The Cytoskeleton + Cell Surfaces (2A)

Cell Wall Composition

• in eukaryotes - made of cellulose

  • molecules bind into microfibrils which provide the cell wall’s rigidity & function

• in prokaryotes - made of peptidoglycan

  • polymer consisting of sugars & amino acids forms mesh-like layer

Cell Wall Location

found on the outermost part of the cell

Cell Wall, Cell Types

can be seen in prokaryotes and plant cells (not animal cells)

Cell Wall Function

provides the cell with structural support, shape, and serves as a barrier, which controls what comes in and out of the cell

• primary - provide protection and structure to the cell

Cell Wall Shape

a rigid structure surrounding the cell membrane (outermost layer of the cell)

Is the Cell Wall Membrane-Bound?

NO! it is outside of the cell membrane

Extracellular Matrix Structure

boundary cell, has strong interwoven fibers

EM Composition

glycoproteins + polysaccharides

EM Shape

resembling a mesh or a lattice

Is the EM Membrane-Bound?

No! located outside of the cell membrane

EM location

attached to the cell membrane through glycoproteins binding to membrane proteins called integrins

EM, Cell Types

eukaryotic animal cells

EM Function

holds one cell to another cell (like glue) + protects and supports cell membrane

• primary - provide structural support for cells within a tissue

EM Interactions

• helps cell membrane (+ connects to it)

• communicates changes occurring inside and outside of the cell through the cytoskeleton

Cilia Shape

short, numerous appendages that propel Paramecium (hairs)

• animal cells

Flagella Shape

tail-like shape, long, identified by looking for a long tail attached to the main body of bacteria + archaea cells

Cilia + Flagella Composition

composed of microtubules unwrapped in an extension of the plasma membrane

• “9+2” pattern

  • nine pairs of doublet microtubules surround a central pair of singlet microtubules

Cilia Function

signal receiving “antenna” for the cell but are nonmotile with this function.

• all cells have a primary cilium that is important in embryonic development, sensory reception, and cell function

Cilia + Flagella Function

help with cell mobility and movement

• dynein proteins are key mechanism in motion of cilia and flagella

Are Cilia + Flagella Membrane-Bound?

Yes! they are both wrapped in an extension of the plasma membrane

Tight Junctions

• made of mainly proteins called “claudins”

• looks like a branch network w/ lots of strands

• attached to the plasma membrane

  • located on the edge because it has to bind to other cells to create a seal

• found in animal cells

Tight Junctions Function

• creates a seal that prevents fluid from moving across a layer of cells

• prevents contents of digestive track from leaking to other tissue

Are Junctions Membrane-Bound?

Yes! they have proteins that directly embed themselves within the plasma membrane of adjacent cells

Anchor Junctions

• intermediate filaments made of sturdy proteins

• anchored in the plasma membrane (membrane-bound)

• found in animal cells

Anchor Junctions Function

• function like “rivets”

  • fasten cells together into strong sheets

Gap Junctions

• set of 6 proteins in the plasma membrane

• small gaps in cell tissue

• attached to plasma membrane

• found in animal cells

Gap Junctions Function

their main function is to transport ions, nutrients, and other substances that allow cells to communicate

Gap Junction Interaction

the gap junctions interact with the plasma membrane of their own cells and the gap junctions of other cells to communicate with each other

Cytoskeleton Composition

• made from microfilaments (10nm) which are made of actin, intermediate filaments (6-7nm)

  • which are made from various proteins (keratin)

• the final type of molecule that makes up the cytoskeleton are microtubules (25nm) (made from tubulin proteins)

Cytoskeleton

• looks like a group of hair

• found in the cytoplasm of both eukaryotic cells (a+p)

Cytoskeleton Function

primary

1. shapes + supports the cell

2. helps things move around the cell

Cytoskeleton Interactions

• supports the plasma membrane

  • helping give the cell its overall shape

• correct positioning of organelles

• provides tracks for the transport of vesicles

• in some cells, allows the cell to move

Is the Cytoskeleton Membrane-Bound?

No! it is not enclosed by a membrane