General Cell And Developmental Biology

Study Notes

The cytoskeleton is a network of protein filaments and tubules in the cytosol of eukaryotic cells.
Bacterial cells also possess cytoskeletal fibers made from similar proteins.

Provides mechanical support and maintains the three-dimensional shape of cells, crucial for animal cells that lack cell walls.
Serves as a transportation system within cells, facilitating movement of organelles and structures.
Aids in cell division and enables movement of cells or parts of cells.
Connects cells to one another.

Composed of three main components: microfilaments, intermediate filaments, and microtubules.
Each component varies in protein type, diameter, and formation, contributing to its structure and function.

Motor proteins use ATP to transport organelles along cytoskeletal filaments or to move the filaments themselves.
Major classes include myosin, kinesin, and dynein.

Comprised of thin rods about 7 nanometers in diameter, built from actin protein.
Features plus and minus ends, forming a twisted double chain of actin subunits.
Functions:
- Provides tensile strength and helps anchor cells together.
- Forms a microfilament network, supporting the cell's shape and contributing to the gel-like consistency of the cortex.
- In specialized cells, bundles of microfilaments increase surface area through structures like microvilli.
- Facilitates cell motility via interactions with myosin, essential for muscle contractions and amoeboid movement.

Intermediate in size, approximately 10 nanometers in diameter, these filaments are made from various protein subunits like keratins.
Functions:
- Reinforces cell shape and anchors organelles to maintain structural integrity.
- Provides tensile strength similar to microfilaments.
- Important for cell adhesion (e.g., desmosomes).
Defects in keratin can lead to diseases like Epidermolysis Bullosa, resulting in skin fragility.

Hollow rods measuring around 23 nanometers, constructed from tubulin protein dimers (α and β).
Functions:
- Provide shape and support to the cell.
- Act as tracks for organelle movement guided by motor proteins kinesin and dynein.
- Involvement in chromosome separation during cell division.
- Create structures like cilia and flagella for cellular movement.

Both are extensions containing microtubules, differing in length, number, and movement patterns.
Cilia are numerous and used for moving fluids over cell surfaces; flagella are longer and used for propulsion.
Cilia also serve as sensory antennas, signaling changes in environmental conditions to the cell.