Cell Biology Lecture Notes

Overview of Cellular Activities

Cells are highly active, with many processes happening simultaneously.
Extracellular Matrix: Sticky coat that holds cells together.
Plasma Membrane: Flexible barrier with projections, docking stations, and channels.

ATP (Adenosine Triphosphate): Energy currency of the cell.
Produced in the mitochondrion.
- Mitochondrion Structure: Outer membrane and inner membrane with numerous infoldings.
- Infolding increases surface area for more ATP production.

Enclosed by a double membrane called the nuclear envelope.
Houses the cell’s genetic material (DNA).
DNA is wrapped around proteins to fit inside the nucleus.
DNA used as a template to make mRNA.
- mRNA (Messenger RNA): Carries instructions for protein synthesis from nucleus to cytoplasm.

Ribosomes: Clamp onto mRNA strands and build new proteins.
Proteins have various fates: some stay in the cytoplasm, others are processed in internal compartments.

Network of internal membranes within the cell.
Endoplasmic Reticulum (ER): Part of the endomembrane system.
- Rough ER: Covered with ribosomes; site of protein synthesis.
- Smooth ER: Lacks ribosomes; site of lipid synthesis.
Proteins made in the rough ER are packaged in vesicles and transported.
Golgi Apparatus: Further processes proteins received from the ER.
- Finished proteins are packaged in vesicles for transport or secretion.
- Some vesicles fuse with the plasma membrane to release contents; others contain digestive enzymes.

Each cell is a hub of continuous activity requiring a large amount of ATP.
Despite this, most people are unaware of the vast amount of work occurring at the cellular level.