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Chapter 7 - Tour of the Cell
Cells vary in size but are typically very
small. The more complex the internal
components the larger the cell can be .
prokaryote->eukaryote cell->protozoan
The small size is a consequence of the
cell volume requiring adequate surface
area to support nutrient demands
1cm sides: SA=? Vol=? Ratio=?
2cm sides: SA=? Vol=? Ratio=?
3cm sides: SA=? Vol=? Ratio=?
Prokaryotes:
Eukaryotic Animal Cell: The basic eukaryotic cell contains the following:
1.plasma membrane
2.cytoplasm (semifluid)
3.cytoskeleton - microfilaments and microtubules that suspend organelles, give shape, and allow motion
4.presence of characteristic membrane enclosed subcellular organelles
Plasma Membrane & Internal Membranes: Selectively permeable barriers
Basic structure & makeup is the same. The specific proteins that are present and in what
concentration will allow different cell types to respond differently to stimuli and
nutrient/waste identification. Glycocalyx identifies cell type. (transplant rejection,
hashimoto’s)
Nucleus - control center
Double membrane surrounding the
chromosomes and the nucleolus.
Pores allow specific communication
with the cytoplasm.
The nucleolus is a site for synthesis
of RNA used to make up ribosomes.
Constant chemical communication
between the cytoplasm and the
nucleus.
Initiation and cessation of life
sustaining chemical reactions is
ordered by the DNA in the nucleus
Endoplasmic Reticulum - assembly line
Attached to the nuclear envelope for immediate response to the
orders of the DNA. A network of interconnected membranes
forming channels and pockets (cisternae) within the cytoplasm.
Rough ER
Covered with ribosomes (causing the "rough”
appearance) which are in the process of synthesizing
proteins for secretion or localization in membranes.
Ribosome: protein RNA complex that is needed for
the synthesis of protein. (free & attached)
Smooth ER
•assembly of lipids & carbohydrate
•detoxifies toxic chemicals (add OH for solubility)
•may store, release & recover cell stimulants
What determines amount & type of ER in cells?
The Golgi - Some manufacture & packaging for export
Chemicals assembled and acquired from the ER are placed in a vesicle whose membrane
contains target (docking) chemicals identifying the final location of its contents (outside
cell or inside organelles)
Lysosome - digests & recycles
Made by the golgi, contains
powerful hydrolytic enzymes that
digests organic compounds
Cells deprived of O2 or
infected by viruses can
trigger lysosomes to
rupture & release
hydrolytic enzymes into
cytosol (immune system,
tadpole tail, fetal fingers)
H+ pump in
membrane enables
the lysosome to
lower pH and
digestion started,
Formation of Lysosomes
The modification and
packaging of glycoproteins
& glycolipids can establish
the glycocalyx on the
plasma membrane
Endomembrane system
A series of closed membranes
within eucaryotic cells that
are either continuous with
each other or communicate
with one another via vesicles
which are formed at one
surface and move to a second
where they are incorporated.
Vacuoles:
Membrane surrounded "bags"
that contain water and storage
materials in plants.
•Contractile Vacuole
•Food Vacuole
•Structural Vacuole
•Storage Vacuole
URL for Contractile Vacuole
The Mitochondrion - Power generator (Respiration)
Organelle that contains its own DNA and ribosomes. It
makes its own proteins. EndoSymbiotic Theory. It converts a
non-readily available chemical energy (PGAL) into a usable
form - ATP as long as O2 is readily available
Cytoskeleton - cell structure
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Cytoskeleton revealed by staining with
a fluorescent labeled actin antibody
Cytoskeleton is composed of three main types of
protein fibers, Microtubules, Microfilaments,
and Intermdiate filaments.
Microtubules and Microfilaments also aid in cellular transport:
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Motor proteins (kinesin and myosin) can attach to the
microtubules or microfilaments and with the use of
ATP glide along the surface. As the motor protein
moves along the surface it can drags organelles through
the cytoplasm
Cytoplasmic streaming
The pigment granules move on fixed pathways inside
the chromatophore cytoplasm, following radially
arranged bundles of microtubules. The process is shown
at 24 times the real speed. Movement is caused by light
stimulus to he eye or emotion. Nerve fibers discharge
transmitters that initiates the movement of the pigment
in the microtubules.
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Chrmatophores
The microtubules can be arranged in elaborate bundles creating specialized
transport structures (cilia, flagella, centriole)
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Quick Time™a nd a Sor ens on Video d ecomp res sor are n eede d to s ee this picture .
Cell Surfaces and Junctions
Occluding
Tight Junctions - keratin proteins fuse the
adjoining membranes in direct contact (no
intracellular space). Weld
Anchoring
Desmosomes & Adhesion Belts intermediate filaments penetrate & are shared
through the membranes of both cells. (collagen,
keratin) Intracellular space still present
Communication
Gap Junctions - pore like conections that allows
cytoplasm to flow easily between connected cells
(plasmodesmata in plant cells)
Plant Cells are structurally very similar to animal cells:
Differences?
Chloroplast - energy transformer (Photosynthesis)
In the presence of light and with the use of chlorophyl, the chloroplast
converts CO2 and H2O into carbohydrate. This may be used for the
production of ATP, storage, or structural material.
Chloroplasts have their own DNA and ribosomes (endosymbiotic theory) and make
their own proteins. They develop from an undifferentiated organelle called a
Protoplast. Depending on location in the plant and or the presence or absence of light,
the protoplast may develop into one of three organelles:
•Chloroplast
•Chromoplast
•Leucoplast
Cell
Wall
Membrane Structure & Transport
Functions?
Cell growth will require formation
of additional membrane and
deposition of essential membrane
chemicals. This is accomplished by
the endomembrane system.
The Golgi & ER work together to
create the key membrane
chemicals which are then
concentrated on the inner surface
of vessicles that are released.
Vessicle membranes and the
plasma membrane fuse much in the
same way as soap bubbles can
fuse.
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Passive Transport:
All cells require nutrients and produce
waste. Movement of these substances into
and out of the cell at the optimum rate is
essential. What mechanisms insures the
proper exchange (nutrients in and wastes
out)?
Molecules own kinetic energy insures
movement from an area of high concentration
to an area of low concentration. The rate at
which this movement will occur depends on?
This type of transport is referred to as Passive.
Why? Organisms without transport systems
depend heavily on this type of movement.
What physical characteristics are typical of
those organisms lacking transport systems?
Methods of Passive Transport
Water moves freely between the shifting lipid molecules. Water will also move
from an area of higher concentration to an area of lower concentration -
Osmosis - diffusion of water through a selectively permeable barrier
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Active Transport: Microtubules
Transport containers filled with basolateral cargo move along microtubules to the
cell periphery
Microtubules responsible for
internal cellular transport were
tagged with fluro dyes. Th area that
is brightly colored is the golgi.
Small packets moving to the cell
periphery are vessicles containing
golgi or ER products.
Sequence of 100 images. Rate was
two images per second
QuickTime™ and a Video decompressor are needed to see this picture.
http://www.mpi-cbg.de/research/simons/Movie.html
Carrier Proteins can actively transport substance in or out of cells
Endocytosis
•Receptor Mediated Endocytosis (example?)
•Pinocytosis (no receptor - example?)
•Phagocytosis (example?)
Exocytosis (example?)
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