Exploring proteins 4 communication across membranes GTP 10 M

What is the structure of eukaryotic cell membranes?

Eukaryotic cell membranes are made up of a phospholipid bilayer, which is semipermeable and fluid. This allows for the movement of proteins and lipids within the membrane.

What are the types of transport mechanisms across the cell membrane?

• Simple Diffusion: Movement of molecules directly through the membrane.

• Passive Transport: Involves channel proteins and transporters that move molecules down their concentration gradient without energy.

• Active Transport: Requires energy (usually from ATP) to move molecules against their gradient.

Types of Transport Proteins

Q: What are the different types of transport proteins?

Transporters: Change conformation to move molecules across the membrane.

Channel Proteins: Form pores that allow specific molecules to pass through.

What are the two types of coupled transport systems?

Symport: Both molecules move in the same direction.

Antiport: Molecules move in opposite directions.

How do GPCRs function in cell signaling?

GPCRs have seven transmembrane domains, bind to extracellular ligands, and activate G proteins inside the cell, initiating various intracellular signaling pathways.

What are second messengers and what is their role?

Second messengers like cAMP and IP3 are produced during signaling and activate further signaling pathways, leading to cellular responses such as gene expression, enzyme activation, and ion channel regulation.

What is the role of cAMP in cell signaling?

cAMP is produced by adenylyl cyclase upon GPCR activation. It activates protein kinase A (PKA), which then phosphorylates target proteins to regulate cellular functions.

How does phospholipid signaling work?

Phospholipase C breaks down phosphatidylinositol (PI) into diacylglycerol (DAG) and IP3. IP3 triggers calcium release from the ER, while DAG activates protein kinase C (PKC), leading to various cellular responses.

What is the difference between active transport and passive transport?

Active transport requires energy to move molecules against their concentration gradient,

while passive transport moves molecules down their gradient without energy input.

Q: How does cholesterol affect membrane fluidity?

Cholesterol makes the membrane less flexible, affecting its fluidity, and is crucial for maintaining the structural integrity of the membrane.