Essay Anatomy Intorduction to the Human Body

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Pages: 6


Plasma Membrane and Cellular Transport
Structure of the Plasma Membrane
1. Why do you think it is important to have a membrane surrounding each of our trillions of cells? Expect varying answers, but the idea is have the students understand the plasma membrane separates the cells from their environment and each other while also regulating the material within each cell. 2. What are two distinctive physical features of phospholipids? Heads are polar (water soluble, hydrophilic) and tails are nonpolar (water hydrophobic).



Describe the conformation of the phospholipid bilayer of the plasma membrane. What abundant fluid leads to his conformation? Because the phospholipids heads are
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Dr. D.

Houston Community College

Page 3


Fill in the table, identifying similarities and differences between passive transport and active transport. Passive Transport Active Transport ATP Usually against the gradient, but can be with it Any size

What drives the movement of the molecules across the plasma membrane? Do the molecules move with or against the concentration gradient? What size are the molecules that are moved across the plasma membrane? 5.

Concentration Gradient With the gradient Small for simple diffusion or osmosis, larger for facilitated diffusion

Recall that a cell needs to maintain homeostasis to perform its functions. If a cell has a higher concentration of substances in the cytoplasm, which direction will water move? How can a cell continue to maintain homeostasis if the concentration of water fluctuates? Water will move into the cell. Active transport can be used to move water and other molecules into the cell or out as needed.

6. Define endocytosis. Endocytosis is an active transport mechanism for moving substances into the cells by vesicles formed from the plasma membrane.


Describe the steps in endocytosis from the following series of illustrations.

7a. Describe this step of endocytosis. The plasma membrane begins engulfing particles from the extracellular fluid.

7b. Describe this step of endocytosis.