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.