Biology 107
Cell III
September 26, 2005
Cell III
Student Objectives: As a result of this lecture and the assigned
reading, you should understand the following:
1.
The mitochondria carry out cellular respiration in which the
chemical energy of foods, such as sugars, is converted to “useful”
chemical energy in the form of the molecule ATP. Mitochondria
are double membrane containing structures.
a. The inner membrane encloses a fluid-filled space called the
mitochondrial matrix.
b. The space between the inner and outer membrane is the
intermembrane space.
Cell III
c. The intermembrane space contains one set of enzymes, while
the mitochondrial matrix contains a different set of enzymes.
Also, the inner cell membrane is highly folded and contains
enzymes that are responsible for ATP production. Each fold is
called a crista (plural, cristae) and the folding increase the
membrane surface area for the enzymes.
d. Mitochondria contain circular DNA and prokaryote-like
ribosomes, suggesting they arose from symbiotic association
between aerobic organisms (the precursors of mitochondria)
and anaerobic organisms (the precursors of the cell in which
the mitochondria reside).
Cell III
2.
Like mitochondria, chloroplasts are double membrane structures
with their own DNA and ribosomes. Like mitochondria,
chloroplasts are fuel processors, but they convert solar energy
into chemical energy, while mitochondria convert one form of
chemical energy into another form of chemical energy. The
membranes partition the chloroplast into three major
compartments involved in photosynthesis.
a. The intermembrane space is between the outer and inner
chloroplast membranes.
b. The space enclosed by the inner membrane, the stroma,
contains the thylakoid membranes, a the network of tubules
and hollow discs.
c. The space inside thylakoid membranes.
Cell III
3.
The cytoskeleton is a supportive network of intracellular linear
polymers. These cytoskeletal elements are important in
maintaining cell shape and motility of cells and their organelles.
a. Microfilaments are long polar filaments composed of actin.
These filaments are involved in cell shape changes; through
interaction with other proteins (e.g., myosin), they participate in
cellular contractility.
b. Intermediate filaments constitute a class of proteins rather than
a single protein species. Intermediate filaments are very stable
linear, rope-like structures that help to anchor structures.
c. Microtubules are composed of tubulin that forms long straight
polymers that are easily assembled and disassembled. These
dynamic structures are involved in the movement of organelles
around the cell.
Cell III
4.
Cells are dynamic structures - they are continually moving
components around and transferring substances between
compartments and regions. Examples of how cells segregate
materials include protein sorting and vesicular transport.
a. Protein sorting relates to the different regions specific proteins
must localize to provide proper functioning in the cell. Some
proteins must enter the nucleus, others enter membranous
organelles such as mitochondria, lysosomes, or chloroplasts,
and still others become integral membrane proteins or secreted
proteins.
b. Vesicular transport carries vesicle contents and membrane to
intracellular sites or to sites on the plasma membrane for
release to the outside of the cell. The various vesicular
transport and secretion pathways use molecular signals or
"tags" to designate the proper sorting.
Structure of a Mitochondrion
Mitochondria are Doublemembrane Structures
Chloroplasts are Doublemembrane Structures
Chloroplast
Cytoskeleton Consist of Three
Elements
Examples of
Microfilament
Function
Micrographs of
Microfilaments and
Intermediate
Filaments
Intermediate filaments
Microtubule Organizing Centers
(MTOCs)
Actin
MTOC
Microtubules
and
Accessory
Proteins are
Involved with
Intracellular
Movement of
Organelles
Cells are Dynamic Structures
Review - Pathway for Movement of
Proteins and Membranes