AP BIOLOGY

THE CELL

TRANSPORT INTO AND OUT OF THE CELL

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
In the phospholipid bilayer, the heads and tails react differently.
A
Hydrophobic heads facing in while the hydrophilic tails face out
B
Hydrophobic tails facing in while the hydrophilic heads face out.
C
No relationship to water so it does not matter which way the head and tails face.
Explanation: 

Detailed explanation-1: -In this energetically most-favorable arrangement, the hydrophilic heads face the water at each surface of the bilayer, and the hydrophobic tails are shielded from the water in the interior. The same forces that drive phospholipids to form bilayers also provide a self-healing property.

Detailed explanation-2: -A phospholipid consists of a hydrophilic (water-loving) head and hydrophobic (water-fearing) tail. In water, phospholipids spontaneously form a double layer called a lipid bilayer, in which the hydrophobic tails of phospholipid molecules are sandwiched between two layers of hydrophilic heads.

Detailed explanation-3: -The heads, which form the outer and inner linings, are “hydrophilic” (water loving) while the tails that face the interior of the cell membrane are “hydrophobic” (water fearing). Water is attracted to the outsides (red) of the membrane but is prevented from going through the non-polar interior (yellow) layer.

Detailed explanation-4: -A Phospholipid Bilayer The head “loves” water (hydrophilic) and the tails “hate” water (hydrophobic). The water-hating tails are on the interior of the membrane, whereas the water-loving heads point outwards, toward either the cytoplasm or the fluid that surrounds the cell.

Detailed explanation-5: -This is because they are two-faced molecules, with hydrophilic (water-loving) phosphate heads and hydrophobic (water-fearing) hydrocarbon tails of fatty acids. In water, these molecules spontaneously align-with their heads facing outward and their tails lining up in the bilayer’s interior.

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