2.B

WEEK 12

I, unfortunately, missed both Monday and Tuesdays class, so I can only recall what we learned and discussed during Thursday’s class.

On Thursday, we mainly learned about the characteristics of the plasma membrane. The plasma membrane is an organelle that is extremely important to the life of a cell. It is through this membrane, also known as a phospholipid bilayer, that the cell acquires its nutrients and carry out cellular respiration, which allows it to keep functioning properly.

The plasma membrane contains many macromolecules called phospholipids. Phospholipids are made up of a phosphate group bonded to the carboxyl group with two different hydrocarbon chains attached to it. (2.B.1). The phospholipid interesting and different macromolecule characteristics because it has one hydrophilic region and a hydrophobic region. There are two sheets of phospholipids in the plasma membrane, which is why, I’m assuming, it is also referred to as the phospholipid bilayer. The hydrophobic regions tend to meet in the middle of the bilayer, so that they don’t have to interact with water and polar molecules in the cytoplasm and the external cellular environment.

The plasma membrane has its two regions, with the hydrophobic regions resting the middle. The different regions make it difficult for polar molecules to diffuse into the cytoplasm or leave the cell. The polar molecules require a transport protein to translocate them across the plasma membrane. When a transport protein works with the concentration gradient, it is called facilitated diffusion. Facilitated diffusion is considered to be passive transport because it doesn’t require added energy or ATP (2.A.2, 2.B.2).

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