1. Lesson Overview
7.2 Cell Structure (PART 1)

2. THINK ABOUT IT
At first glance, a factory is a puzzling place, and the sheer diversity of activity can be confusing.
However, if you take your time and watch carefully, what might at first seem like chaos begins to make sense.
The same is true for the living cell.

3. Cell Organization
What is the role of the cell nucleus?

4. Cell Organization What is the role of the cell nucleus?
The nucleus contains nearly all the cell’s DNA and, with it, the coded
instructions for making proteins and other important molecules.

5. Cell Organization
The eukaryotic cell can be divided into two major parts: the nucleus and the cytoplasm.
The cytoplasm is the fluid portion of the cell outside the nucleus.
Prokaryotic cells have cytoplasm as well, even though they do not have a nucleus.

6. Cell Organization
Many cellular structures act as if they are specialized organs. These structures are known as organelles, literally “little organs.”
Understanding what each organelle does helps us to understand the cell as a whole.

7. Comparing the Cell to a Factory
The is much like a living version of a modern factory.
The specialized machines and assembly lines of the factory can be compared to the different of the cell.
Cells, like factories, and .

8. The Nucleus
In the same way that the controls a large factory, the nucleus is the of the cell.
The nucleus contains nearly all the cell’s and, with it, the and other important molecules.

9. The Nucleus
The is surrounded by a composed of two membranes.

10. The Nucleus
The nuclear envelope is dotted with thousands of , which allow material to move into and out of the nucleus.

11. The Nucleus
Like messages, instructions, and blueprints moving in and out of a main office, a steady stream of move through the nuclear pores to and from the rest of the cell.

12. The Nucleus
contain the that is passed from one generation of cells to the next.
Most of the time, the threadlike chromosomes are spread throughout the nucleus in the form of —a complex of DNA bound to proteins.

13. The Nucleus
When a cell divides, its and can be seen under a microscope.

14. The Nucleus
Most nuclei also contain a small, dense region known as the .
The nucleolus is where the begins.

15. Organelles That Store, Clean Up, and Support
What are the functions of vacuoles, lysosomes, and the cytoskeleton?

16. Organelles That Store, Clean Up, and Support
What are the functions of vacuoles, lysosomes, and the cytoskeleton?
Vacuoles
Lysosomes into small
molecules that can be used by the rest of the cell. They are also involved
in that have outlived their usefulness.
The cytoskeleton helps the cell and is also involved in
movement.

17. Vacuoles and Vesicles
Many cells contain large, saclike, membrane-enclosed structures called
that store materials such as water, salts, proteins, and
carbohydrates.

18. Vacuoles and Vesicles
In many plant cells, there is a single filled with liquid. The pressure of the central vacuole in these cells increases their rigidity, making it possible for plants to support heavy structures such as leaves and flowers.

19. Vacuoles and Vesicles
are also found in some unicellular organisms and in some animals.

20. Vacuoles and Vesicles
Nearly all eukaryotic cells contain smaller membrane-enclosed structures called . Vesicles are used to between cell organelles, as well as to and from the cell surface.

21. Lysosomes
are small organelles filled with enzymes that function as the cell’s cleanup crew. Lysosomes perform the vital function of that might otherwise accumulate and clutter up the cell.

22. Lysosomes
One function of lysosomes is the breakdown of into small molecules that can be used by the rest of the cell.

23. Lysosomes
Lysosomes are also involved in that have outlived their usefulness.
Biologists once thought that lysosomes were only found in animal cells, but it is now clear that lysosomes are also found in a few specialized types of plant cells as well.

24. The Cytoskeleton
Eukaryotic cells are given their shape and internal organization by a network of protein filaments known as the
Certain parts of the cytoskeleton also help to transport materials between different parts of the cell, much like conveyer belts that carry materials from one part of a factory to another.
Microfilaments and microtubules are two of the principal protein filaments that make up the cytoskeleton.

25. Microfilaments Microfilaments are threadlike structures called actin.
They form extensive networks in some cells and produce a that supports the cell.
Microfilaments .
Microfilament assembly and disassembly is responsible for the that allow cells, such as amoebas, to crawl along surfaces.

26. Microtubules
Microtubules are hollow structures made up of proteins known as .
They play critical roles in maintaining cell shape.
Microtubules are also important in cell division, where they form a structure known as , which helps to .

27. Microtubules
In animal cells, structures known as are also formed from tubulins.
Centrioles are located near the nucleus and
Centrioles are .

28. Microtubules
Microtubules help to build projections from the cell surface, which are known , that enable cells to swim rapidly through liquids.
Microtubules are arranged in a “9 + 2” pattern.
Small cross-bridges between the microtubules in these organelles use chemical energy to pull on, or slide along, the microtubules, allowing cells to