Plasma Membrane Flashcards
What is a plasma membrane?
The outermost layer of a cell, it is made up of a phospholipid bilayer, which controls what enters and exits the cell.
What are the two main characteristics of a plasma membrane?
- Selectively permeable
- Composed of a lipid bilayer
What does it mean to be selectively permeable?
It means that the plasma membrane controls what goes into and what comes out of a cell.
What is a lipid bilayer?
A double layer of lipids that makes up the plasma membrane. The specific lipid is a phospholipid.
What is a phospholipid?
The main lipid composing the lipid bilayer of plasma membranes. They are made of a hydrophilic head and two hydrophobic tails.
What does hydrophilic mean?
It means that something is attracted to water.
What does hydrophobic mean?
It means that something is repelled by water.
Does the head of a phospholipid face towards a cell?
Yes, because they are hydrophilic. The tails are hydrophobic, so they face towards each other, away from the water.
Are plasma membranes rigid?
No, they have a very fluid quality. They are also very thin. 1,000 plasma membranes stacked on top of each other equal the thickness of one piece of paper.
Is the plasma membrane also made up of other molecules?
Yes, like cholesterol.
What are some of the structures/molecules that the selectively permeable membrane will let through on their own?
- Oxygen
- Carbon Dioxide
- Water
- Very small non-polar molecules
The plasma membrane is embedded with several different proteins. What are these proteins?
- Enzymes
- Channels
- Transporter Proteins
- Receptors for signaling molecules
- Recognition proteins that help identify what type of cell it is.
What is a transporter protein?
A protein that transports a molecule from the outside of the cell to the inside of the cell and vice versa.
What is an example of a receptor for signaling molecules.
Hormones.
What are the types of molecules that cannot cross the plasma membrane on their own?
Some bigger molecules, and hydrophilic molecules.
