Cell walls and their role in regulating plant cell shape

Question 1

Major component in the cell wall

Answer 1

Cellulose

Question 2

Describe cellulose

Answer 2

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

Question 3

Cellulose forms

Answer 3

Microfibrils

Question 4

Microfibrils

Answer 4

Highly organised structures that are strong and form a major component of both primary and secondary cell walls

Question 5

Two phases of the cell wall structure

Answer 5

Microfibrils and matrix

Question 6

What consists of microfibrils

Answer 6

Cellulose

Question 7

What consists of matrix

Answer 7

• Pectin polysaccharides
• Hemicellulose polysaccharides plus a network of Extensin

Question 7

Hemicellulose

Answer 7

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

Question 8

Pectin

Answer 8

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

Question 8

The extensibility (expansion) of cells can be controlled by

Answer 8

extensin cross linking

Question 8

Effect of extensin cross linking of pectin and cellulose

Answer 8

It dehydrates the cell wall, reducing extensibility and increasing strength. The cell cannot expand in size

Question 8

The synthesis of the primary cell wall consists of the o-ordinated synthesis and delivery of: A

Answer 8

Cellulose microfibrils at plasma membrane

Question 8

The synthesis of the primary cell wall consists of the o-ordinated synthesis and delivery of: B

Answer 8

Polysaccharide (pectin and hemicellulose) in the golgi apparatus are transported to the wall in vesicles

Question 8

The vesicles fuse to

Answer 8

the plasma membrane

Question 9

The synthesis of the primary cell wall consists of the o-ordinated synthesis and delivery of: C

Answer 9

Cell wall proteins (extensins) from the rough endoplasmic reticulum

Question 9

Exocytosis

Answer 9

Transports material out of the cell or delivers it to the cell surface

Question 9

Constitutive exocytosis releases

Answer 9

extracellular matrix proteins

Question 9

Cytoskeleton

Answer 9

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

Question 10

Functions of the cytoskeleton

Answer 10

Maintaining the position of organelles and providing structural support

Question 11

The cellulose producing rosettes move

Answer 11

parallel to the cortical microtubules

Question 11

Cellulose producing rosettes are

Answer 11

protein complexes (enzymes) that span the plasma membrane

Question 11

Orientation of the cellulose microfibrils influences..

Answer 11

cell morphology

Question 12

Cell wall functions in regulating cell shape

Answer 12

• Influences cell morphology
• Provides structural support
• Prevents excessive water uptake

Question 13

If the cellulose microfibrils are orientated where the right angles to the ultimate long axis to the cell,

Answer 13

the cell will expand longitudinally along that axis

Question 13

if the cellulose microfibrils are randomly oriented,

Answer 13

the cell will expand equally in all directions

Question 14

The cell wall provides..

Answer 14

structural support

Question 15

The protoplast pushes against the cell wall.

Answer 15

The cells become rigid and this maintains the plant structure

Question 16

Wilting occurs when..

Answer 16

the protoplast is not pushing against the cell wall.

Question 17

Water loss from cells reduces the protoplast volume ..

Answer 17

and the protoplast does not press on the cell wall

Question 18

The cell wall prevents ..

Answer 18

excessive water uptake

Question 19

As water enters the cell by osmosis,

Answer 19

the protoplast expands and pushes against the cell wall.

Question 20

Pressure from the cell wall limits..

Answer 20

the volume of water that can be taken up

Question 21

Vacuoles are important because..

Answer 21

they contain water and make up such a large portion of the protoplast.

Question 22

A vacuole is..

Answer 22

an organelle surrounded by a single membrane

Question 23

Vacuole is highly selective,

Answer 23

controlling much of what enters and leaves the vacuole

Question 24

Water moves in the vacuoles by..

Answer 24

osmosis (passive transport)

Question 25

Typical mature plant cell has..

Answer 25

a single large vacuole

Question 26

Osmosis is..

Answer 26

the diffusion of water across a selectively permeable membrane

Question 27

Movement in osmosis occurs from

Answer 27

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

Question 28

There is high concentration of solutes in the vacuole. This results in...

Answer 28

water uptake into the vacuole by osmosis

Question 29

The plant cell wall limits...

Answer 29

water uptake and prevents the cell bursting.

Question 30

Plant cell builds up a large internal pressure that contributes to..

Answer 30

plant structural support

Question 31

Not all plants cells have..

Answer 31

a secondary cell wall

Question 32

The secondary cell wall is produced only after...

Answer 32

cell growth has stopped

Question 33

The secondary cell wall is ..... than primary cell walls

Answer 33

thicker and stronger

Question 34

The secondary cell wall provides more..

Answer 34

structural support than primary cell wall

Question 35

The secondary cell wall structure

Answer 35

- Made up of multiple layers - Microfibrils in each layer have different orientations -This strengthens the secondary wall

Question 36

Chemical characteristics of the secondary cell wall

Answer 36

- more cellulose -less pectin -lignin

Question 37

Lignin is the second most

Answer 37

abundant organic macromolecule

Question 38

Lignin is a complex

Answer 38

polymer

Question 39

Lignin confers...

Answer 39

strength and rigidity to the secondary cell wall and acts to exclude water

Question 40

The secondary cell wall provides structural support for:

Answer 40

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

Question 41

Plasmodesmata

Answer 41

are intercellular connections, that enable cell to cell communication

Question 42

Is the plasma membrane continuous

Answer 42

Yes

Question 43

The plasmodesmata is small enough to prevent organelle movements,,

Answer 43

although endoplasmic reticulum is connected through plasmodesmata.

Question 44

Plasmodesmata allows

Answer 44

the free exchange of small molecules