EPOB 1210 Lecture 13, 1996
THE CELL part 2

This has been the 1608th visit to this site since Sept. 24, 1996.

OUTLINE:
ENDOMEMBRANE SYSTEM

ENDOPLASMIC RETICULUM (=ER)
SMOOTH ER
ROUGH ER
GOLGI APPARATUS
LYSOSOME
VACUOLES
CENTRAL VACUOLE
MITOCHONDRIA
CHLOROPLASTS

Word Roots:
cist (G) = a box
ret (L) = a net
phago (G) = to eat
cyte (G) = a hollow place, cell

ENDOMEMBRANE SYSTEM:

1. Nuclear envelope
2. Endoplasmic Reticulum
3. Golgi Apparatus
4. Lysosomes
5. Vacuoles
6. (plasma membrane) not actually "endo" but part of the whole system nonetheless.

ENDOPLASMIC RETICULUM (=ER)

Most extensive part of Endomembrane system.
CISTERNAL space = separated from the cytosol and Continuous with nuclear membrane

(Fig. 7.11)

2 types of ER:

1) SMOOTH ER

Lacks Ribosomes

Functions:

1. Synthesizes lipids, phospholipids and steroids therefore important in cells that excrete these things

2. Detoxifies poisons esp. in liver, enzymes that add hydroxyl groups to drugs

2) ROUGH ER = rough because ribosomes in membrane.
Functions:

Makes secretory proteins
and new membrane Phospholipids and Proteins

Membrane destined for other parts of the cell pinch off in little sacs called transport VESICLES

one destination =

GOLGI APPARATUS = The major storage and processing center in Eukaryotic cells.

(FIG. 7.12)


CIS FACE accepts vesicles from ER
TRANS FACE vesicles pinch off for transport to other sites.

Enzymes in the Golgi modify products

Golgi can also synthesize new macromolecules.

e.g. products destined for secretion leave the trans face in vesicles that dock with the plasma membrane.

e.g.
LYSOSOME = contains hydrolytic enzymes to digest macromolecules for recycling
pH of 5 maintained in lysosomes for optimal enzyme activity.

(Fig. 7.14)

Other Functions of Lysosomes:
Phagocytosis = Engulfing of particles by plasma membrane forming a FOOD VACUOLE.

Especially important in PHAGOCYTES (Macrophages) and organisms like AMOEBA both of which engulf and digest bacteria.

(PLAY 31692)

VACUOLES = Membrane enclosed sacs (larger than vesicles)
e.g. CENTRAL VACUOLE in Plant Cells or food vacuole described above.
CENTRAL VACUOLE is enclosed by a membrane called the Tonoplast.
functions:
1. Increases membrane surface to cytoplasm volume
2. Storage (e.g. proteins in seeds)
3. Waste storage
4. Can absorb water & contribute to cell growth

Review relationship among endomembranes

(Fig. 7.16)

Other membrane bound organelles:

MITOCHONDRIA AND CHLOROPLASTS are semiautonomous organelles that grow and reproduce in the cytoplasm of Eukaryotic cells.

Have their own internal membranes, DNA and ribosomes.

They are thought to have once been free living bacteria that were engulfed by an ancient ancestor of the modern day Eukaryotes

(see pgs. 518 - 520 and Fig. 26.1)

The MITOCHONDRION
2 membranes, INNER and OUTER
Inner membrane is folded into CRISTAE enclosing the MATRIX. The space betweeen the inner and outer membranes is called the intermembrane space.

(Fig. 7.18)

The CHOROPLAST
has inner and outer membranes which enclose the STROMA in which are THYLAKOID sacs that are stacked in stacks call the GRANA. Each stack (a granum) is connected by membrane channels to the other grana of the chloroplast.
(Fig. 7.19)