Lesson 4

Question 1

Do animal cells have vacuoles?

Answer 1

Yes mostly small ones

Question 2

Is cork living tissue?

Answer 2

No

Question 3

Who discovered the cell wall?

Answer 3

Robert Hooke

Question 4

What dies the cell wall do?

Answer 4

Gives shape to the cell
Constrain expansion of the protoplast
Limits the expansion and direction of cell
Physical barrier
Offers structure and rigidity
Hold toxic substances

Question 5

What is the protoplast?

Answer 5

Anything that isn’t the cell wall in the cell

Question 6

Why do we say that the cell wall is a living barriers?

Answer 6

It has enzymes
Chemicals
And is constantly changing (thickening/thinning)
Has proteins linked with enzymes and sugar

Question 7

What does cytotoxic mean?

Answer 7

Toxic to the cell that produces it

Question 8

What is the toxic compound found in California poppies?

Answer 8

Sanguinarine

Question 9

What does sanguinarine do to the cell?

Answer 9

Cytotoxic
Cell is elicited to produce sanguinarine
Cell is plasmolyze and it stays in the cell wall

Question 10

What does plasmolyse mean?

Answer 10

Plasma membrane and cell wall collapse when put in a highly concentrated solution

Question 11

Where are the enzymes in the cell wall located and what do they do?

Answer 11

Incredibly specialized in localization
Cell corners of fibre
Lamellar junction
They deposit pictin

Question 12

How does cell wall deposition work?

Answer 12

It is carried out by enzymes
Lignin and other fortifying structures are deposited
It develops over time
The cell expands and specializes
Vessel elements have high concentration of lignin

Question 13

What are the substances in the matrix?

Answer 13

Hemicellulose
Pectin
Glycoproteins

Question 14

How are the substances of the matrix carried to the cell wall?

Answer 14

In secretory vesicles

Question 15

What happens in the matrix if there is more hemicellulose?

Answer 15

Less extensibility

Question 16

What happens in the matrix if there is more pectin?

Answer 16

More elastic (but depends on stage)

Question 17

What does the type of matrix in a plant cell depend on?

Answer 17

The cell type and species of plant

Question 18

What do the cortical microtubules?

Answer 18

Guide complexes to form parallel microfibril which gives rigidity

Question 19

How does cellulose growth work?

Answer 19

Cellulose synthase
Form enzyme complexes called rosettes embedded in plasma membrane
The substrate is UDP-glucose (linked beta 1-4)

Question 20

What is expansin?

Answer 20

It loosens the structure if the cell wall

Question 21

What are the three structures of the cell wall?

Answer 21

Middle lamella
Primary cell wall
Secondary cell wall

Question 22

Do all types of plants have a secondary cell wall?

Answer 22

No

Question 23

What is the primary cell wall made of?

Answer 23

Cellulose
Hemicellulose
Pectin
(Some have lignin, suberin, sutin)
(Proteins aka enzymes and glycoproteins)

Question 24

True or false? Most plants have more then one primary cell wall

Answer 24

False

Question 25

When is the primary cell wall deposited?

Answer 25

While cells are growing and dividing

Question 26

What is the plasmodesmata?

Answer 26

Channel between the cells thin line that connects the cells

Question 27

What does the desmotubule do?

Answer 27

Make the endoplasmic reticulum be shared by two cells

Question 28

Explain the middle lamella.

Answer 28

Composed mainly of pectin
Difficult to distinguish from primary cell wall
Thin layer between adjacent cells
Bisected by plasmodesmata in the pit-field

Question 29

After the elongation of the cell, what happens in regards to pectin?

Answer 29

Ca2+ cross linking of pectin which prevents further stretching (signal molecule)

Question 30

What is pectin, what does it do and where can we find it?

Answer 30

Pectin is a hydrophilic polysaccharide (pretty much the glue)
What do: causes plasticity or rigidity (water imparts plasticity, Ca2+ makes it more rigid)
It allows mobement during cell expansion
It is present in both primary cell wall and middle lamella

Question 31

What is lignocellulose?

Answer 31

Crystalline cellulose molecules which are tethered together with hemicellulose molecules

Question 32

What is hemicellulose and what does it do?

Answer 32

It’s a long cellulose making a network. Not straight (amorphous). It is hydrogen-bonded to cellulose microfibrils
What do: limit extensibility of the cell wall, tethering adjacent microfibrils to each other
Regulate cell expansion (how long they grow)

Question 33

What is cellulose?

Answer 33

The most abundant macromolecule on Earth.
A polymer
A very high energy molecule to make or break

Question 34

What is a polymer?

Answer 34

Multiples of a basic unit

Question 35

What is cellulose made of and what can it make?

Answer 35

Linear chain of hundreds to thousands of beta-(1-4)-linked D-glucose
Repeating monomers of glucose attached to the end
Micelles
What make: microfibrils and macrofibril

Question 36

What does wound together cellulose microfibrils do?

Answer 36

Fine threads, macrofibrils, cell wall
Strength exceeding steel and can withstand vacuolic pressure.)

Question 37

Explain the secondary cell wall.

Answer 37

Present in cells with strengthening role and water transport (like phloem)
Three-layered(opposing orientation of cellulose
Rigid because mostly dead
Cell growth stopped
More of a physical structure instead of living tissue

Question 38

What is present and absent in secondary cell wall?

Answer 38

Abundant cellulose
Matrix of hemicellulose
Pectin absent
Membrane protein absent
Some proteins for transport present in cell wall

Question 39

What is an amorphous layer?

Answer 39

Ball

Question 40

What is elongating layer?

Answer 40

Microfibrils deposited in regular plane/perpendicular axis of elongation
Expancive guide by plant hormone
Adirectional

Question 41

How does the extension of the cell wall work?

Answer 41

Complex biochemical process
Primary cell wall must yield and constrain
Expands
New cellulose microfibrils are placed layer upon layer