1. Chapter 3 Cells: The Living Unit Part C Shilla Chakrabarty, Ph.D.

2. A Panoramic View Of The Eukaryotic Cell
ENDOPLASMIC RETICULUM (ER)
Rough ER
Smooth ER
Nuclear envelope
Nucleolus
Chromatin
Plasma membrane
Ribosomes
Golgi apparatus
Lysosome
Mitochondrion
Peroxisome
Microvilli
Microtubules
Intermediate filaments
Microfilaments
Centrosome
CYTOSKELETON:
Flagellum
NUCLEUS
Figure 6.8 Exploring: Eukaryotic Cells

3. Cytoplasm Located between plasma membrane and nucleus Cytosol
Water with solutes (protein, salts, sugars, etc.)
Cytoplasmic organelles
Metabolic machinery of cell
Inclusions
Granules of glycogen or pigments, lipid droplets, vacuoles, and crystals

4. Cytoplasmic Organelles
Membranous
Mitochondria
Peroxisomes
Lysosomes
Endoplasmic reticulum
Golgi apparatus
Nonmembranous
Cytoskeleton
Centrioles
Ribosomes

5. Ribosomes
Granules containing protein and rRNA
Site of protein synthesis
Free ribosomes synthesize soluble proteins
Membrane-bound ribosomes (on rough ER) synthesize proteins to be incorporated into membranes or exported from the cell

6. Mitochondria Double-membrane structure with shelf-like cristae
Enzymes
Matrix
Cristae
Mitochondrial
DNA
Ribosome
Outer
mitochondrial
membrane
Inner
(b)
(a)
(c)
Double-membrane structure with shelf-like cristae
Provide most of cell’s ATP via aerobic cellular respiration
Contain their own DNA and RNA
Figure 3.17

7. Endoplasmic Reticulum (ER)
Interconnected tubes and parallel membranes enclosing cisternae
Continuous with nuclear membrane
Two varieties: Rough ER and Smooth ER
Figure 3.18a
Nuclear
envelope
Ribosomes
Rough ER
Smooth ER
(a) Diagrammatic view of smooth and rough ER

8. Rough And Smooth ER Rough ER External surface studded with ribosomes
Manufactures all secreted proteins
Synthesizes membrane integral proteins and phospholipids
Smooth ER
Tubules arranged in a looping network
Enzyme (integral protein) functions:
In the liver—lipid and cholesterol metabolism, breakdown of glycogen, and, along with kidneys, detoxification of drugs, pesticides, and carcinogens
Synthesis of lipids including oils, phospholipids and steroid-based hormones
In intestinal cells—absorption, synthesis, and transport of fats
In skeletal and cardiac muscle—storage and release of calcium

9. Golgi Apparatus Stacked and flattened membranous sacs
Modifies, concentrates, and packages proteins and lipids
Transport vessels from ER fuse with convex cis face of Golgi apparatus
Proteins then pass through Golgi apparatus to trans face
Secretory vesicles leave trans face of Golgi stack and move to designated parts of cell
Protein-
containing
vesicles pinch
off rough ER
and migrate to
fuse with
membranes of
Golgi
apparatus.
Proteins are
modified within
the Golgi
compartments.
then packaged
within different
vesicle types,
depending on
their ultimate
destination.
Plasma
mem-
brane
Secretion by
exocytosis
Vesicle becomes
lysosome
apparatus
Rough ER ER
membrane
Phagosome
Proteins in
cisterna
Pathway B:
Vesicle membrane
to be incorporated
into plasma
Pathway A:
Vesicle contents
destined for exocytosis
Extracellular fluid
Secretory
vesicle
Pathway C:
Lysosome containing
acid hydrolase
enzymes 1 3 2
Figure 3.20

10. Lysosomes
Spherical membranous bags containing digestive enzymes (acid hydrolases)
Digest ingested bacteria, viruses, and toxins
Degrade nonfunctional organelles
Break down and release glycogen
Break down bone to release Ca2+
Destroy cells in injured or non-useful tissue (autolysis)

11. Endomembrane System Components of the endomembrane system are:
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane
Components of the endomembrane system are either continuous or connected via transfer by vesicles
Overall function
Produce, store, and export biological molecules
Degrade potentially harmful substances

12. Endomembrane System Nucleus Nuclear envelope Smooth ER Rough ER
Golgi
apparatus
Transport
vesicle
Plasma
membrane
Vesicle
Smooth ER
Rough ER
Nuclear envelope
Lysosome
Nucleus
Figure 3.22

13. Peroxisomes Membranous sacs containing powerful oxidases and catalases
Detoxify harmful or toxic substances
Neutralize dangerous free radicals (highly reactive chemicals with unpaired electrons)

14. Cytoskeleton Elaborate series of rods throughout cytosol
Microfilaments
Intermediate filaments
Microtubules

15. Dynamic actin strands attached to cytoplasmic side of plasma membrane
Microfilaments
Strands made of spherical
protein subunits called actins
(a) Microfilaments
Actin subunit
7 nm
Microfilaments form the blue network
surrounding the pink nucleus in this
photo.
Dynamic actin strands attached to cytoplasmic side of plasma membrane
Involved in cell motility, change in shape, endocytosis and exocytosis
Figure 3.23a

16. Intermediate Filaments
(b) Intermediate filaments
Tough, insoluble protein fibers
constructed like woven ropes
10 nm
Fibrous subunits
Intermediate filaments form the purple
batlike network in this photo.
Tough, insoluble ropelike protein fibers
Resist pulling forces on the cell and attach to desmosomes
Figure 3.23b

17. Microtubules Dynamic hollow tubes Most radiate from centrosome
(c) Microtubules
Hollow tubes of spherical protein
subunits called tubulins
25 nm
Tubulin subunits
Microtubules appear as gold networks
surrounding the cells’ pink nuclei in
this photo.
Dynamic hollow tubes
Most radiate from centrosome
Determine overall shape of cell and distribution of organelles
Figure 3.23c

18. Motor Molecules
Protein complexes that are powered by ATP and function in motility (e.g., movement of organelles and contraction)
Cytoskeletal elements
(microtubules or microfilaments)
Motor molecule (ATP powered)
ATP
(b) In some types of cell motility, motor molecules attached to one element of the cytoskeleton can cause it to slide over another element, as in muscle contraction and cilia movement.
Vesicle
(a) Motor molecules can attach to receptors on vesicles or organelles, and “walk” the organelles along the microtubules of the cytoskeleton.
Microtubule of cytoskeleton
Receptor for motor molecule
Figure 3.24

19. Centrosome Centrosome matrix Centrioles (a) Microtubules
“Cell center” near nucleus
Generates microtubules; organizes mitotic spindle
Contains centrioles: Small tube formed by microtubules
Figure 3.25a
Centrosome matrix
(a)
Centrioles
Microtubules

20. Cellular Extensions Cilia and flagella
Whip-like, motile extensions on surfaces of certain cells
Contain microtubules and motor molecules
Cilia move substances across cell surfaces
Longer flagella propel whole cells (tail of sperm)
Direction of swimming
(b) Motion of cilia
Direction of organism’s movement
Power stroke Recovery stroke
(a) Motion of flagella
5 m
15 m

21. Ciliary Motion Figure 3.27 (a) Phases of ciliary motion.
(b) Traveling wave created by the activity of many cilia acting together propels mucus across cell surfaces.
Power, or
propulsive,
stroke
Layer of mucus
Cell surface
Recovery stroke, when
cilium is returning to its
initial position 1 2 3 4 5 6 7
Figure 3.27

22. Cellular Extensions Figure 3.26 Outer microtubule doublet Dynein arms
The doublets
also have
attached motor
proteins, the
dynein arms.
Central
microtubule
Cross-linking
proteins inside
outer doublets
The outer
microtubule
doublets and
the two central
microtubules
are held
together by
cross-linking
proteins and
radial spokes.
Radial spoke
TEM
A cross section through the
cilium shows the “9 + 2”
arrangement of microtubules.
Microtubules
Cross-linking
proteins inside
outer doublets
Radial spoke
Plasma
membrane
Plasma
membrane
Cilium
Triplet
Basal body
TEM
TEM
A longitudinal section of a
cilium shows microtubules
running the length of the
structure.
Basal body
(centriole)
A cross section through the
basal body. The nine outer
doublets of a cilium extend into
a basal body where each doublet
joins another microtubule to
form a ring of nine triplets.
Figure 3.26

23. Cellular Extensions Microvilli
Fingerlike extensions of plasma membrane
Increase surface area for absorption
Core of actin filaments for stiffening
Microvillus
Actin
filaments
Terminal
web

24. Nucleus
Genetic library with blueprints for nearly all cellular proteins
Responds to signals and dictates kinds and amounts of proteins to be synthesized
Most cells are uninucleate; red blood cells are anucleate; skeletal muscle cells, bone destruction cells, and some liver cells are multinucleate
Chromatin (condensed)
Nuclear envelope
Nucleus
Nuclear pores
Nucleolus
Cisternae of rough ER
(a)

25. Nuclear Envelope Double-membrane barrier containing pores
Outer layer is continuous with rough ER and bears ribosomes
Inner lining (nuclear lamina) maintains shape of nucleus
Pore complex regulates transport of large molecules into and out of nucleus

26. Nuclear Envelope Surface of nuclear envelope. Fracture line of outer
Nucleus
Nuclear
pores
Fracture
line of outer
membrane
Nuclear pore complexes.
Each pore is ringed by
protein particles.
Surface of nuclear envelope.
Nuclear lamina. The netlike
lamina composed of inter-
mediate filaments formed by
lamins lines the inner surface
of the nuclear envelope.
(b)

27. Nucleoli Dark-staining spherical bodies within nucleus
Involved in rRNA synthesis and ribosome subunit assembly
Chromatin (condensed)
Nuclear envelope
Nucleus
Nuclear pores
Nucleolus
Cisternae of rough ER
(a)

28. Chromatin
Threadlike strands of DNA (30%), histone proteins (60%), and RNA (10%)
Arranged in fundamental units called nucleosomes
Condense into bar-like bodies called chromosomes when the cell starts to divide
Metaphase
chromosome
(at midpoint
of cell division)
Nucleosome (10-nm diameter; eight
histone proteins wrapped by two
winds of the DNA double helix)
Linker DNA
Histones
(a)
(b) 1
DNA double
helix (2-nm diameter) 2
Chromatin
(“beads on a
string”) structure
with nucleosomes 3
Tight helical fiber
(30-nm diameter) 5
Chromatid
(700-nm diameter) 4
Looped domain
structure (300-nm
diameter)
Figure 3.30