1. Section 3.2: Cytoskeleton and Nucleus
Cell Organelles
Section 3.2: Cytoskeleton and Nucleus
A Mitochondrion

2. Objectives SWBAT describe the internal structure of eukaryotic cells.
SWBAT visualize the structures and functions of organelles in plant and animal cells.

3. Vocabulary – Section 3.2
Cytoskeleton (microtubules, intermediate filaments, microfilaments)
Nucleus
Rough endoplasmic reticulum (rough ER)
Smooth endoplasmic reticulum (smooth ER)
Ribosome
Golgi apparatus
Vesicle
Mitochondrion (mitochondria is plural)
Vacuole
Lysosome
Centriole
Cell wall
Chloroplast

4. Animal Cell

5. Plant Cell

6. Cellular Structure Eukaryotic cell organization:
Surrounded by a protective membrane.
Containing membrane bound organelles, which perform specific cellular processes, divide certain molecules into compartments, and help to regulate the timing of key events.
Organelles and molecules are anchored to specific sites in the cell – based on the cell’s type.

7. Cellular Structure Each eukaryotic cell has a cytoskeleton.
Network of proteins that is constantly changing to meet the cell’s needs.
the proteins form long threads which “crisscross” the entire cell holding organelles in place.
If the cell membrane were “evaporated,” the cell would maintain shape through the cytoskeleton (for a short time).

8. Cytoskeleton photo: 750X magnification

9. Cytoskeleton Cytoskeleton is made up of three main types of fibers:
Microtubules – long hollow tubes giving cell its shape and acting as tracks for organelle movements.
Intermediate filaments – smaller than microtubules giving cell strength.
Microfilaments – tiny threads which enable cells to move and divide (during mitosis and meiosis).

10. Microtuble Network

11. Microfilament Bundles

12. The Nucleus
The storehouse for DNA (deoxyribonucleic acid) in your cells.
DNA contains the genes – which are instructions – for making proteins.
The Nucleus must:
Protect the DNA and
Make the DNA available for use at the proper time (DNA transcription).

13. Cell Nucleus

14. The Nucleus
The nucleus protects the cell’s DNA from molecules that might damage it.
At the same time, the nucleus makes the DNA available to the many proteins that are involved in turning genes on and off.
The nucleus is composed of the cell’s DNA enclosed in a nuclear envelope (a double membrane).

15. The Nucleus
The nuclear envelope is pierced with pores (nuclear pores) which allow large molecules to pass between the nucleus and cytoplasm.
RNA passes through the nuclear envelope between the nucleus and cytoplasm.
The nucleolus is also found in the nuclear envelope.
Its main purpose is producing the “subunits (the parts)” from which ribosomes are assembled.