An introduction to the plant cell

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• An introduction to the plant cell

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Chapter 3 checkpoints

• How does the structure of a prokaryotic cell
  differ from that of a eukaryotic cell?
• What are the various types of plastids and what
  role(s) does each play in the cell?
• What are the principal components of the
  endomembrane system and what role does each play
  in that system?
• What is meant by the cytoskeleton of the cell,
  and with what cellular processes is it involved?
• How do primary cell walls differ from secondary
  cell walls

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Cell theory

• All living things are composed of one or more
  cells
• The chemical reactions of a living organism take
  place within cells
• Cells arise from other cells
• Cells contain hereditary information

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Membranes are very important to eukaryotes Know
about the endo- membranesystem
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Prokaryotes Eukaryotes

• Bacteria or archea
• Circular, naked DNA in nucleoid
• Cell membrane
• Ribosomes
• No membrane-bounded organelles
• No cytoskeleton

• Eukarya
• Linear DNA with histones in nucleus
• Cell membrane
• Ribosomes
• Membranes play a large role in physiology
• Cytoskeleton

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Study hint

• Look at the terms in Table 3-3
• Draw out the structures
• Note the hierarchy
• The cytoplasm is composed of organelles and
  watery bits

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Inventory of plant cell components

• Protoplast (everything inside the cell wall)
• Nucleus
• Endomembrane system
• Organelles
• one membrane
• double membrane
• Cytoskeleton
• Ribosomes

• Cell Wall
• Middle lamella
• Primary cell wall
• Secondary cell wall
• Plasmodesmata

http//botit.botany.wisc.edu/images/130/Plant_Cell
/Electron_Micrographs/Plamodesmata_RE.html
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Cell walls
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Plant cell components

• Protoplast
• Nucleus
• Nuclear envelope
• Nucleoplasm
• Chromatin
• Nucleolus
• Vacuole
• Tonoplast membrane
• Cytoplasm
• Endomembrane system
• Organelles

• Cytoplasm
• Plasma membrane, plasmalemma, cell membrane
• Cytosol organelles
• Plastids
• mitochondria
• peroxisomes (microbodies)

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Figure 7.10 Ribosomes
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Plant cell componentsIn the cytoplasm there are

• Endomembrane system
• Nuclear envelope
• Endoplasmic reticulum
• Golgi apparatus
• Vesicles

• Cytoskeleton
• Microtubules
• Actin filaments
• Cytoplasmic streaming

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Function of endomembrane system
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Cell membrane
Components of the endomembrane system 1. Nuclear
envelope 2. Enoplasmic reticulum 3. Golgi
apparatus 4. Vesicles
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Plastids

• A family of organelles
• Site of important biochemical reactions
• Photosynthesis
• Essential amino acids
• Fatty acids
• Sulfur reduction
• Nitrite reduction
• Many vitamins (A,C,E,K, riboflavin B2, thiamin
  B6)

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Plastids

• Plastids inherited from maternal parent
• Proplastids develop into different types
• Chloroplasts (photosynthesis)
• Chromoplasts (contain pigments)
• Amyloplasts (contain starch)
• Etioplasts (develop in the absence of light)
• All come from the same progenitor

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Chloroplast structure
Outermembrane
Envelope
Innermembrane
Envelope membrane
Stroma
Oil body
Thylakoid
Grana stack
Chloroplasts have three membranes
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Figure 7.19 Peroxisomes
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Figure 7.19 Peroxisomes
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Mitochondrial structure
Outermembrane
Envelope
Cristae
Innermembrane
Matrix
Mitochondria have two membranes
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Mitochondrial structureintermembrane space
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Mitochondrial structurematrix
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Endosymbiosis of bacteria to make plastids and
mitochondria

• The energy organelles of plant cells are believed
  to be endosymbionts
• Phagcytosis, the process of taking up solids into
  cells, arose with eukaryotes
• Things from outside the cell taken into lysosomes
  for digestion

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The universal tree of life
LIFE
Bacteria
Archaea
Plants Animals
Chloroplasts
The universal ancestor or Last Common Ancestor
Mitochondria
?
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Phagcytosis movie
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Possible steps of endosymbiosis

• Phagocytosis, but dont digest immediately
• Allow replenishment of proteins etc.
• Allow reproduction of bacterium
• Allow for passing from one generation to the next
  (horizontal versus vertical transmission)
• Increased specialization, gene transfer

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Who gets what?

• The protoeukaryotic cell gets photosynthesis
• Also, the ability to use acetic acid and other
  acids built up in the environment during
  anaerobic metabolism
• The protochloroplast and protomitochondrion gets
  better storage of its DNA

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Cytoskeletal elements

• Microtubules
• Dimers of ?- and ?-tubulin (protein) made into a
  coil to form a tube 25 nm OD, 15 nm ID
• Resists compressive force
• cell motility (cilia, flagella)
• Chromosome movements
• Centrioles in animals
• Organelle movements
• Known for rapid disassembly and reassembly

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Cytoskeletal elements

• Actin filaments
• Intertwined strands of protein
• 7 nm diameter (not a tube)
• Muscle contraction
• Cytoplasmic straming
• Cell division
• Can be disaasembled and reassembled
• Intermediate filaments
• A cable
• Keratin
• More permanent than tubulin or actin

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Flagella of eukaryotes have a distinctive 9 pairs
plus 2 arrangement of microtubules
The base of the flagellum has 9 triplets. Animal
basal bodies have this structure as well.
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Figure 7.21 Motor molecules and the cytoskeleton
Dynein
Kinesin
Motor molecules use the energy in ATP to move
things within the cell.
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Function of endomembrane system
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Cell membrane
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Function of endomembrane systemvesicle shuttle
hypothesis
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Function of endomembrane systemcisternal
progression hypothesis