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© Cengage Learning 2015 p50
Chapter 4: Cell theory
Components of all cells
Prokaryotic Cells
Eukaryotic cells: parts & functions
Plants cells vs. animal cells
© Cengage Learning 2015
• Every living organism consists of one or
more cells.
• The cell is the smallest unit of life.
• All cells arise by division of preexisting cells.
• Cells contain hereditary material which they
pass to offspring when they divide.
Cell Theory
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Components of All Cells
• Plasma membrane, Cytoplasm, DNA
• Also: RNA, proteins doing work, and
ribosomes
Cell Membranes
A phospholipid bilayer that
separates the inside of the cell
from the external environment
Figure 4.6a
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Phospholipid bilayer
one layer
of lipids
one layer
of lipids
Helps membranes to be selectively permeable
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Fluid Mosaic Model
The phospholipids, proteins and other
molecules move within the bilayer
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• Recognition (identify “self”)
• Receptor (receive hormones or other signals
• Transport (allow substances to enter or leave the cell)
Functions of Membrane Proteins
Recognition Transport Receptor
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CATEGORIES OF CELLS
Prokaryotic Cells Eukaryotic Cells
• Smaller
• Simpler
• Lack membrane-bound organelles
• Found in bacteria and archaea
• Larger
• More complex
• Have membrane-bound organelles
• Found in protists, plants, fungi, animals
Prokaryotic vs. Eukaryotic Cells
© Cengage Learning 2015 Figure 4-8 p58
Prokaryotic Cells
(Bacteria and
Archaea)
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Biofilms: Community of microorganisms
living within a shared mass of secreted slime
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Eukaryotic Cells: The Nucleus
Contains and protects DNA
Nuclear envelope controls access to DNA
DNA = directions for protein synthesis
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Eukaryotic Cells: The
Endomembrane System
Vesicles – Sacs that transport, store, or
break down substances
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Eukaryotic Cells: The
Endomembrane System
Rough Endoplasmic Reticulum (ER) –
Ribosomes attached to surface; folds proteins
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Eukaryotic Cells: The
Endomembrane System
Smooth ER – no ribosomes; makes lipids,
breaks down toxins
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Eukaryotic Cells: The
Endomembrane System
Golgi Bodies – put finishing touches on
proteins delivered from ER
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Eukaryotic Cells: Mitochondria
Produces ATP by aerobic cellular respiration
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Some Eukaryotic Cells: Plastids
Function in photosynthesis, storage, or
pigmentation (plant and algal cells)
Ex: chloroplasts
Eukaryotic Cells: Cytoskeleton
sheet of
tetramers
coiled sheet
dimer
actin
subunit tubulin
subunit
A Microtubule B Microfilament C Intermediate filament
tetramer
•Network of
interconnected
protein filaments
•Supports,
organizes, and
moves
eukaryotic cells
and their parts
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LM
(a) Microtubules in the cytoskeleton
Figure 4.19-1
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SOME Eukaryotic Cells: ECM
primary wall plasma membrane
cytoplasm
Extracellular Matrix: secreted on outside of cell
(ex: cell wall in plants, fungi, some protists)
• 3 types in animals:
- Tight junctions
- Adhering junctions
- Gap junctions
• In plants:
- Plasmodesmata
Cell Junctions (in multicellular organisms)
Connect cells to other cells and to their environment
