Membrane Proteins and Their Functions

Peripheral membrane proteins

One of the three main types of membrane proteins found in the plasma membrane.

Integral membrane proteins

One of the three main types of membrane proteins found in the plasma membrane.

Lipid-anchored proteins

One of the three main types of membrane proteins found in the plasma membrane.

Channel protein

An integral protein that spans the membrane and allows specific substances to pass through it.

Glycoprotein

A protein with carbohydrate chains attached, often involved in cell-cell recognition.

Cytoskeleton

Provides structure, shape, and anchors membrane proteins.

Micelle

A small spherical structure with a hydrophobic core formed by single-layered lipids used in hydrophobic molecule transport.

Vesicle

A double-layered lipid sac with a hydrophilic center used for transporting substances; it can acidify its contents using ATPase H+.

Differences between micelles and vesicles

Micelle: single lipid layer, hydrophobic center, smaller. Vesicle: double lipid layer, hydrophilic center, larger, capable of pH regulation.

Phosphoglyceride structure

A glycerol backbone, two fatty acid tails (nonpolar), and a phosphate-containing polar head group.

Functions of glycerophospholipids

Provide membrane stability, fluidity, permeability, and serve as reservoirs for signaling molecules.

Cholesterol's role in plasma membrane

Regulates membrane fluidity and helps maintain structural integrity.

Integral membrane protein structure

An extracellular receptor, a hydrophobic transmembrane region (often α-helices or β-barrels), and an intracellular domain that initiates signaling pathways.

Signal transmission by integral membrane proteins

A ligand binds the receptor, causing a conformational change that activates kinase activity on the intracellular domain.

Common secondary structures in membrane proteins

α-helices, α-helical bundles, and β-barrels.

Anchoring of peripheral membrane proteins

Through acylation (covalent bonding), prenylation (via cysteine residues), or a GPI anchor.

Blood type distinction at molecular level

Know that blood types are distinguished by diverse carbohydrate structures.

Stabilizing membrane-bound proteins in lab

By using non-ionic detergents, lipid mimics, controlling temperature, adding protease inhibitors, optimizing buffers, and minimizing time outside their native membrane.

Critical Micelle Concentration (CMC)

The concentration at which detergents form micelles; below 0.2 this, membrane proteins may denature.

Function of flippase

Moves phospholipids from one leaflet of the bilayer to the other, typically from the cytosolic side to the lumen.

• Flippases are proteins that facilitate the movement of phospholipids between the two layers (leaflets) of a cell membrane

Lipid raft

If you have a plasma membrane and a couple of proteins and they are close together and some interaction happen 

Lipid rafts are dynamic assemblies of proteins and lipids that float freely within the liquid-disordered bilayer of cellular membranes.

Cholesterol transport within cells

By vesicles or micelles, specific cholesterol transport proteins, and HDL/LDL carriers (with HDL being the safer, non-inflammatory option).