4.3 Defining Features of Eukaryotic Cells!
Organelle = an
internal, membranebound sac or
compartment that
serves one or more
specialized functions.!
A. Major Cellular Components!
!" Include:
nucleus, endoplasmic reticulum
(ER), golgi body, vesicles, mitochondria,
ribosomes, cytoskeleton.!
Advantages of
compartmentalization!
1."
2."
Allows a large number of activities to
occur simultaneously in a very limited
space (i.e.: Organelle membranes
physically separate incompatible
reactions)!
Allow compatible and interconnected
reactions to proceed at different times.!
B. Plant Cells vs.. Animal Cells!
Plants!
Large central
vacuole!
Chloroplasts!
Cell wall!
cuboidal
!
Other plant organelles!
Animals!
!" A
few small vacuoles!
!" Cytoskeleton!
!" Spherical shape!
!" Centrioles (2)!
!" Lysosomes!
4.4 The Nucleus!
!" A
cell#s structure and function begin with
proteins.!
!" Instructions
for building proteins are
contained in DNA.!
Functions of the Nucleus!
1."
2."
Localizes DNA - makes it easier for
parent cells to copy their genetic
instructions.!
Outer membranes form a boundary
where cells can control the passage of
substances and signals to and from the
cytoplasm!
Parts of the Nucleus!
1."
2."
3."
4."
Nuclear envelope = double membrane!
Nucleoplasm = semisolid gel w/i
nucleus.!
Pores = openings in envelope!
Nucleolus = dark body or bodies w/i
nucleus that synthesize proteins and
RNA that will be used to assemble
ribosomes.!
5. DNA = genetic material!
!" Chromatin
= unorganized DNA and
proteins (long & stringy)!
!" Chromosomes = organized, coiled DNA
and proteins (X#s)!
4.5 Cytomembrane System!
!" Cytomembrane
system = the series of
organelles in which lipids are assembled
and new polypeptide chains are modified
into final proteins.!
!" Includes the ER (rough & smooth, Golgi
bodies, vesicles)!
A. Endoplasmic Reticulum (ER)!
!" Rough
ER = covered with ribosomes,
abundant in cells that make and secrete
enzymes (ex: pancreas)!
!" Smooth ER = lack ribosomes; abundant
in cells that assemble lipids (ex: seeds,
liver, muscle)!
B. Golgi bodies!
!" Process,
package & secrete cellular
substances!
C. Vesicles!
!" Tiny
membranous sacs that transport
substances throughout the cytoplasm.!
!" Examples: !
! !lysosomes = intercellular digestion!
! !peroxisomes = break down fatty acids
and amino acids!