Download Chapter 4: A Tour of the Cell 1. Cell Basics

Chapter 4:
A Tour of the Cell
1. Cell Basics
2. Prokaryotic Cells
3. Eukaryotic Cells
1. Cell Basics
Limits to Cell Size
There are 2 main reasons why cells are so small:
If cells get too large:
1) there’s not enough membrane surface area to facilitate the
transfer of nutrients & wastes…
10 μm
30 μm
2) it would
take too
long for
materials
to diffuse
within the
the cell
30 μm 10 μm
Surface area
of one large cube
= 5,400 μm2
Total surface area
of 27 small cubes
= 16,200 μm2
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Prokaryotic vs Eukaryotic
Prokaryotic cells (i.e, bacteria) are quite small and
don’t have internal organelle structures.
Prokaryotic cell
Eukaryotic
cells tend to
be much
larger and
contain
organelles
such as a
nucleus.
Nucleus
Eukaryotic cell
Organelles
2. Prokaryotic Cells
General Characteristics of
Prokaryotic Cells
Lack membrane-enclosed compartments
• do not have a nucleus
• prokaryotic means “before nucleus”
• do not have any other organelles
All prokaryotes are small, single-celled organisms
• bacteria and archaea
Have a single, circular chromosome
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Typical Prokaryotic Cell
Outside:
• cell wall
(protects cell)
• capsule
Prokaryotic
flagella
(outermost layer)
• flagella
(propels cell)
Ribosomes
Capsule
Inside:
Cell wall
Plasma
membrane
• cytoplasm
(liquid inside)
• nucleoid
(chromosome)
Nucleoid
region (DNA)
• ribosomes
(protein synthesis)
3. Eukaryotic Cells
General Characteristics of
Eukaryotic Cells
Have a nucleus and internal organelles
• eukaryotic means “true nucleus”
Eukaryotes can be single-celled, or multi-cellular
organisms
• Protists, Fungi, Plants & Animals
Much larger than prokaryotic cells
• ~10-100 μm (vs ~1-10 μm for prokaryotes)
Have multiple, linear chromosomes
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A typical Animal Cell
Rough
endoplasmic
reticulum
Smooth endoplasmic
reticulum
Nucleus
Flagellum
Not in most
Lysosome
plant cells
Ribosomes
Centriole
Golgi
apparatus
Peroxisome
Microtubule
Cytoskeleton
Plasma membrane
Intermediate
filament
Mitochondrion
Microfilament
A typical Plant Cell
Nucleus
Golgi
apparatus
Rough
endoplasmic
reticulum
Ribosomes
Smooth
endoplasmic
reticulum
Microtubule
Intermediate
Cytoskeleton
filament
Microfilament
Central
vacuole
Not in
animal
Chloroplast
cells
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
The Nucleus
• enclosed by nuclear envelope (a double membrane)
Two membranes of
nuclear envelope
Nucleus
Nucleolus
Chromatin
Nuclear
pore
Endoplasmic
reticulum
Ribosomes
• contains chromosomes (DNA + proteins)
• nucleolus (ribosomes assembled from RNA & proteins)
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The Endoplasmic Reticulum (ER)
Nuclear
envelope
Ribosomes
• smooth ER
(new lipid
production)
• rough ER
(protein
synthesis by
ribosomes)
Smooth ER
Rough ER
Synthesis and packaging of a
protein by the rough ER
transport vesicle
buds off
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ribosome
secretory
protein inside
transport vesicle
3
sugar
chain
1
2
glycoprotein
polypeptide
rough ER
Proteins made in the RER are transported within
membrane-enclosed vesicles to the Golgi apparatus…
The Golgi Apparatus
“Receiving” side of
Golgi apparatus
Golgi
apparatus
Golgi apparatus
Transport
vesicle
from ER
New vesicle
forming
“Shipping” side
of Golgi apparatus
Transport
vesicle from
the Golgi
• protein modification, sorting and distribution
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Lysosomes
Lysosome
Digestion
Vesicle containing
damaged mitochondrion
Membrane bound compartments derived from the Golgi:
• acidic and contain digestive enzymes
• fuse with vesicles containing material to be broken down
and digest the contents
The Secretory Pathway
Nucleus
Nuclear
membrane
Rough ER
Smooth
ER
Transport
vesicle
Transport
vesicle
Golgi
apparatus
Lysosome
Vacuole
Plasma
membrane
Mitochondria
Mitochondrion
Site of
cellular
respiration
Outer
membrane
Intermembrane
space
• conversion of
“food energy”
to energy
stored in ATP
molecules
Inner
membrane
Cristae
Matrix
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Chloroplasts
site of
photosynthesis
in plant cells
Chloroplast
Stroma
Inner and outer
membranes
Granum
Intermembrane
space
• production of glucose from CO2 and H2O using sunlight
• the basis of essentially all ecosystems
Central Vacuole
in Plants
Storage of water,
waste, & nutrients
Source of “turgor
pressure” that
maintains rigidity of
plant cells
• swells when water is
plentiful due to osmosis
• cell wall provides
support, prevents lysis
The Cytoskeleton
Nucleus
Nucleus
Actin subunit
Fibrous subunits
Microfilament
Tubulin subunit
10 nm
7 nm
25 nm
Intermediate filament
Microtubule
Internal network of protein fibers important for:
• cell structure & shape
• cell movement
• internal transport
• cell division
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Flagella & Cilia
Cellular projections involved in movement.
flagellum
cilia
Tracheal
Epithileum
Sperm Cell
Found only on certain cell types
• cilia move material across cell surface or provide motility
• flagella are used for cell motility
Key Terms for Chapter 4
• prokaryotic, eukaryotic
• cell wall, capsule, flagella, nucleoid, cytoplasm
• nucleus, endoplasmic reticulum, ribosome
• Golgi apparatus, lysosome
• endomembrane system, central vacuole
• mitochondria, chloroplasts
• cytoskeleton, cilia
Relevant Review Questions
1-3, 5-11, 13-15
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