Lecture 1: Introduction to Cell Biology
• Biology is studied at different levels of organization
• [Figure 1-9] How big is a cell and how big are its parts?
• There are important similarities that all cells share; however, there are also important differences among various cell types (for example, animal cells vs. bacterial cells)
• [Figure 3-23] The inside of a cell is loaded (crowded, packed) with molecules including RNA, ribosomes and proteins.
o A cell is already packed, even with these few components; without even considering other organelles and components present in cells, the cell is already crowded; crowding changes the behavior of cellular components
• Many different kinds of cells exist; however, there are just two fundamental types:
o Prokaryotic cells
o Eukaryotic cells ( the focus of BISC 315
• Bacterial cells are prokaryotic.
o Escherichia coli (E. coli) [Figure 1-11]
• Eukaryotic cells are found in organisms other than bacteria. [Figure 1-8a]
o They are characterized by membrane-surrounded organelles. In this class, an organelle is a compartment in a cell that is surrounded by a membrane. Ribosomes are not surrounded by a membrane; therefore, they are not organelles.
o Organelles only occur in eukaryotic cells.
Tools for Cell Biology Research
• Some common tools
• Model Organisms
o See Chapter 1 for related information.
o Historically major tool
o Until the early 1960’s, this was the primary technique [Figure 1-6]
▪ Eggs are individual cells that are large enough to see; however, most cells are too small to see.
▪ Microscopy is not our ONLY major tool anymore, but it is still very important.
o There is a reason why most cells are small. This reason has to do with the ratio between surface area and volume.
▪ �������������� ��������=4,��-2.
▪ ������������= ,4-3.��,��-3.
▪ As cell size increases, volume increases much more rapidly than surface area. If the volume gets too big, the surface area becomes unable to handle all of the input and output functions of the cell; thus, the cell cannot survive.
Cell Volume (
( Cell Surface Area
o Light microscopy magnification ~ 1,000X
o Electron microscopy magnification ~ 1,000,000X
o [Panel 1-1, Figure 1-7, and Figure 1-8b]
• Cell Fractionation by Centrifugation
o Cell disruption/homogenization
o Separation of molecules
o [Panel 4-4, 4-5, and 4-6]
o Example: protein separation
o [Panel 4-4] Breaking open (lysing) cells
▪ Detergent lyses cells
• In vitro environment is quite different than in vivo environment; that is, the environment inside the cell is quite different than the environment outside of the cell, inside a test tube. This difference could cause cellular components to behave differently than normal.
• Centrifugation separates materials by density.
o The faster the panel spins, the greater the force exerted; you can use different speeds to separate different molecules.
o [Panel 4-4]
o The densest particles separate to the bottom.
• Know how each process separates materials (by density, mass, etc)!!!
• Molecules (proteins, DNA, and even carbohydrates) can be separated by...