SHAPE, MOBILITY, AND PROTECTION OF CELLS BY MARCO KAISTH, WES WANG, SONIA KAPIL, GABBY SAADE, AND ANDREW ESTES

HOW ARE SOME CELLS PROTECTED? CELL WALLS!

CELL WALL Found in cells of:  Plant  Bacteria  Fungi  Algae  Archaea Primary and Secondary walls  Primary is on outside  Secondary is found between Primary Wall and Membrane Used for protection Maintains the cell’s shape

PRIMARY WALL Outside layer of protection Thin and flexible Main use as a Pressure Vessel  Used for Osmosis such that water does not cause expansion Shapes the cell and maintains shape Surrounds cell to allow growth

SECONDARY WALL Stronger and more durable Located between Primary Wall and Cell Membrane Main use as protection  Contains lignin which strengthens and makes the wall waterproof  Lignin abundant in trees Some organisms use for food storage

HOW DO CELLS MOVE? FLAGELLA CILIA

FLAGELLA An appendage that protrudes from the body of most prokaryotic and eukaryotic cells Used for “swimming” or movement in its environment Vary in protein composition, structure, and mechanism of propulsion depending on cell Can be more than one on one cell Three types: Bacterial, Archaeal, Eukaryotic Generally rotates in a counterclockwise motion to propel the cell forward

Flagellum of Gram-Negative Bacteria Flagella Made of protein flagellin 20 nanometer-thick hollow tube Helical Has a sharp bend right outside the membrane forming a “hook” which allows it to point directly away from the cell Cylindrical

CILIA Microscopic hair-like organelles 1-10 micrometers long Less than 1 micrometer wide Play a vital role in human and animal development Two types: Motile and Non-motile (primary)

MOTILE CILIA Found in the lungs, respiratory tract, and middle ear Rhythmic waving or beating motion Help to propel a cell Keep our airways clean of mucus and dirt which lets us to breathe easily and without irritation

HOW DO CELLS SUSTAIN SHAPE? CYTOSKELETON!

CYTOSKELETON The cytoskeleton is a three-dimensional structure that is located in the cytoplasm. It acts as both muscle and skeleton if the cell lacks a cell wall.

COMPOSITION The cytoskeleton is composed of three primary protein filaments: intermediate filaments, microfilaments, and microtubules. Micro(Actin) filaments: These are the thinnest filaments of the cytoskeleton. They are linear polymers of actin, a globular, multi-functional protein. They help with cell/organelle movement as well as structural support. Intermediate Filaments: Tough fibers composed of polypeptides. These help strengthen the cytoskeleton and help the cell retain shape stability. Microtubules: The components of flagella, cilia, and centrioles, microtubules play an important role in cell motility and structure.

MOVEMENT The cytoskeleton allows for the movement and contraction of various cells. For example: The contraction of a muscle cell is allowed by the presence of a cytoskeleton. The movement of a white blood cell across a surface.

STRUCTURE RELATES TO FUNCTION EXAMPLES:

XYLEM - Vascular tissue found in plants which provides support for a plant. - Cell wall: is necessary to keep the xylem stiff which will help support the plant and keep it stable. - Cell walls have lignin, which strengthens it and allows it to withstand tension. - No cell wall= xylem not stable= plant not stable

EUGLENA CELL - Euglena are unicellular organisms - Flagellum: Allows euglena to move. Pushes the organism through water. Without flagella, euglena cannot move. - Structure=Flagella - Function= Movement - Video!Video!

MUSCLE CELL - Cytoskeleton: consists of microfilaments (actin filaments) in muscle cells. - Microfilaments are solid rods that help with muscle contraction. - Cytoskeleton gives muscle cell its shape and supports it. - Cytoskeleton is necessary so the muscle cells can do their job involving movement.

BIBLIOGRAPHY

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