Cells – The Units of Life

1. Cells – The Units of Life 7th Grade Science (Glencoe Science)

2. Starting With… Vocabulary words

3. Vocabulary Words • Bacteria – smallest organisms on Earth, each of which is made up of only one cell (the only cells that do not have organelles). • Cell membrane – flexible structure that holds a cell together, forms a boundary between the cell and its environment, and helps control what enters and leaves the cell. • Cell wall – structure of plants, algae, fungi, and many types of bacteria that supports and protects the cell membrane. • Cytoplasm – gelatin-like substance inside the cell membrane that contains water, chemicals, and cell parts.

4. Cont. • Organelles – specialized cell parts that perform a cell’s activities. • Nucleus – cell organelle that contains the hereditary material (controls most of the cell’s activities). • Vacuole – balloon-like cell organelle in the cytoplasm that can store food, water, and other substances. • Mitochondria – cell organelles where cellular respiration takes place. • Photosynthesis – process by which plants, algae, and many types of bacteria make their own food. • Chloroplast – green organelle in a plant’s leaf cells where most photosynthesis takes place.

5. Last Page of Vocab. • Tissue – group of similar cells that all do the same work. • Organ – structure made of two or more different tissue types that work. • Organ system – group of organs that work together to perform a certain job.

6. Section 1 The World of Cells

7. Importance of Cells • A cell is the smallest unit of life in all living things. • Cells are organized structures that help carry on the activities of life, such as the breakdown of food, movement, growth, and reproduction. • Different cells have different jobs. • Your body contains more than 10 trillion cells!

8. Observing Cells • Cells were not observed until microscopes were invented. • Robert Hooke observed tiny, boxlike things in a thin slice of cork using a microscope in 1665. They reminded him of the small, boxlike rooms (called cells) where monks lived.

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

10. The Microscopic Cell • The smallest organisms on Earth are bacteria, which are one-celled organisms.

11. microscopes • The microscope used in most classrooms is called a compound light microscope – light passes through the object you are looking at and then through two or more lenses. • The number on each lens that is followed by an X is the power. • The magnification of a microscope is found by multiplying the power of the eyepiece and the objective lens.

12. Cell = Bakery • A cell can be compared to a bakery.

13. Bakery Cell

14. Cell Bakery

15. Animal Cell Mitochondrion Cytoplasm Vacuole Nucleus (also contains the chromosomes) Cell membrane

16. Plant Cell Vacuole Cytoplasm Chloroplast Cell membrane Nucleus (also contains the chromosomes) Mitochondrion Cell wall

17. Energy and the Cell • Cells (besides bacteria) have organelles called mitochondria. • An important process called cellular respiration takes place inside a mitochondrion. • Cellular respiration is a series of chemical reactions in which energy stored in food is converted to a form of energy. (This energy is released as food and oxygen. Waste products of this process are carbon dioxide and water.) • All cells with mitochondria use the energy from cellular respiration to do all of their work.

18. Photosynthesis • Plants, algae, and many types of bacteria make food through a process called photosynthesis. • Chloroplasts (usually found in the leaf cells) capture light energy and combine carbon dioxide from the air with water to make food. • The captured light energy is passed to other organisms when they eat organisms that carry on photosynthesis.

19. Section 2 The Different Jobs of Cells

20. Special Cells for Special Jobs • Different kinds of specialized cells do different jobs to perform the life activities of a many celled organism.

21. Different Cells Found in Humans • Fat Cells Fat cells can store so much fat that the nucleus gets pushed against the cell membrane. • Skin Cells Skin cells are mostly flat and close together. They form a protective layer for your body. • Bone Cells Bone cells are surrounded by a hard substance made of calcium and phosphorous. • Nerve Cells Nerve cells are long and have many branches. This allows them to receive and deliver messages quickly. • Muscle cells Muscle cells are usually long and have many fibers that can contract and relax.

22. Different Types of Plant Cells • Stem Cells • Many of the cells in stems are long and tube-shaped. They move water and other materials throughout the plant. • Leaf Cells • Some leaf cells are brick shaped and contain many chloroplasts. • Root Cells • Most root cells are block shaped and do not contain chloroplasts.

23. Cell Organization • Cells are organized into systems that perform functions that keep the organism healthy and alive.

24. Levels of Organization Simple Cell Tissue Organ Organ System Organism

25. Are you ready??? Questions

26. Section 1 • How many cells does each bacterium have? • Which important chemical determines the traits of an organism? • What are the three main ideas of cell theory? • Why is the nucleus so important to the living cell? • How do cells get the energy they need to carry on their activities? • What is the purpose of a cell membrane?

27. Section 2 • What do long, tube like cells do in plants? • Which term means “two or more tissue types that work together?” • Describe three types of cells found in the human body. • Compare and contrast the cells found in a plant’s roots, stems, and leaves. • What is the difference between a cell and a tissue? What is the difference between a tissue and an organ? • Give an example of a human organ system, and name some of the organs in that system.

28. Checking Concepts • What controls what enters and leaves the cell? • What is found inside the nucleus of the cell? • What is the gelatin like substance in a cell that contains water and chemicals? • True or false: The stomach is an organ. • What does photosynthesis make for a plant? • What does DNA do? • True or false: Your blood is a tissue. • Name an organ system. • What cell structure helps support plants? • What is an example of a one-celled organism?

29. That’s all for now! Tune in for the next chapter… Bacteria!