Plant and Cell Architecture Flashcards
(108 cards)
1
Q
Model organisms
A
Plants with short generation times and small genomes
2
Q
Genomes
A
The sum of their genetic information
3
Q
Major unifying principles of plants
A
- ultimate solar collectors-convert light energy to chemical energy
- sessile; evolved to grow towards essential resources (light, water, and mineral nutrients)
- structurally reinforced to support mass toward sunlight against the pull of gravity
- mechanisms to move water and minerals from soil to sites of photosynthesis and growth
- lose water continuously but have evolved mechanisms for avoiding desiccation
- develop embryos that derive nutrients from the mother plant
4
Q
Plants (embryophytes)
A
Share the evolutionarily derived traits for surviving on land that are absent in algae
5
Q
Nonvascular plants (bryophytes)
A
Mosses, hornworts, and liverworts
6
Q
Vascular plants (tracheophytes)
A
Consist of non-seed plants (ferns and their relatives) and seed plants (gymnosperms and angiosperms)
7
Q
Gymnosperms
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- Seed plants “naked seed”
- include conifers, cycads, ginkgo, and gnetophytes
- 800 species known
8
Q
Conifers
A
- Largest group of gymnosperms which include such commercially important forest trees as pine, fir, spruce, and redwood
- “cone bearers”
9
Q
Angiosperms
A
- “vessel seed”
- evolved about 145 million years ago
- include 3 major groups: monocots, eudicots, and basal angiosperms
10
Q
Flowering plants
A
- angiosperms
- major anatomical innovation is the flower
11
Q
Alternation of generations
A
Plants alternate between two distinct multicellular generations to complete their life cycle
-one generation is diploid (two copies of each chromosome 2N) and the other is haploid (one copy of each chromosome 1N)
12
Q
Gametes
A
Egg and sperm
13
Q
Meiosis
A
Cell division resulting in a reduction of the number of chromosomes from 2N to 1N
14
Q
Spores
A
The products of meiosis in diploid plants
15
Q
Sporophytes
A
Diploid plant forms are called this
16
Q
Gametophyte
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A new haploid multicellular individual
17
Q
Pollen
A
Bees carry around the male gametophyte which is a multicellular structure that produces sperm cells
18
Q
Two separate generations in the plant life cycle
A
The diploid, spore-producing sporophyte generation and the haploid, gamete-producing gametophyte generation
19
Q
Megaspores
A
Develop into the female gametophyte
20
Q
Microspores
A
Develop into the male gametophyte
21
Q
Monoecious
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- “one house”
- has flowers that produce both male and female gametophytes
22
Q
Dioecious
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- “two houses”
- male and female flowers occur on separate individuals
23
Q
Megastrobili
A
Female cones
24
Q
Microstrobili
A
Male cones
25
Double fertilization
Two sperm produced, only one of which fertilizes the egg
The other sperm fuses with two nuclei in the female gametophyte to produce the 3N endosperm, the storage tissue for the angiosperm seed
26
Ferns and mosses
Sporophyte generation gives rise to spores that grow into adult gamteophytes that differentiate into male and female structures, the male antheridium and the female, archegonium
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Prothallus
- in ferns, the gametophyte is this small monoecious
| - has antheridia and archegonia that divide mitotically to produce motile sperm and egg cells
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Stem
Grows upward and supports the above ground part of the plant
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Root
Anchors the plant and absorbs nutrients and water, grows down below the ground
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Leaves
Primary function is photosynthesis
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Nodes
Leaves grow out laterally from the stem
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Shoots
Leaves and stems together
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Internode
The region between two nodes
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Primary plant axis
The main stem and taproot
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Plasma membrane (also called plasmalemma)
Outer fluid boundary of the living cytoplasm of plant cells
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Cytoplasm
All of the organelles and cytoskeleton suspended within the cytosol
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Cytosol
The water-soluble and colloidal phase residing within the plasma membrane
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Nucleoplasm
The internal compartment of the membrane-bounded nucleus in eukaryotes
39
Cell wall
Plants cells further enclosed by this rigid, cellulosic wall
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Middle lamella
Prevents cell migrations and has each cell wall cemented to its neighbors
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Primary cell walls
Typically thin (less than 1 micrometer) and characteristic of young, growing cells
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Secondary cell walls
Thicker and stronger than primary walls and are deposited on the inner surface of the primary wall after most cell enlargement has ended
43
Lignin
Secondary cell walls owe their strength to this
| A brittle, gluelike material
44
Plasmodesmata
Connects cytoplasm of neighboring cells
Tubular channels 40 to 50 nm in diameter and formed by the connected plasma membranes of adjacent cells
Facilitate intercellular communication during plant development, enabling cytoplasmic exchange of vital developmental signals in the form of proteins, nucleic acids, and other macromolecules
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Symplast
Plant cells interconnected with the plasmodesmata form a cytoplasmic continuum
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Symplastic transport
Intercellular transport of small molecules through the plasmodesmata
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Apoplastic transport
Transport through the wall spaces which constitute the apoplast
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Primary plasmodesmata
Created as the primary cell wall assembled during and following cell division
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Secondary plasmodesmata
Form after cell division is completed, across primary or secondary cell walls, when small regions of the cell walls are digested by enzymes and plasma membranes of adjacent cells fuse to form the channel
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Desmotubule
The endoplasmic reticulum network of adjacent cells is also connected forming this that runs through the center of the channel
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Spokes
Filamentous proteins that connect the two surfaces of the desmotubule and inner surface of the plasma membrane
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Cytoplasmic sleeve
Spokes divide this into microchannels
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Wall collars
Valvelike, composed of the polysaccharide callose, surround the necks of the channel at either end and serve to restrict the size of the pore
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Size exclusion limit
Restricts the size of molecules that can be transported via the symplast
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Simple plasmodesmata
Single channels can form branched plasmodesmata when they connect with each other
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Movement proteins
Encoded by the virus genome facilitate viral movement by interacting with plasmodesmata through one of two mechanisms
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Meristem
Plant growth is concentrated in localized regions of cell division
Nearly all nuclear division (mitosis) and cell division (cytokinesis) occurs in this region
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Apical meristems
in a young plant, most active meristem; located at the tips of the stem and the root
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primary growth
- the phase of plant development that gives rise to new organs and to the basic plant form which gives rise to the primary plant body
- results from the activity of apical meristems
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Three major tissue systems present in all plant organs
dermal tissue, ground tissue, and vascular tissue
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Dermal tissue
forms the outer protective layer of the plant and is called the epidermis in the primary plant body
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Ground tissue
fills out the three-dimensional bulk of the plant and includes the pith and cortex of primary stems and roots and the mesophyll in leaves
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Vascular tissue
which moves, or translocates, water and solutes throughout the length of the plant, consists of two types of tissues: xylem and phloem
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axillary buds
- meristems that develop in the node, or axil-the region between the leaf and the shoot
- become the apical meristems of branches
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lateral roots
- branches of roots arise from meristematic cells in the pericycle, or root branch meristem
- becomes the apical meristem of the lateral root
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cambium
gives rise to the secondary growth which produces an increase in width or diameter of the plants, having radial (inside-to-outside) polarity
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vascular cambium
- the cambial layer that produces wood; arises between the xylem and phloem of the primary plant body
- cells divide longitudinally to produce derivatives toward the inside or the outside of the stem or root
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rays
cells of the vascular cambium also divide transversely to transmit material radially outward
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secondary xylem
conducts water and nutrients from the soil upward to other plant organs
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secondary phloem
like primary phloem, conducts the products of photosynthesis downward from the leaves to other organs of the plant
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phloem fibers
add tensile strength to the stem
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cork cambium
- phellogen; the cambial layer that produces the protective periderm on the outside of the woody plants
- typically arises each year within the secondary phloem
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bark
collective term for several tissues-the secondary phloem, secondary phloem fibers, cortex (in stems), pericycle (in roots) and periderm that can be peeled off as a unit at the soft layer of vascular cambium
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fluid-mosaic model
all biological membranes have the same basic molecular organization: consist of a double layer (bilayer) of lipid in which proteins are embedded
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plastids
the group of membrane-bound organelles to which chloroplasts belong are unique in that their lipid component consists almost entirely of glycosylglycerides-the glycosyl polar head groups of which are galactose derivatives
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galactolipids
may contain galactose, digalactose, or sulfated galactose in their head group, but have no phosphate
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sterols
- another lipid component of plant cells
| - contribute to the formation and assembly of membranes and the waxy cuticles on the surfaces of plants
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three main types of proteins in lipid bilayer
integral, peripheral, and anchored
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integral proteins
- embedded in the lipid bilayer
- most span the entire width of the phospholipid bilayer; one part interacts with the hydrophobic core of the membrane and the other interacts with the outside of the cell and third part interacts with interior of the cell the cytosol
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peripheral proteins
-bound to the membrane surface by noncovalent bonds, such as ionic bonds or hydrogen bonds, and can be dissociated from the membrane with high-salt solutions or chaotropic agents which break ionic and hydrogen bonds
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anchored proteins
-bound to the membrane surface via lipid molecules to which they are covalently attached
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nucleus
the organelle that contains the genetic information primarily responsible for regulating the metabolism, growth, and differentiation of the cell
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nuclear envelope
nucleus is surrounded by this double membrane; a subdomain of the endoplasmic reticulum
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nuclear pores
form selective channels across both membranes, connecting the nucleoplasm (the region inside the nucleus) with the cytoplasm
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nuclear pore complex (NPC)
an elaborate structure composed of more than 100 different nucleoporin proteins arranged octagonally
86
nuclear localization signal
a specific amino acid sequence required for a protein to gain entry into the nucleus
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chromosomes
composed of DNA and its associated proteins
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chromatin
DNA-protein complex
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nucleosome
- arranged like beads on a string along the length of each chromosome
- segments of the linear double helix of DNA are coiled twice around a solid cylinder of eight histone protein molecules
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30-nm chromatin fiber
during mitosis, the chromatin condenses with six nucleosomes per turn
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heterochromatin
- highly compact and transcriptionally inactive form of chromatin and accounts for about 10% of the DNA
- concentrated along the periphery of the nuclear membrane and is associated with regions of the chromosome containing few genes, such as telomeres and centromeres
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euchromatin
- dispersed, transcriptionally active form
| - only about 10% of this is transcriptionally active at any given time
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nucleolus
nuclei contain a densely granular region which is the site of ribosome synthesis
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nucleolar organizer region (NOR)
nucleolus includes portions of one or more chromosomes where ribosomal RNA (rRNA) genes are clustered
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transcription
nucleus is the site of read-out
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translation
regions of the DNA are transcribed into transfer RNA (tRNA) and rRNA
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co-translational insertion
mechanism of proteins into the ER is complex, involving the ribosomes, the mRNA that codes for the secretory protein, and a special protein-translocating proe, the translocon, in the ER membrane
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cisternae
tubules join together to form a network of polygons and flattened saccules
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cortical ER
- the ER that lies just under and is probably attached to the plasma membrane resides in the outer layer of cytoplasm called the cell cortex
- forms a polygonal network of tubules that is traversed by dynamic, flowing tubule bundles
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internal ER
the inner layer of the cytoplasm and can traverse the cell via transvacuolar strands--strands of cytoplasm that extend through the central vacuole wrapped in vacuole membrane
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reticulons
form tubules from membrane sheets
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flippases
membrane asymmetry can be counteracted by enzymes which "flip" newly synthesized phospholipids across the bilayer to the inner leaflet
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fission
because membranes are fluid, new membrane constituents can be transferred to an existing membrane even if the new membrane subsequently separates from the existing membrane
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SNAREs and Rabs
a special class of targeting recognition proteins that selective fusion and fission of vesicles and tubules that serve as transporters between the compartments of the endomembrane system
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signal peptide
a hydrophobic leader sequence of 18 to 30 amino acid residues at the amino-terminal end of the chain
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signal recognition particle (SRP)
made up of protein and RNA binds both to this hydrophobic leader and to the ribosome interrupting translation
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SRP receptors
in the rough ER membrane that can associate with th translocons through which the newly synthesized protein is threaded
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glycoproteins
many of the proteins found in the lumen of the endomembrane system--proteins with small sugar chains convalenly attached
