Finish first draft of the bio chapter by adding a section about clathrin

texts/smlm-lab-course/smlm-lab-manual.tex

@@ -409,7 +409,20 @@ \section{Mitochondria}
 
 A STORM image of the mitochondrial network is seen in \autoref{fig:cos7-mitochondria}. Clearly, there is not one sole parameter that describes their shape. However, sites of mitochondrial fission and fusion are good targets for SMLM because the diameter of the mitochondria becomes less than the diffraction limit at these sites.
 
+\section{Clathrin}
 
+Clathrin is a protein that is involved in the formation of vesicles, which are small, membrane-bound sacs that transport molecules within the cell. Clathrin forms a lattice-like structure that is found on the cytoplasmic side of the cell membrane. Clathrin proteins group together to form a shape known as a \textit{triskelion}. Multiple triskelia further combine to form polyhedral lattices, like the one shown in \autoref{fig:clathrin-em}. These polyhedra form the scaffolding of the vesicles known as clathrin-coated pits.
+
+Clathrin-coated pits are the sites of endocytosis, which is the process by which cells absorb molecules from the extracellular environment. The clathrin-coated pits form a vesicle around the molecule to be absorbed, and the vesicle is then transported into the cell. The clathrin-coated pits are then recycled back to the cell membrane.
+
+\begin{figure}
+    \centering
+    \includegraphics[width=0.6\textwidth]{clathrin-em.jpg}
+    \caption{CryoEM map of a clathrin polyhedral cage with a single triskelion highlighted in blue. Mazuraan, CC BY-SA 4.0 \url{https://creativecommons.org/licenses/by-sa/4.0}, via Wikimedia Commons}
+    \label{fig:clathrin-em}
+\end{figure}
+
+Due to their location on the cell membrane, clathrin-coated pits are ideal structures to image with TIRF, which improves the signal-to-noise ratio of objects located within one wavelength of the cloverslip.
 
 \subfile{chapters/lab-Instructions}