Cell Bio Lecture 20

How can membrane proteins be solubilized?

By the use of Detergents such as SDS and Triton X-100

What is the difference between SDS and Triton X-100?

• SDS

  • stronger, breaks everything down, denatures proteins

• Triton X-100

  • Mild

  • used to just permeabilize the membrane without completely destroying everything

How are detergent micelles formed?

Formed by amphiphilic molecules

They interact with proteins’ hydrophobic membrane spanning portion, FORMING PROTEIN-DETERGENT COMPLEXES

What is the CELL CORTEX?

Dense network of STRUCTURAL proteins located just beneath the cell membrane

How does Spectrin provide support?

• Structural support that gives RBCs their biconcave, flattened shape

• Spectrin dimers link to form tetramers, CREATE A MESH WITH ACTIN THAT SUPPORTS MEMBRANE

• Anchored to membrane via attachment proteins linking to transmembrane proteins

Which experiment showed that proteins move laterally in the lipid bilayer?

Formation of mouse-human hybrid cells:

1. Cell Fusion - mouse and human cells fuse, but membrane proteins and lipids are kept separate

2. Protein intermixing - overtime membrane proteins and lipids from both cells intermingle

3. Fluorescent labeling - antibodies labeled with fluorescent tags track protein movement

How can lateral movement of plasma membrane proteins be restricted?

• Tethering to cell cortex

• tethering to extracellular matrix

• tethering to cell surface proteins of another cell

• diffusion barriers

In gut epithelial cell membranes, how are membrane proteins restricted?

TIGHT JUNCTIONS

What are glycoproteins?

These are proteins with short chains of sugars

What are proteoglycans?

Proteins with one or more LONG chains of sugars

What are the functions of cell surface carbohydrates?

• PROTECT CELL

  • chemical and mechanical damage

• Absorb water, giving cells a slimy surface

• Helps mobile cells (WBCs) to squeeze through narrow spaces

• prevents blood cells from sticking to one another

How does carbohydrate recognition drive neutrophil migration from blood to infected site?

1. Neutrophil with specific oligosaccharide binds to a lectin

2. lectin recognizes specific sugar

3. Neutrophil adheres to the endothelial cell and craws along the blood vessel wall

4. Neutrophil is able to be secreted out of blood vessel to travel to infected tissue.

What is electrolyte imbalance?

Too high or too low levels of essential minerals that carry an electrical charge in body fluids

• Hyponatremia (Low Na+)

  • Swelling of cell

  • CNS alterations, lung congestion, muscle weakness

  • leads to cardio respiratory arrest and death

• Hypernatremia (High Na+)

  • Shrinking of cell

  • Cerebral edema, hyperventilation, muscle cramps, lower cardioactivity

  • leads to coma and death

What are electrolytes vital for?

• Maintaining fluid balance

• nerve and muscle function

• pH balance

• transport of nutrients and waste

Balance crucial

Imbalances triggered by diarrhea, fluid balance interruption, kidney problems.