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White Ash Tree
Botany Unit 1
Chapter 3
Plant Cells
Deep Narrow Ridges/Diamond
shaped pattern
1.
2.
3.
The cell is the basic unit of life
All living things are composed of cells
All cells are derived from preexisting
cells
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 Prokaryotic
Cells (Prokaryotes) –
• Greek: Pro = “before” kary “nucleus”
• Cells lack nuclei
• Cells do not have membrane bound organelles
• Organisms in Domains Bacteria & Archea
 Eukaryotic
Cells (Eukaryotes) –
• Greek: Eu = “true” kary “nucleus”
• Cells have nuclei
• Cells have membrane bound organelles
• Organisms in Domain Eukarya
 Nucleus
 Cytoplasm
(cytosol + organelles)
 Cell Membrane
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 Plasma
Membrane – a boundary that
confines contents to the cell
 Cytosol – fluid that suspends organelles
 Ribosomes – organelles composed of
protein and RNA
 Genetic Information – DNA & RNA
A
boundary that confines contents to the
cell
 Regulates what enters and exit the cell
 This membrane is selective
• Some substances pass through freely
• Some in a controlled fashion
• Some are denied entrance or exit
 Located
outside the plasma membrane
 A coating secreted by the cell
 Support and protects the plant cell
 Provides routes for water and dissolved
materials to pass into and from the cell
 Composed of cellulose fibers

Primary Cell Wall
• Stretches and expands as the
cell increases in size

Middle Lamella
• A layer of pectic compounds
• Acts as a cement between the primary cell walls of
adjacent cells

Secondary Cell Wall
• Forms after growth ceases
• Forms between primary wall and the plasma membrane
• Contains cellulose and lignin
 Lignin (a hard substance that gives wood its distinctive
texture)
 Large, membrane-bound
sacs
 Filled with water that contains
•
•
•
•
Salts
Ions
Pigments
Waste products – to be recycled
 Helps
cell maintain Turgid shape
 Provide strength for non-woody plants
 Temporary storage area for excess
materials
 Structures
within cells that perform
photosynthesis or store starches, oils, or
proteins
 Provide Energy and Storage
 Three Types
• Chloroplast
• Leucoplast
• Chromoplast
A
type of plastid
 Disc shaped
 Has a photosynthetic function
• Convert light energy to chemical energy
• Water + Carbon Dioxide + Sunlight = Glucose + Oxygen
+ Water
 Found
in certain leaf & stem cells
 Contain Chlorophyll
• A molecule with the vital role of absorbing light
energy
• Absorbs blue and red light (reflects green)
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 Thylakoids
– flat,
disc-like sacs
 Grana – stacks of
thylakoids
 Stroma – jellylike
fluid in which grana
are embedded
• Contains enzymes that
speed up chemical
reactions of
photosynthesis
 Leucoplasts
• Colorless plastids
• form and store starches, oils, or proteins
• Common in seed, root, & stem cells
 Chromoplasts
• Contains yellow, orange, and red pigments
• Often form from chloroplasts when chlorophyll
breaks down
 Ex: Tomatoes; deciduous tree leaves
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 Center
for processing, sorting, and
packaging proteins
 Consist of several flattened sacs
 The edges of the sac bulge out and
detach as vesicles
• vesicles- sacs that contain cellular products
 Composed
of RNA and Protein
 Use instructions from DNA to build proteins
• Joins amino acids in precise sequences
 Whorls
of Ribosomes are called Polysomes
 Are not enclosed by a membrane
 Ribosomes are found:
•
•
•
•
•
In the nucleus
In Plastids
In the Mitochondrion
In Cytoplasm
On the Rough Endoplasmic Reticulum (Rough ER)
 An
extensive network of parallel
membranes that extends throughout the
cells interior
 Likely a continuation of the cell membrane
and the nuclear envelope
 Rough ER
• Flattened and studded with ribosomes
• Location of Protein synthesis (proteins are made
here)
 Smooth ER
• Tubular, no ribosomes
• Location of lipid synthesis (fats are made here)
 Tiny
organelles bounded by a double
membrane
• Inner membrane called cristae
 Using
Cellular Respiration, converts the
chemical energy (glucose) in food
molecules to ATP
 Distributes ATP to the rest of the cell
 Produces
ATP “Adenosine Triphosphate”
• “Energy Carriers”
• ATP is a nucleotide
• Has a large amount of energy stored in its
phosphate bonds
• Energy is released when the bond is broken
• ATP becomes ADP (Adenosine Diphosphate)
A
network of fiber that extends through
the cytoplasm
 Provides structure to a Eukaryotic cell
 Composed of two types of fibers
• Microtubules – make up the spindle; involved in
the addition to cell wall
• Microfilaments – thinner than microtubules,
responsible for cytoplasmic streaming
(movement of cytoplasm)
 The
garbage eaters
 Break down cellular wastes
 An
organelle that contains DNA
 Serves as the control center of the cell
 Contains nucleoplasm
• Substance that contains DNA
• DNA associates with certain protein molecules to
form chromatin
• Chromatin strands coil and thicken during cell
division to form chromosomes
Nucleolus
 Involved in making and assembling the
subunits of ribosomes
Nuclear Envelope
 Separates the nucleus from the rest of the
cell
 Has a double membrane
 Contains pores lined with protein
molecules
 Centrioles
• Made out of spindle fibers
• Used during cell division to retract spindle
fibers; thus separating sister chromatids
 Cytosol
• Intracellular fluid that suspends organelles
 Cytoplasm
• Collectively all organelles and cytosol (excludes
nucleus and plasma membrane & cell wall)
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ORGANELLES FOUND IN PLANT
CELLS
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








Plasma membrane
Nucleus
Mitochondrion
Ribosomes
ER
Golgi Apparatus
Cytoskeleton
Cell Walls
Plastids
Vacuoles
ORGANELLES FOUND IN
ANIMAL CELLS









Plasma membrane
Nucleus
Mitochondrion
Ribosomes
ER
Golgi Apparatus
Cytoskeleton
Centrioles
Lysosomes
 Fluid
Mosaic Model – see Figure 3-13
• The current model for the structure of membranes
• Protein molecules “float” in a fluid phospholipid
bilayer
• Characterizes the plasma membrane and other cell
membranes as consisting of a double layer (bilayer)
of lipid molecules
• Proteins are embedded in the lipid bilayer in a way
the resembles a mosaic pattern
• The membrane structure is fluid rather than static
 Lipids & proteins move sideways within the membrane
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 Components of Membranes
• Phospholipid
 1 glycerol molecule + 2 fatty acids + a molecule
containing a phosphate group
 The phosphate end is polar (slightly charged)
 Polar end is hydrophilic (hydro- “water” phil “love”)
 Fatty acid chains are nonpolar
 Nonpolar end is hydrophobic (hydro- “water” phobos
“fear”)
 Arrange hydrophilic heads toward the watery
surroundings inside and outside of the cell
 Hydrophobic tails form the inside of the double layer
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Fluid Mosaic Model
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 Membrane
perform many functions
• Membranes are selectively permeable
 They regulate the passage of materials to maintain
homeostasis
 Homeostasis is a relatively constant set of internal
conditions
• Membranes receive information from their
surroundings
 Use cell signaling, hormones, & chemicals
 Help the cell to respond to its environment
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 Materials move passively or actively
• Passive transport
 Diffusion – the net movement of particles (atoms,
molecules, or ions) from a region of higher
concentration to a region of lower concentration
 Moves materials through the cytoplasm and into and out of
cells
 Ex. Sugar cube in a beaker of water – Fig. 3-14
 Osmosis – the diffusion of water across a selectively
permeable membrane
 Water moves from a solution with a higher concentration of
water to a solution with a lower concentration of water
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 Osmosis
• Solution
 A mixture in which salts, sugars, and other materials
are dissolved in water
 3 types of solutions
 Isotonic (iso – “equal”)
 Equal concentrations of solute inside and outside of membrane
 Hypertonic (hyper – “over”)
 Water flows out of cell – cell shrivels
 Hypotonic (hypo – “under”)
 Water flows into cell – cell becomes turgid/swells
• Solvent
 The substances dissolved in water
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 Turgor
Pressure
• The internal pressure of water against the cell
wall
• As pressure increases, an equilibrium is
reached
• The pressure forces water molecule out of the
cell in equal amounts as to what is coming in by
osmosis
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• Facilitated Diffusion
 Materials diffuse from a region of higher
concentration to a region of lower concentration
through special passageways
 Passageways are called carrier proteins
 “conveyor belts” in the direction of the concentration
gradient (from high to low concentration)
• Active Transport – requires the cell to use
energy (ATP)
 The assisted movement of a substance from a lower
concentration to a higher concentration
 Substances move against concentration gradient
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