1. Chapter 7 Inside the Cell Biological Science, Third Edition
– Scott Freeman
Lectures by Cheryl Ingram-Smith

2. What’s Inside the Cell?
Looking at cell structure, there are two broad groupings of life:
Prokaryotes, which lack a membrane-bound nucleus.
Eukaryotes, which have such a nucleus.
Looking into groupings by evolutionary history, there are two types of prokaryotic cells, called Bacteria and Archaea, in addition to the Eukarya.
For the Discovery Channel Video Cells, go to Animation and Video Files

3. Prokaryotic Cells
The prokaryotic plasma membrane surrounds the cytoplasm, a term that includes all the contents of the cell. Prokaryotic cells generally have few or no substructures separated from the rest of the cell by internal membranes.
Prokaryotes have a tough cell wall that protects the cells and gives them shape and structure.

4. A Prokaryotic Cell Ribosomes Plasmids Cytoplasm Chromosome Flagellum
Plasma
membrane
Cell wall

5. Prokaryotic Cells
Most prokaryotic species have one supercoiled circular chromosome containing DNA that is found in the nucleoid region of the cell.
All prokaryotic cells contain ribosomes for protein synthesis. Ribosomes have a large and a small subunit and contain both RNA and protein molecules.
The inside of prokaryotic cells is supported by a cytoskeleton of protein filaments.
Some prokaryotes have tail-like flagella on the cell surface that spin around to move the cell.

6. Eukaryotes and Prokaryotes Compared
Major differences between typical eukaryotes and prokaryotes are as follows:
(1) Eukaryotic chromosomes are found inside a membrane- bound compartment called a nucleus.
(2) Eukaryotic cells are often much larger.
(3) Eukaryotic cells contain extensive amounts of internal membrane.
(4) Eukaryotic cells feature a diverse and dynamic cytoskeleton.

7. Eukaryotic Cells
The relatively large size of the eukaryotic cell makes it difficult for molecules to diffuse across the entire cell. This problem is partially solved by breaking up the large cell volume into several smaller membrane-bound organelles.
The compartmentalization of eukaryotic cells increases chemical reaction efficiency by separating incompatible chemical reactions and grouping enzymes and substrates together.
For the Cell Biology Video Movement of Organelles in Vitro, go to Animation and Video Files
For the Cell Biology Video Movement of Organelles in Vivo, go to Animation and Video Files

8. Animal and Plant Cells Generalized animal cell Generalized plant cell
Nuclear envelope
Nucleolus
Nucleus
Chromosomes
Rough endoplasmic
reticulum
Centrioles
Ribosomes
Peroxisome
Structures that
occur in animal cells
but not plant cells
Smooth endoplasmic
reticulum
Golgi apparatus
Lysosome
Mitochondrion
Cytoskeletal element
Plasma membrane
Generalized plant cell
Nuclear envelope
Nucleolus
Nucleus
Chromosomes
Rough endoplasmic
reticulum
Structures that
occur in plant cells
but not animal cells
Ribosomes
Smooth endoplasmic
reticulum
Cell wall
Golgi apparatus
Vacuole (lysosome)
Chloroplast
Peroxisome
Mitochondrion
Plasma membrane
Cytoskeletal element
On average, prokaryotes are about 10
times smaller than eukaryotic cells in
diameter and about 1000 times smaller
than eukaryotic cells in volume.

9. Animal and Plant Cells Generalized animal cell Nuclear envelope
Nucleolus
Nucleus
Chromosomes
Rough endoplasmic
reticulum
Centrioles
Ribosomes
Peroxisome
Structures that
occur in animal cells
but not plant cells
Smooth endoplasmic
reticulum
Golgi apparatus
Lysosome
Mitochondrion
Cytoskeletal element
Plasma membrane

10. Animal and Plant Cells Generalized plant cell Nuclear envelope
Nucleolus
Nucleus
Chromosomes
Rough endoplasmic
reticulum
Structures that
occur in plant cells
but not animal cells
Ribosomes
Smooth endoplasmic
reticulum
Golgi apparatus
Cell wall
Vacuole (lysosome)
Chloroplast
Peroxisome
Mitochondrion
Plasma membrane
Cytoskeletal element
On average, prokaryotes are about 10
times smaller than eukaryotic cells in
diameter and about 1000 times smaller
than eukaryotic cells in volume.

11. The Endomembrane System
Ions, ATP, amino acids, and other small molecules diffuse randomly throughout the cell, but the movement of proteins and other large molecules is energy demanding and tightly regulated.
In the endomembrane system, proteins that are synthesized in the rough ER move to the Golgi apparatus for processing, and from there travel to the cell surface or other destinations (Figure 7.26).

12. The Secretory Pathway Hypothesis
THE SECRETORY PATHWAY: A MODEL
RNA
Rough ER
1. Protein enters
ER while being
synthesized by
ribosome.
2. Protein exits ER,
travels to cis face
of Golgi apparatus.
cis face of
Golgi apparatus
Golgi apparatus
3. Protein enters
Golgi apparatus and
is processed as the
cisternum moves
toward the trans face.
4. Protein exits Golgi
apparatus at trans
face and moves to
plasma membrane.
trans face of
Golgi apparatus
Plasma membrane
5. Protein is
secreted from cell.

13. How Are Products Shipped from the Golgi?
Each protein that comes out of the Golgi apparatus has a molecular tag that places it in a particular type of transport vesicle. Each type of transport vesicle also has a tag that allows it to be transported to the correct destination.
Figure 7.30 illustrates the current model for how proteins are sorted into distinct vesicles in the Golgi and then targeted to their correct destination.
Some proteins are sent to the cell surface in vesicles that fuse with the plasma membrane, releasing their contents to the exterior of the cell in a process called exocytosis.
For the Cell Biology Video Secretion from the Golgi, go to Animation and Video Files

14. The Golgi Apparatus: Proteins Are Sorted into Vesicles
PROTEIN SORTING AND VESICLE TRANSPORT
1. In the endomembrane
system, proteins bound
for lysosomes or rough
ER are given different
carbohydrate “tags.”
Proteins bound for
secretion have built-in
export signal.
Lumen of
Golgi apparatus
2. Proteins are sorted
in the Golgi when they
bind to different
receptors.
“Tags”
3. Transport vesicles
bud off the trans face of
the Golgi and travel to
their destinations.
Receptors
Cytosol
Transport
vesicles
4. Proteins on vesicle
surface interact with
receptors at destination.
To plasma membrane
for secretion
Return to the ER
Lysosome
5. Vesicle delivers
contents.

15. The Dynamic Cytoskeleton
The cytoskeleton is a complex network of fibers that helps maintain cell shape by providing structural support. The cytoskeleton is dynamic; it changes to alter the cell’s shape, to transport materials in the cell, or to move the cell itself.
The three types of cytoskeletal elements are actin filaments, intermediate filaments, and microtubules.
For the Cell Biology Video Cytoskeleton Protein Dynamics, go to Animation and Video Files

16. A Motor Protein Moves Vesicles along Microtubules
Structure of kinesin
Tail
Stalk
Head

17. A Motor Protein Moves Vesicles along Microtubules
Kinesin “walks” along a microtubule track.
Transport
vesicle
Kinesin
Every step
requires energy
Microtubule
 end
 end