Read Chapter 4 (all of it) you have a test soon!

What is the endomembrane system?
◦ A network of membranous organelles that partition
the cytoplasm of eukaryotic cells into functional
compartments. Some organelles are structurally
connected to each other (Nucleus to Rough ER and
Smooth ER), whereas others are structurally
separated but are functionally connected by the
traffic of membranous vesicles that travel between
them (ER to Golgi to Lysosomes/Vesicles).

What organelles are involved?
◦ Nucleus, ER, Golgi Apparatus, Lysosomes, &
Vesicles

Explain the difference between the structural
and functional connections within the
endomembrane system.
◦ If organelles are not structurally connected then a
transport vesicle is required to move the contents
of one organelle to the next for the contents to be
further processed. Each organelle plays a role in
modify the product.
◦ Connections – physical or by vesicle – allow the cell
to be efficient in producing cell products either for
use in the cell or for export out of the cell.
Fig. 6-16-3
Nucleus
Rough ER
Smooth ER
cis Golgi
trans Golgi
Plasma
membrane

What surrounds a plant cell?
◦ Plant cells have cell walls. The cell walls may have
multiple layers:
 Primary cell wall: relatively thin and flexible
 Middle lamella: thin layer between primary walls of
adjacent cells
 Secondary cell wall (in some cells): added between the
plasma membrane and the primary cell wall

How do plant cells communicate (cell to cell)?
◦ Plasmodesmata are channels between adjacent plant
cells that allow for cell to cell communication
Fig. 6-28
Secondary
cell wall
Primary
cell wall
Middle
lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata

Animals cells don’t have cells walls – so what
do they have outside their cell membranes?
◦ Animal cells lack cell walls but are covered by an
elaborate extracellular matrix (ECM)
◦ The ECM is made up of glycoproteins such as
collagen, proteoglycans, and fibronectin
◦ ECM proteins bind to receptor proteins in the
plasma membrane called integrins
◦ Functions of the ECM include: Support, Adhesion,
Movement, and Regulation
Fig. 6-30
Collagen
Proteoglycan
complex
EXTRACELLULAR FLUID
Polysaccharide
molecule
Carbohydrates
Fibronectin
Core
protei
n
Integrins
Proteoglycan
molecule
Plasma
membran
e
Proteoglycan complex
Microfilaments
CYTOPLASM

How do animal cells communicate (cell to
cell) and stick together?
◦ At tight junctions, membranes of neighboring cells are
pressed together, preventing leakage of extracellular fluid
◦ Desmosomes (anchoring junctions) fasten cells together
into strong sheets
◦ Gap junctions (communicating junctions) provide
cytoplasmic channels between adjacent cells
Fig. 6-32
Tight junctions prevent
fluid from moving
across a layer of cells
Tight
junction
0.5 µm
Tight junction
Intermediate
filaments
Desmosome
Gap
junctions
Space
between
cells
Plasma membranes
of adjacent cells
Desmosome
1
µm
Extracellular
matrix
Gap junction
0.1
µm

Which organelles produce cell products?
◦ Nucleus, Ribosomes, ER, Golgi Apparatus

Which organelles breakdown materials?
◦ Lysosomes, Vacuoles, Peroxisomes

Which organelles produce energy?
◦ Chloroplast & Mitochondria

Which organelles are involved in support,
movement, and communication?
◦ Cytoskeleton, Cell Walls, Extracellular Matrix, & Cell
Junctions
Fig. 6-UN1a
Structure
Cell Component
Concept 6.3
The eukaryotic cell’s
genetic
instructions are housed in
the nucleus and carried out
by the ribosomes
Surrounded by nuclear
envelope (double
membrane)
perforated by nuclear pores.
The nuclear envelope is
continuous with the
endoplasmic reticulum (ER).
Nucleus
Function
Houses chromosomes, made of
chromatin (DNA, the genetic
material, and proteins); contains
nucleoli, where ribosomal
subunits are made. Pores
regulate entry and exit os
materials.
(ER)
Ribosome
Two subunits made of riboProtein synthesis
somal RNA and proteins; can be
free in cytosol or bound to ER
Fig. 6-UN1b
Cell Component
Concept 6.4
The endomembrane system
regulates protein traffic and
performs metabolic
functions
in the cell
Structure
Extensive network of
membrane-bound tubules
(Nuclear and
envelope)
sacs; membrane separates
lumen from cytosol;
continuous with
the nuclear envelope.
Endoplasmic reticulum
Golgi apparatus
Lysosome
Vacuole
Stacks of flattened
membranous
sacs; has polarity
(cis and trans
faces)
Membranous sac of
hydrolytic
enzymes (in animal cells)
Large membranebounded
vesicle in plants
Function
Smooth ER: synthesis of
lipids, metabolism of carbohydrates, Ca2+ storage,
detoxification of drugs and poisons
Rough ER: Aids in sythesis of
secretory and other proteins
from bound ribosomes; adds
carbohydrates to glycoproteins;
produces new membrane
Modification of proteins,
carbohydrates on proteins, and
phospholipids; synthesis of many
polysaccharides; sorting of
Golgi products, which are then
released in vesicles.
Breakdown of ingested substances cell macromolecules,
and damaged organelles for
recycling
Digestion, storage, waste
disposal, water balance, cell
growth, and protection
Fig. 6-UN1c
Cell Component
Concept
6.5
Mitochondria and chloro-
Mitochondrion
plasts change energy from
one form to another
Structure
Bounded by double
membrane;
inner membrane has
infoldings (cristae)
Function
Cellular respiration
Chloroplast
Typically two membranes
around fluid stroma, which
contains membranous
thylakoids
stacked into grana (in plants)
Photosynthesis
Peroxisome
Specialized metabolic
compartment bounded by a
single membrane
Contains enzymes that transfer
hydrogen to water, producing
hydrogen peroxide (H2O2) as a
by-product, which is converted
to water by other enzymes
in the peroxisome
Fig. 6-9a
ENDOPLASMIC RETICULUM (ER)
Flagellum
Rough ER
Smooth ER
Nuclear
envelope
NUCLEUS
Nucleolus
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome
Fig. 6-9b
NUCLEUS
Nuclear envelope
Nucleolus
Chromatin
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Ribosomes
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
Cell wall
Wall of adjacent cell
Plasmodesmata
CYTOSKELETON