Transcript Cell Biology

Cell Biology
Part 2
Cytoskeleton
Network of protein fibers and
in the cytoplasm.
Functions
• Cell structure and shape.
• Cell movement.
• Cell division - helps build
cell walls and move the
chromosomes apart.
Components of the Cytoskeleton
Organized in deceasing diameter
• Microtubules
• Microfilaments
• Intermediate Filaments
Microtubules
• Structure - small hollow tubes
made of the protein “tubulin”.
• Size - 25 nm outer diameter
with a 15 nm inner diameter.
Can be 200 nm to 25 mm in
length.
Microtubules
• Found in the “spindle”
apparatus (during cell
division), cilia, flagella, basal
bodies and centrioles.
Functions
• Maintenance of cell shape.
• Hold organelles in place.
Microfilaments
• 5 to 7 nm in diameter.
• Structure – made up of the
protein “actin”
Functions
• Muscle contractions.
• Cytoplasmic streaming.
• Pseudopodia (amoeboid
movement) found in amoebae and
phagocytes (white blood cells).
• Cleavage furrow formation.
• Maintenance and changes in cell
shape.
Microfilaments
are stained green.
Cilia and Flagella
Classified by their lengths and numbers
• Cilia - short, but numerous.
• Flagella - long, but few.
• Function - to move cells or
to sweep materials past a
cell.
Cilia and Flagella
• Structure - 9+2 arrangement
of microtubules, covered by
a plasma membrane
(different in bacteria)
• Made of contractile proteins
• Uses ATP
Centrioles and Basal Bodies
act as “microtubule
organizing centers”
or MTOC’s
Centrioles
• Usually one pair per cell,
located close to the nucleus.
• Found in animal cells only.
• 9 sets of triplet microtubules.
• Help in cell division.
Basal Bodies
• Same structure as a
centriole.
• Found at the base of the
cilia and flagella.
Plant Cells
Plant Cell
Cell Wall
• Nonliving jacket that surrounds
some cells.
• Found in:
–Plants
–Prokaryotes
–Fungi
–Some Protists
Plant Cell Walls
• All plant cells have a
Primary Cell Wall.
• Some cells will develop a
Secondary Cell Wall.
Cell Walls
• Plant cell walls are made of cellulose
( a polysaccharide made of b-glucose).
• Fungi cell walls are made of chitin (a
polysaccharide)
• Function as the cell's exoskeleton for
support and protection.
Middle Lamella
• Thin layer rich in pectin
(used to make jelly) found
between adjacent plant
cells.
• Glues cells together.
Vacuoles and Vesicles
Fluid-filled, membrane-bound bodies
5 Types of Vacuoles and Vesicles
• Transport vesicles
• Food vacuoles
• Storage vacuoles
• Central vacuoles
• Contractile vacuoles
The function of the vacuole
depends on the organism.
In Protists
(single-cell organisms)
• “Food” vacuoles store newly
ingested food until the lysosomes
can digest it.
• “Contractile” vacuoles pump out
excess water.
Contractile Vacuole
Contractile Vacuole
Food Vacuoles
Central Water Vacuole
• Large single vacuole when
mature making up to 90% of
the cell's volume.
Function of Central
Water Vacuole
• Water regulation.
• Storage of ions.
• Storage of hydrophilic
pigments. (e.g. red and
blues in flower petals).
Other vacuoles and vesicles
• Storage vacuoles in plants store
starch, pigments and toxic
substances (such as nicotine)
• Transport vesicles move materials
from one organelle to another, or
from organelle to the plasma
membrane. (“exocytic vesicles”
move materials to the plasma
membrane for export, “endocytic
vesicles” transport materials from
outside the cell to the plasma
membrane to be imported)
Chloroplasts
• Contain DNA.
• Can reproduce themselves.
• Often contain starch.
• May have been
independent cells at one
time.
Function of Chloroplasts
• Photosynthesis - chloroplasts
use of light energy to make
food. (sugars)
• Contain the green pigment
chlorophyll.
Chloroplasts
Enzymes in a
crystal
Chromoplasts
store plant pigments such as chlorophyll,
carotene.
• Found in plants only.
• Classified (named) by color example:
Chloro means green, therefore a
chloroplast is a green plastid that
stores chlorophyll
• Leuco means white, therefore
Leucoplasts (AKA Amyloplasts) are
white plastids that store starch.
Comparing
Plant Cells and Animal Cells
Plant Cells
Animal Cells
Have cell walls,
chloroplasts, and
central water
vacuoles…animal
cells do not!!
Have lysosomes
and centrioles….
Plant cells do not!!