1. Chapter 4 Cells Dr. Joseph Silver

2. in 1665 Robert Hooke using a primitive magnifying system saw little compartments in samples of cork and called them cells meaning “little rooms”

4. a few years later Anton van Leeuwenhoek using a primitive microscope was the first to observe little “animals” in drops of water he called them “animalcules”

5. in 1838 Matthias Schleiden stated that all plants are made up of cells and in 1839 Theodor Schwann stated that all animals are made up of cells and the cell theory was born

8. the cell theory 1. all living things are made up of one or more cells 2.cells are the basic building block of all organisms 3. cells come from other cells

9. most cells are vey small large cells are not as efficient why? Read fig. 4.1 page 60

12. it has to do with the ratio between surface area compared to volume surface area is represented by the cell membrane volume is represented by the cytoplasm and contents

13. in every cell there is a cell membrane which regulates what goes in and out of the cell and the inside of the cell where all of the work that the cell does takes place in the cytoplasm the membrane and the cytoplasm must work together but as the cell gets larger problems take place

14. as a cell grows the surface area increases but not as fast as the cytoplasm inside the cell eventually the cell becomes too big and the cell membrane can no longer keep up with the needs of the inside of the cell and this becomes the stimulus for the cell to divide and become two smaller cells

16. scientists use microscopes and biological stains (chemicals which stain specific cell parts) to study the make up of cells

19. the ability of scientists to see inside of a cell is limited by the wavelength of the beam or energy passing through a cell the wavelengths of light are much larger than the smaller wavelengths of an electron beam electron beams allow microscopes to show structures almost down to the level of an atom

22. cells are divided into two groups prokaryotes and eukaryotes

23. prokaryotes primitive cells 1 strand of DNA cell membrane and cell wall move by pili and flagella have free ribosomes no membrane bound organelles no nucleus scavengers, carnivores, photosynthetic, decomposers

25. eukaryotes advanced cells compartmentalized organelles nucleus protects genetic material internal endomembrane system internal transport system you have eukaryotic cells in your bodies

27. terms you should be able to describe and explain cell membrane – nucleus – nuclear membrane – nucleolus – chromatin – nuclear pores – ribosome – rough endoplasmic reticulum – smooth endoplasmic reticulum – vesicle – Golgi apparatus – cisternae -mitochondria – peroxisome – lysosome – cytoplasm – centriole – cytoskeleton – filaments –microtubules – actin – nucleoplasm – chloroplast – central vacuole – DNA – RNA – mRNA – rRNA – tRNA – endocytosis – exocytosis – phagocytosis – endosymbiosis – molecular motor – flagella – extracellular matrix -

28. in chapter 5 we will study the structure and functions of the cell membrane and put knowledge of all of these terms together to understand how a cell responds to a message from in or out of the cell to produce a product or produce a change in the cell

29. every cell has a cell membrane made up of a double phospholipid layer the polar phosphate ends are in contact with the liquid material inside and outside of the cell the lipid part is present inside the membrane (we saw this in chapter 3)

31. the cell membrane separates the cell components from the fluids outside of the cell the many structures found in the membrane regulate what goes in and out of the cell many membrane structures act as receptors to hormones, nutrients, and other chemicals and by interacting with these chemicals begins the process of gene activation and cell response

32. the nuclear membrane surrounds the nucleus it has pores which allow material to go in and out it keeps the genetic material separate from the cytoplasm the DNA is present as chromatin (an unwound state) dark areas called nucleolus are areas where RNAs are being made

34. DNA contains the genetic code one gene makes one kind of RNA mRNA goes to the cytoplasm and an enzyme is made there are thousands of mRNAs rRNAs form ribosomes in the cytoplasm (protein factories) tRNAs bring amino acids to ribosomes to make up a protein

35. mRNA leaves the nucleus links up with a free ribosome or a ribosome on the rough endoplasmic reticulum and stimulates the production of protein enzymes

37. the enzymes then link up with other cell components and cause the chemical reactions of those components to work millions of times faster then when the enzymes are not present in other words enzymes tell the cell what work to do when done the enzymes are recycled

39. some enzymes go to the smooth endoplasmic reticulum where manufacture of lipids takes place calcium is stored, steroids are made, chemicals are rearranged, non protein products produced

43. materials enter the Golgi apparatus from the RER and the SER are rearranged and are packaged (made ready for delivery to where they are needed) these products are pushed out of the Golgi at the ends of the membranes (cisternae) in the from of secretory vesicles

44. the vesicles which leave the Golgi can be used outside of the cell or in the cell the secretory vesicles combine with the cell membrane and by exocytosis are moved out of the cell

46. a cell is very sensitive to its internal and external environment when a structure or compound is no longer necessary a membrane bound vesicle called a lysosome which contains digestive enzymes break down and recycle structures and chemicals for new uses

48. another important vesicle is the peroxisome it contains enzymes for destroying lipids when activated the enzymes produce hydrogen peroxide

49. the various vesicles which have many cytoplasmic functions are collectively known as microbodies

50. in order to survive a cell needs energy mitochondria produce a high energy phosphate molecule known as ATP adenosine tri phosphate which produces the energy used by cells to do work

51. when a cell is not doing too many things the cell contains few mitochondria but when a cell is very active there are many mitochondria

52. mitochondria are -sausage shaped organelles -have an inner and outer membrane -the inner membrane is very folded -the folds are known as cristae -the space in the cristae is the matrix -the space between the layers is the intermembrane space -the inner membrane contains enzymes for making ATP -mitochondria have their own (non human) DNA

53. mitochondrial DNA rarely mutates a cell within a cell makes many of the enzymes for braking down glucose

56. as with mitochondria plant chloroplasts which produce ATP and glucose by photosynthesis are double membrane and have their own DNA plants also contain other organelles which have their own DNA collectively these are known as plastids

58. mitochondria and plastids are believed to at one time be independent prokaryotic cells which “eaten” by a eukaryotic cell and provided some benefit to the cell so was not destroyed and over time have each adapted to this beneficial relationship endosymbiosis

59. the inside of a cell is a thin Jello-like cytoplasm the cell membrane is a thin layer of phospholipid if this was all that a cell had the cell would collapse but a cell has a cytoskeleton a series of actin filaments, microtubules, and intermediate filaments which allow a cell to retain a circular shape

61. actin filaments allow cell and organelle movement and cell membrane extensions microtubules aid cell movement organize the cytoplasm are short lived and move materials about the cell

62. intermediate filaments are tough long lasting fibrous stable proteins which provide -support for the membrane -anchor organelles in place -anchor the nucleus -acts as a true skeleton for the membrane, cytoplasm, and membrane projections

63. many of the cells components are organized into functional complexes organelles, enzymes, microbodies, molecular motors and more are in close proximity to each other so that all of the things needed to do work are right next to each other

64. but in many cases when a cell makes a product it is not always made exactly where it will b used a cell has an internal highway system which is used to move materials about the cell it is called a molecular motor

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68. look at fig 4.21 page 77 actin and dynein are the same chemicals which allow movement of prokaryotes, sperm, and cell projections microtubules form an internal highway system this complex is used to move material to where it is needed

69. a cell membrane is much more than a simple skin animal cells secrete an extracellular matrix which is made up of fibrous proteins (collagen) glycoproteins (receptors, transporters) elastin (membrane strength & shape) integrins (chemical & mechanical signals)

70. the extracellular matrix -connects the interior of the cell with the exterior of the cell -provides strength for cell shape -anchors internal and external structures -responds to external hormones & chemicals

72. now let’s integrate all of this information and some which we will get from chapter 5 into a logical sequence of events of what happens in a cell

73. -a chemical is floating in the liquid outside a cell -a membrane projection links up with the chemical -causes change in shape of a membrane chemical -cause chemical change in cytoplasm -change eventually causes chemical change in nucleus -one gene is opened up and copied as mRNA -mRNA leaves nucleus links up with ribosome -ribosome makes an enzyme -enzyme stimulates 1 chemical reaction to work very fast -product goes to Golgi for rearrangement and packaging -Golgi releases vesicle which is moved by molecular motor -vesicle use in cell or is moved out of cell

74. look at fig 4.12 fig 4.13 fig 4.19 fig these figures show all of the structures and steps from cell interaction to outside of cell to movement of a cell product to where it is needed in or out of the cell

78. parts of chapter 4 not included here will be addressed when we do chapter 5