Chapter 5: Cell Membranes Homework
1. The phospholipid bilayer is selectivity permeable which means that the membrane allows only some substance to cross more easily than others. This is a stable boundary because of the hydrophilic and hydrophobic regions. Hydrophilic means that a substance loves water. The head of the phospholipid faces towards the water inside/outside of the cell. The middle layer of the membrane consists of the hydrophobic region. They form the lipid tails and they hate water. Since lipids and water does not mix well together, the middle of the phospholipid bilayer does not allow water to go inside.
2. An amphipathic molecule has both a hydrophilic and hydrophobic region. It refers to the “personality” of the molecule. The phospholipid bilayer is a amphipathic molecule since in has a hydrophilic
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Endocytosis is a common cellular process which involves the uptake of bulk material outside of the cell (extracellular material) and bringing in into the cell using a membrane. There are three types of endocytosis: phagocytosis, pinocytosis, and receptor mediated endocytosis. In simple terms, pinocytosis is like the process of cell drinking. This is where the cell uses the invagination (gap in cell membrane) to take the liquid/aqueous solution outside of the cell membrane inside. The substance is stored in a vesicle which is like a bubble in side of the cell. Pinocytosis has a small vesicle. This is a method for the cells get nutrients and take up signals from the environment. Pinocytosis is summarized as the uptake of small soluble components into the cell. Phagocytosis can be referred to a form of cell eating. Instead of the invagination the phagocytosis process uses pseudopodia. The pseudopodia envelop large particles like bacteria and dead cells. In comparison to pinocytosis, the vesicle is large to hold the particle. This process is commonly used in the immune system because the particle in the vesicle ends up being broken down using