Bell Work • What is a centriole? • What is the nucleolus?
Intro to Biology – Lecture 41 Cell Communication and Cell Movement
Cell Communication • Gap Junctions • Desmosomes • Tight Junction
Gap Junctions • An opening from one cell to another, between two cells that are touching. • Cytoplasm can move from one cell to another through “tunnels”.
Desmosomes • Proteins that bond the membrane of one cell to its neighbor communicate. • Cells are touching, but there is not an opening.
Tight Junction • Two membranes actually bonded into one. • It makes a very strong barrier between two cells. • Form solid walls to protect the contents of a cell.
Microtubules • Round, tube-shaped proteins • Thick proteins that are involved in cell movement.
Microtubules • Combine with the microfilaments to form the cytoskeleton of the cell.
Microtubules • Combine in very specific arrangements to form cilia and flagella.
Flagella and Cilia Movement • Cilia and flagellum cause movement on the cellular level.
Cilia and Flagella • Structural components of the cell • Maintained by microtubules • Considered part of the cytoskeleton
Cilia • Flap back and forth to help the cell move. • Can also pass objects down a “cell line”.
Primary Cilia • Serve as sensory organelles
Examples of Cilia • lining of the trachea (windpipe) - they sweep mucus and dirt out of the lungs • Cilia in the Fallopian tubes moves the ovum from the ovary to the uterus
Flagellum • Long, thick tails. • Used for “swimming” • They whip around and sometimes twirl, pushing the cell along.
Types of Flagellum • Prokaryotic • Eukaryotic • Differ in protein composition, structure, and mechanism of propulsion.
Example of Flagellum • Swimming of sperm cells
Microfilaments • Long, thin, and stringy proteins (mainly actin). • Work with microtubules to form the structure that allows a cell to hold its shape, move itself, and move its organelles.
Microfilaments • Also found in muscle tissue (called myofibrils) • The two proteins myosin and actin work together to help the muscle cells relax and contract.
Myosin and Actin • Together, they are called actomyosin. • All of the muscle cells work together to make a muscle contract.
Where are Microfilaments? • Attached to proteins in the cell membrane, floating free in the cytoplasm, or connected to other filaments or tubules.
How do they Cause Movement • Binding proteins allow microfilaments to push and pull on the cell membrane to help the cell move.
The Cytoskeleton • All of the microfilaments and microtubules combine to form the cytoskeleton of the cell
The Cytoskeleton • The cytoskeleton provides structure. • The cytoskeleton connects to every organelle and every part of the cell membrane.
The Cytoskeleton • Plays important roles in both intracellular transport (the movement of vesicles and organelles, for example) and cellular division.