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Transcript
Ch 4
Tour of the Cell
Microscopic Worlds
• Microscopes led to the
discovery of the cell
– Light microscopes
–
–
–
–
Cell membrane - yes
Large macromolecules - no
Microtubules - no
Mitochondria - maybe just
barely
– Many bacteria - yes
Microscopic Worlds
Light microscope
Scanning Electron
Differential Inference-contrast
Transmission Electron
Cell Size
• House DNA, protein molecules and internal
structures
• Obtain nutrients and diffuse nutrients and O2
• Smaller cells have a greater surface area to
volume ratio than do larger cells
– Surface area is significant for diffusion and
osmosis
Surface area : Volume
10 m
30 m
30 m
Surface area
of one large cube
 5,400 m2
10 m
Total surface area
of 27 small cubes
 16,200 m2
• Volume= 30 um *30 um* 30 um=27000um
• SA (large)= 6*(30um*30um)=5,400 um
• SA (small)=(6*(10um*10um))*27=16,200 um
Domains of Life
• The 3 domains of life
– Bacteria (prokaryotic cells)
– Archaea (prokaryotic cells)
– Eukarya (all other life forms)
Cells
• Prokaryotic
• Eukaryotic
– Protists, fungi,
plants, animals
Colorized TEM 15,000 
– Bacteria & Archaea
Prokaryotic cell
Nucleoid
region
Nucleus
Eukaryotic cell
Organelles
Prokaryotic cells are simpler & usually smaller than
Eukaryotic cells
In Common
•
•
•
•
Bounded by plasma membrane
Ribosomes
Cytoplasm
DNA as genetic material
Prokaryote
• Do not have membrane
bound nucleus
• Have a cell wall outside
their plasma membrane
• Circular DNA strands
• No membrane bound
organelles
Prokaryotic
flagella
Ribosomes
Capsule
Cell wall
Plasma
membrane
Nucleoid region (DNA)
Pili
Eukaryote
Rough
endoplasmic
reticulum
Smooth endoplasmic
reticulum
• Membrane
bound nucleus
• Linear DNA
• Membrane
bound organelles
Nucleus
Flagellum
Not in most
Lysosome
plant cells
Centriole
Peroxisome
Microtubule
Intermediate
Cytoskeleton filament
Microfilament
Ribosomes
Golgi
apparatus
Plasma membrane
Mitochondrion
Eukaryotic Cells
• A typical animal cell:
• Contains a variety of membranous organelles (underlined)
Rough
endoplasmic
reticulum
Smooth endoplasmic
reticulum
Nucleus
Flagellum
Not in most
plant cells
Lysosome
Ribosomes
Centriole
Golgi
apparatus
Peroxisome
Microtubule
Cytoskeleton
Plasma membrane
Intermediate
filament
Mitochondrion
Figure 4.4A
Microfilament
Eukaryotic Cells
Rough endoplasmic
reticulum
• A typical plant cell
NUCLEUS
Golgi
apparatus
Ribosomes Smooth
endoplasmic
reticulum
CYTOSKELETON:
Central vacuole
Microtubule
Chloroplast
Intermediate
filament
Cell wall
Plasmodesmata
Microfilament
Mitochondrion
Peroxisome
Plasma membrane
Cell wall of
adjacent cell
Categories of Organelles
• Structural support, movement, communication
– Cytoskeleton, plasma membrane, cell wall (plants)
• Manufacturing
– Nucleus, ribosomes, endoplasmic reticulum, Golgi
apparatus
• Energy processing
– Mitochondria (animal), chloroplasts (plants)
• Hydrolysis
– Lysosomes (animals), vacuoles (plants),
peroxisomes
Plasma Membrane
• Forms boundary around cell
• Controls and regulates material
transport
-Semi permeable
• Phospholipid bilayer
Plants and Cell Walls
• Cell wall
– Cellulose
• Connect by plasmodesmata
– Channels between adj. cells
Walls of two
adjacent plant
cells
Vacuole
Plasmodesmata
Layers of one
plant cell wall
Cytoplasm
Plasma membrane
Cytoskeleton
• Cell’s internal skeleton
– Helps organize structure and activities
– Consists of network of protein fibers
Tubulin subunit
Actin subunit
Fibrous subunits
25 nm
7 nm
Microfilament
10 nm
Intermediate filament
Microtubule
Cytoskeleton
• Microfilaments (actin filiments)
– Enable cells to change shape and move
• Intermediate filaments
– Reinforce the cell and anchor certain organelles
• Microtubules
– give the cell rigidity, provide anchors for organelles,
act as tracks for organelle movement
Tubulin subunit
Actin subunit
Fibrous subunits
7 nm
Microfilament
25 nm
10 nm
Intermediate filament
Microtubule
Nucleus
Chromatin
Nucleolus
Pore
Nucleus
• Contains most of the
Two membranes
cells DNA
of nuclear
envelope
• Eukaryotic
chromosomes made of
chromatin
• Enclosed by nuclear
enveloper
• Nucleolus
Rough
endoplasmic
reticulum
Ribosomes
– rRNA synthesized
Ribosomes
• Free and bound ribosomes
• Composed of 2 subunits
– Involved in protein synthesis
Endomembrane System
• Interconnected structurally and functionally
– Physically connected
Rough ER
OR
– Connected via
vesicles
Transport vesicle
from ER to Golgi
Transport vesicle from
Golgi to plasma membrane
Plasma
membrane
Nucleus
Vacuole
Lysosome
Smooth ER
Nuclear envelope
Golgi apparatus
Rough Endoplasmic Reticulum
• Membrane continuous
with nuclear envelope
Rough ER
Nuclear
envelope
• Bound ribosomes
– Produces proteins
– Transported or secreted
Figure 4.7
Ribosomes
Smooth ER
Rough ER
TEM 45,000
– Makes more membrane
– Transferred via vesicles
Smooth ER
Fig. 4-9b
Transport vesicle
buds off
4
Ribosome
Secretory
protein
inside transport vesicle
3
Sugar
chain
1
2 Glycoprotein
Polypeptide
Rough ER
Smooth ER
• Lacks bound ribosomes
• Involved in metabolic
processes
– Synthesis of lipids,
hormones, enzymes
• Stores calcium
Golgi Apparatus
• Vesicles from ER go to Golgi
• Receives and modifies products
“Receiving” side of
Golgi apparatus
Golgi apparatus
Golgi
apparatus
New vesicle
forming
“Shipping” side
of Golgi apparatus
Transport
vesicle from
the Golgi
TEM 130,000
Transport
vesicle
from ER
Mitochondria
• Cellular respiration
Outer
membrane
Inner
membrane
Cristae
Matrix
TEM 44,880
– Converts chemical energy
to ATP
Mitochondrion
– Phospholipid bilayer
membrane
– Has own DNA and
Intermembrane
space
ribosomes
Chloroplasts
• Convert solar energy to chemical energy (photosynthesis)
• Stroma
– Contains DNA, ribosomes and enzymes
• Thylakoids
– Interconnected sacs that form stacks called granum
Endosymbosis
• Hypothesis of endosymbosis
– Mitochondria and chloroplasts were once small
prokaryotes living independently
– At some point, began living within larger cells
Lysosomes
• Digestive enzymes enclosed by membrane sac
• Destroy ingested bacteria, recycle damaged
Lysosome
organelles
• Break down food
Digestion
Vesicle containing
damaged mitochondrion
Lysosome
Digestive
enzymes
Plasma
membrane
Digestion
Food vacuole
Lysosomes
Rough ER
Transport vesicle
(containing inactive
hydrolytic enzymes)
Golgi
apparatus
Plasma
membrane
“Food”
Engulfment
of particle
Lysosomes
Food
vacuole
Figure 4.10A
Digestion
Lysosome
engulfing
damaged
organelle
Vacuoles
• Membranous sac
• Central Vacuole
Nucleus
– hydrolytic function
Chloroplast
• Contractile
• Food
Colorized TEM 8,700
Central
vacuole
Perixosomes
• Metabolize fatty acids
• Enzymes that digest peroxides
• Come only from ER
• Cilia
Movement
– Short appendage, numerous
• Flagella
– Long appendage
• Microtubules wrapped in plasma membrane
– Anchored by basal body
• Moves via bending
Figure 4.17A
LM 600
Colorized SEM 4,100
Movement
Figure 4.17B
Extracellular matrix
• Holds cells to tissues
• Protect and support PM
– Integrins
• Regulate behavior,
transmit information,
coordinate cells
Cell Junctions
•Tight junctions can bind cells together into leakproof sheets
•Anchoring junctions link animal cells into strong tissues
•Gap junctions allow substances to flow from cell to cell
Tight junctions
Anchoring junction
Gap junctions
Extracellular matrix
Space between cells
Figure 4.18B
Plasma membranes of adjacent cells
Fig. 4-23