Lesson 4 bio101 (c)Dr. Evangelista
-
Upload
girliefan-wrighter -
Category
Documents
-
view
308 -
download
1
Transcript of Lesson 4 bio101 (c)Dr. Evangelista
THE PROTOPLAST
The Cell the basic unit of life
came from the Latin word cella meaning storeroom or chamber
term first used by Robert Hooke in 1665 while observing cork cells
The Cell Composed of:
1. Protoplast – the site of cellular metabolism
2. Cell wall-outermost part of a plant cell
THE PROTOPLAST Made up of:
1. Nucleus
2. Cytoplasm consists of a liquid, colloidal phase of the
protoplast (cytosol/hyaloplasm/cytoplasmic ground substance)
with membrane-bound organelles
THE PROTOPLAST 2. Cytoplasm
with membrane-bound organelles Bounded by double membranes Bounded by single membrane
ribosomes
endomembrane systems
cytoskeleton
PLASMA MEMBRANE (ectoplast/plasmalemma) Controls passage of various substances into
and out of the protoplast In transfer cells, are highly invaginated,
which facilitates transfer of materials
It coordinates the synthesis and assembly of cell wall microfibrils (cellulose)
BIOLOGICAL MEMBRANES Composition
1. Phospholipids
2. Proteins
3. Carbohydrates
• Are amphipathic molecules with hydrophobic nonpolar hydrocarbon tails and hydrophilic heads
Membrane bilayer
Phospholipids
BIOLOGICAL MEMBRANES
Membrane Protein
2 types: Integral proteins- integrated into the bilayer
• May have access to only one side of the membrane
• Span the entire bilayer and have access to both sides of the membrane (transmembrane protein)
Peripheral proteins- bound to the hydrophilic surface of transmembrane protein
BIOLOGICAL MEMBRANES
BIOLOGICAL MEMBRANES
Membrane Protein F
U
N
C
T
I
O
N
S
:
Rosette of enzymes mediate the synthesis of cellulose microfibrils
BIOLOGICAL MEMBRANES
PROTOPLAST
Composed of:
Nucleus
Cytoplasm
NUCLEUS
• Information center of the cell
• Contains the bulk of the cell’s DNA
• Nucleolus- site of rRNA synthesis
NUCLEUS
Cytoplasm Cytosol Non-particulate portion; the liquid portion
Contains proteins and other solutes
Often assumes the physical properties of a gel
Endomembrane system These membranes are either in direct contact
or connected via transfer of vesicles, sacs of membrane.
Endomembrane system System includes the nuclear envelope,
endoplasmic reticulum, Golgi apparatus, vacuoles, and the plasma membrane.
Cellular organelles Membrane-limited compartments Serve to compartmentalize the cells
Cytoskeleton
Cytoplasm
ribosome
Sites of protein synthesis
• Small spherical bodies about 15-20 nm in diameter
• Consist of protein and RNA
• Found along ER, cytoplasm, within mitochondria and plastids
RIBOSOMES
ENDOMEMBRANE SYSTEM
Nuclear envelope with 2 membranes; with pores through
which molecules of RNA may leave the nucleus and enter the cytoplasm
• Endoplasmic reticulum- continuous with nuclear envelope
• 2 types of ER
-smooth- tubular; site of lipid synthesis
-rough - lamellar; site of synthesis of membrane proteins and proteins to be secreted outside the cell and into the vacuole
• Golgi bodies (also called dyctyosomes, golgi stacks, golgi apparatus or simply golgi) -Consist of stacks of cisternae
-polarized structure
-receiving end from ER is cis face
-shipping side is the trans face
-finishes, sorts and ships cell products
Cell wall
chloroplast
cytosol
VACUOLE • Enveloped by tonoplast/vacuolar membrane
• Contains a variety of inorganic ions,organic acids, sugars, enzymes and secondary metabolic products including pigments
• plays a role in maintaining water balance of cells; active absorption of ions result in increase in turgor pressure in the cell and its expansion and growth
• Comparable to lysosomes of animal cells
Plasma Membrane
Cellular organelles and cytoskeleton
• Sites of respiration and synthesis of ATP
• Enveloped by 2 membranes
• Inner membrane is invaginated (cristae)
• Enzymes for ATP production found in inner membrane
mitochondrial matrix,a fluid- filled space with DNA, ribosomes, and enzymes.
MITOCHONDRIA
PLASTIDS • Originate from proplastid pigments
Types:
Chloroplastids
• Contain photosynthetic pigments
• Site of photosynthesis
Chromoplastids
• Contain carotenoid pigments
• Often so concentrated that they form crystalline deposits
Leucoplastids
• Colorless plastids
• Types:
1. Amyloplastids
store starch
2. Elaioplastids store fats
3. proteinoplasts- store
proteins
PLASTIDS
PLASTID TYPES ARE INTERCONVERTIBLE
-etioplast is a plastid that develops in the absence of light; no chloroplast, no chlorophyll; characterized by prolamellar bodies composed of tubular membranes which comprise a paracrystalline lattice
MICROBODIES
• Bounded by a single membrane
• Peroxisomes-
-major site of O2 consumption; uses O2 in oxidation reactions that convert harmful m e t a b o l i c b y - p r o d u c t s i n t o n o n t o x i c substances such as water
-break down fats
-participate in photorespiration; enzymes in peroxisomes help minimize the loss of organic products due to photorespiration.
Peroxisome
Glyoxysomes- contain enzymes for the conversion of fats to carbohydrates during seed germination
Cytoskeleton is a network of fibers extending throughout the cytoplasm.
It provides mechanical support and maintains shape of the cell. It provides anchorage for many organelles and cytosolic enzymes.
plays a major role in cell motility.
-This involves limited movements of parts of the cell (streaming cytoplasm, vesicle and organelle movement).
-The cytoskeleton interacts with motor proteins.
-Three main types of fibers in the cytoskeleton:
• microtubules
• microfilaments
• intermediate filaments.
CYTOSKELETON
Approx 25 nm diameter
Composed of 13 spherical protein subunits (dimers of α and ß tubulin)
Comprise the spindle fibers in dividing cells that move chromosomes during cell division.
MICROTUBULES
function as tracks that guide motor proteins carrying organelles to their destination.
resists compression to the cell.
MICROTUBULES
CYTOSKELETON
phragmoplast, a complex of microtubules that guides the orderly alignment of the vesicles in the midzone
MICROTUBULES
exert some control over orientation of microfibrils because in regions of cell wall growth and cellulose microfibril synthesis , microtubules below the plasmalemma are routinely observed in an orientation parallel to that of the newly synthesized microfibrils
MICROTUBULES
about 7 nm in diameter
Composed of globular actin.
An actin microfilament consists of a twisted double chain of actin subunits.
help maintain cell shape.
ACTIN MICROFILAMENTS
Involved in cleavage furrow formation
On the cytoplasmic side of the cleavage furrow a contractile ring of actin microfilaments and the motor protein myosin form.
Contraction of the ring pinches the cell in two
ACTIN MICROFILAMENTS
involved in cytoplasmic streaming
-This speeds the distribution of materials within the cell.
ACTIN MICROFILAMENTS
intermediate in size at 8 - 12 nanometers are specialized for bearing tension. are more permanent fixtures of the cytoskeleton than are the other two classes. they reinforce cell shape nuclear side of the envelope is lined by the nuclear lamina, a network of intermediate filaments that maintain the shape of the nucleus.
Intermediate filaments
ERGASTIC SUBSTRANCES- products of cell metabolism
Storage products
starch in the form of starch grains
proteins which form aleurone grains
oils in elaioplasts or spherosomes (enveloped by single membrane or may be lacking)
waxes- long-chain lipid compounds, that occur as part of the protective coating (cuticle) on the epidermis
LIPID BODIES OR OLEOSOMES • function: storage and transport of lipids
ERGASTIC SUBSTRANCES- products of cell metabolism
Waste products
Crystals -calcium oxalate crystals
-calcium carbonate crystals
Silica –common constituent of epidermal cell wall of grasses
-silica bodies – masses of silica which fill some epidermal cells
-provides protection from herbivory and mechanical strength
May be a form of stored calcium
CRYSTALS
ERGASTIC SUBSTRANCES Tannins and tanniniferous substances are
phenolic by-products primary function – protective,their
astringency serving as a repellent to predators an impediment to the invasion of parasitic
organisms
The End