Which statement about phospholipids is true? 1. Heads of phospholipids are hydrophobic.
2. Phospholipids allow any particle to freely pass through the phospholipid bilayer.
3. Tails of phospholipids are hydrophobic.
4. Phospholipids do not allow small particles to freely pass through the phospholipid bilayer.

3. Tails of phospholipids are hydrophobic.

Explanation:

According to the fluid mosaic model, the plasma or cell membrane contains components such as: proteins, phospholipids etc. The phospholipid forms a layer called PHOSPHOLIPID LAYER, which comprises of a phosphate head and a fatty acid (lipid) tail.

The phosphate head is HYDROPHILIC i.e. water-logging while the fatty acid/lipid tail is HYDROPHOBIC i.e. water-fearing. Hence, according to this question, it is TRUE that the tails of phospholipids are hydrophobic.

Note: Phospholipid layer, which are selectively-permeable i.e do not allow the passage of molecules, allows the passage/diffusion of small molecules like oxygen gas.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.