Cell Structure and Function

1. Cell Structure and Function Chapter 7 Biology Miller • Levine

2. The Scientists… • Robert Hooke (1665) • Viewed cork under a microscope • Called the chambers he saw “cells” • Anton van Leeuwenhoek (1674) • First to see living organisms in a drop of water

3. The Scientists… • Matthias Schleiden (1838) • All plants are made of cells • Theodor Schwann (1839) • All animals are made of cells • Rudolf Virchow (1855) • All cells come from preexisting cells

4. The Cell Theory • All living things are composed of cells • Cells are the basic units of structure and function in living things • New cells are produced from existing cells

5. Unicellular vs. Multicellular • Unicellular – single-celled organism • Multicellular – many-celled organism • Cell specialization – cells are specialized to perform certain functions • Cells → Tissues → Organs → Organ systems → Organism

6. Prokaryotes vs. Eukaryotes • Prokaryotes • Have a cell membrane & cytoplasm, but do not have a nucleus • Ex. Bacteria such as E.coli • Eukaryotes • Have a nucleus, cell membrane, cytoplasm & organelles • Ex. Plants, Animals, Fungi

7. Prokaryotes vs. Eukaryotes

8. Basic Cell Structures • Cell membrane – thin, flexible barrier around the cell; protects the cell • Present in all cells • Cytoplasm – material inside the cell membrane (not including the nucleus) • Prokaryotes & Eukaryotes

9. Cell Wall • Found in many organisms, including plants, algae, fungi and nearly all prokaryotes • Not found in animal cells • Lies outside the cell membrane • Main function is to provide support & protection for the cell

10. Nucleus • Almost all eukaryotic cells, including plants and animals have a nucleus • Prokaryotes do not have a nucleus • Controls most cell process and contains the DNA

11. Nucleolus and Nuclear Envelope • Nucleolus: • Inside the nucleus • Where ribosomes are made • Nuclear Envelope: • Double-membrane layer around the nucleus • Allows material to move into and out of the nucleus

12. Nucleus

13. Cytoskeleton • Found in all eukaryotic cells • Not found in prokaryotes • A network of protein filaments that helps the cell maintain its shape • It also is involved in cell movement

14. Ribosomes • Found in all cells • Main function is to make proteins • Can be found floating in the cytosol or attached to endoplasmic reticulum

15. Endoplasmic Reticulum (ER) • Found only in eukaryotic cells • Where components of the cell membrane are assembled • Two kinds: Smooth ER & Rough ER • Smooth ER: no ribosomes; makes lipids • Rough ER: has ribosomes; involved in making proteins

16. Endoplasmic Reticulum

17. Golgi Apparatus • Found only in eukaryotic cells • Enzymes attach carbohydrates & lipids to proteins • Send proteins to their final destination

18. Lysosomes • Found in animal cells only • Break down lipids, carbohydrates & proteins from food into particles that can be used by the cell • Also break down “dead” organelles

19. Vacuoles • Not found in prokaryotes • Animal cells have small or no vacuoles • Plant cells have a large central vacuole • Store materials such as water, salts, proteins & carbohydrates

20. Chloroplasts • Found in all plant cells • Some prokaryotes have them, but most do not • Use the energy from sunlight to make energy-rich food molecules during photosynthesis

21. Chloroplasts

22. Mitochondria • Found in eukaryotic cells only • Release energy from stored food molecules

23. Cell Membrane • Regulates what enters and leaves the cell (selectively permeable) • Provides protection and support • Lipid bilayer – two layers of lipids • Proteins run through the layers • Carbohydrates are attached to some of the proteins • Fluid Mosaic Model

24. Cell Membrane

25. Diffusion • Molecules move from an area of high concentration to an area of low concentration • Movement continues until equilibrium is reached • Many substances move across the membrane by diffusion • Does not require energy (passive transport)

26. Diffusion

27. Osmosis • The diffusion of water • Isotonic – equal concentration • Nothing happens • Hypertonic – higher concentration • Water moves out of the cell • Hypotonic – lower concentration • Water moves into the cell • No energy is required

28. Effects of Osmosis on Cells

29. Osmotic Pressure • In pure water, an animal cell would burst • Plant cells are protected by their cell wall • Some freshwater organism have special structures like contractile vacuoles to get rid of extra water

30. Facilitated Diffusion • Some molecules cannot cross the membrane without help • Some of the proteins in the membrane form protein channels • Materials still move from higher to lower concentrations • No energy is required

31. Facilitated Diffusion

32. Active Transport • Materials move from lower concentration to higher concentration • Requires an input of energy • Works kind of like a pump

33. Transport of Large Amounts • Endocytosis – movement into the cell • Phagocytosis – “cell eating” – solid particles • Pinocytosis – “cell drinking” – particles dissolved in water • Exocytosis – movement out of the cell

34. Phagocytosis

35. Pinocytosis