Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CELS191 - Laksh > lecture 7 - plant cell wall > Flashcards

lecture 7 - plant cell wall Flashcards

1
Q

What does the plant cell wall enclose?

A

The protoplast.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the major component of the plant cell wall?

A

Cellulose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the structure of cellulose?

A

Chains of glucose (a polymer), forming ribbons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are cellulose micro fibrils?

A

Layers of cellulose ribbons bonded together into strong chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the 2 phases of the cell wall?

A

Crystalline microfibrillar phase and Non-crystalline matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the chemical component of the Cell Wall Phase 1?

A

Cellulose molecules (which form cellulose/fibre microfibrils)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the three components of Phase 2 of the plant cell wall?

A

Pectin and hemicellulose polysaccharides, extensin (a protein)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the structure of hemicellulose?

A

Long chains of 1 type of sugar, with oligosaccharide side chains.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the properties of hemicellulose?

A

Rigid structure, but not as strong as cellulose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the structure and properties of pectin?

A

Branched negatively charged polysaccharides, which bind water, giving it gel-like properties.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What element of plant cell structure does extensin determine?

A

Extensibility (expansion)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does extensin limit extensibility?

A

When extension fibres crosslink pectin and cellulose, the cell wall become dehydrated, and the cell cannot expand as the wall becomes more rigid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where are cellulose microfibrils synthesised?

A

At rosettes on the cell membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Where are cell wall polysaccharides synthesised?

A

Pectin and hemicellulose are made in the golgi, and transported via vesicles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where are cell wall proteins (extensin) synthesised?

A

In the Rough Endoplasmic Reticulum, then transported by vesicles to the cell wall.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the process of cellulose microfibril production?

A

Rosettes at the plasma membrane move parallel to the underlying cortical microtubules, forming parallel microfibrils on the other side of the plasma membrane.

17
Q

How are the cell wall components structured in the wall?

A

Microfibrils of cellulose form layers, each with microfibrils running in different directions. Hemicellulose molecules sit around the larger microfibrils. Pectin sits within the wall as well as forming a gel-like layer between the cell walls of neighbouring cells - csalled the middle lamellae

18
Q

What are the functions of the plant cell wall? (3)

A

Influence cell morphology, structural support, prevent excessive water uptake

19
Q

How does the cell wall influence cell morphology?

A

The direction of microfibrils in the cell wall determines the direction of expansion when the protoplast pushes against it. Randomly/evenly oriented will allow the cell to expand in all directions into a spherical shape. If the microfibrils are at right angles to the long axis of the cell, it will expand longitudonally.

20
Q

How does the cell wall provide structural support to a plant cell?

A

The protoplast (filled with the water filled central vacuole) pushes against the cell wall until it becomes rigid.

21
Q

What is wiliting, and how does it affect the cell wall?

A

When water flows out of the protoplast/vacuole, there is less pressure on the cell wall, so it becomes less rigid

22
Q

How does the cell wall prevent excessive water uptake by the cell?

A

When the vacuole absorbs large amounts of water via osmosis, the cell wall exerts pressure on the protoplast, preventing it from expanding more.

23
Q

What is the central vacuole in plant cells?

A

A membrane bound organelle, which takes up lots of water and molecules, taking up a large amount of the protoplast.

24
Q

What is osmosis, in terms of the vacuole?

A

The process in which water flows from a low solute concentration to a high solute concentration, allow it to flow in and out of the vacuole, expanding or diminishing it.

25
Q

What are the 3 states of the cell wall, which are dependent on the water levels within the cell?

A

Turgid, flaccid, plasmolyzed

26
Q

What does turgid mean in terms of a plant cell?

A

The vacuole is filled with water, so the protoplast pushes out firmly onto the cell way, making it stiff

27
Q

What does flaccid mean in terms of the plant cell?

A

There is less water in the vacuole, so the protoplast exerts less force on the cell wall, and it does become as rigid and is flaccid

28
Q

What is a plasmolyzed plant cell?

A

A cell which has lost a lot of water, so the cell wall loses a lot of strength.

29
Q

What is the purpose of secondary cell walls?

A

To provide thicker, stronger structural support to specfic types of cells.

30
Q

Do all plant cells have a secondary cell wall?

A

No

31
Q

What is the structure of the secondary cell wall?

A

Three layers of cellulose microfibrils
* Made up of multiple layers
* Microfibrils in each layer have different orientations
* This strengthens the secondary wall

32
Q

Chemical difference of secondary cell wall

A

new - lignin
More Cellulose
Less - pectin

33
Q

What is lignin? And what does it do?

A

Lignin is a complex polymer
Confers strength, rigidity to the secondary cell wall and acts to exclude water

34
Q

What are plasmodesmata?

A

Intercellular connections - gaps in the cell wall that allow molecules to pass to neighbouring cells so they can communicate.

35
Q

Are the plasmodesmata small enough to prevent organelles from getting through?

A

Yes, except some pieces of ER slip through in parts.

36
Q

What are the bits of ER passing through plasmodemata called?

A

Demosomes

37
Q

How is the plasma membrane continuous at the plasmodesmata?

A

It lines the cell wall on either side and coats the sides of the plasmodesmata gaps.

38
Q

What cell wall components does extensin cross link?

A

cellulose and pectin

CELS191 - Laksh (35 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions