Membrane Structure: Proteins and Their Movement along the Bilayer — Practice Flashcards

A set of 20+ study flashcards covering membrane protein types, structure, diffusion, FRAP, lipid rafts, cell cortex, glycocalyx, and anaerobic metabolism.

What are the two main types of membrane proteins?

Integral membrane proteins and peripheral membrane proteins.

How do transmembrane proteins cross the lipid bilayer?

They cross as alpha-helices or beta-sheets (often amphipathic).

What carries out the majority of the membrane's functions?

Membrane proteins.

What is the sugar coat on the plasma membrane called?

Glycocalyx.

What reinforces the plasma membrane?

A cell wall or an underlying cell cortex.

Why might some cells have a cortex richer in actin and myosin?

Because they need to change shape and migrate (e.g., neutrophils).

Which part acts as the primary barrier against the outside of the cell?

The phospholipid (lipid) bilayer.

What are glycocalyx components composed of?

Glycosylated membrane proteins (the glycocalyx).

Do glycocalyx components block hydrophilic molecules from entering the cell?

No; glycocalyx does not block hydrophilic molecules.

What structures can membrane lipids form that affect diffusion?

Domains called lipid rafts.

Which lipids are enriched in lipid rafts?

Sphingomyelin and cholesterol.

Why are lipid rafts more rigid than surrounding membrane?

Higher cholesterol content and longer hydrocarbon tails of sphingolipids increase thickness and rigidity.

What does FRAP stand for?

Fluorescence Recovery After Photobleaching.

In FRAP, what does fluorescence recovery indicate?

Movement of unbleached fluorescent proteins into the bleached area; mobility of membrane proteins.

What does no recovery in a FRAP experiment imply?

The protein is tightly anchored to the membrane and immobile.

What experimental technique allows live visualization of fluorescent-tagged membrane proteins?

Fluorescence microscopy.

If Protein A recovers more slowly than Protein B in FRAP, what does that suggest?

Protein A is more tightly anchored to the lipid bilayer than Protein B.

What role does the cell cortex play in neutrophil migration through blood vessel walls?

It enables the cell to change shape and migrate; cortex composition adapts to function.

How can diffusion of membrane proteins be restricted?

Cortex tethering, extracellular matrix interactions, and confinement to lipid domains.

What is the extracellular matrix?

A complex network of sugars and proteins secreted by cells; supports cell function.

Which cellular processes are anaerobic?

Glycolysis and fermentation (the electron transport chain is aerobic).