In this lecture, we will build on the knowledge gained from lecture 5 to look into the structure and function of membrane proteins.

The plasma membrane is an important cellular organelle that delineates the perimeter of the biological cell and allows the cell to communicate with the outside world. After covering briefly the diverse roles played by the membrane, we will explore the molecules that make up most of the membrane: lipids. We will see how they arrange to form a bilayer in a way that is thermodynamically favorable.

We will then look at the structure of membrane proteins and characterize in which way they are different from globular proteins. This will be based on their interaction with the lipid membrane described in the first part. In particular, we will talk about the types of aminoacids that are favored in membrane proteins and why.

Then we will move on to describing the families of proteins involved in the transport of solutes across the membrane. We will see that there are several types of transport, passive/active and non-mediated/mediated and we will go through the classes of proteins that support different types of transport (water and ion channels, transporters and pumps). We will in particular focus on the relationship between protein structure and function and explore how a particular 3d arrangement allows a specific type of transport.

Finally, we will move into signal transduction: in this class of phenomena, no solute is transported across the membrane, yet a signal is communicated from the outside of the cell to the inside of it. We will go through two classes of proteins that enable this crucial biological function and here also explore how their structure is related to their function.

Reading suggestions

Finkelstein - Chapter 12

Lecture recording

Playlist of all lecture 8 concepts

Isolated concepts:

Slides with still images from videos

(Some students found these useful to take notes)

Full-format slides

Handout-format slides

Study questions

What are the roles of biological membranes?
What is the main component? Can you mention some other components?
How is the membrane itself stabilised?
What is the Singer-Nicholson, or "fluid mosaic" model?
How are membrane proteins stabilised in the membrane?
How are the interactions in membrane proteins different from globular ones?
Describe some typical functions of membrane proteins!
What is the basics of the energetics of solute movement across a biological membrane?
What is the difference between mediated and non-mediated transport?
What's the difference between passive and active transport?
What is an ion channel? Why are they necessary?
What is a transporter?
What is the NKA (or Na/K ATPase)? How is it different from an ion channel?
Where does NKA get its energy from?
What is signal transduction?
What is a "GPCR"? Describe how it works!
Describe the structure and function of an RTK / protein-tyrosine kinase receptor!
Describe some roles of ligand-gated ion channels!
Describe how viral fusion happens, and how proteins are involved!

Scientific papers

The molecular mechanism of anaesthetics and benzodiazepines

Cryo-tomography imaging of an entire membrane with GABA receptors resolved

Paper on the first native GABA structures from brain tissue

Manuscript on simulation of ligand-gated ion channel gating