Bulk Transport Across Membranes

How does Bulk Transport across Membranes occur?

Exocytosis and Endocytosis

How do small molecules and water enter/leave cell?

Through lipid bilayer or by transport proteins

How do Large Molecules cross the membrane?

In bulk via vesicles

What is required for Bulk Transport?

Energy

What is Exocytosis?

Transport vesicles migrate to membrane & fuse w/ it, releasing their contents

What is Endocytosis?

Cell takes in macromolecules by forming vesicles from plasma membrane

What is the relationship between Endocytosis and Exocytosis?

Endo is the reversal of exo, inloves different proteins

What are the 3 types of Endocytosis?

Phagocytosis, Pinocytosis, Receptor-mediated Endocytosis

What is the simple definition of Phagocytosis?

Cellular eating

What is the simple definition of Pinocytosis?

Cellular drinking

What is Receptor-Mediated Endocytosis?

Binding of ligands to receptors triggers vesicle formation

What is a Ligand?

Any molecule that binds specifically to a receptor site of another molecule

How are processes combined in endocytic receycling?

Fungi combine endo/exo in a circular movement

What are the roles of Exocytosis?

• Enzymes

• Cell Wall

Secrete digestive enzymes, deposit cell wall material for protein

What are the roles of Endocytosis?

• Recycling

• Congestion

Recycle membrane lipids and proteins, avoids congestion

Where is it important to maintain Endo/Exocytosis in Fungi?

Locally at tip

How does the Tip relate to membrane fluidity?

More rigid plasma membrane than further back in tubular phungus

Is the Phospholipid bilayer symmetrical?

No

When a platelet contacts a damaged blood vessel, it is stimulated to release thromboxane A₂. Thromboxane A₂ in turn stimulates vascular spasm and attracts additional platelets to the injured site. In this example, thromboxane A₂ is acting as a

Local regulator

Steroid hormones can enter a cell by simple diffusion. Therefore, steroids

Don’t initiate cell signaling by interacting w/ a receptor

Phosphorylation’s relationship with Proteins

Either activate or inactivate a protein