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Cell Theory
Robert Hooke
first saw cells
in 1665
• All living things are
made of cells
• Cells are the basic
unit of life
• Cells today come
only from other
living cells
The Structure of a Cell
• All cells have
– Plasma membrane
– Cytosol
– DNA
– Ribosomes
Two Major Types of Cells
• Prokaryotic
– No membrane bound organelles
– Make up Domains Archaea and Eubacteria
• Eukaryotic
– Membrane-bound organelles
– Make up Kingdoms Plantae, Animalia,
Protista, and Fungi
A prokaryotic cell
Overview of an animal cell
Cytoplasm:
everything inside
the cell but the
nucleus
Overview of a plant cell
Cell size
The human body has over 5 billion
cells. The largest animal is the blue
whale, Balaenoptera musculus. It is
known to reach lengths over 100
feet (30+ meters) and weigh 120
tons.
Cell size
So, why aren’t there organisms composed of one
really big cell?
Surface Area and Volume
Surface area of a sphere = 4r2
Volume of a sphere = (4/3) r3
So as a sphere gets bigger,
its volume increases faster than its surface area
Figure 7.5 Geometric relationships explain why most cells are microscopic
Let’s look at the interior of Eukaryotic cells…
• Nucleus
• Ribosomes
• Endomembrane System
–
–
–
–
–
–
Nuclear envelope
Endoplasmic Reticulum
Golgi Apparatus
Vesicles
Lysosomes
Vacuoles
• Other organelles: mitochondria, chloroplasts,
peroxisomes
• Cytoskeleton
DNA RNA  protein: a diagrammatic overview of information
flow in a cell
Figure 7.9 The nucleus and its envelope
Figure 7.10 Ribosomes
Figure 7.11 Endoplasmic reticulum (ER)
In the rough ER, proteins are modified by
the addition of a carbohydrate group
COOH
Protein
H2N
Carbohydrate
group
Now = GLYCOPROTEIN
Figure 7.12 The Golgi apparatus
THE SECRETORY PATHWAY: A MODEL
RNA
1. Proteins are
synthesized in the RER
Rough
ER
2. Protein exits
RER in a vesicle.
cis face of Golgi
apparatus
3. Protein travels
through the cisternae of
the Golgi apparatus.
trans face of
Golgi
apparatus
Plasma
membrane
4. Protein enters a
secretory vesicle that
fuses with cell
membrane.
5. Protein is
secreted from cell.
Figure 7.13 Lysosomes
Figure 7.14 The formation and functions of lysosomes (Layer 1)
Figure 7.14 The formation and functions of lysosomes (Layer 2)
Figure 7.14 The formation and functions of lysosomes (Layer 3)
Figure 7.15 The plant cell vacuole
Figure 7.16 Review: relationships among organelles of the endomembrane system