale</u> and <u>stratum spinosum</u>, 7-dehydrocholesterol (pro-vitamin D3) is converted to vitamin D3. This process takes place in the presence of ultravoilet radiations. Briefly, upon exposure, the pro-vitamin D3 is photolyzed to pre-vitamin D3. The pre-vitamin D3 then isomerized to form vitamin D3.
Moving thing in and out requires surface area, many small cells have much more surface area for much less volume than one big cell so it is more efficient.
The molecules in the sugar<span> move from an area of higher concentration to an area of lower concentration in the water. </span>Describe<span> how water molecules move through the cell membrane during osmosis.</span>