D’YOUVILLE COLLEGE
BIOLOGY 102 - INTRODUCTORY BIOLOGY II
LECTURE # 8
CELL STRUCTURE II
4.
Energy-producing Organelles:
• mitochondria (fig. 6 – 17 & ppt. 1): frequently sausage-shaped; important
generator of energy (ATP) for the cell (aerobic respiration)
- membranes: organized into outer and inner membranes; inner is folded into
cristae
- compartments: intermembrane space + internal matrix
• chloroplasts (fig. 6 – 18 & ppt. 2): specialized plastid containing chlorophyll
for photosynthesis
- internal organization: elliptical shape with internal stroma; pigment
photosystems are highly ordered and arrayed on thylakoids (membranes with granal &
intergranal regions)
5.
Cytoskeleton: fibrous substances acting to maintain integrity and shape of cell
structure (intermediate filaments); also instrumental in cell motility (fig. 6 – 20, table 6
– 1 & ppts. 3 & 4)
• microtubules: composed of protein, tubulin; capable of lengthening or
shortening to direct movements of attached structures (chromosomes); provide tracks for
movement through cytosol (collaborate with motor proteins) (fig. 6 – 21 & ppt. 5)
- microtubular organizing centers: animal cells grow microtubules from
centrosomes, some with centrioles (microtubular structures with 9 triplet arrangement –
fig. 6 – 22 & ppt. 6)); in plants this function is performed by an unidentified organelle
Biology 102, lec 8 - Spring ‘12
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- cilia & flagella (fig. 6 –23, 6 – 24 & ppts. 7 & 8): involve microtubular cores
with a “9 + 2” arrangement (derived from basal bodies); involved in extracellular motility
(collaborate with motor proteins) (fig. 6 – 25 & ppts. 9 & 10); flagellar motion –
undulating action generates motion parallel to flagellum axis; ciliary motion – oar-like
action generation motion perpendicular to cilium axis (fig. 6 – 23 & ppt. 7)
- spindle apparatus of cell division: microtubules direct movements of
chromosomes in cell division
• microfilaments (fig. 6 – 26, 6 – 27 & ppt. 11): threadlike strands composed of
actin confer gel-like quality to external cytoplasm (cortical cytoplasm), helping stabilize
shape; interaction with myosin at one end of cell extrudes liquid central cytoplasm at
other end into pseudopodium
- in skeletal muscle, thicker myosin microfilaments overlap with actin to cause
contractile movements
6.
Cell Periphery:
• cell walls (fig. 6 – 28 & ppt. 12): non-living outer layers (plants, fungi, bacteria)
- plant cell wall – cellulose impregnated with various other substances; fungi
and some bacteria feature walls of chitin (polysaccharide)
• extracellular matrix: mixture of proteins, polysaccharides and proteincarbohydrate complexes; facilitate communication between extracellular milieu & cell
interior (animal cells – fig. 6 – 30 & ppt. 13)
• cell-to-cell junctions: cytoplasmic bridges span walls of adjacent plant cells
(plasmodesmata) (fig. 6 – 31 & ppt. 12)
Biology 102, lec 8 - Spring ‘12
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- animal cell junctions serve to seal intercellular spaces (tight junctions), to
hold cells together (desmosomes), or to facilitate intercellular transmission of materials
(gap junctions) (fig. 6 – 32 & ppt. 14)