Cell Physiology - Topic 2 Slides Flashcards
What are the 3 types of Endocytosis?
- Phagocytosis
- Pinocytosis
- Receptor-mediated endocytosis
What is Vesicular Transport?
Using vesicle to move substance into or out of the cell
What do substance bypass when using Vesicular Transport?
Substances do not need to cross the plasma membrane but instead use vesicles formed by the plasma membrane
What are Vesicles composed of?
Phospholipids and may contain proteins
What is Endocytosis?
A form of vesicular transport which used vesicles to bring molecules into the cell
What is Phagocytosis?
When cells engulf bacteria or large particles such as cell debris from damaged tissue
What is another name for Phagocytosis?
Cell Eating
What occurs in Phagocytosis?
A large particle is surrounded by pseudopodia and folds around the surface of the particle engulfing it completely and pinches off from the cell membrane within the cell
What is a Vesicle in Phagocytosis called?
A Phagosomes
After Phagocytosis occurs what happens to the Phagosome?
It fuses with the lysosome in the cell
What occurs after the Phagosome fuses with the Lysosomes in the cell?
The lysosome digests the contents of the phagosome with digestive enzymes
Which cells use Phagocytosis the most?
Macrophages of the immune system
What is another name for Pinocytosis?
Cell drinking
What occurs in Pinocytosis?
The membrane of the cell invaginates forming a pock with material from the cell exterior bringing things in via a vesicle
What is the specificity of Pinocytosis?
It is non specific
What can pinocytosis take in?
Ions or Nutrients
What is the specificity of Receptor Mediated Endocytosis?
It has high affinity so it very specific
What is the first step in Receptor Mediated Endocytosis?
A receptor on the cell membrane binds with high affinity to a ligand
What occurs after a ligand binds to a receptor in Receptor Mediated Endocytosis?
Clathrin is recruited to the membrane and links to the receptor ligand complex
What does the Receptor, Ligand and Clathrin form?
A cage like structure
What does the cage-like structure of the receptor, ligand and clathrin lead to?
The accumulation of receptor ligand complexes in a localized region of the membrane
What occurs after the accumulation of receptor, ligand and clathrin at the membrane?
The membrane indents forming a coated pit
What is the Coated Pit known as after it pinches off?
A Coated vesicle
What occurs after the Coated vesicle enters the cell?
It loses its Clathrin coat which is recycled
What occurs in Receptor Mediated Endocytosis after the coated vesicle loses clathrin?
The vesicle is free to fuse with other intracellular membranes
What are Endosomes?
Organelles which perform assorting functions and sort contents of the vesicle
In what way does Cholesterol enter the cell?
Receptor Mediated Endocytosis
What is Cholesterol important in?
Building the plasma membrane and the intracellular membranes in the cell
What is most of the Cholesterol in the bloodstream associated with?
Proteins forming a complex term load density lipo proteins or LGLs
How can cells take up Cholesterol?
By the binding of LGLs of to receptors on the membrane
Once LGLs have been ingested by the membrane what separates them from the receptor protein?
When they fuse with a lysosomes the enzymes separate the proteins from cholesterol so it can be used by the cell
What are the 3 functions of Exocytosis?
- Secrete membrane impermeable molecules synthesized by the cell
- Release waste products that cannot be digested by the cell
- Add components to the plasma membrane
What examples of Membrane impermeable molecules synthesized by the cell?
Antibodies synthesized by WBCs or Protein hormones
Which process replaces portions of the membrane that were removed by Endocytosis?
Exocytosis
What occurs in Exocytosis?
A secretory vesicle in the cell migrates to the surface and dock to peripheral proteins of the plasma membrane. The proteins pull the plasma membrane inward forming a dimple that fuses with the membrane of the vesicle
What is Transcytosis?
The movement of receptor bound macromolecules through the cell using endocytosis and exocytosis
Where is Transcytosis more common?
In polarized cells like epithelials
What makes Epithelia polar?
They have distinctly two different membranes on the two sides that differ in structure and function
What does the Basolateral membrane refer to?
The membrane on the base and sides of the cell
What is the best studied example of Transcytosis?
The absorption and transport of antibodies across the epithelial lining of the gut
What occurs in Transcytosis in the gut?
- An antibody binds to specific receptors on the apical surface of intestinal cell
- It is internalized by receptor mediated endocytosis
- It is transported to an endosome
- The endosome delivers it to the opposite end of the cell
- The receptor and antibody dissociate and the antibody can now enter the bloodstream
What are the two types of Passive Transport?
Channel mediated and carrier mediated transport
What is Simple Diffusion?
When a substance move through the membrane down its concentration gradient without the use of a transport protein
What occurs in Channel Mediated Transport?
The Channel opens and the ions simply move through the channel down in electrochemical gradient
What occurs in Carrier Mediated Transport
A protein carrier and ligand binds to the binding sites on the carrier on one side of the membrane. The carrier then reorientated so the binding site is facing the other side of the membrane and the ligand is released
Is Carrier Mediated Transport Passive or Active?
Passive
What does Active transport require?
Energy in the form of ATP or an Electrochemical gradient
What is Simple Diffusion?
The Passive movement of molecules through a biological membrane lipid bilayer
What is the order of permeability of things that can move by simple diffusion through the lipid bilayer?
- Nonpolar uncharged molecule
- Small uncharged polar molecules
- Water
- Large uncharged polar molecules
- Ions
- Charged polar molecules
What are examples of Nonpolar uncharged molecules?
CO2
O2
Fatty acids
What is an example of a small uncharged polar molecule?
Ethanol
What is an example of Large uncharged polar molecules?
Glucose
What are examples of Charged Polar Molecules?
ATP and Glucose 6-phosphate
What is the permeability of Nonpolar uncharged molecules?
Very Permeable
What is the Permeability of Small uncharged polar molecules?
Very Permeable
What is the Permeability of water?
Slightly permeable
What is the permability of LArge uncharged polar molecules?
Impermeable
What is the Permeability of Ions?
Impermeable
What is the Permeability of Charged polar molecules?
Impermeable
Which molecules are Impermeable?
- Large uncharged polar molecules
- Ions
- Charged polar molecules
Which molecules on Permeable?
- Nonpolar uncharged molecules
* Small uncharged polar molecules
Which molecules are slightly permeable?
Water
What materials can penetrate the bilayer by simple diffusion?
Lipid soluble substances
What energy causes diffusion?
The energy of the normal kinetic motion of matter
What two properties determine whether or not a molecules can cross the plasma membrane by simple diffusion?
- Solubility of the molecule in the lipid
* Size of the molecule
What causes the flux due to simple diffusion to increase?
The concentration of the gradient increases
What factors influence the rate of Simple Diffusion?
- Magnitude of driving force (conc. gradient)
- Membrane surface area
- Membrane permeability
How does Temperature increase diffusion rate?
Increasing temperature increases diffusion rate