Membrane Proteins and their functions

Where are membrane proteins found

They are embedded in or attached to the phospholipid bilayer of the cell membrane

How can membrane proteins be attached

They may be permanently or temporarily attached to the membrane

What are integral proteins

Proteins that penetrate the bilayer and are permanently attached to the membrane

Can integral proteins be easily removed from the membrane

No — removing them would disrupt the bilayer

What are examples of integral proteins

Glycoproteins, ion channels, carrier proteins, and protein pumps

What are peripheral proteins

Proteins that attach temporarily to one side of the membrane

How are peripheral proteins held in place

By attaching to integral proteins, phospholipid heads, or the cytoskeleton/extracellular matrix

How can peripheral proteins be removed

They can be removed by polar solvents without damaging the membrane

What is an example of a peripheral protein

Receptor complexes involved in cell signalling, like G proteins

What determines the composition of a membrane protein

Its function within the cell — structure matches purpose

How do non-polar (hydrophobic) amino acids behave in the membrane

They face the lipid bilayer, helping the protein stay anchored

How do polar (hydrophilic) amino acids behave in the membrane

They face the watery surroundings inside and outside the cell

What lines the inside of protein channels

Polar amino acids, allowing charged or polar molecules to pass through safely

What are the six main functions of membrane proteins

Junctions, Enzymes, Transport, Recognition, Anchorage, and Transduction

What is the role of junction proteins

They connect and join two cells together, helping form tissues

What do enzyme proteins do in membranes

They speed up chemical reactions and localise metabolic pathways

What is the function of transport proteins

They help move materials across the membrane by facilitated diffusion or active transport

What is the function of recognition proteins

They act as markers to help cells identify each other

What do anchorage proteins do

hey provide attachment points for the cytoskeleton inside the cell and the extracellular matrix outside

What is the role of transduction proteins

They act as receptors that receive signals — for example, binding peptide hormones to trigger a response inside the cell

What are the 3 types of memebrane protiens