Brainscape's Knowledge GenomeTM

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


See full index

PLANTBIO > Features of Plant Cells > Flashcards

Features of Plant Cells Flashcards

1
Q

Plant Cell Wall

A

shape, controls growth, structural barrier, food, fiber, energy

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

Function of Cell Wall

A

rigidity and form to the plant
barrier: permeable only to small molecules (water, ions, etc.)
exist with small molecules from the environment
large molecules are synthesized

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

Composition of Cell wall

A

Primary wall and secondary wall

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

Primary wall

A
  • young, undifferentiated cells
  • in nearly all cells
  • resists the pressure that builds up when water accumulate by osmosis
  • composed of cellulose, hemicellulose, pectin, and protein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Secondary wall

A
  • differentiated cells
  • in only specialized cells
  • lignin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Primary and Secondary wall

A
  • both external to cell membrane
  • extremely complex
  • little known about regulation of synthesis
  • provide support and structure to the plant but they also limit what can enter cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Primary wall composition

A 
"fibers embedded in a matrix"
"steel rods in concrete"
90% polysaccharide 
(hemicellulose, pectin - matrix/ cellulose fibers)
10% protein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Cellulose

A 
least complex
long, unbranched polymer of glucose
beta 1 -> 4 linkage
not known what controls length
2 cellulose chains H-bonded forms dimer
synthesized at cell surface: UDP-glucose precursor (2 binding sites)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Microfibrils

A

determine direction of growth:
- random: multidirectional (storage tissue)
- oriented: growth perpendicular to microfibrils, elongating cells (roots/stems)
outside of cell

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

How is orientation achieved?

A

microtubules orient microfibrils

separated by cell membrane

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

Microtubules

A

composed of tubulin, inside the cell

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

Hemicellulose and Pectin

A

more complex than glucose

golgi -> vesicles -> cell membrane

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

Hemicellulose

A 
heterogenous, branched polysaccharide
beta 1 -> 4 backbone
monosaccharide side chains
xyloglucan - major hemicellulose
H-bonded to each other and microfibril
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Pectin

A 
heterogenous, branched polysaccharide
many galacturonic residues
Ca+2 binds to negative charges
covalently attached to hemicellulose
l.is abundant in the middle lamella
middle lamella is a pectin layer which cements the cell walls of two adjoining plant cells together, outside the cell membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why is Ca+2 levels low in actively growing cells?

A

Ca2+ plays a key role in cross-linking acidic pectin residues. Low [Ca2+] levels increases the permeability of the plasma membrane.

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

Hemicellulose and Pectin Synthesis

A

little is known
defining structure
complexity of polymers suggests a complex enzymatic system (delicate coordination)

17
Q

Proteins/Enzymes in the Cell Wall

A

Visualize with antibodies
Copurification with cell wall
Enzyme activity lost during protoplast isolation
Substrates can be modified that don’t penetrate cell wall
enzymes include transglycosylases and expansins

18
Q

transglycosylase

A

specific for xylose (hemicellulose)

19
Q

expansins

A

break H-bonds between cellulose and hemicellulose

20
Q

Secondary Cell Wall

A

not present in all cells
outside cell membrane, inside primary wall
(PM -2 CW - 1 CW)
thicker than primary wall
can kill protoplast
50% cellulose, 25% hemicellulose, 25% lignin

21
Q

Lignin

A

insoluble in water/ water-resistant
polymer of oxidized, aromatic alcohols
exact structure not known
fibers and wood (fuels)

22
Q

Functions of Secondary Cell wall

A 
strengthens cell and plant
impermeable to water
component of the xylem (water transport)
wood = secondary cell wall
lignin strengthens and waterproofs cell wall
23
Q

Plasmodesmata

A

a system of small, narrow cytoplasmic channels (about 40-50 nm diameter)
700-1000 daltons MW can pass through
allows communication and transport between cells
includes desmotubule and cytoplasmic sleeve
formed during cytokinesis

24
Q

Desmotubule

A

narrow cylindrical tube that runs through cytoplasmic channel
continuous with ER
16-20 nm diameter

25
Q

Cytoplasmic sleeve

A

main pathway for transport
fluid-filled space
continuous with cytosol

26
Q

Function of Plasmodesmata

A

1) cell-cell communication
- prevalent in secretory tissues
2) transport (two transport systems)
- desmotubule and cytoplasmic sleeve

27
Q

What drives transport through the plasmodesmata?

A

symplast and apoplast pathway systems tranport ions and molecules such as water

28
Q

Symplast

A

transport within cytoplasm, which are interconnected by plasmodesmata

29
Q

Apoplast

A

transport along cell wall and intercellular spaces

helps to transport water and ions from the soil through root to xylem elements.

30
Q

Vacuole

A

large, central compartment surrounded by a differentially permeable outer membrane called tonoplast
immature cells have many small vacuoles
mature cells have one large vacuole
vacuole is in osmotic equilibrium
vacuole composition is different from
cytoplasm

31
Q

Tonoplast

A

tonoplast thicker than cell membrane tonoplast has permeability characteristics

32
Q

Functions of Vacuole

A

Degradation, Storage, and Space-Filling

33
Q

Degradation

A

comparable to lysosome
contains hydrolytic activities
enzymes may be exocytosed (out of cell)
organelles endocytosed (into cell) - active ingestion, entrapment
recovery of nutrients at senescence (aging)

34
Q

Storage

A

vacuole content different from cytoplasm
lower pH (3.5-5.5) than cytoplasm (7)
molecules accumulate in vacuole by membrane bound transporters
vacuole helps maintain cell homeostasis
regulate enzyme activity - energy required (ATP)
to accumulate ions, amino acids, organic acids, glucose/sucrose, pigments (anthocyanins) via transport reactions (H+-ATPase, proton cotransport via symporter) proton gradient across tonoplast transport ions and molecules into the vacuole

35
Q

Space Filling

A

costly for cell to be filled with cytoplasm
high solute concentration in vacuole
water enters vacuole by osmosis
water accumulation in vacuole creates pressure (turgidity)
despite resistance of cell wall, turgidity results in cell expansion and plant growth.

36
Q

Plastids

A 
virtually in every cell (except sperm)
double outer membrane, large cytoplasmic organelles
has an internal membrane system (thylakoids)
   - grana
   - stroma lamellea
Has a stroma
   - multiple copies of DNA
interconvertible
	capable of division
	differentiate into each other
37
Q

Types of Plastids

A

1) Proplastid - precursor
2) Leucoplast - nonpigmented storage
3) Chromoplast - nonphotosynthetic pigments (fruit/flower)
4) Chloroplast - most important

38
Q

Chloroplast

A 
plastid that contains chlorophyll and in which photosynthesis takes place
has an outer and inner membrane 
stroma - space
thylakoids - flattened sacs
grana - stacks of thylakoids
stroma lamellae - connects grana

PLANTBIO (15 decks)

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