Transport Mechanisms Flashcards
What is the cell membrane highly permeable to ?
-Water
-Lipid-soluble substances
-Dssovled gasses(O2, CO2)
-Small uncharged molecules
What is the cell membrane less permeable to ?
-Larger molecules
-Charged particles
What is the cell membrane impermeable to ?
-Very large molecules
Characteristics of the cell membrane?
- Phospholipid bilayer
- Amphipathic (polar and nonpolar ends)
What does the cholesterol in the phospholipid bilayer do?
At higher temps. = keeps the membrane more rigid
At lower temps. = keeps the mebrane fluid
-Helps form lipid rafts
-Helps form vesicles
Is cholesterol slightly amphipathic?
Yes
What types of proteins are found in the cell membrane?
Integral proteins - Imbedded within the cell membrane
ex. Transmembrane proteins : type of integral protein that spans the cell membrane
Peripheral - found on the outside of the cell membrane, attached to it but not integrated within it
What does glycocalyx do in the cell membrane and what is it made of?
Sugar coating that surrounds the cell membrane made up of glycans, glycoproteins and glycolipids (sugary molecules)
-Function: contributes to cell-cell recognition, communication, adhesion and protection. Helps control vascular permeability (at the endothelial cells)
Why is the cell membrane called the fluid mosaic model?
- Not a static structure
-Proteins are constantly being turned over
Name the 6 functions of plasma proteins?
- Channels/Transporters
- Amino acid transport/ Na-K pump
- Cell surface receptor
- Cell surface identity marker
5.Cell adhesion
6.Attachment to the cytoskeleton
Name the two ways to cross the cell membrane?
Via the phospholipid bilayer
Or via interaction with a transmembrane protein (channel/carrier)
What is passive transport vs Active?
Passive : energy independent
Active : Energy dependent
What are examples of passive transport?
- Diffusion
- Facilitated Diffusion
- Osmosis (water)
What are examples of active transport?
- Primary active transport
- Secondary active transport
- Pino/Phagocytosis
What is simple diffusion?
The movement of molecules from one location to another as a result of random thermal motion goes with the concentration gradient
What is flux?
Amount of particles crossing a surface per unit time
What is Net flux?
Movement from high to low concentration
At equilibrium what is flux and net flux?
-Net flux is zero
-Fluxes are equal
Net movement is zero but movement never stops molecules are always moving just equally in all directions
Why is diffusion only effective over short distances?
Diffusion time increase in proportion to the square of the distance
What are the most important components of the cell membrane?
The proteins
What determines how well a molecule will diffuse across the membrane?
- Mass of the molecule
- Concentration Gradient
- Lipid Solubility
- Electrical Charge
- Ion channel
- Membrane Carriers
How do non-polar molecules and gasses diffuse?
Across the lipid bilayer
How do ions diffuse?
Through channels
What is an ion channel?
A transmembrane protein that shows ion selectivity