Transport across membranes Flashcards
What is the function of the plasma membrane?
To separate the internal and external environment of a cell and control what can enter and exit the cell.
What are the components of phospholipids?
A hydrophilic polar head and hydrophobic non-polar fatty acid tails.
What is the role of the phospholipid bilayer?
Allows lipid-soluble molecules to pass and prevents water-soluble molecules from entering.
What are intrinsic proteins?
Proteins spanning the membrane, functioning as channels or carriers for specific molecules like ions and glucose.
What are extrinsic proteins?
Proteins on the membrane surface that may associate with carbohydrates to form glycoproteins.
What are glycoproteins?
Carbohydrates attached to proteins, aiding in cell recognition, tissue formation, and receptor function
What are glycolipids?
Carbohydrates attached to lipids, involved in cell recognition and providing structural strength.
What is the role of cholesterol in membranes?
- reduces movement of molecules
- maintains fluidity
- prevents leakage of water and ions.
Why is the membrane called a “fluid mosaic model”?
Phospholipids move freely (fluid), and proteins are distributed unevenly like a mosaic.
Define simple diffusion.
Passive movement of molecules from high to low concentration until evenly distributed.
What molecules use simple diffusion?
Small, non-polar molecules like oxygen and carbon dioxide.
What factors influence diffusion rate?
- Concentration gradient
- distance
- surface area
- temperature.
What is facilitated diffusion?
The passive movement of large or polar molecules via transport proteins from high to low concentration.
How does facilitated diffusion differ from simple diffusion?
- requires specific proteins like carrier or channel proteins
- only occurs at specific points in the membrane.
What happens during facilitated diffusion when a molecule binds to a carrier protein?
The protein changes shape, allowing the molecule to cross the plasma membrane.
