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

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
2
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
Rough
endoplasmic
reticulum
Nucleus
Ribosomes
Smooth
endoplasmic
reticulum
Golgi
apparatus
Microtubule
Intermediate
Cytoskeleton
filament
Microfilament
Central
vacuole
Not in
animal
Chloroplast
cells
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
The Nucleus
• enclosed by nuclear envelope (double membrane)
• contains chromosomes (DNA + proteins)
• nucleolus
• ribosome production
• nuclear pores
• allow transport
4
The Endoplasmic Reticulum (ER)
Convoluted membrane continuous with the nuclear env.
• smooth ER (new lipid production)
• rough ER (protein synthesis by ribosomes)
Synthesis and packaging of a
protein by the rough ER
transport vesicle
buds off
4
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
Discontinuous membrane stacks distal to the ER:
• receive proteins, lipids from ER via vesicles
• site of modification, packaging, sorting and distribution
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Lysosome formation & function
rough ER
Lysosomes are
membrane bound
compartments
derived from the
Golgi apparatus
1 transport vesicle
(containing inactive
hydrolytic enzymes)
Golgi
apparatus
plasma
membrane
engulfment
of particle
lysosome
engulfing
damaged
organelle
2
“food”
They are acidic
and break down
materials from
inside & outside
of the cell.
lysosomes
3
food
vacuole
4
5
digestion
The Endomembrane System
Newly made lipids & proteins in the ER travel to the
Golgi apparatus and then to various destinations:
transport vesicle
Rough ER from ER to Golgi
transport vesicle from
Golgi to plasma membrane
• plasma
membrane
Plasma
membrane
• cell exterior
Nucleus
• lysosomes
Vacuole
Lysosome
Smooth ER
Nuclear envelope
• other
organelles
Golgi apparatus
Mitochondria
Main site of energy production (i.e., ATP, heat):
• break down of food molecules (sugars and fatty acids)
• the process of respiration (requires O2)
6
Chloroplasts
Site of photosynthesis in plant cells:
• 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
Internal network of protein fibers important for:
• cell structure & shape
• cell, organelle movement
• cell division
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Flagella & Cilia
Cellular projections involved in movement.
Found only on certain cell types
• e.g., respiratory tract (cilia), sperm (flagellum)
• move the cell itself, or material across its surface
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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