Question

How is the plasma membrane of a cell organized?

Question 15 options:

one layer of phospholipids, through which proteins freely move

one layer of phospholipids, which are laid out end-to-end, with a hydrophobic tail touching a hydrophilic head

two layers of phospholipids, each of which has its hydrophilic side turned inward

two layers of phospholipids, with their polar hydrophilic heads facing away from each other

Answer 1

The plasma membrane is organized into a phospholipid bilayer with hydrophilic heads facing the aqueous environments and hydrophobic tails facing each other, creating a barrier. Integral and peripheral proteins embedded within this bilayer perform essential functions for the cell.

Step-by-step explanation:

The plasma membrane of a cell is intricately organized into what is known as the phospholipid bilayer. This structure is composed of two layers of phospholipids, with each molecule consisting of a hydrophilic (water-loving) head and two hydrophobic (water-hating) tails. The hydrophilic heads face outwards towards the watery environments both inside and outside the cell, while the hydrophobic tails face each other, creating a water-resistant barrier in the middle of the bilayer. This organization allows the plasma membrane to protect the cell’s internal environment and regulate the movement of substances in and out of the cell.

Additionally, scattered throughout the phospholipid bilayer, there are various proteins, including integral proteins and peripheral proteins, which play critical roles in cell function such as transporting molecules, acting as enzymes, or serving as receptors.

Answer 2

The correct option is D. two layers of phospholipids, with their polar hydrophilic heads facing away from each other

Step-by-step explanation:

The cell membrane is made up of two layers of phospholipids. The structure of phospholipids comprises of a hydrophobic tail which is made up of fatty acids and a hydrophilic head that is made up of phosphate. The structure of a cell membrane contains two fatty acid tails.

As the tail is hydrophobic, hence it is shielded and located inwards. The hydrophilic heads are located outwards in opposite directions.