Lecture 6 Flashcards
Plant Cell =
Cell Wall + The Protoplast
What is the Cell Wall made of
Cellulose, Glucose polymer
long highly ordered ribbons-bond to form microfibrils
What are the two phases if the cell wall
Phase 1: Crystalline microfibrillar phase
Phase 2: Noncrystalline Matrix
What are the factors of the Noncrystalline Matrix
Hemicellulose, Pectin and the Protein Extension
What is hemicellulose
a heterogeneous group of polysaccharides
long chain of one sugar type and short side chains
rigid structure
What is Pectin
Branched, negatively charged polysaccharides
bind water and have gel-like properties
What is Protein Extension
cross-linking in mature cells
What is the function of Protein Extension
controls expansion of cells
dehydrates cell wall
reduces extensibility
increases strength
how to cellulose producing rosettes move
parallel to the cortical microtubules
what are the three functions of the Cell Wall
Cell Morphology, Provides Structural Support, Prevents Excessive Water Uptake
What is Cell Morphology
an orientation of cellulose microfibrils,
Randomly Orientated-expands equally in all directions
Right angles to ultimate long axis of cells-expands longitudinally along that axis
How does the Cell Wall Provide Structural Support
Protoplast pushing against the cell wall gives it structure and makes cell rigid
How does the Cell Wall Prevent Excessive Water Uptake
Water entering the cell expands protoplast to push against the wall.
Pressure from the cell wall limits the volume of water uptake
Vacuoles important as they contain water and make up a large portion of protoplast
What are Vacuoles
Organelles surrounded by a single membrane
they control what enters and leaves vacuole
function in Regulation of cell shape
how does the vacuole regulate cell shape
High concentration of solutes in vacuole causes osmosis of water
Cells internal pressure contributes to structural support
