Transcript Chapter 7 A tour of the Cell - Foothill Technology High School

Chapter 7
A tour of the Cell
What do all cells have in common?
Prokaryotic Cells
•Pro = before;
Karyon = nucleus
•Cells w/o nucleus
•Circular DNA free
in “nucleoid” region
•1 – 10 micrometers in
size (size of
mitochondria)
•No membrane
organelles
•Cell wall
•Ex. bacteria
Eukaryotic Cells
•Eu = true; Karyon =
nucleus
•Phospholipid plasma
membrane
•Cytoplasm
•Ribosomes
•Genetic Material
(DNA)
•Cells w/ nucleus
•Linear DNA
contained in nucleus
•10 – 100
micrometers in size
•With membraneorganelles
(endomembrane
system)
•Cell wall only in
plants
•Ex. Plants and
animal cells
Prokaryotic Bacteria
Animal
Cells
Plant Cells
Nucleus
• Contain DNA of
eukaryotic cells
• Porous phospholipid
membrane
• Inner membrane lined
with intermediate
filaments of the
cytoplasm
• ER often is an
extension of the
nuclear membrane
Condensation of Eukaryotic
Chromosomes
Nucleosome = DNA coils
around histone proteins
Chromatin = supercoiled
nucleosomes
Looped Domains =
supercoiled chromatin
Chromosome =
supercoiled looped
domains
Ribosomes
•Assembles AA into polypeptide chain, which eventually
folds into functional protein
•Made of rRNA and protein
•2 subunits: large and small
Nucleolus
•Located inside nucleus
•makes ribosomal subunits by
combining rRNA and proteins
imported from cytoplasm
•subunits leaves nuclear pore and assembles into a
ribosome in the cytoplasm
What is the endomembrane
system?
• System of membrane-bound organelles in euk.
cells that work cooperatively together to create
secretory proteins, membrane-bound proteins,
or plasma membrane proteins
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Nucleus
ER
Golgi
Transport Vesicles
Lysosomes
Peroxisomes
Vacuoles
Plasma Membrane
Rough Endoplasmic Reticulum
RER w/ bound ribosomes
Space w/in ER = cisternae space
Fcn: to fold and modify secretory proteins (glycoproteins)
within cisternae space
- attaches CHO called
oligosaccharides to
growing and folding
polypeptide chain (2o 
3o)
- vesicles bud off from
RER and delivers
glycoprotein to Golgi
Golgi Apparatus
Accepts vesicles from RER (cis side)
Adds and removes monomers to oligosach. of glycoproteins
Adds “ID” tags (like phosphate groups) and uses these to
“sort” proteins into different vesicles
Dispatches vesicles w/glyco-proteins for shipping (trans side)
3 destinations for proteins within
Golgi vesicles
1) Secreted from cell
2) Remains within vesicles  vacuole,
lysosome, peroxisome
3) Protein becomes part of plasma
membrane
Lysosomes
• Membrane-bound sac
of digestive enzymes
• Acidic env’t
maintained by
pumping H+ ions from
cytoplasm
• Digests food, worn
out cell parts,
programmed cell
death (webbing b/t
fingers, tadpole tails)
Peroxisome
• Breaks down toxic substances in liver
• Breaks down fatty acids into CHO for use
in CR
• In breakdown process, oxygen and
hydrogen combine to create  H2O2
• Peroxide = metabolic waste
Smooth ER
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•
•
•
ER w/o ribosomes
Makes lipids, oils, steroids
Helps break down CHO
Detoxifies drugs by adding –OH groups 
water soluble toxins  flushed from body
Vacuoles
Contractile vacuole
- pumps excess water
out for freshwater
organisms
Central vacuole
- Stores water, organic
compounds, ions, and
helps increase turgor
pressure in plant cells
Mitochondria and Chloroplasts
Mitochondria
- CR site
- Generates ATP
(usable E) from
glucose
Chloroplasts
- PS site
- Generates glucose
(stored E) from
inorganic compounds
and light
Cytoskeleton
Network of fibers in the cytoplasm that
a) maintains cell shape/mechanical
support
b) anchors organelles
c) helps w/ cell motility
3 components
1) microtubules
2) microfilaments
3) intermediate filaments
Microtubules
Structure:
Hollow tube made up of α
and β tubulin polypeptide
25 nm diameter
Compression Resistent 
supports cell shape
Forms spindle fibers for
separation of
chromosomes, makes up
centrioles, and cilia/flagella
Microtubule
9 sets of 3 arrangement
(ring formation)
Ex. Centrioles, spindle
fibers, basal body of
cilia and flagella
9 + 2 arrangement (9
doublets surrounding
a pair in the center)
Ex. Cilia and Flagella
Radial Spokes and Dynein Arms of
Microtubule
• Dynein arms “walk”
along the
microtubules to bend
and move flagella,
using ATP energy
Microfilaments
AKA: actin fibers
Structure: twisted double chain of
actin protein that forms a solid rod
7 nm diameter
Tension resistent (protects against
“pulling” forces)
Makes up microvilli core, contracts
muscles, causes cytoplasmic
streaming and pseudopod
extensions in cells
Intermediate Filaments
• In btwn microtubules and
microfilaments in size (10 nm)
• Fixes positions of organelles
• Organelles w/motor proteins
can move by “walking” along
intermediate filaments (as if
along a track)
• Helps to maintain cell shape
Cell Wall and Plasmodesmata
• In plants, bacteria, protists, fungi
• Maintains shape, prevents excessive
water uptake
• Cell walls are non-continuous:
plasmodesmata connects cytoplasm btwn
2 plant cells and helps them communicate
Animal Cell Junctions
Desmosomes:
AKA
“anchoring”
junctions
-Holds together
tissues under
stress
-Disc-shaped w/
protein fibers
extended into
cytoplasm
Tight Junctions:
Gap
Junctions:
-Fuses cell
membranes of
Type
of
neighboring
communicati
cells; prevents
ng
junction
leakage
btwn
cellsprovides
(ex.
that
Digestive tract)
cytoplasmic
channels
btwn cells