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

2. What’s a Cell?
The cell is the simplest collection of matter that can be alive
Looking at cell structure, there are two broad groupings of life:
Prokaryotes, which lack a membrane-bound nucleus.
Eukaryotes, which have such a nucleus.
For the Discovery Channel Video Cells, go to Animation and Video Files

3. Prokaryotic Cells
. Prokaryotic cells generally have few or no substructures separated from the rest of the cell by internal membranes.
Along with a membrane, 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. 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.

6. Eukaryotic Cells
The relatively large size of the eukaryotic cell makes it difficult for molecules to diffuse across the entire cell.
Organelles help solve this problem by breaking up the large cell volume into several smaller functional units.
chemical reaction efficiency by separating incompatible chemical reactions and grouping enzymes and substrates together.
The quantity/size of organelles is determined by the function of the cell, but all eukaryotic cells share some common features.
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

7. 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

8. 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.

9. The Nucleus It houses the cell’s genetic material (DNA)
Directs protein synthesis by synthesizing mRNA
contains most of the cell’s genes and is usually the most conspicuous organelle
Enclosed by the nuclear envelope, separating it from the cytoplasm

10. Close-up of nuclear envelope Chromatin Nucleus Nucleolus Chromatin
Figure 4.8a
Nucleus
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Rough ER
Figure 4.8a The nucleus and its envelope (part 1: detail of art)
Pore
complex
Ribosome
Close-up
of nuclear
envelope
Chromatin 10

11. Ribosomes The protein factory of the cell
Composed of complexes of ribosomal RNA and protein
Ribosomes carry out protein synthesis in two locations
In the cytosol (free ribosomes)-make Proteins used in the cell
On the outside of the endoplasmic reticulum (bound ribosomes)-make Proteins for the membrane or export

12. Free ribosomes in cytosol
Figure 4.9
0.25 m
Ribosomes ER
Free ribosomes in cytosol
Endoplasmic reticulum (ER)
Ribosomes bound to ER
Large
subunit
Figure 4.9 Ribosomes
Small
subunit
TEM showing ER and ribosomes
Diagram of a ribosome 12

13. Endomembrane System Components of the endomembrane system
Nuclear envelope
Endoplasmic reticulum (smooth and rough)
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane
These components are either continuous or connected through transfer by vesicles

14. Endoplasmic Reticulum
Accounts for more than half of the total membrane volume in many eukaryotic cells
Continuous with the nuclear envelope
Two distinct regions of ER
Smooth ER: lacks ribosomes
Rough ER: surface is studded with ribosomes

15. Functions of Smooth ER Synthesizes lipids—such as hormones
Detoxifies drugs and poisons—by adding hydroxyl, making molecule more soluble.
Stores calcium ions—drives muscle cell contraction
© 2014 Pearson Education, Inc. 15

16. Functions of Rough ER
bound ribosomes, secrete glycoproteins used for cell signaling
Distributes transport vesicles, proteins surrounded by membranes
Most proteins synthesized in rough ER are bound for membranes or excretion from cell
Is the membrane factory for the cell
© 2014 Pearson Education, Inc. 16

17. Endoplasmic Reticulum
Transport vesicle
Smooth ER
Rough ER
Ribosomes
Transitional
Cisternae
ER lumen
Rough ER
Nuclear
envelope
0.2 m

18. Golgi Apparatus Consists of flattened membranous sacs called cisternae
Functions of the Golgi apparatus
Modifies products of the ER
Manufactures certain macromolecules
Sorts and packages materials into transport vesicles
Can be thought of as the warehouse of the cell. Stores & coordinates the transport of materials made by the cell.

19. Golgi Apparatus Golgi apparatus 0.1 m cis face (“receiving” side of
TEM of Golgi apparatus
Golgi
apparatus
trans face
(“shipping”
side of Golgi
apparatus)
Cisternae
0.1 m
cis face
(“receiving” side of
Golgi apparatus)

20. Lysosomes
Membranous sac of hydrolytic enzymes that digest macromolecules for energy
Creates an acidic environment for enzymes to digest food
Can fuses with the food vacuole and digests the molecules
Also use enzymes to recycle the cell’s own organelles and macromolecules, a process called autophagy

21. Lysosomes 1 m Nucleus Lysosome Digestive enzymes Plasma membrane
Food vacuole
Lysosomes: Phagocytosis
Digestion

22. Vacuole
Large vesicles derived from the endoplasmic reticulum and Golgi apparatus
Food vacuoles are formed by phagocytosis
Contractile vacuoles, found in many freshwater protists, pump excess water out of cells
Central vacuoles, found in many plant cells, hold organic compounds and water (storage)

23. Vesicles

24. Energy Organelles
Mitochondria are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP
Chloroplasts, found in plants and algae, are the sites of photosynthesis
Both contain their own DNA, separate from the DNA in the Nucleus!

25. Energy Organelles

26. Endosymbiont Theory
An early ancestor of eukaryotic cells engulfed a prokaryotic cell
The host cell and endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion
Some then engulfed a photosynthetic prokaryote, creating the early ancestors of plants and alage

27. Endosymbiont Theory Mitochondrion Nonphotosynthetic eukaryote
At least
one cell
Chloroplast
Engulfing of
photosynthetic
prokaryote
Nucleus
Nuclear
envelope
Endoplasmic
reticulum
Ancestor of
eukaryotic cells
(host cell)
Engulfing of oxygen-
using nonphotosynthetic
prokaryote, which
becomes a mitochondrion

28. Cytoskeleton
The cytoskeleton is a network of fibers extending throughout the cytoplasm
It organizes the cell’s structures and activities, anchoring many organelles

29. Cytoskeleton
The cytoskeleton helps to support the cell and maintain its shape
It interacts with motor proteins to produce motility
Inside the cell, vesicles and other organelles can “walk” along the tracks provided by the cytoskeleton
(b) SEM of a squid giant axon
Receptor for
motor protein
Vesicle
Motor protein
(ATP powered)
ATP
Microtubule
of cytoskeleton
Motor proteins “walk” vesicles along cytoskeletal
fibers.

30. Cytoskeleton Three main types of fibers make up the cytoskeleton
Microtubules (thickest)
Shape and support the cell
Guide movement of organelles
Separate chromosomes during cell division
Microfilaments (thinnest)
bear tension, resisting pulling forces
Create movement & shape changes of cell
Initiates cell division
Intermediate filaments
Anchors organelles within cell

31. Cytoskeleton