1. How thick is an average cell membrane in mm?
The average cell membrane is 0.000006 mm to 0.00001 mm thick.
2. Explain how science knows that the membrane is a bilayer.
In the early 1900’s, two physiologists, Gorter and Grendel, performed an experiment that indicated that the membrane is a bilayer. This experiment can be summarized in three steps.
1. They purified membrane lipids from red blood cell (they chose these because they have lack internal membranes). They estimated the number of starting cells and the surface area of each cell. This allowed the two scientists to calculate the total area of the membrane they purified.
2. They then dissolved the erythrocyte (red blood cell) lipids in benzene. From here they evaporated the benzene
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After completing this, the two scientists measured the area of this monolayer they created, and found that the area was double the estimated area of the starting membrane. This indicated that the original membranes were made of two layers of lipids, or a lipid bilayer, instead of one layer.
3. What is the answer to pop quiz question #1?
Lipids are the primary determinants (deciding factor) of membrane structure, while proteins carry out membrane functions.
4. Which organelles are surrounded by plasma membranes?
(Eukaryotic cells possess additional internal membranes that surround organelles like) the nucleus, the endoplasmic reticulum, the Golgi apparatus, mitochondria, and lysosomes.
5. Which 2 internal membranes are one and the same?
The outer nuclear membrane and the endoplasmic reticulum membrane (the inner and outer membrane of the nucleus is continuous with the inside of the ER).
6. Explain each of the 5 functions of the cell
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Why is membrane asymmetry important?
In the plasma membrane, glycoproteins are found only on the outer side of the bilayer (facing the extracellular area), they play important roles in interactions of the cell with its surrounding environment. A certain phospholipid, phosphatidyl inositol, is in the inner layer of the membrane (facing the intercellular area), from there it plays an important role in signal transduction (cell signaling).
23. Explain the terms integral and peripheral protein?
An integral protein is a protein that interacts with the hydrophobic part of the membrane. They are attached through an area of hydrophobic amino acids. These proteins can extend into the hydrophobic part of the membrane or go through it. A peripheral protein is a protein that is attached to only one side of the lipid bilayer. This protein does not go past into the hydrophobic part of the membrane.
24. What is cytosol?
The cytosol is the name given for the inside of a cell, but it does not include the membrane-bound organelles. Basically, the (liquid) cytoplasm of the