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CELS191 > cell walls & their role in regulating plant cell shape > Flashcards

cell walls & their role in regulating plant cell shape Flashcards

1
Q

what are the components of the plant cell?

A
  • nucleus
  • endomembrane reticulum
  • Golgi apparatus
  • mitochondrion
  • central vacuole
  • chloroplast
  • cell wall
  • plasmodesmata
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2
Q

a plant cell = ?

A

the cell wall + the protoplast

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3
Q

what are the components of the cell wall structure cellulose?

A
  • The most abundant organic macromolecule on Earth
  • Glucose polymer
  • Highly ordered
  • Long, ribbon-like structures
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4
Q

what does cellulose form?

A

microfibrils
- highly organized structures are strong and form a
a major component of both primary and secondary cell walls

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5
Q

what are the two phases in the cell wall structure?

A

Phase 1: Crystalline Microfibrillar Phase
- Cellulose
Phase 2: Noncrystalline Matrix
- Pectin polysaccharides
- Hemicellulose polysaccharides
- plus a network of Extensin (a protein)

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6
Q

what is hemicellulose?

A
  • A hemicellulose is a heterogeneous group of polysaccharides.
  • Long chains of one type of sugar and short side chains form a rigid structure.
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7
Q

what is pectin?

A
  • Pectin branched, negatively charged polysaccharides.
  • Bind water and have gel-like properties
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8
Q

what happens in the cell wall structure: the protein extensin?

A
  • The extensibility (expansion) of cells can be controlled by extensin cross-linking
  • Extensin cross-linking of pectin and cellulose dehydrates the cell wall, reduces extensibility, and increases strength
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9
Q

what happens during the coordinated synthesis and delivery of synthesis of the Primary Cell Wall?

A
  • Cellulose microfibrils at plasma membrane
  • Polysaccharides (pectin & hemicellulose) in the Golgi apparatus are transported to the wall in vesicles.
  • Cell wall proteins (extensins) from the rough ER.
  • The vesicles fuse to the plasma membrane
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10
Q

what happens during exocytosis?

A
  • Transports material out of the cell or delivers it to the cell surface
  • Constitutive exocytosis releases extracellular matrix proteins
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11
Q

what is the protoplast?

A

plasma membrane+all the organelles+cytoplasm that sit inside the plasma membrane

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12
Q

what is a cellulose-producing rosette?

A
  • is a protein complex enzyme
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12
Q

what is a cellulose-producing rosette?

A
  • is a protein complex enzyme
  • The cellulose-producing rosettes move parallel to the
    cortical microtubules
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13
Q

what does the cellulose-producing rosette do?

A
  • sits across the plasma membrane + joins together glucose molecules = to make cellulose
  • The cellulose-producing rosettes move parallel to the
    cortical microtubules
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14
Q

what determines the cell wall shape?

A

Where the cortical microtubules are = cellulose producing enzyme attaches = position of microtubules determine = cellulose laydown = determines the cell shape

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15
Q

what happens with the cortical microtubules?

A

cortical microtubules are right up against the plasma membrane associated with this is the rosette that makes the cellulose = goes all the way down = rosette goes with it = as it goes along produced cellulose microfibril

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16
Q

what is the primary cell wall?

A
  • primary cell wall
  • middle lamella
  • pectin
  • cellulose
  • hemicellulose
17
Q

what is the middle lamella?

A
  • above the cell wall
  • mostly pectin (sticky substance)
  • stick cells together
18
Q

cellulose forms microfibrils that are highly ordered and provide strength to the cell wall (true or false)?

A

true

19
Q

extensins cross-links polysaccharides this increases the extensibility of the cell (true or false)?

A

false

20
Q

pectin and hemicellulose are transported to the cell surface by exocytosis (true or false)?

A

true

21
Q

what is the cell walls’ function that helps with regulating the cell shape?

A
  • influences cell morphology
  • provides structural support
  • prevents excessive water uptake
22
Q

what is cell morphology?

A
  • Orientation of the cellulose microfibrils influences cell morphology
23
Q

what are the two types of cell morphology?

A
  • Randomly oriented - The cell will expand equally in all directions
  • Right angles to the ultimate long axis of the cell - the cell will expand longitudinally along that axis.
24
Q

how does the cell wall provide structural support?

A

-The protoplast pushes against the cell wall. The cells become rigid and this maintains the plant structure
- Wilting occurs when the protoplast is not pushing against the cell wall.
- Water loss from cells reduces the protoplast volume and the protoplast does not press on the cell wall

25
Q

how does the cell wall prevent excessive water intake?

A
  • As water enters the cell by osmosis, the protoplast expands and pushes against the cell wall.
  • Pressure from the cell wall limits the volume of water that can be taken up
  • Vacuoles are important in this process because they contain water and makeup such a large portion of the protoplast
26
Q

what is the structure of the vacuoles?

A
  • It is highly selective, controlling much of what enters and leaves the vacuole
  • Water moves in the vacuoles by osmosis (passive transport)
27
Q

what is a vacuole?

A

A vacuole is an organelle surrounded by a single membrane
- Typical mature plant cell has a single large vacuole

28
Q

what is the vacuole function in the regulation of cell shape?

A
  • There are high concentrations of solutes in the vacuole
  • This results in water uptake into the vacuole by osmosis
  • The plant cell wall limits water uptake and prevents the cell from bursting.
  • Plant cells build up a large internal pressure that contributes to plant structural support.
29
Q

what is osmosis?

A

The diffusion of water across a selectively permeable membrane (around the vacuole for plants)

30
Q

how does the movement in osmosis work?

A

High water (low solute) concentration
to
Low water (high solute) concentration

31
Q

what is really important for managing water uptake?

A

pressure against the cell wall = if no cell wall water would keep being taken up by osmosis and it would brust

32
Q

in the cell wall, carbohydrates are diverse and functional important molecules (true or false)?

A

true

33
Q

what is the secondary cell wall?

A
  • Produced only after cell growth has stopped
  • Thicker and stronger than primary cell walls
  • Provides more structural support than the primary cell wall
34
Q

what is the structure of the secondary cell wall?

A
  • Made up of multiple layers
  • Microfibrils in each layer have different orientations
  • This strengthens the secondary wall
35
Q

what are the chemical characteristics of the secondary cell wall?

A
  • More cellulose
  • Less pectin
  • Lignin
36
Q

what is lignin in the secondary cell wall?

A
  • Lignin is the second most abundant organic macromolecule
  • Lignin is a complex polymer
  • Confers strength, rigidity to the secondary cell wall and acts to exclude water
37
Q

what does the secondary cell wall provide structural support for?

A

specific cell types - such as water transporting cells, and for the whole plant

38
Q

what are plasmodesmata?

A

Plasmodesmata are intercellular connections, that enable cell-to-cell communication.

39
Q

what do plasmodesmata do in terms of cell communication?

A
  • The plasma membrane is continuous
  • Small enough to prevent organelle movements – although the endoplasmic reticulum is connected through plasmodesmata.
  • Allows the free exchange of small molecules
40
Q

what is closer to the cell?

A

secondary cell wall

CELS191 (19 decks)

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