1. Chapter: Cells—The Units of Life
Table of Contents
Chapter: Cells—The Units of Life
Section 1: The World of Cells
Section 2: The Different Jobs of Cells

2. Importance of Cells The World of Cells 1
A cell is the smallest unit of life in all living things.
Cells are important because they are organized structures that help living
things carry on the activities of life.
Different cells have different jobs in living things.

3. Cell Theory The World of Cells 1
The three main ideas of the cell theory are:
1. All living things are made of one or
more cells.
2. The cell is the basic unit of life in which
the activities of life occur.
3. All cells come from cells that already
exist.

4. The Microscopic Cell The World of Cells 1
The smallest organisms on Earth are bacteria.
They are made up of only one cell.

5. The Microscopic Cell The World of Cells 1
Larger organisms are made many cells.
These cells work together to complete all of the organism's life activities.
Your body contains more than 10 trillion (10,000,000,000,000) cells.

6. What are cells made of? The World of Cells 1
As small as cells are, they are made of even smaller parts, each doing a different job.

7. The World of Cells 1
What are cells made of?

8. Outside the Cell The World of Cells 1
The cell membrane is a flexible structure that holds the cell together.
The cell membrane forms a boundary between the cell and its environment.

9. Outside the Cell The World of Cells 1
Some cells also have a structure outside the cell membrane called a cell wall.
The cell wall helps support and protect these cells.

10. Inside the Cell The World of Cells 1
The inside of a cell is filled with a gelatin like substance called cytoplasm (SI tuh pla zum).
Approximately two-thirds of the cytoplasm is water, but it also contains many chemicals that are needed by the cell.

11. Organelles The World of Cells 1
Except for bacterial cells, cells contain organelles (or guh NELZ).
These specialized cell parts can move around in the cytoplasm and perform activities that are necessary for life.

12. The World of Cells 1
Organelles

13. The Nucleus The World of Cells 1
In the cells of organisms except bacteria, the hereditary material is in an organelle called the nucleus (NEW klee us).

14. The Nucleus The World of Cells 1
Inside the nucleus are chromosomes (KROH muh zohmz).
Chromosomes contain an important chemical called DNA. It determines which traits an organism will have.

15. Storage The World of Cells 1
In cells, food, water, and other substances are stored in balloon like organelles in the cytoplasm called vacuoles (VA kyuh wohlz).
Some vacuoles store wastes until the cell is ready to get rid of them.

16. Energy and the Cell The World of Cells 1
Cells, except bacteria, have organelles called mitochondria (mi tuh KAHN dree uh).
An important process called cellular respiration takes place inside a mitochondrion.

17. Energy and the Cell The World of Cells 1
Cellular respiration is a series of chemical reactions in which energy stored in food is converted to a form of energy that the cell can use.

18. Nature's Solar Energy Factories
The World of Cells 1
Nature's Solar Energy Factories
Animals obtain food from their surroundings.
Plants, algae, and many types of bacteria make food through a process called photosynthesis (foh toh SIHN thuh sus).

19. Nature's Solar Energy Factories
The World of Cells 1
Nature's Solar Energy Factories
Most photosynthesis in plants occurs in leaf cells.
Inside these cells are green organelles called chloroplasts (KLOR uh plats).

20. Nature's Solar Energy Factories
The World of Cells 1
Nature's Solar Energy Factories
During plant photosynthesis chloroplasts capture light energy and combine carbon dioxide from the air with water to make food.
As the plant needs energy, its mitochondria release the food's energy.

21. Diffusion and Osmosis
Diffusion is the tendency of a substance to move from an area of higher concentration to an area of lower concentration. Ex: the iodine moved from outside of the baggy to inside the baggy in the activity “Moving in and Out of Cells”.
Osmosis is the diffusion of water through a membrane such as the cell membrane in order to maintain a balance of water inside and outside of the cell. Ex: the raisin activity.

22. Special Cells for Special Jobs
The Different Jobs of Cells 2
Special Cells for Special Jobs
Cells that make up many-celled organisms, like you, are specialized.
Different kinds of specialized cells work as a team to perform the activities of a many-celled organism.

23. Types of Human Cells The Different Jobs of Cells 2
Your body is made up of many types of specialized cells.
A cell's shape and size can be related to its function.

24. Types of Plant Cells The Different Jobs of Cells 2
Plants also are made of several different cell types.
Plants have different types of cells in their leaves, roots, and stems.

25. Types of Plant Cells The Different Jobs of Cells 2
Some cells in plant stems are long and tubelike. Together they form a system through which water, food, and other materials move in the plant.
Other cells are smaller or thicker. They provide strength to the stems.

26. Cell Organization The Different Jobs of Cells 2
Many-celled organisms are not just mixed-up collections of different types of cells.
Cells are organized into systems that, together, perform functions that keep the organism healthy and alive.

27. Tissues and Organs The Different Jobs of Cells Blood is a Tissue 2
Cells that are alike are organized into tissue (TIH shewz).
Blood is a Tissue
Tissues are groups of similar cells that all do the same sort of work.

28. Tissues and Organs The Different Jobs of Cells 2
Different types of tissues working together can form a structure called an organ (OR gun).
The stomach is an organ that includes muscle tissue, nerve tissue, and blood tissue.
Other human organs include the heart and the kidneys.

29. Organs Systems The Different Jobs of Cells 2
A group of organs that work together to do a certain job is called an organ system.
Organ systems found in your body include the respiratory system, the circulatory system, the reproductive system, and the nervous system.
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30. Organs Systems The Different Jobs of Cells 2
Organ systems also work together.
For example, the muscular system has more than 600 muscles that are attached to bones.
The contracting cells of muscle tissue cause your bones, which are part of the skeletal system, to move.