1. Chapter 6
Part B
A tour of The Cell

2. Smooth ER & its Functions
It lacks the surface ribosomes
Its functions include:
Synthesizes lipids
Metabolizes carbohydrates
Stores calcium
Detoxifies poison

3. The Golgi Apparatus The Golgi apparatus
Consists of flattened membranous sacs called cisternae
Works in partnership with the ER.
Receives many of the transport vesicles produced in the rough ER
Refines, stores, and distributes the chemical products of the cell.

4. Figure 4.12

5. Functions of the Golgi apparatus
cis face
(“receiving” side of
Golgi apparatus)
Vesicles move
from ER to Golgi
Vesicles also
transport certain
proteins back to ER
Vesicles coalesce to
form new cis Golgi cisternae
Cisternal
maturation:
Golgi cisternae
move in a cis-
to-trans
direction
Vesicles form and
leave Golgi, carrying
specific proteins to
other locations or to
the plasma mem-
brane for secretion
Vesicles transport specific
proteins backward to newer
Cisternae
trans face
(“shipping” side of
0.1 0 µm 1 6 5 2 3 4
Golgi
apparatus
Figure 6.13
TEM of Golgi apparatus

6. A lysosome is a membrane-enclosed sac.
Lysosomes
A lysosome is a membrane-enclosed sac.
It contains digestive enzymes.
The enzymes break down macromolecules.
Lysosomes have several types of functions:

7. They fuse with food vacuoles to digest the food.
digestive
Lysosome Formation

8. They break down damaged organelles.

9. Vacuoles are membranous sacs. Two types:
the contractile vacuoles of protists
the central vacuoles of plants.

10. Figure 4.14

11. A review of the endomembrane system

12. Chloroplasts and Mitochondria:
Both energy transformers with two membranes
Mitochondria (two membranes)
Found in nearly all eukaryotes
Are the sites of cellular respiration
Chloroplasts (two membranes)
Found only in plants
Member of the plasid family
Contain chlorophyl
Sites of photosynthesis

13. Chloroplasts and Mitochondria: Energy Conversion
Cells require a constant energy supply
Chloroplasts:
The sites of photosynthesis, which is:
the Conversion of light energy to chemical energy
Mitochondria:
The sites of cellular respiration, which involves:
the production of ATP from food molecules.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

14. Chloroplast structure includes
Thylakoids, membranous sacs
Stroma, the internal fluid

15. Are found in leaves and other green organs of plants and in algae
Chloroplasts
Are found in leaves and other green organs of plants and in algae
Chloroplast
DNA
Ribosomes
Stroma
Inner and outer
membranes
Thylakoid
1 µm
Granum
Figure 6.18

16. Mitochondria are enclosed by two membranes A smooth outer membrane
An inner membrane folded into cristae
Mitochondrion
Intermembrane space
Outer
membrane
Free
ribosomes
in the
mitochondrial
matrix
Mitochondrial
DNA
Inner
Cristae
Matrix
100 µm
Figure 6.17

17. Mitochondria and chloroplasts share another feature unique among eukaryotic organelles.
They contain their own DNA.
They contain their own ribosomes
The existence of separate “mini-genomes” is believed to be evidence that
Mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past.

18. Peroxisomes: Oxidation
Produce hydrogen peroxide and convert it to water
Chloroplast
Peroxisome
Mitochondrion
1 µm
Figure 6.19

19. A cellular infrastructure of a network of fibers.
The Cytoskeleton:
A cellular infrastructure of a network of fibers.
Provides mechanical support to the cell
Maintain the shape of the cell
Forms tract for organelles movement
Can change the shape of a cell allowing cells like amoebae to move.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

20. Cytoskeleton Three main types of fibers making the cytoskeleton:
Microtubules:
Shape the cell & guide movement of organelles
Help separate chromosome in dividing cells
Intermediate filaments:
Support cell shape
Fix organelles in place
Microfilaments
Made of actin and involved in motility

21. Figure 4.18a

22. Centrosomes and Centrioles
The centrosome
Is considered to be a “microtubule-organizing center”

23. Contains a pair of centrioles
Centrosome
Microtubule
Centrioles
0.25 µm
Longitudinal section
of one centriole
Microtubules
Cross section
of the other centriole
Figure 6.22

24. Cilia and Flagella
Cilia and flagella are motile appendages.
Flagella propel the cell in a whiplike motion.
Cilia move in a coordinated back-and-forth motion.

25. Figure 4.19a, b

26. Some cilia or flagella extend from nonmoving cells.
The human windpipe is lined with cilia.

27. The Extracellular Matris (ECM)
made up of glycoproteins and other macromolecules
Collagen
Fibronectin
Plasma
membrane
EXTRACELLULAR FLUID
Micro-
filaments
CYTOPLASM
Integrins
Polysaccharide
molecule
Carbo-
hydrates
Proteoglycan
Core
protein
Integrin
Figure 6.29
A proteoglycan
complex

28. Functions of the ECM include
Support
Adhesion
Movement
Regulation

29. Intercellular Junctions
Plant Plasmodesmata
Are channels that perforate plant cell walls
Interior
of cell
0.5 µm
Plasmodesmata
Plasma membranes
Cell walls
Figure 6.30

30. Animals: Tight Junctions, Desmosomes, and Gap Junctions
In animals, there are three types of intercellular junctions
Tight junctions
Desmosomes
Gap junctions

31. Types of intercellular junctions in animals
Tight junctions prevent
fluid from moving
across a layer of cells
Tight junction
0.5 µm
1 µm
Space
between
cells
Plasma membranes
of adjacent cells
Extracellular
matrix
Gap junction
Tight junctions
0.1 µm
Intermediate
filaments
Desmosome
Gap
junctions
At tight junctions, the membranes of
neighboring cells are very tightly pressed
against each other, bound together by
specific proteins (purple). Forming continu-
ous seals around the cells, tight junctions
prevent leakage of extracellular fluid across
A layer of epithelial cells.
Desmosomes (also called anchoring
junctions) function like rivets, fastening cells
Together into strong sheets. Intermediate
Filaments made of sturdy keratin proteins
Anchor desmosomes in the cytoplasm.
Gap junctions (also called communicating
junctions) provide cytoplasmic channels from
one cell to an adjacent cell. Gap junctions
consist of special membrane proteins that
surround a pore through which ions, sugars,
amino acids, and other small molecules may
pass. Gap junctions are necessary for commu-
nication between cells in many types of tissues,
including heart muscle and animal embryos.
TIGHT JUNCTIONS
DESMOSOMES
GAP JUNCTIONS
Figure 6.31