Cell Structure and Function

1. Cell Structure and Function

2. Cells • Smallest living unit • Most are microscopic

3. Discovery of Cells • Robert Hooke (mid-1600s) • Observed sliver of cork • Saw “row of empty boxes” • Coined the term cell

4. Cell theory • (1839)Theodor Schwann & Matthias Schleiden “ all living things are made of cells” • (50 yrs. later) Rudolf Virchow “all cells come from cells”

5. Cell Structure Reflects Function • Cellular structures have evolved because of a need for a particular function, for example: • Neurons have axons to transfer information to other cells • Sperm have whiplike tails to enable them to swim • Eggs have large quantities of nutrients to aid early embryonic development

6. Principles of Cell Theory • All living things are made of cells • Smallest living unit of structure and function of all organisms is the cell • All cells arise from preexisting cells (this principle discarded the idea of spontaneous generation)

7. Cells are Small!

8. Characteristics of All Cells • A surrounding membrane • Protoplasm – cell contents in thick fluid • Organelles – structures for cell function • Control center with DNA

9. Cell Types • Prokaryotic • Eukaryotic

10. Prokaryotic Cells • First cell type on earth • Cell type of Bacteria and Archaea

11. Prokaryotic Cells • No membrane bound nucleus • Nucleoid = region of DNA concentration • Organelles not bound by membranes

12. Eukaryotic Cells • Nucleus bound by membrane • Include fungi, protists, plant, and animal cells • Possess many organelles Protozoan

13. Representative Animal Cell

14. Representative Plant Cell

15. Organelles • Cellular machinery • Two general kinds • Derived from membranes • Bacteria-like organelles

16. Bacteria-Like Organelles • Derived from symbiotic bacteria • Ancient association • Endosymbiotic theory • Evolution of modern cells from cells & symbiotic bacteria

17. Distinguishing Features of the Two Major Cell Types

18. Homeostasis • All organisms must maintain a balance regardless of internal and external conditions • This task is controlled by the plasma membrane

19. Plasma Membrane • Contains cell contents • Double layer of phospholipids & proteins

20. Phospholipids • Polar • Hydrophylic head • Hydrophobic tail • Interacts with water

21. Movement Across the Plasma Membrane • A few molecules move freely • Water, Carbon dioxide, Ammonia, Oxygen • Carrier proteins transport some molecules • Proteins embedded in lipid bilayer • Fluid mosaic model – describes fluid nature of a lipid bilayer with proteins

23. Membrane Proteins 1. Channels or transporters • Move molecules in one direction 2. Receptors • Recognize certain chemicals

24. Plasma Membrane • The plasma membrane serves as the boundary between the cell and its environment • Allows specific amount of nutrients to enter and allow waste to exit

25. Characteristics of cell membrane • Selectively permeable – allows some molecules to enter and keeps others out • Like a screen door

26. Plasma Membrane • Made up of two layers of phospholipids • Controls what moves into and out of the cell • Selectively permeable • AKA: Lipid Bilayer, Fluid Mosaic, Cell Membrane

27. Capsule • Found on some prokaryotic bacterial cells. • Layer that lies outside the cell wall • Usually composed of polysaccharides • It enhances the ability of bacteria to cause disease (ie. E. coli) • Slippery • Contains water (protection from desiccation) • Helps cells stick to surfaces (other cells)

28. Cell Wall • Rigid structure • Located outside of plasma membrane • Found in plant cells, fungi, some bacteria and protists • Provides support and protection • Composed of cellulose (carbohydrate)

29. Nucleus • Control center of the eukaryotic cell • Contains directions to make proteins • Chromatin – strands of genetic material (DNA)

30. Nucleolus • Structure within the nucleus • Produces ribosomes

31. Ribosomes • The site of protein synthesis • Found in the cytoplasm or on the Endoplasmic Reticulum

32. Cytoplasm • Clear, gelatinous fluid inside the cell • Helps suspend organelles

33. Endoplasmic Reticulum • Site of cellular chemical reactions • Series of highly folded membranes • Rough Endoplasmic Reticulum – have ribosomes attached • Smooth Endoplasmic Reticulum – does not have ribosomes attached

34. Golgi Apparatus • AKA: Golgi Body • Flattened system of tubular membranes • Modifies and packages proteins • Sort proteins to be sent to appropriate destination

35. Vacuoles • Temporary storage of materials • Store food, enzymes, other materials needed by the cell, and waste • Plant cells usually have one large vacuole, animal cells usually contain many smaller vacuoles

36. Lysosomes • Contain digestive enzymes that digest excess or worn out organelles, food particles, viruses and bacteria

37. Chloroplasts • Found in the cells of green plants • Organelle that captures light energy and produces food to store for later use • Contains chlorophyll – gives plants their green color

38. Mitochondria • Organelles that transform energy for the cell • Double membrane structure with highly folded inner membrane

39. Cytoskeleton • Support structure for the cell • Composed of microtubules and microfilaments • Helps cell to maintain shape

40. Cilia and Flagella • Aid in locomotion or feeding • May move the entire cell, or aid in movement of substances across the cell surface Cilia and Flagella video

41. Pseudopodia • Means fake or false feet • Temporary projections of eukaryotic cells. • This is how amoebas move, as well as some cells found in animals, such as white blood cells • Pseudopodia extend and contract by the reversible assembly of actin subunits into microfilaments. Filaments near the cell's end interact with myosin which causes contraction. • Amoeboid movement

42. More on the Cytoskeleton • Mitosis • Specific cellular forms • Muscle • Nerve cells • Video link

43. Animal Cells - Don’t have a cell wall - Contain centrioles - Contain many small vacuoles Plant Cells - Generally larger than animal cells - Have a cell wall - Contain chloroplasts - Have one large central vacuole Plant and Animal Cells Critical Thinking : Why are plant and animal cells similar?

44. Identify the Following Cellular Structures

45. Advantages of highly folded Membranes • Folded membranes are an advantage to a cell because • Cell processes can be more efficient • Membranes provide a larger surface area for cell process to take place • Remember all cell membranes are made up of phospholipids • Examples: • folded membranes in organelles like mitochondria • Microvilli

46. Endomembrane System • The endomembrane system is composed of a number of inter-related membrane sacs within the cytoplasm of the cell • Rough and smooth ER, Golgi apparatus, Vessicles, Lysosomes • The endomembrane system functions in protein synthesis, protein modification, sorting and transport • Animation

47. Inner Life of the Cell • Long Version • Short Version