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Transcript
The Cell
Chapter 3
10 m
History of the Cell

Robert Hooke
 first
to name cells

Van Leuwenhooke
 First
to identify cells as
living structures
The Cell Theory: Schleiden & Schwann
1. All organisms are made of cells
2. The cell is the simplest collection of matter
that can be alive
3. Cell structure is correlated to cellular function
4. All cells are related by their descent from earlier
cells
Comparing Prokaryotic & Eukaryotic Cells

Basic features of ALL cells
 Plasma
membrane
 Semifluid substance called cytosol within cytoplasm
(area between PM and nucleus)
 Genetic Material
 Ribosomes

Prokaryotic cells are characterized by having
 No
nucleus
 Free-floating circular DNA
 No membrane-bound organelles
 Cell walls
Fimbriae
Nucleoid
Ribosomes
Plasma
membrane
Bacterial
chromosome
Cell wall
Capsule
0.5 m
(a) A typical
rod-shaped
bacterium
Flagella
(b) A thin section
through the
bacterium Bacillus
coagulans (TEM)
Eukaryotic Cells
 we will focus on plant & animal cells
Eukaryotic Cells  membrane bound organelles
1. plasma membrane
- selectively permeable
.
2. Nucleus
- surrounded by 2 membranes (nuclear envelope)
- interrupted by pores
- stores DNA
1 m
Nucleus
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Rough ER
Surface of nuclear
envelope
Pore
complex
Ribosome
Chromatin
1 m
0.25 m
Close-up
of nuclear
envelope
Pore complexes (TEM)
Nuclear lamina (TEM)
3. endoplasmic reticulum (ER)
- continuous with the nuclear envelope
- there are two distinct regions of ER
Smooth ER
 Rough ER

Smooth ER
Nuclear
envelope
Rough ER
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
Transitional ER
Rough ER
200 nm
Functions of Smooth ER

The smooth ER
 Synthesizes
lipids
 Metabolizes carbohydrates
 Detoxifies drugs and poisons
Functions of Rough ER

The rough ER
 Has
bound ribosomes  make proteins
- glycoproteins
- transport vesicles
4. Golgi apparatus consists of flattened membranous
sacs

Functions
 Modifies
products of the ER
 Manufactures certain macromolecules
 Sorts and packages materials into transport vesicles
cis face
(“receiving” side of
Golgi apparatus)
0.1 m
Cisternae
trans face
(“shipping” side of
Golgi apparatus)
TEM of Golgi apparatus
Nucleus
Rough ER
Smooth ER
cis Golgi
trans Golgi
Plasma
membrane
5. lysosome is a membranous sac of digestive
enzymes
- Undergoes autophagy to digest old, worn-out
organelles & macromolecules
Nucleus
Vesicle containing
two damaged
organelles
1 m
1 m
Mitochondrion
fragment
Peroxisome
fragment
Lysosome
Digestive
enzymes
Lysosome
Lysosome
Plasma membrane
Peroxisome
Digestion
Food vacuole
Vesicle
(a) Phagocytosis
(b) Autophagy
Mitochondrion
Digestion
6. Vacuoles – diverse maintenance compartments
- derived from ER and Golgi apparatus
Examples
 Food vacuoles
 Contractile vacuoles (found in many freshwater protists 
pump excess water out of cells)
 Central vacuoles (found in many mature plant cells hold
toxins and water)
Central vacuole
Cytosol
Nucleus
Central
vacuole
Cell wall
Chloroplast
5 m
Endomembrane System regulates protein
traffic and performs metabolic functions
in the cell

Components
 Nuclear
envelope
 Endoplasmic reticulum
 Golgi apparatus
 Lysosomes
 Vacuoles
 Plasma membrane

These components are either continuous or connected
via transfer by vesicles
7. Mitochondria (power house of the cell)
- surrounded by a double membrane
- cellular respiration
- a single cell may have a few hundred
10 m
Intermembrane space
Mitochondria
Outer
membrane
DNA
Free
ribosomes
in the
mitochondrial
matrix
Inner
membrane
Mitochondrial
DNA
Cristae
Matrix
(a) Diagram and TEM of mitochondrion
Nuclear DNA
0.1 m
(b) Network of mitochondria in a protist
cell (LM)
8. Chloroplasts
- contain the green pigment chlorophyll & enzymes that
function in photosynthesis
- found in leaves & other green organs of plants &
algae
* Belong to a group of plant organelles called
plastids
Figure 6.18
50 m
Ribosomes
Stroma
Inner and outer
membranes
Granum
DNA
Intermembrane space
Thylakoid
(a) Diagram and TEM of chloroplast
Chloroplasts
(red)
1 m
(b) Chloroplasts in an algal cell

The Endosymbiont theory
 An
early ancestor of eukaryotic cells engulfed a
nonphotosynthetic prokaryotic cell, which formed an
endosymbiont relationship with its host
 The host cell and endosymbiont merged into a
single organism, a eukaryotic cell with a
mitochondrion
 At least one of these cells may have taken up a
photosynthetic prokaryote, becoming the ancestor
of cells that contain chloroplasts
Endoplasmic
reticulum
Nucleus
Engulfing of oxygenNuclear
using nonphotosynthetic envelope
prokaryote, which
becomes a mitochondrion
Ancestor of
eukaryotic cells
(host cell)
Mitochondrion
Nonphotosynthetic
eukaryote
At least
one cell
Engulfing of
photosynthetic
prokaryote
Chloroplast
Mitochondrion
Photosynthetic eukaryote
9. cytoskeleton is a network of fibers extending
throughout the cytoplasm
 It organizes the cell’s structures and activities,
anchoring many organelles
* Technically not an organelle.