1. 4.5-4.19 ORGANELLES OF THE ENDOMEMBRANE SYSTEM
4.5: The nucleus
The nucleus is the cell's genetic control center
The nucleus contains the cell's DNA
Controls cellular activities by directing protein synthesis
Forms long fibers of chromatin (loose, threadlike form of DNA) that make up chromosomes (made of scrunched up DNA and proteins and are ONLY seen during active cell division)

2. The nucleus is separated from the cytoplasm by the nuclear envelope—which is a double membrane
Pores in the envelope control flow of materials in and out
Ribosomes are synthesized in the nucleolus

3. Main functions of the Nucleus
Contain DNA and pass it to daughter cells during cell division
Build ribosomes (occurs in the nucleolus)
Copy DNA instructions to mRNA (messenger RNA)
mRNA leaves the nucleus through nuclear pores and then travels to ribosomes where it is translated into the amino acid sequences of proteins

4. LE 4-5 Nucleus Chromatin Two membranes of nuclear envelope Nucleolus
Pore
Rough
endoplasmic
reticulum
Ribosomes

5. 4.6 Overview of Organelles
Many cell organelles are connected through the endomembrane system
The endomembrane system is a collection of membranous organelles. The system is aided by vesicles (sacs made of membane that transfer membrane segments).
Divide the cell into compartments
Work together in the synthesis, storage, and export of molecules
Prime example: Endoplasmic reticulum (ER)
A continuous network of flattened sacs and tubes

6. There are two regions of ER: rough and smooth They differ in function, but the membranes that form them are continuous. The rough ER is also continuous with the nuclear envelope.

7. 4.7 Smooth ER
Smooth endoplasmic reticulum has a variety of functions; most of its activity results from enzymes embedded in its membrane
Smooth endoplasmic reticulum (smooth ER) lacks attached ribosomes
Synthesizes lipids—including fatty acids, phospholipids, and steroids
Processes materials such as toxins and drugs in liver cells
Stores and releases calcium ions in muscle cells, regulating muscle contractions

8. LE 4-7 Smooth ER Rough ER Nuclear envelope Ribosomes Smooth ER
TEM 45,000

9. Rough endoplasmic reticulum makes more membrane and modifies proteins
4.8 Rough ER
Rough endoplasmic reticulum makes more membrane and modifies proteins
Rough endoplasmic reticulum (rough ER) is studded with ribosomes (looks “rough” in electron micrographs)
Manufactures more membrane
Modifies and packages proteins that will be
Transported to other organelles
Secreted by the cell (like insulin)
See page 59

10. Transport vesicle buds off Secretary Ribosome (glyco-) protein
inside trans-
port vesicle
Ribosome
Sugar
chain
Glycoprotein
Polypeptide
Rough ER

11. 4.9 The Golgi apparatus finishes, sorts, and ships cell products
The Golgi apparatus consists of stacks of flattened membranous sacs
Receives and modifies substances manufactured by ER
Ships modified products to other organelles or the cell surface

12. LE 4-9 Golgi apparatus Golgi apparatus “Receiving” side of
Transport
vesicle
from ER
New vesicle
forming
“Shipping”
side of Golgi
apparatus
TEM 130,000 
Transport
vesicle from
the Golgi

13. Animation: Lysosome Formation
4.10 Lysosomes are digestive compartments within a cell
Lysosomes are sacs of enzymes that form from the Golgi apparatus
Function in digestion within a cell
Destroy bacteria that have been ingested into white blood cells
Recycle damaged organelles
Animation: Lysosome Formation

14. LE 4-10a Rough ER Transport vesicle (containing inactive
hydrolytic enzymes)
Plasma
membrane
Golgi
apparatus
Engulfment
of particle
Lysosome
engulfing
damaged
organelle
“Food”
Lysosomes
Food
vacuole
Digestion

15. 4.11 Abnormal lysosomes can cause fatal diseases
CONNECTION
4.11 Abnormal lysosomes can cause fatal diseases
Lysosomal storage diseases
Result from an inherited lack of one or more lysosomal enzymes
Seriously interfere with various cellular functions

16. Video: Paramecium Vacuole
4.12 Vacuoles function in the general maintenance of the cell
Plant cells contain a large central vacuole
Has lysosomal and storage functions
Some protists have contractile vacuoles
Pump excess water out of cell
Video: Paramecium Vacuole
Video: Chlamydomonas

17. Animation: Endomembrane System
4.13 A review of the endomembrane system
The various organelles of the endomembrane system are interconnected structurally and functionally
Animation: Endomembrane System

18. Transport vesicle from Golgi to plasma membrane Rough ER
from ER to Golgi
Transport vesicle from
Golgi to plasma membrane
Rough ER
Plasma
membrane
Nucleus
Vacuole
Lysosome
Smooth ER
Nuclear envelope
Golgi apparatus

19. ENERGY-CONVERTING ORGANELLES
4.14 Chloroplasts convert solar energy to chemical energy
Chloroplasts are found in plants and some protists
Are the site of photosynthesis
Have a complex membranous structure for capturing and converting light energy

20. LE 4-14 Stroma Chloroplast Inner and outer membranes Granum TEM 9,750
Intermembrane
space

21. 4.15 Mitochondria harvest chemical energy from food
Mitochondria are found in nearly all eukaryotic cells
Divided into two membranous compartments
Intermembrane space
Second compartment enclosed by inner membrane
Contains fluid mitochondrial matrix
Membrane folded into cristae

22. Carry out cellular respiration
Convert the chemical energy in food to ATP for cellular work

23. LE 4-15 Mitochondrion Outer membrane Intermembrane space Inner
Cristae
TEM 44,880
Matrix

24. THE CYTOSKELETON AND RELATED STRUCTURES
4.16 The cell's internal skeleton helps organize its structure and activities
The cytoskeleton is network of three types of protein fibers
Microfilaments
Rods of globular proteins
Enable cells to change shape and move

25. Intermediate filaments
Ropes of fibrous proteins
Reinforce the cell and anchor certain organelles
Microtubules
Hollow tubes of globular proteins
Give the cell rigidity
Anchor organelles and act as tracks for organelle movement

26. 4.17 Cilia and flagella move when microtubules bend
Eukaryotic cilia and flagella are locomotor appendages that protrude from certain cells
Move whole cells or materials across the cell surface

27. The structure and mechanism of cilia and flagella are similar
Microtubules wrapped in an extension of the plasma membrane
9 + 2 arrangement
Extend into basal bodies
Movement of dynein arms produces microtubule bending

28. CELL SURFACES AND JUNCTIONS
4.18 Cell surfaces protect, support, and join cells
Cells interact with their environments and each other via their surfaces
Many cells are protected by more than the plasma membrane

29. Plant cell walls
Made largely of cellulose
Provide protection and support
Connect by plasmodesmata, channels through the wall

30. Walls of two adjacent plant cells Vacuole Plasmodesmata Layers
LE 4-18a
Walls
of two
adjacent
plant cells
Vacuole
Plasmodesmata
Layers
of one plant
cell wall
Cytoplasm
Plasma membrane

31. Connect by cell junctions
Animal cells
Embedded in an extracellular matrix that binds cells together in tissues
Connect by cell junctions
Tight junctions bind cells into leakproof sheets
Anchoring junctions link cells into strong tissues
Gap junctions allow substances to flow from cell to cell

32. LE 4-18b
Tight junctions
Anchoring junction
Gap junctions
Extracellular matrix
Space between cells
Plasma membranes of adjacent cells

33. FUNCTIONAL CATEGORIES OF ORGANELLES
4.19 Eukaryotic organelles comprise four functional categories
Eukaryotic organelles fall into four functional categories that work together to produce the cell's emergent properties
Manufacturing
Breakdown
Energy processing
Support, movement, and communication between cells