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.

Muscles Contracting

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.