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CELS191 - Grace Watson > Lecture 8 - Cell walls & their role in regulating plant cell shape > Flashcards

Lecture 8 - Cell walls & their role in regulating plant cell shape Flashcards

1
Q

What is the main component of a cell wall?

A

Cellulose - Organic macromolecule of glucose polymers

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2
Q

Cellulose forms…

A

Microfibrils

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3
Q

What are the two phases of cell wall structure?

A

P1 - Microfibrils (Cellulose)
P2 - Matrix (Pectin and hemicellulose)

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4
Q

What is hemicellulose?

A

A heterogeneous group of
polysaccharides. Long chain
of one type of sugar and
short side chains form a rigid
structure.

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5
Q

What is pectin?

A

Branched, negatively charged
polysaccharides. Bind water and have gel-like properties.

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6
Q

The extensibility (expansion) of cells can be controlled by…

A

Extensin cross-linking

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7
Q

What does extensin cross-linking of pectin and cellulose do?

A

Dehydrates the cell wall, reduces extensibility and increases strength

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8
Q

Cellulose is a polymer of ___________________ subunits linked together to
form strong structures called _________________.

A

Cellulose is a polymer of GLUCOSE subunits linked together to
form strong structures called MICROFIBRILS.

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9
Q

Synthesis of cellulose microfibrils occurs at:

A

Plasma membrane

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10
Q

Synthesis of pectin and hemicellulose occurs in:

A

The Golgi apparatus where they are then delivered to cell wall in vesicles

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11
Q

Pectin and hemicellulose are which type of saccharide?

A

Polysaccharide

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12
Q

What are extensins?

A

Cell wall proteins

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13
Q

Synthesis of extensins occurs at:

A

Rough ER, where they then fuse into plasma membrane

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14
Q

What is the structure of the cytoskeleton?

A

A network of microtubules,
microfilaments (and intermediate filaments) that extend throughout
the cytoplasm

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15
Q

What is the main function of the cytoskeleton?

A

Structural support

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16
Q

What produces cellulose microfibrils?

A

Rosettes in the plasma membrane

17
Q

What are rosettes?

A

Protein complexes (enzymes) that span the plasma membrane

18
Q

What is the basic structure of a cell wall?

A

Plasma membrane, primary cell wall, middle lamelae

19
Q

T or F

Cellulose forms microfibrils that are highly ordered and provide strength to the cell wall

A

True

20
Q

T or F

Extensin cross links polysaccharides this increases the extensibility of the cell wall

A

False, it decreased the extensibility

21
Q

T or F

Pectin and hemicellulose are transported to the cell surface by exocytosis

A

True

22
Q

T or F

The plant cell wall allows excessive water uptake

A

False

The cell wall PREVENTS excessive water uptake

23
Q

T or F

Orientation of the cellulose microfibrils influences cell morphology

A

True

24
Q

What happens to cell shape if cellulose microfibrils are ordered randomly?

A

The cell will expand
equally in all
directions.

25
Q

What happens to cell shape if cellulose microfibrils are ordered right angles to the ultimate long axis of the cell?

A

The cell will expand longitudinally
along that axis.

26
Q

What is a protoplast?

A

Inside of the cell (cell minus call wall)

27
Q

Why does wilting of a plant occur?

A

The protoplast is not pushing
against the cell wall.

28
Q

Protoplast pushing against the cell wall leads the plant to be…

A

Rigid and maintaining structure

29
Q

What is a vacoule? (3 statements)

A
  • Organelle with single membrane
  • Highly selective
  • Water enters and leaves via osmosis
30
Q

What is osmosis?

A

The diffusion of water across a
selectively permeable membrane

A high water (low solute)
concentration to a low water (high solute) concentration

31
Q

T or F

All plant cells have a secondary cell wall

A

False

32
Q

T or F

The secondary cell wall is produced only after cell growth has stopped

A

True

33
Q

T or F

The secondary cell wall provides more structural support than the
primary cell wall

A

True

It is thicker and stronger

34
Q

Why is the secondary cell wall thicker and stronger than primary cell walls? (3)

A
  • Made up of multiple layers
  • Microfibrils in each layer have different orientations
  • More cellulose
35
Q

Where is ligin found?

A

In the secondary cell walls

36
Q

What is ligin?

A

A complex polymer that confers strength and rigidity to the secondary
cell wall and acts to exclude water

37
Q

What is plasmodemata?

A

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

CELS191 - Grace Watson (14 decks)

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