Question

cell defense: the plasma membrane (interactive activity)
go to the following website:
https://biomanbio.com/html5gamesandlabs/cellgames/celldefensehtml5page.html
click:
o start a new game
o build a membrane
read first:
o “your mission”
o “urgent messages”
this is where your answers to these questions will come from.
build a membrane:

1. what is the function of a plasma membrane that all living cells depend on?
2. without a plasma membrane, what would cells be unable to maintain?
3. what is a phospholipid made of? which part is hydrophilic, and which is hydrophobic?
4. why do phospholipids form a bilayer? sketch a phospholipid bilayer with 6 total phospholipids.
5. what is the role of cholesterol in a membrane? what does cholesterol touch in the membrane?
6. what property of the membrane describes how it allows some molecules to pass but not others? why is it important?

Explanation:

1. The plasma membrane is a selective - barrier. It controls the movement of substances in and out of the cell, maintaining homeostasis.
2. Without a plasma membrane, cells would be unable to maintain a stable internal environment (homeostasis), including proper ion concentrations and protection from the external environment.
3. A phospholipid is made of a glycerol backbone, two fatty - acid tails, and a phosphate - containing head group. The phosphate - containing head group is hydrophilic, and the fatty - acid tails are hydrophobic.
4. Phospholipids form a bilayer because the hydrophilic heads are attracted to water (the extracellular fluid and the cytoplasm), while the hydrophobic tails repel water and cluster together in the interior away from water. For the sketch, draw two rows of 3 phospholipids each with heads facing outward and tails inward.
5. Cholesterol in the membrane helps to maintain membrane fluidity. It touches the fatty - acid tails of the phospholipids.
6. The property of the membrane that allows some molecules to pass but not others is called selective permeability. It is important because it enables the cell to take in necessary nutrients, expel waste products, and maintain a proper internal environment.

Answer:

1. It is a selective - barrier that controls the movement of substances in and out of the cell.
2. A stable internal environment (homeostasis).
3. Made of a glycerol backbone, two fatty - acid tails, and a phosphate - containing head group. The head group is hydrophilic, and the tails are hydrophobic.
4. Because the hydrophilic heads are attracted to water and the hydrophobic tails repel water. (Sketch: two rows of 3 phospholipids each with heads facing outward and tails inward)
5. Helps maintain membrane fluidity. Touches the fatty - acid tails of phospholipids.
6. Selective permeability. It enables the cell to take in nutrients, expel waste, and maintain a proper internal environment.