9: Lecture Eukaryotic Cell
Structure and Cytoskeleton
Todays Concepts
Eukaryotes have elaborate internal and
external structure
Endomembrane system is a coordinated
membranous system of information
transfer in a cell.
Cytoskeleton has three main components
each with diverse functions
Communication occurs at the plasma
membrane and in extracellular spaces.
Inner Life of the Cell
On line movie
Eukaryotes have
plasma membrane
cytoplasm
Ribosomes
membrane-enclosed compartments called
organelles
Nuclear membrane.
>1 linear chromosomes
Ribosomessites of protein synthesis
Found in both
prokaryotic and
eukaryotic cells
Structure of one
larger and one
smaller subunit.
Each subunit
consists of
ribosomal RNA
Bound vs free ribosomes
Translation complex: two subunits of the
ribosome, mRNA, tRNA, many other
enzymes and proteins
Bound ribosomes: synthesis of
proteins for export and PM
Newly made proteins enter the RER
function
lumen.
Once inside, proteins are chemically
modified and tagged for delivery.
All secreted proteins and most membrane
proteins travel from RER to Golgi
Endomembrane system: Coordinated
system of compartments and
information transfer.
the nuclear envelope
rough and smooth endoplasmic reticulum,
Golgi apparatus,
lysosomes,
vacuoles and vesicles
plasma components membrane
7 that share
information in the form of
membrane-bound vesicles
Golgi apparatus
Receives and
modifies proteins
from the RER
Concentrates,
packages, and
sorts proteins
Adds
carbohydrates to
proteins
Three regions of the golgi
The cis region
receives vesicles
containing protein
from the RER.
At the trans region,
vesicles bud off
and travel to the
plasma membrane
or to lysosomes.
The medial region
The Cytoskeleton Provides Strength and
Movement
Supports and
maintains cell
shape
Holds organelles in
position
Moves organelles
Is involved in
cytoplasmic
streaming
Interacts with
Cytoskeleton has three components made
up of proteins.
Microfilaments
Cell motility
Determine cell
shape
Are made from the
protein actin
Non-covalent
interaction with
protein myosin
promote cell
motility, muscle
contraction
Intermediate filaments
Anchor cell
structures in place
Resist tension,
maintain rigidity
Diverse proteins:
some are keratins,
collagens
Structural functions
Intermediate Filaments
Microtubules
Forms rigid internal
skeleton
Act as a framework
for motor proteins
to move structures
in the cell
Move vesicles,
chromosomes
Made up of tubulin
proteins
Kinesinmotor protein that binds to vesicles
in the cell and walks them along the
microtubule