RIBOSOMES
&
ENDOPLASMIC
RETICULUM
.
Ribosomes

Made of ribosomal RNA
and protein
Synthesized by nucleolus of
cell
 Proteins from cytoplasm are
brought to nucleus and
made with rRNA into large
and small subunits of
ribosomes
 Subunits leave the nucleus
and assemble into
ribosomes


Carry out protein synthesis
Ribosomes Cont.

Two Types

Bound ribosomes
 Most proteins
made here
function in the
cytosol
 Free

ribosomes
Most proteins
made here are
for excretion,
insertion into
membranes, or
packaging in
other organelles
Endoplasmic Reticulum (ER)





Endoplasmic: “within the
cytoplasm”
Reticulum: “little net”
An organelle in eukaryotic cells
that is an extensive network of
membranes
ER consists of cisternae
(network of membranous
tubules)
Two types of ER: SMOOTH and
ROUGH
SMOOTH ER


Tasks: synthesis of lipids,
metabolism of
carbohydrates,
detoxification of drugs
and proteins, and
storage of calcium ions
Named “smooth”
because of the lack of
ribosomes
ROUGH ER



Cells that secrete proteins
produced by ribosomes attach
to the ER
“rough” because it is studded
with ribosomes
Makes secretory proteins, also
is a membrane factory for the
cell – it grows by adding
membrane proteins and
phospholipids to its own
membrane