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Chapter 2

Chapter 2. Cells. Comparing Cells. Cells differ in size and shape depending on their function Ex: nerve cell needs to communicate between places, so it is a long cell Ex: a muscle cell can contract and change it’s shape Two cell types:

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Chapter 2

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  1. Chapter 2 Cells

  2. Comparing Cells • Cells differ in size and shape depending on their function • Ex: nerve cell needs to communicate between places, so it is a long cell • Ex: a muscle cell can contract and change it’s shape • Two cell types: • Prokaryotic – lack membrane-bound internal structures • Eukayrotic – contain membrane-bound internal structures

  3. Cell Organization Cell wall • Tough, rigid outer coverings that protect the cell and give it shape • Made of cellulose • Only in plants, algae, fungi and most bacteria • “frame of a house” • Cell Membrane • A protective layer around all cells • Inside the cell wall, if it is present • Allows food and gasses into the cell and waste products out of the cell • “the bouncer”

  4. Cell Structures • Cytoplasm • A gelatin-like substance inside the cell membrane • Medium for things to move about in the cell • Cytoskeleton • Scaffolding-like structure in cytoplasm which helps cell keep its shape • Organelles • Membrane bound structures inside eukaryotic cells that helps the cell perform life processes

  5. Cell Structures • Nucleus • Organelle that directs all cell activities • Contains instructions for everything a cell does (within the DNA) • “foreperson”

  6. Cell Structures • Chloroplasts • Organelles in plants and a few bacteria that help the organism make food • Photosynthesis occurs here • Mitochondria • Organelles in all eukaryotes that release the energy from food and turn it into something the organism can use • “powerhouse”

  7. Cell Structures • Ribosomes • Organelles that make proteins • Produced in the nucleus • Endoplasmic Reticulum (ER) • Series of folded membranes from the nucleus to the cell membrane • Moves materials around in a cell • Two types of ER • Rough – ribosomes are attached • Smooth – no ribosomes attached • Material movement and lipid processing

  8. Cell Structures • Golgi Bodies • Sort proteins and other cellular substances and package them into membrane-bound structures called vesicles • “post office” • Vacuoles • Organelles that serve as temporary storage for materials • Can be water, waste products, food, etc. • Vacuoles make up most of the volume of plant cells

  9. Cell Structures • Lysosomes • Organelles that contain digestive chemicals that help break down food molecules, cell wastes, and worn-out cell parts • “recycler”

  10. From Cell to Organism • Cell • Tissues • Groups of similar cells working together on one job • Ex: muscle tissue, nervous tissue • Organ • Different types of tissues working together • Ex: muscle, brain

  11. From Cell to Organism • Organ System • A group of organs working together on a particular function • Ex: muscular system, nervous system • Organism • All of organ systems working together to create a particular organism

  12. Review Questions • Explain the important role of the nucleus in the life of a cell. • Compare and contrast the energy processing organelles. • Why are digestive enzymes in a cell enclosed in a membrane-bound organelle? • How are cells, tissues, organs and organ systems related? • How is the cell of a one-celled organism different from the cells in many-celled organisms? • What are some differences between plant and animal cell? • List 3 organelles and give their functions.

  13. Early Microscopes • Dutch reading glass maker put two lenses at ends of a tube (1500s) • Larger image • Antonie van Leeuwenhoek (Dutch fabric merchant) • First simple microscope (p. 50 in book) • Could magnify up to 270 times

  14. Modern Microscopes • Use lenses to bend light • A simple microscope has one lens while a compound microscope (what we have here) has mulitple lenses • Ex: one lens at 10x – 10 times bigger • Two lenses at 10x – 100 times bigger • Stereomicroscopes have two eyepieces, which create a three-dimensional image

  15. Electron Microscopes • Use a magnetic field inside a vacuum to bend electronic beams • Scanning Electron Microscope (SEM) bounce electrons off the sample to create a 3-D image • Transmission Electron Microscope (TEM) send electrons through a sample to see internally • Either way, electons then end up on a screen to produce an image (kind of like older TVs)

  16. Cell Theory • 1665, Robert Hooke looked at cork under a microscope • Made of little boxes he named cells • 1830s, Matthias Schleiden studied plant parts • Concluded all plants are made of cells

  17. Cell Theory • Theodor Schwann looked at animal cells • Concluded all animals are made up of cells • Rudolf Virchow • Said that cells come from other cells that already exist

  18. Cell Theory • All organisms are made up of one or more cells • The cell is the basic unit of organization in organisms • All cells come from pre-existing cells

  19. Review Questions • Explain why the invention of the microscope was important in the study of cells. • What is stated in the cell theory? • What is the difference between a simple microscope and a compound microscope? • What was Virchow’s contribution to the cell theory? • How do electron microscopes work? • Why would it be better to look at living cells rather than dead cells?

  20. Cell Processes • Passive Transport – the movement of substances through a cell membrane without the use of energy • Diffusion or Osmosis • Active Transport – the movement of substances through the cell membrane using energy • Endocytosis & Exocytosis – vesicles transport large materials into (endocytosis) and out of (exocytosis) the cell

  21. Cell Processes • Photosynthesis • The process plants and other organisms use to convert sunlight energy into chemical energy or sugars to be used as food • Respiration • The process in which chemical reactions break down food molecules into simpler substances and release stored energy • Fermentation • Cells that do not have enough oxygen for respiration use this process to release some of the stored energy in glucose molecules

  22. Cell Processes • Cell Division – process where one cell splits into two cells • Mitosis – process in which the nucleus divides to form two identical nuclei • Four stages: Prophase, Metaphase, Anaphase, Telophase • Happens during growth of organism or during asexual reproduction • Meiosis – process in which the nucleus divides to form cells with half the genetic material of the original • Eight Stages: Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II • Happens when an organism produces gametes (sex cells) for sexual reproduction

  23. Review Questions • What is active transport? • What are the two main types of passive transport? • How do cells get large materials out? • What is photosynthesis? • What is respiration? • What is mitosis and when does it happen? • What is meiosis and when does it happen?

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