Introduction to Botany
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Transcript Introduction to Botany
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PPT is very long… condense for next
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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
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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