Download Ch 7_cells - Manasquan Public Schools

Chapter 7
• A Tour of the Cell
Evolution of cells …sometime around 3.8 BYA
•
Organic molecules formed
from simple compounds,
surrounded by lipids, formed
microspheres & coacervates
•
Exemplify the basic structure
of all cells
–
Outer layer – plasma
membrane
–
inner “stuff” –cytosol &
cytoplasm
–
Ribosomes – make
proteins
–
genetic material –
ribozymes -> RNA ->
DNA (makes
chromosomes)
1st cells - Prokaryotes
• Domain Archaea
• Domain Bacteria
– Simple, heterotrophic, chemosynthetic,
anaerobic bacteria that gave rise to autotrophic
bacteria
 aerobic bacteria
 more complex eukarya such as plants,
animals, fungi and protists
Eukarytoes – about 1.5 BYA
http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation__endosymbiosis.html
• Eukaryotic cells are characterized by having
–
DNA in a nucleus that is bounded by a membranous nuclear
envelope
–
Membrane-bound organelles
–
Cytoplasm in the region between the plasma membrane and
nucleus
• Prokaryotic
cells
Fimbriae
or pili
Nucleoid
–
Ribosomes
Plasma membrane
Bacterial
chromosome
(a) A typical
rod-shaped
bacterium
Cell wall
Capsule
Flagella
No nucleus
– DNA in an
unbound
region called
the nucleoid
– No
membranebound
organelles
– Special cell
wall peptidoglycan
Outer ‘barrier’of cells define how they interact
with the environment
• plasma membrane selective barrier that
allows sufficient
passage of oxygen,
nutrients, and waste to
service the volume of
every cell
Amphipathic molecules
contain hydrophobic and hydrophilic regions
Carbohydrate side chain
Hydrophilic
region
Hydrophobic
region
Hydrophilic
region
Phospholipid
Proteins
(b) Structure of the plasma membrane
The Fluidity of Membranes
• Phospholipids drift laterally &
rarely flip-flop
(~107
• The temperature when a
membrane solidifies depends
on lipid type
• Membranes rich in
unsaturated fatty acids are
more fluid that those rich in
saturated fatty acids
• Cholesterol at warm temps
restrains movement at cool
temps but maintains fluidity
by preventing tight packing
Lateral movement
Flip-flop
times per second) (~ once per month)
(a) Movement of phospholipids
Fluid
Unsaturated hydrocarbon
tails with kinks
Viscous
Saturated hydrocarbon tails
(b) Membrane fluidity
Cholesterol
(c) Cholesterol within the animal cell membrane
Fig. 7-7
Fibers of
extracellular
matrix (ECM)
Glycoprotein
Carbohydrate
Glycolipid
EXTRACELLULAR
SIDE OF
MEMBRANE
Cholesterol
Microfilaments
of cytoskeleton
Peripheral
proteins
Integral
protein
CYTOPLASMIC SIDE
OF MEMBRANE
•Six major functions of membrane proteins:
Signaling molecule
Enzymes
ATP
(a) Transport
Receptor
Signal transduction
(b) Enzymatic activity
(c) Signal transduction
Glycoprotein
(d) Cell-cell recognition
(e) Intercellular joining
(f) Attachment to the cytoskeleton
and extracellular matrix (ECM)
A Panoramic View of the Eukaryotic Cell
http://www.youtube.com/watch?v=yz4lFeqJPdU
• A eukaryotic cell has internal membranes that
partition the cell into organelles
• Plant and animal cells have most of the same
organelles
Plasma membrane is the ultimate deciding factor
for how large and how small cells can be based
on basic geometry as well as metabolism
requirements.
• If a eukaryotic cell has a diameter that is 10
times that of a bacterial cell, proportionally how
much more surface area would the eukaryotic
cell have? (SA is proportional to square of
linear dimension)
• Proportionally, how much more volume would it
have? (volume is proportional to its cube
Nuclear
envelope
ENDOPLASMIC RETICULUM (ER)
Flagellum
Rough ER
NUCLEUS
Nucleolus
Smooth ER
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome
NUCLEUS
Nuclear envelope
Nucleolus
Chromatin
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Ribosomes
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
Cell wall
Plasmodesmata
Wall of adjacent cell
CYTOSKELETON
Cell components can be organized:
• Infoldings –> endomembrane system
• NRG conversions
• Support and signaling
• Connections to other cells to form tissues, send
messages
The endomembrane system regulates protein
traffic and performs metabolic functions in the cell
• Components of the endomembrane system:
– Nuclear envelope
– Endoplasmic reticulum (smooth & rough)
– Golgi apparatus
– Lysosomes
– Vacuoles
– Plasma membrane
• These components are either continuous or connected via
transfer by vesicles
• Proteins made by bound ribosomes
Whats the pathway for input of molecules?
Output?
• Vesicle connection
• Exocytosis
• Endocytosis
– Phagocytosis
– Pinocytosis
NRG conversions
• Mitochondria
• Chloroplasts
–
Chloroplasts,
chromoplasts,
amyloplasts
• peroxisomes
Cellular support
•
cytoskeleton helps to support the cell and maintain its shape
•
It interacts with motor proteins to produce motility
•
Inside the cell, vesicles can travel along “monorails” provided by the
cytoskeleton – act in cellular communication
•
Recent evidence suggests that the cytoskeleton may help regulate
biochemical activities
ATP
Vesicle
Receptor for
motor protein
Motor protein Microtubule
(ATP powered) of cytoskeleton
Now, you learn it…
http://www.sp.uconn.edu/~bi107vc/sp03/terry/cells.html
• View interactives and animations from your
internet support of the book, the above link,
and any other websites of interest (google!)
Components of the Cytoskeleton
http://www.northland.cc.mn.us/biology/biology1111/animations/flagellum.html
• Three main types of fibers make up
the cytoskeleton:
– Microtubules - hollow, thick tubes of
tubulin
– Microfilaments - also called actin
filaments, are the thinnest components
• Muscle contraction, pseudopod
movement, cytoplasmic streaming
– Intermediate filaments are fibers with
diameters in a middle range
• Cell shape; laminin of nuclear
envelope
• Plant cell walls may
have multiple layers:
– Primary cell wall:
– Middle lamella:
– Secondary cell
wall (in some
cells):
Secondary
cell wall
Primary
cell wall
Middle
lamella
• Plasmodesmata
• Cell walls are also
found in bacteria, fungi
and some protists –
but each are structured
differently and are
used as a way of
identification
1 µm
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata
Cellular connections
• Outer connections – ECM
• Inner and cell makeup –
– Plasmodesmata (plant)
– Gap junctions (animal)
– Tight
– desmosomes
The Extracellular Matrix (ECM) of Animal Cells
•
•
•
The ECM is made up of
glycoproteins such as
collagen,
proteoglycans, and
fibronectin
ECM proteins bind to
receptor proteins in the
plasma membrane
called integrins –
integral proteins
Collagen
Proteoglycan
EXTRACELLULAR FLUID complex
Fibronectin
Integrins
Functions of the ECM:
–
–
–
–
Support
Adhesion
Movement
Regulation
Plasma
membrane
Microfilaments
CYTOPLASM
Tight Junctions, Desmosomes, and Gap Junctions in
Tight junctions prevent
Animal Cells
fluid from moving
across a layer of cells
• tight junctions,
• Desmosomes
(anchoring junctions)
• Gap junctions
(communicating
junctions
• Plasmodesmata
–
A gap junction in a plant
–
Symplastic movement
of solutes & water
Tight junction
Intermediate
filaments
Desmosome
Gap
junctions
Space
between
cells
Plasma membranes
of adjacent cells
Extracellular
matrix