1. CELL STRUCTURES Sources:
Campbell, N Biology Third Edition. Benjamin Cummings Publishing. United States.
Wallace, S Biology

2. The Cytoskeleton
The cytoskeleton (high voltage transmission electron microscope)
Microfilaments (very fine; 6 nm in diameter). mostly made up of protein actin. Have a variety of roles depending on the type of proteins they are associated with:
one is to provide support to the plasma membrane
form supportive network of microvilli (intestinal wall)
also involved in the pinching of the cell membrane during cell division

3. Intermediate filaments (diameter 7 nm): Role is poorly understood.
Found in epithelial cells, nerve cells, muscle cell fibers and blood cells.
Made up of the protein keratin.
Microtubules (diameter 22 nm):
Formed from the globular protein tubulin
form cilia, flagella, centrioles, basal bodies
Important in cell division where they take a spindle form.

4. The Endoplasmic Reticulum (ER)
Endoplasmic = inside the cytoplasm; Reticulum = network
Function
Plays a role in the cell’s synthetic ability: newly synthesized proteins, lipids and carbohydrates are transported within the endoplasmic reticulum’s lumen.

5. The ER ...
Structure:
The ER consists of membranous tubules and sacs called cisternae. Membranes separate the cytosol from the internal compartment of the lumen
Have the same phospholipid bilayer seen in the plasma membrane
The ER membrane is continuous with the outer of the two membranes of the nuclear envelope

6. The Rough Endoplasmic reticulum (RER)
Occurs in cells that manufacture proteins for secretion outside of the cell (i.e digestive enzymes and hormones)
The Smooth Endoplasmic reticulum (SER)
Abounds in cells that synthesize secrete, and store carbohydrates, steroids, lipids and other non-protein products.
Found in testis cells; oil glands; some hormone producing gland cells; intestinal cells, where they collect products of lipid digestion; in liver cells the SER is associated with glycogen, the animal storage carbohydrate (starch).

7. Ribosomes
Structure: Large molecular structures consisting of ribosomal rRNA sub-units and proteins.
Consists of 2 sub-units (large and small) which join together to form a functional ribosome only when they attach to mRNA
Ribosomes are constructed in the nucleolus from RNA
Are too large to be considered molecules. The ribsomal sub-units in prokaryotes are smaller and differ chemically.

8. Ribosomes...
Function: Where the cell assembles proteins following genetic (DNA) instructions. Ribosomes translate message from mRNA
There are two forms:
Polyribosomes or polysomes: Free
Bound ribosomes: Attached to the ER

9. Sometimes called Dyctiosomes in plant cells
The Golgi Apparatus
Sometimes called Dyctiosomes in plant cells
Structure (see diagram)
Component of the endomembrane system
Made up of flattened bag-like sacs called cisternae. Found near the nucleus. (cis phase = forming face; trans face = maturing phase)
Function
Manufacturing, warehousing, sorting, and shipping center of materials in the cell

10. Mitochondria Structure (see diagram) Have double membranes
Have their own circular DNA and ribosomes (make their own proteins)
Smaller than chloroplasts
develop from pre-existing mitochondria

11. Mitochondria... Function
ATP (adenosine tri-phosphate) generating molecules

12. Peroxisomes (Microbodies)
Structure:
Sacs bound by a single membrane
Function: (see transparency)
organelles found in nearly all eukaryotic cells that contain specialized enzymes for specific metabolic activities
All contain peroxide-producing oxidases (enzymes) that transfer H from various substrates to O producing H2O2