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BIO203 > Cells and Meristems > Flashcards

Cells and Meristems Flashcards

1
Q

What does the size of a meristem indicate about the organ it is made for?

A

The shape.

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2
Q

Why are plant cells and stem cells important?

A

Plant cells and stem cell
niches have unique
properties and
characteristics
*
These underlie their
abilities and vital role to
us and ecosystems

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3
Q

Why are vacuoles so much larger in plant cells compared to animal cells?

A

Plant cells do not have the energy to make new cytoplasm. The cell instead grows using water pressure. This is called the hydroskeleton.

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4
Q

What is one of the main functions of a plant cell’s vacuole?

A

One of the main roles of the vacuole and tonoplast is to provide pressure that increases the rigidity of the plant.

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5
Q

What is the difference between a vacuole in a young plant cell and that of a mature plant cell?

A

Young plant cells usually have multiple smaller vacuoles that eventually fuse together at maturity.

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6
Q

What is contained in the vacuole? What is this composed of and where are the components made?

A

Vacuoles contain cell sap, which is mainly water, mixed with other components such as inorganic ions, sugars, organic acids, and amino acids. The contents of the vacuole are not made there, but are transferred there from the cytoplasm.

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7
Q

What is the tonoplast? What does it do?

A

Semi-permeable membrane surrounding the vacuole. Selects what can enter and exit.

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8
Q

Other than acting as the hydroskeleton of the plant, what are some other functions of the vacuole?

A

Storage/isolation of wastes and harmful materials
Regulating pH
Resource storage

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9
Q

What are transvacuolar cytoplasmic strands?

A

thin tubular structures that traverse the vacuole

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10
Q

What are some functions of trancvacuolar cytoplasmic strands?

A

Aid in cell division
Distribution routes for organelles and metabolites
Golgi and ER move inside

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11
Q

What is dynamic instability in regards to the transvacuolar cytoplasmic strands?

A

Dynamic instability refers to the regular sequences of breakdown, re-formation and rearrangement experienced by the microtubules.

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12
Q

What are plastids?

A

Plastids are unique to plant cells. They revolve around different processes such as photosynthesis and storage.

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13
Q

List the 5 plastids discussed in lecture.

A

Chloroplasts, chromoplasts, proplastids, lecuoplasts, etioplasts

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14
Q

What are thylakoids?

A

Flattened sacs in the membrane system of plastids.

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15
Q

What is the stroma?

A

Matrix of plastids.

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16
Q

How are plastids believed to have evolved?

A

evolved from free-living cyanobacteria, which explains its having its own genome

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17
Q

What are proplastids?

A

Proplastids develop into the more differentiated plastids from the previous page.

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18
Q

What happens if proplastid development is interrupted? What are they then called?

A

If this development is interrupted, they may form prolamellar bodies. Plastids containing these bodies are called etioplasts.

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19
Q

What are etioplasts?

A

Etioplasts form in leaf cells of plants that are grown in the dark. Once exposed to light, the etioplasts turn into chloroplasts and the membranes of the prolamellar bodies turn into thylakoids.

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20
Q

What are leucoplasts?

A

Transitionary plastid. Gives rise to amyloplasts, elaioplasts and proteinoplasts.

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21
Q

What is the difference between leucoplasts and chromo/chloroplasts?

A

Leucoplasts lack the pigment and elaborate inner membranes of chloro- and chromoplasts.

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22
Q

What are grana?

A

Stacks of thylakoids.

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23
Q

What pigment is found in chromoplasts? What is it responsible for?

A

Chromoplasts do not contain chlorophyll, but instead have carotenoid pigments. These pigments are responsible for the colouring of many flowers, leaves, fruits, etc.

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24
Q

What is the function of the chromoplast?

A

The exact function of chromoplasts is uncertain, but they can act as attractants to pollinators they’ve coevolved with

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25
Q

Why are chloroplasts called semi-autonomous organelles?

A

Chloroplasts contain the components needed to assemble some of their polypeptides

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26
Q

Where are amylo-, proteino-, and elaioplasts found in the seed?

A

Storage organ

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27
Q

WHat are amyloplasts?

A

Stores starch (energy)

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28
Q

What is the function of the elaoplast?

A

Lipid/oil storage.

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29
Q

What is the function of the proteinoplast?

A

Protein storage.

30
Q

What colour are proplastids?

A

Colourless

31
Q

WHat cells are proplastids found in?

A

Found in meristematic cells of shoots, roots, embryos, and endosperm.

32
Q

Explain the typical morphology of proplastids.

A

No distinctive morphology, vary in shape.

33
Q

What pigment is found in the chloroplast?

A

Chlorophyll

34
Q

Explain the morphology of the choroplast.

A

Green, lens shaped.

35
Q

Where are chloroplasts located?

A

Present in all photosynthetic
tissues and organs. E.g. leaves, storage cotyledons, seed coats, embryos, outer layers of unripe fruits.

36
Q

What colour(s) are chromoplasts?

A

Red, orange, yellow

37
Q

Where are chromoplasts found?

A

Often found in flowers, fruits, senescing leaves and certain roots.

38
Q

What may chromoplasts develop from?

A

Chromoplasts often
develop from chloroplasts, but may also form from proplastids & amyloplasts

39
Q

What are leucoplasts? How do they differ from proplastids?

A

colourless plastids, distinct
from proplastids having lost their
progenitor function.

40
Q

Provide examples of leucoplasts.

A

Amylo, elaio, proteino

41
Q

Aside from storage of starch, what is another function of amyloplasts?

A

can redifferentiate into other plastid types.

42
Q

Where are amyloplasts found?

A

Found in roots &
storage tissues (e.g. cotyledons,
endosperm, & tubers)

43
Q

What is cytoplasmic streaming? What does it do?

A

Cytoplasmic streaming is the constant movement of the cytoplasm and its contents. This movement allows for the transport of materials within the cell and between the cell and the environment.

44
Q

What is the function of the cell wall in plant cells?

A

The reason plant cells cannot move during development, why plants can grow so quickly. Pressure of vacuole is resisted, leading to the structural integrity of the plant.

45
Q

Do cell walls completely inhibit cell growth?

A

Cell walls can be loosened for growth.

46
Q

List the cell walls in order of development.

A

Middle lamella, primary cell wall, secondary cell wall

47
Q

Where is the middle lamella located?

A

Between adjacent cells.

48
Q

What is the middle lamella composed of?

A

Pectin

49
Q

WHat is the function of the middle lamella?

A

Semi-permeable membrane; provides lubrication for expansion.

50
Q

What is the primary cell wall composed of?

A

composed of strands of cellulose (microfibrils), ridges between strands composed of hemicellulose.

51
Q

How does the primary cell wall expand?

A

Breakage of hemicellulose allows the expansion of cell wall.

52
Q

When and where does the secondary cell wall grow?

A

Inside primary after complete expansion.

53
Q

What is the secondary cell wall composed of? What does it do?

A

Lignin strengthens and water proofs secondary cell wall. lignin also has anti-microbial benefits as it contains phenol, which is toxic.

54
Q

Is a plant cell limited to one secondary cell wall?

A

No, can have multiple with varying lignification, different directions of cross linking.

55
Q

What cell wall are stem cells mainly composed of?

A

Secondary

56
Q

What is the plasmodesmata? How does it work?

A

: Channel for cell to cell
communication. cells in plasmodesmata are linked cytoplasmically (share cytoplasm) can share large molecules through each other.

57
Q

How does movement through plasmodesmata differ for small and large molecules?

A

Small can move freely, large are regulated or prevented.

58
Q

Where does mitosis occur in plant cells?

A

Meristems

59
Q

Why don’t meristems divide a lot?

A

stem cells don’t divide much because every time they do, there are mutations.

60
Q

What is the tunica of the meristem?

A

Tunica: one or more peripheral
layers of cells which divide in planes
perpendicular to the surface of the
meristem ( anticlinal divisions)

61
Q

What is the corpus of the meristem?

A

Corpus: Body of cells several
layers deep in which cells divide in
two planes ( anticlinal and periclinal

62
Q

Assign names to the labels in this figure.

A

L1: epidermal (Tunica)
L2:
subdermal (
L3: core (Corpus)

63
Q

List the 3 zones of the SAM.

A

CZ: Central Zone
PZ: Peripheral Zone
RZ: Rib Zone/Rib meristems

64
Q

List the functions of the CZ, PZ and RZ.

A

CZ Slowly dividing
stem cells
*
PZ Rapid cell division. Cells incorporated into leaf & flower primordia
*
RZ Division and subsequent elongation of these cells generates stem

65
Q

Where is the organizing centre/medullary meristem of the SAM? What does it do?

A

Between RZ and CZ is organizing centre that contains cells that produce signals that help with positioning of other cell types and the identity and function of stem cells.

66
Q

Where is WUS expressed and what does it do?

A

The
WUSCHEL WUS ) gene is expressed in the Organizing center and
is needed to maintain stem cell fate in cells of the CZ

67
Q

What does CLAVATA 3 do and where is it expressed?

A

The
CLAVATA 3 gene limits production of stem cells; expressed in stem cells of CZ

68
Q

What would happen if a SAM did not have a WUS gene? A CLV3?

A

No WUS = no stem cells
no CLAVTA 3 = infinite growth of stem cells

69
Q

Explain the negative feedback loop that regulates stem cell population size.

A

shoot stem cells make clavata 3, which inhibits WUS (determines if they are stem cells or not), less stem cells = less CLV3, WUS reduces, increasing stem cells and CLV3, and so on.

70
Q

Explain the difference between SAM and RAM in terms of location and what they produce.

A

SAM: Stem cells above OC
generating L1, L2 L3 layers
*
RAM: Stem cells around QC
generating central root cap,
Cortex/endodermis, stele
(vascular cylinder)

71
Q

Differentiate between the genes used in the SAM and RAM and where they are expressed.

A

SAM:
WUSCHEL WUS )
expressed in the OC
*
RAM:
WUSCHEL RELATED
HOMEOBOX GENE5 WOX5 )
expressed in the QC
OC and QC have homologous functions. These genes probably arose due to genome repicatione events.

72
Q

How does shoot system development differ between arabidopsis (a eudicot) and bryophytes & ferns? WHich is more ideal.

A

In Bryophytes & Ferns the entire
shoot system is elaborated from
a single Apical cell. Arabidopsis is more ideal. If this one cell has one mutation, it will pass it on to all daughter cells. Whereas in a population of stem cells, you can recover.

BIO203 (12 decks)

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