Exploring Cells: Origins, Structures, and Functions

1. Chapter7 Looking at cells

2. Where does cork come from? • The bark of an oak tree that grows in Spain and Portugal • The bark is dead • All that is left are the cell walls enclosing air

3. Microscopes reveal cell structure • Robert Hooke , an English scientist, invented the microscope in the 1600’s to view cork • He named the “little boxes” he saw, “cells”

4. Anton van Leeuwenhoek • 10 years after Hooke’s findings • Used a microscope to view pond water • He named the single-celled organisms he discovered “animalcules”

5. The Cell Theory • All living things are made of cells • Cells are the basic units of structure and function in organisms • All cells arise from existing cells

6. Measuring the size of cell structures • Measurements are in metric units • International System of Measurements (SI) • Based on powers of 10 • Micrometers are one-millionth of a meter ( the size of a bacterial cell)

7. Cells must be small • Lower surface area to volume ratio = inability to move substances across the membrane in large enough numbers • Higher surface area to volume ratio = greater ability to exchange substances Small is good! Big is bad!

8. Common features of all cells • Cell membrane • Cytoplasm • Cytoskeleton • Ribosomes • Genetic material

9. Prokaryotes do not contain internal compartments • No nucleus • Smaller • Ex: bacteria

10. Characteristics of bacteria • Prokaryotes • All have a cell wall surrounding the cell membrane • Some have flagella for movement • DNA is circular instead of linear • Some have a capsule for clinging

11. Eukaryotic cells are organized • Have a nucleus • Have other membrane enclosed organelles • Some have flagella or cilia for movement

12. Eukaryotes • Larger • More complex • Many are highly specialized • Plants, animals, fungi, and many protists

13. Cell Organization • Two divisions: • Nucleus- eukaryotes only • Cytoplasm- fluid portion of the cell outside the nucleus • Eukaryotes and prokaryotes

14. Organelles • Specialized structures • “Little organs”

15. Nucleus • Controls cell functions • Surrounded by a double membrane with nuclear pores • Contains DNA wound around proteins • Wind up into chromosomes before division takes place

16. Nucleus • Nucleolus- where ribosomes are made • Nuclear pores- allow materials in and out

17. Vacuoles • Large, saclike, membrane-enclosed structures that store materials such as water, salts, proteins, and carbohydrates

18. Vacuoles • Plants- large central vacuole, helps keep leaves and flowers rigid • Found in some unicellular organisms and animals • Contractile vacuole in paramecium

19. Vesicles • In almost all eukaryotic cells • Used for storage and movement

20. Lysosomes • Small organelle filled with enzymes • Digest old organelles, cellular “junk,” lipids, proteins, and carbohydrates • Type of vesicle, found in animal and some plant cells

21. Ribosomes • Made of RNA and protein • Produce proteins • Found in the cytoplasm (free) and rough ER (attached)

22. Endoplasmic Reticulum (ER) • A system of internal membranes that moves proteins and other substances through the cell • Rough ER- has ribosomes on the surface that create exported proteins • Smooth ER- no ribosomes, makes lipids for the cell membrane • Detoxifies drugs

23. Golgi Apparatus • Stack of flattened sacs • Modifies, sorts, and packages proteins made from the rough ER • Sent into or out of the cell

24. Sources of Energy • Mitochondria- animal and plant cells • Chloroplasts- plant cells

25. Chloroplasts • Converts sunlight into food energy in a process called photosynthesis • Double membrane • Contains a green pigment called chlorophyll

26. Mitochondria • In eukaryotic cells • Power plant of the cells • Converts food energy into smaller units the cell can more easily use • Double membrane

27. Mitochondria • Inherited only from your mother • A way to trace the maternal lines of animals

28. Endosymbiotic Theory • Chloroplasts and mitochondria have their own DNA and double membranes • Theory states: • These may have been independent organisms at one time • Create their own energy • May have been beneficial once absorbed and found to be beneficial

29. Unique features of plant cells • Cell wall -surrounds the cell membrane, supports and protects the cell • Chloroplasts- green structures that absorb sunlight and produce glucose • Central vacuole- stores water and other substances, when full makes a cell rigid

30. Cytoskeleton • Network of protein filaments • Gives cells their shape and internal organization • Helps to transport materials inside the cell • Protein filaments • Microtubules • Microfilaments

31. Microfilaments • Threadlike structures made of protein called actin • Make up a tough flexible framework that helps support the cell • Help cells move • Amoebas- assemble and disassemble to help them move

32. Microtubules • Hollow structures • Made of protein tubulin • Maintains cell shape • Centrioles • Makes spindle during mitosis to separate chromosomes

33. Microtubules • Make up cilia and flagella • Used for swimming • Arranged in a 9+2 pattern • Small bridges between aid in movement

34. Cell Boundries • Cell wall • Cell membrane

35. Cell Wall • Prokaryotes, plants, algae, fungi • Animal cells do not • Outside the cell membrane • Strong supporting layer • Porous- allows water, carbon dioxide and oxygen to pass through

36. Cell Membrane • Protects and supports cell • Regulates what enters and leaves • Phospholipid bilayer- to layers of lipids