Transcript AP Biology Ch6

A Tour of
the Cell
AP Biology:
Chapter 6
What are Cells?
• Cells are the basic unit of ALL LIFE
– The single cell is a microcosm of life:
• Interactions among all the other cellular
components
• Structure and Function are connected
• Interaction with other cells outside the
environment
Plasma Membrane
The plasma membrane (5) bounds the
cell and encloses the nucleus and
cytoplasm.
The cytoplasm consists of specialized
bodies called organelles. They are
suspended in a fluid matrix called
cytosol (cytoplasm).
Plasma Membrane
• The plasma membrane separates
internal metabolic events from the
outside environment.
• The membrane is made of a double
phospholipid bilayer.
• The membrane has polar hydrophilic
heads and nonpolar hydrophobic
tails.
Cell Fractionation
• Cell Fractionation enables
researchers to isolate organelles.
That is, cells are taken apart,
separating the major organelles so
that their function can be studied.
Overview of all Cells
• Prokaryotic –No Nucleus
– --No internal membrane structures
– –Include bacteria and archaea
• Eukaryotic –Nucleus Present
– –Include protists, plants, fungi, and
animals
Cell Size
• Cell size is typically 1-100 microns
• There is a LARGE surface area per
volume ratio in order for a cell to
grow successfully. WHY?
• Compartmental Organization
increases the possibility of division of
labor
Nucleus or Nucleoid
• The nucleus (4) is bound by the nuclear
envelope (1), a phospholipid bilayer similar to
the plasma membrane.
• Eukaryotic Cells: membrane bound nucleus
• Prokaryotic Cells: nucleoid mass of “naked
DNA”
• Nucleus contains DNA, the DNA is spread
out within the nucleus as a threadlike matrix
called Chromatin (3)
• When the cell begins to divide, the chromatin
condenses into rod-shaped bodies called
Chromosomes.
Nucleus/Histones/Nucleoli
• Before dividing, the chromosomes
are made up of 2 long DNA
molecules and various histones.
• Histones are proteins that organize
the lengthy DNA, coiling it into
bundles called nucleosomes.
• Nucleoli (2) are also found in the
nucleus, they are concentrations of
RNA in the process of manufacturing
ribosomes
Endoplasmic Reticulum
• Endoplasmic Reticulum (ER)(**)
consists of stacks of flattened sacs
involved in the production of various
materials.
• When ribosomes are present around
the ER, it is considered rough ER.(**)
• When ribosomes are present, the ER
will make glycoproteins. (a protein
with a carbohydrate component)
ER
• If there are no ribosomes present, the ER
is considered smooth ER (6).
• Smooth ER synthesizes lipids and
hormones.
• Smooth ER produces substances that
help the cell export materials out of the
cell.
• Smooth ER helps break down toxins,
drugs and toxic products from cellular
reactions.
Golgi (7)
• Golgi apparatus is also a group of
flattened sacs, they are located away
from the nucleus.
• Golgi modify and package proteins
and lipids into vesicles that will bud
out from the surface of the Golgi.
Vesicles will migrate to and merge
with the membrane and release their
contents outside of the cell.
Lysosome (8)
• Lysosomes are vesicles from a Golgi
that contain digestive enzymes.
• They break down food, cellular
debris, and foreign invaders.
• Lysosomes are not found in plant
cells.
p115
Peroxisomes
• Peroxisomes break down
substances with in cells and tissues.
• For example, cellular respiration
produces H2O2, which is toxic to
cells, peroxisomes assist in breaking
the H2O2 into H2O. (Enzyme present?)
• Common in liver and kidney cells
where they break down toxic
substances.
Mitochondria (9)
• Mitochondria carry out aerobic
respiration, a process in which
energy (ATP) is obtained from
carbohydrates.
p117
Chloroplasts (15)
• Chloroplasts carry out
photosynthesis, the plant process of
incorporating energy from sunlight
into carbohydrates (CH20)
Ribosomes (6)
• Ribosomes are made of 2 subunits. The two
subunits are labeled 60S and 40S and are
made of proteins and RNA molecules.
• Ribosomes move across the nuclear envelope
and into the cytoplasm to be assembled into a
single ribosome.
• In the cytoplasm, ribosomes assist in the
assembly of amino acids into proteins.
Microtubules (11)
• Microtubules, intermediate filaments,
and microfilaments are 3 proteins
fibers of decreasing diameter.
(microtubules are largest,
microfilaments are smallest)
• All are involved in establishing the
shape of the cytoplasm AND
coordinating movements of the
cytoplasm.
Microtubules/Cytoskeleton
• Microtubules are made of the protein
TUBULIN and provide support and
motility for cellular activities. Cells
are active, not “STILL”. (largest of all
3 protein fibers)
• The are found in the spindle
apparatus in cell division and in
flagella and cilia.
• These are best known for providing
MOTILITY to the cell.
Intermediate
filaments/Cytoskeleton
• Intermediate filaments provide
support for maintaining the shape of
the cell.
Microfilaments/Cytoskeleton
• Made of the protein actin, and are
also involved in cell motility. They
are found in muscle cells, and in
cells that change shape (phagocytes,
WBC).
Flagella/Cilia (14)
• Structures that protrude from a cell
membrane and make wavelike
movements.
• Flagella are long and few
– A single flagella propels sperm
• Cilia are short and many
– Numerous cilia line the respiratory tract to
sweep away debris
• Both are arranged in a “9+2” array.
– 9 pairs (doublets) of microtubules arranged in
a circle surrounding a pair of microtubules
Centrioles (13) &
basal bodies
• Centrioles and basal bodies act as
microtubule organizing centers
• Centrioles make up the spindle
apparatus in cell division…they
organize microtubular movement
• Basal Bodies are at the base of
flagella and cilia, they organize
development of the flagella and cilia.
• They have a 9-triplet configuration.
Cell Walls (16)
• Cells walls are found in plants, fungi,
protists, and bacteria.
• They develop outside the cell
membrane and provide support for
the cell.
• In plants, the cell wall consists of
cellulose (found in Plant Kingdom).
• Cell walls can also be made of chitin
(found in Fungi Kingdom).
Cell Walls p119
Vacuoles (17) and Vesicles
• Fluid-filled membrane bound bodies.
• There are many different types of
vacuoles/vesicles.
– Transport vesicles, move materials between
organelles and/or the membrane
– Food vacuoles, temporarily store nutrients
– Storage vacuoles, in plants store starch, pigments,
toxic substances
– Central vacuoles, large bodies in plant cells that
store nutrients. They exert pressure (turgor) on the
cells, making them rigid.
– Contractile vacuoles, collect and pump excess water
out of the cell.
Cell Junctions
• Serve to anchor cells to another or to
provide a passageway for cellular
exchange.
Intercellular Junctions
Page 121
• Tight Junctions: the membranes of
neighboring cells are fused, forming belts
around the cells. Prevents leakage (i.e.
intestinal epithelium)
• Desmosomes: fasten cells together into
strong sheets.
• Gap Junctions: provide cytoplasmic
channels between adjacent cells. Salts,
sugars, amino acids and other small
molecules can pass from cell to cell.
Common in animal embryos, allows for
chemical communication
Cell Junctions
• Narrow channels between PLANT
cells. A narrow tube of ER, called
desmotubule, surrounded by a
cytoplasm and plasma membrane,
passes through the channel.