2.1, 2.2, 2.3 Cells


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  • Topic 2: Cells
  • Topic 2: Cells
  • Topic 2: Cells
  • Topic 2: Cells
  • Topic 2: Cells
  • Topic 2: Cells 10/05/11
  • 2.1, 2.2, 2.3 Cells

    1. 1. Topic 2 : Cells
    2. 2. 2.1 Cell Theory Learning Objectives <ul><li>Outline cell theory </li></ul><ul><li>Discuss the evidence for cell theory </li></ul><ul><li>State unicellular organisms carry out all the functions for life </li></ul>
    3. 3. Cell Theory <ul><li>• All organisms are made of one or more cells </li></ul><ul><li>• Cells are the basic living units within </li></ul><ul><li>organisms; all chemical reactions of life take place within cells </li></ul><ul><li>• All cells come from pre-existing cells via mitosis or meiosis </li></ul>
    4. 4. TASK: Evidence for Cell Theory <ul><li>State the 5 summary statements of Cell Theory (use your text books) </li></ul><ul><li>Use your text book pages 3 and 4 to summarize the evidence we have to support each statement of cell theory. </li></ul><ul><li>(HINT: you should read these pages FIRST then summarize the key pieces of evidence </li></ul>
    5. 5. Mix and Match: 5 minutes 1 Movement A Producing offspring 2 Respiration B Getting rid of waste products 3 Sensitivity C Being able to move their parts 4 Growth D Turning food and oxygen into energy 5 Reproduction E Getting to full size, repairing old cells 6 Excretion F Responding to the outside world 7 Nutrition G Getting food where it’s needed
    6. 6. Functions of Life <ul><li>MRS GREN is the pneumonic to help us remember the functions of life. </li></ul><ul><li>Unicellular organisms carry out all the functions of life. This is what defines a “living thing”. </li></ul><ul><li>Identify the functions of life Viruses carry out. </li></ul><ul><li>Do they qualify as a “living” thing? Why? Why not? </li></ul><ul><li>Is FIRE alive? Use MRS GREN to justify your answer </li></ul>
    7. 7. 2.1 Learning Objectives continued <ul><li>Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells </li></ul><ul><li>Calculate the linear magnification of drawings and / or the actual size of specimens in images of known magnification </li></ul>
    8. 8. Measurements & equivalents 1 millimetre (mm) 10 -3 metre (m) 1/1 000 m 1 micrometre (µm) 10 -6 metre (m) 1/1 000 000 m 1 nanometre (nm) 10- 9 metre (m) 1/ 1 000 000 000 m
    9. 9. Measuring Cells <ul><li>To accurately measure cellular structures we need a suitable scale </li></ul>
    10. 10. Estimating cell size Graticule = eypiece micrometer – a fine scale that fits inside an eyepiece lens Stage micrometer = slide with a fine scale of known dimension etched onto it
    11. 11. Comparing relative sizes of molecules
    12. 12. Magnification <ul><li>The size of an image of an object compared to its actual size. </li></ul><ul><li>Calculated using the formula M = I /A </li></ul><ul><li>I = size of image </li></ul><ul><li>A = actual size of object </li></ul><ul><li>M = magnification </li></ul><ul><li>BUT you must remember to </li></ul><ul><li>convert values to the same unit FIRST </li></ul>M A I
    13. 13. Calculations M = I /A I = M x A A = I /M X ÷ ÷ M A I
    14. 14. Eg. Calculating Magnification <ul><li>It is essential that the same unit is used for the size of the image and the size of the object : </li></ul><ul><li>Eg. If an image measures 50mm (as printed on paper) and the object actually measures 5µm; </li></ul><ul><li>The size of the image should be converted to µm: </li></ul><ul><li>Size of image = 50mm = 50 000µm </li></ul><ul><li>Then you can use this to calculate magnification: </li></ul><ul><li>Therefore, magnification = 50 000/5 = 10,000 </li></ul>
    15. 15. Practice Question: Calculate the linear magnification <ul><li>If a red blood cell has a diameter of 8 µm and a student shows it with a diameter of 40 mm in a drawing, what is the magnification of the drawing? </li></ul>
    16. 16. Another Practice Question; <ul><li>An image of a liver cell has a real scale bar next to it recording 10um, but you measure the scale bar and find it is 20mm. What is the magnification used? </li></ul><ul><li>ANSWER: </li></ul><ul><li>20mm = 20,000 um </li></ul><ul><li>Magnification = 20,000 10 </li></ul><ul><ul><ul><ul><ul><li>= 2000 X </li></ul></ul></ul></ul></ul>
    17. 17. Resolution <ul><li>Ability of a microscope to distinguish two objects as separate from one other </li></ul><ul><li>The smaller & closer together the objects that can be distinguished as separate, the higher the resolution (resolving power) </li></ul><ul><li>The resolving power of the light microscope is limited by the wavelength of light. It cannot resolve detail finer than 0.2µm </li></ul>
    18. 18. The importance of resolution Light Microscope, low resolution Electron Microscope, high resolution
    19. 19. The light microscope
    20. 20. The Electron Microscope
    21. 21. Chromosomes Light Microscope Scanning Electron Microscope
    22. 22. Light Microscope: Anaphase Animal Cell Plant Cell
    23. 23. TEM – Spindle Fibres
    24. 24. Light vs. Electron microscopes Feature Light microscope Electron microscope Radiation used Light rays Electron beams Magnification x 2000 x 500 000 Resolving power 200 nm 0.2nm Focused by Glass lenses Electromagnets Biological material Living or dead Dead Size Small & portable Very large & static Preparation of material Quick & simple Time-consuming & complex Cost Relatively cheap VERY expensive
    25. 25. Learning Objective <ul><li>Topic 2.1 Cell Theory continued </li></ul><ul><li>2.1.6. Explain the significance of surface area to volume ratio as a factor limiting cell size </li></ul>
    26. 26. Investigating the importance of Surface Area for Cells <ul><li>Raw materials enter a cell by diffusion via the cell membrane. The number of molecules which diffuse into a cell depends on its surface area. To function efficiently a cell needs a large surface area relative to its volume </li></ul><ul><li>Diffusion is the passive movement of molecules from an area where they exist in higher concentration to an area of lower concentration </li></ul><ul><li>Osmosis is a specialized type of diffusion describing the movement of water molecules specifically </li></ul>
    27. 27. Surface Area: Volume ratio Object A Object B Volume (cm 3 ) How many blocks are there? Surface Area (cm 2 ) How many 1cm 2 faces are facing outwards? Surface Area: Volume Ratio (surface area/volume)
    28. 28. Agar Cells Experiment <ul><li>You will be given an experiment sheet </li></ul><ul><li>Follow the instructions carefully! </li></ul><ul><li>Remember to wear safety googles. </li></ul><ul><li>You have 20 minutes to complete the experiment & have it cleaned up  </li></ul><ul><li>When you have finished you will have 15 minutes to complete the worksheet using the data you collect </li></ul>
    29. 29. Task: Hypothetical cells A B C E D 1cm 1.5 cm 2 cm 2.5 cm 3 cm Cell Length Surface Area Volume SA:Vol Ratio A 1cm 6x1x1=6cm 2 1x1x1=1cm 3 6:1 B C D E
    30. 30. QUESTIONS on the importance of Surface Area <ul><li>Which increase faster as cell size increases: volume or surface area? </li></ul><ul><li>Describe what happens to the ratio of SA / V as cell size increases </li></ul><ul><li>Predict which cell would have the most efficient rate of diffusion—justify your answer </li></ul><ul><li>Is the shape of the cell important? I.e does it matter if a cell is round and fat compared to long and thin as long as the volume remains the same? Why? </li></ul>
    31. 31. Answers <ul><li>Volume increases faster than surface area </li></ul><ul><li>The ratio falls as cell size increases ie. Less SA compared with vol </li></ul><ul><li>Cell A – the smallest cell </li></ul><ul><li>Yes, shape is important the long cell would be more efficiently supplied (faster rate of diffusion) with materials via diffusion as it has a greater surface area compared to its volume </li></ul>Cell Length Surface Area Volume SA:Vol Ratio A 1cm 6x1x1=6cm 2 1x1x1=1cm 3 6:1 B 1.5cm 13.5cm 2 3.375cm 3 4:1 C 2cm 24cm 2 8cm 3 3:1 D 2.5cm 37.5cm 2 15.625cm 3 2.4:1 E 3cm 54cm 2 27cm 3 2:1
    32. 32. HOMEWORK TASK You are to complete the discussion questions (on the back of the Investigation Sheet) about how surface area to volume ratio acts as a limiting factor to cell size
    33. 33. 2.1 Cell Theory Learning Objectives <ul><li>State that multicellular organisms show emergent properties </li></ul><ul><li>State the multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others </li></ul><ul><li>State stem cells have the capacity to divide and have the ability to differentiate along different pathways </li></ul><ul><li>Outline at least one therapeutic use of stem cells </li></ul>
    34. 34. Emergent Properties <ul><li>Emergent properties are those where the whole is more than the sum of their parts. Good examples of emergence is a termite hill, an ant hill or the human brain. </li></ul><ul><li>In the case of the human brain the individual neurons are not capable of thought but the communication and cooperation between the neurons makes it possible for the brain to think. </li></ul>
    35. 35. Multicellular Organisms show Emergent Properties <ul><li>This means that the organism can achieve MORE than the sum of what each cell could achieve individually. </li></ul><ul><li>This is caused by the fact that cells interact, allowing them to perform tasks together that they could not achieve, even in part, if they were alone. </li></ul>
    36. 36. How Cells Differentiate <ul><li>All multicellular organisms begin their lives as a single cell that divides rapidly, and as it does so the cells, although identical genetically, differentiate. </li></ul><ul><li>Cells are able to differentiate and carry out specialized functions by expressing some of their genes but not others. </li></ul><ul><li>E.g. Cells in your toe’s, fingers and heart all have the information (genes) to make the protein pigment for the color of your eyes but do not use it. </li></ul><ul><li>The genes that are not expressed by the cell are still </li></ul><ul><li>present in the nucleus, but are packed away tightly so they cannot be accessed. </li></ul>
    37. 37. Stem Cells—Unspecialized cells <ul><li>The have the capacity to divide and differentiate along a number of different pathways. </li></ul><ul><li>They are different to other cells in two ways </li></ul><ul><li>They are undifferentiated which means they have not specialized into a certain type of cell. This means all their genes can still be expressed </li></ul><ul><li>They are self-sustaining —they can divide and replicate for long periods of a time </li></ul>
    38. 38. Sources and Types of Stem Cells <ul><li>A zygote is a source of stem cells because the cells can become any type of cell and are therefore said to be ‘ totipotent ’. </li></ul><ul><li>After the zygote cells divide many times it becomes a ball of cells (blastocyst). These cells can become almost any kind of cell and are considered ‘ pluripotent ’. </li></ul><ul><li>Another source of stem cells is the umbilical cord of a new baby. Cells from the blood of the cord are considered ‘ multipotent ’ because they can become a limited number of particular cell types. </li></ul><ul><li>Adults have stem cells in their bone marrow, brain and a limited number in muscles—these are all only multipotent </li></ul>
    39. 39. Therapeutic Uses of Stem Cells
    40. 40. The Promise of Stem Cells Stem cells are able to differentiate into a particular cell type when given a specific signal. Theoretically this means you could signal a stem cell to specialize into a liver cell, then divide until you grow a whole liver!
    41. 41. Stem Cells are found in adults, but the Most promising types of Stem Cells for Therapy are Embryonic Stem Cells
    42. 42. Embryonic Stem Cells The embryo is destroyed by separating it into individual cells for the collection of ICM cells.
    43. 43. Some Thorny Ethical Questions Is it ethical to harvest embryonic stem cells from the “extra” embryos created during in vitro fertilization? Are these masses of cells a human?
    44. 44. TASKS Use your text books to outline at least TWO therapeutic uses for stem cells. You should describe WHY the use is needed AND how stem cells are used (where are they obtained from, how…) Outline the ethical debate surrounding stem cell research—why are embryonic stem cells more favored that adult? What are some the issues people have with this research?
    45. 45. 2.2 Prokaryotic cells Learning Objectives <ul><li>Draw and label a diagram of E.coli as an example of a Prokaryote </li></ul><ul><li>Annotate the diagram of E.coli to describe the function of each structure </li></ul><ul><li>Identify structures of </li></ul><ul><li>E.coli in electron micrographs </li></ul><ul><li>State that prokaryotic cells </li></ul><ul><li>divide by binary fission </li></ul>
    46. 46. Prokaryotes = before the nucleus <ul><li>Primitive cells – do not have a nucleus or any membrane-bound organelles </li></ul><ul><li>Probably the first living things to evolve on Earth a few billion years ago </li></ul>
    47. 47. Prokaryotes <ul><li>Eg. bacteria & blue-green algae </li></ul><ul><li>May have plasmids (satellite DNA( which can replicate independent of the main chromosome </li></ul><ul><li>Rigid cell wall containing murein </li></ul><ul><li>Mesosomes = inner extensions </li></ul><ul><li>of the cell membrane = site </li></ul><ul><li>of respiration </li></ul>
    48. 48. Prokaryotes
    49. 49. Prokaryotic Features
    50. 50. Binary Fission
    51. 52. Prokaryotes vs Eukaryotes
    52. 53. Prokaryotic vs Eukaryotic Cells <ul><li>• “ pro” = before </li></ul><ul><li>• “ eu” = true </li></ul><ul><li>• “ karyo” = nucleus </li></ul><ul><li>• Therefore Prokaryotic cells lack a nucleus </li></ul><ul><li>• Eukaryotic cells possess a nucleus </li></ul><ul><li>• Several other differences </li></ul>
    53. 54. Eukaryotes
    54. 55. 2.3 Eukaryotic Cells Learning Objectives <ul><li>Draw and label the structures of a liver cell as an example of an animal cell </li></ul><ul><li>Annotate the labelled liver cell to describe the functions of each structure in an animal cell </li></ul><ul><li>Identify structures in electron micrographs of liver cells </li></ul>
    55. 57. Generalised Animal Cell
    56. 58. Plasma Membrane
    57. 59. Nucleus <ul><li>Largest organelle in cell </li></ul><ul><li>10µm diameter </li></ul><ul><li>Surrounded by nuclear membrane which has pores to allow materials to pass into/out of nucleus </li></ul><ul><li>Connected to ER </li></ul>
    58. 60. Nucleus
    59. 61. Nuclear Envelope & Pores
    60. 62. Nucleolus <ul><li>Not an organelle </li></ul><ul><li>dark-staining region inside the nucleus - cloud of ribosome parts in the process of being constructed. </li></ul><ul><li>May be several nucleoli </li></ul><ul><li>Once the ribosome parts are constructed, they are exported to the cytoplasm and incorporated into the rough endoplasmic reticulum. </li></ul>
    61. 63. Nucleolus <ul><li>Site of rRNA synthesis & ribosome assembly </li></ul>
    62. 64. Cells without nuclei <ul><li>Red blood cells – lose their nuclei and this enables them to carry more haemoglobin & so can pick up more oxygen </li></ul><ul><li>Phloem sieve tubes provide the transport system for sucrose in plants – they have lost most of the cell organelles including nuclei to make it easier for materials to flow through the cell </li></ul>
    63. 65. Endoplasmic Reticulum <ul><li>Structure: </li></ul><ul><ul><li>Complex system of double membranes </li></ul></ul><ul><ul><li>The fluid-filled spaces between the membranes are called cisternae </li></ul></ul><ul><ul><li>The ER is continuous with the nuclear membrane </li></ul></ul>h
    64. 66. Endoplasmic Reticulum (ER) Double membrane of RER Cisternae Chromatin Nucleolus Pore NUCLEUS Two membranes of nuclear envelope ROUGH ENDOPLASMIC RETICULUM Ribosomes
    65. 67. Endoplasmic Reticulum (ER) <ul><li>Functions: </li></ul><ul><ul><li>Form an extensive transport system throughout cell </li></ul></ul><ul><ul><li>Production & packaging of proteins (RER) </li></ul></ul><ul><ul><li>Synthesis of lipids & steroids (SER) </li></ul></ul><ul><ul><li>Collection, storage & distribution of these materials </li></ul></ul>
    66. 68. Rough Endoplasmic Reticulum 1 2 3 4 Transport vesicle buds off Ribosome Sugar chain Glycoprotein Secretory (glyco-) protein inside transport vesicle ROUGH ER Polypeptide
    67. 69. Smooth Endoplasmic Reticulum (SER) <ul><li>No ribosomes </li></ul><ul><li>Site of lipid synthesis </li></ul><ul><li>Cells that make lipids/steroids eg. liver cells & testis contain lots of SER </li></ul>SMOOTH ER ROUGH ER Nuclear envelope Ribosomes SMOOTH ER ROUGH ER
    68. 70. The Golgi Apparatus <ul><li>Structure – stacks of membranous sacks </li></ul><ul><li>Function – Receives and modifies molecules from the ER that need to be secreted from the cell. </li></ul><ul><li>Directs proteins made in the ER to the correct cellular compartment or to the plasma membrane for secretion. </li></ul><ul><li>ANY CELL that secretes STUFF has lots of these! (e.g. glands in the pancreas and intestinal wall, salivary glands) </li></ul>
    69. 71. Golgi Apparatus Golgi & Protein Trafficking Golgi apparatus “ Receiving” side of Golgi apparatus Transport vesicle from ER New vesicle forming Transport vesicle from the Golgi Golgi apparatus “ Shipping” side of Golgi apparatus
    70. 72. Golgi - Functions <ul><li>Assembling glycoproteins such as mucin by combining carbohydrate and protein </li></ul><ul><li>Transporting and storing lipids </li></ul><ul><li>Formation of lysosomes </li></ul><ul><li>Production of digestive enzymes </li></ul><ul><li>Secretion of carbohydrates for the formation of plant cell walls and insect cuticles </li></ul>
    71. 73. Golgi Apparatus
    72. 74. Lysosomes <ul><li>Structure – small vacuoles formed from Golgi; contain hydrolytic enzymes which can digest material </li></ul><ul><li>Function – release enzymes to destroy worn-out organelles ; phagocytosis; exocytosis; cause the cell to self-destruct (autolysis) by releasing enzymes </li></ul>
    73. 75. Lysosomes <ul><li>Phagocytosis: </li></ul><ul><li>Digestion of material that has been taken into the cell eg. White blood cells engulf bacteria – lysosome fuses with vesicle to digest the bacterium </li></ul>
    74. 76. <ul><li>Lysosomes release enzymes that destroy worn-out organelles in the cell </li></ul>Lysosomes
    75. 77. Cell Transport Rough ER Transport vesicle (containing inactive hydrolytic enzymes) Golgi apparatus Plasma membrane LYSOSOMES “ Food” Engulfment of particle Food vacuole Digestion Lysosome engulfing damaged organelle
    76. 78. Cell Transport Transport vesicle from ER Rough ER Transport vesicle from Golgi Plasma membrane Vacuole Lysosome Golgi apparatus Nuclear envelope Smooth ER Nucleus
    77. 79. Mitochondria <ul><li>Structure - 2 membranes – outer membrane controls the entry & exit of materials; inner membrane forms many folds called cristae; filled with jelly-like matrix </li></ul><ul><li>Function – site of aerobic respiration (creation of ATP) </li></ul>
    78. 80. Mitochondria
    79. 81. Mitochondria – False colour SEM
    80. 82. Mitochondria - TEM
    81. 83. Mitochondria: Cristae & Matrix <ul><li>Cristae – surface of crista covered in cytochromes which create ATP </li></ul><ul><li>Matrix - contains ribosomes and loops of DNA which enables the mitochondria to replicate themselves when the cell divides </li></ul>
    82. 84. Ribosomes <ul><li>Structure – small, dense organelles approx 20nm diameter composed 1 large & 1 small subunit. Manufactured in nucleolus from rRNA and protein </li></ul><ul><li>Function – site of protein synthesis in the cell </li></ul>
    83. 85. <ul><li>Site of protein synthesis </li></ul>Ribosomes Many of the cell’s ribosomes are attached to the ER (Rough ER). However they also occur free in they cytoplasm
    84. 86. Ribosomes
    85. 87. Ribosomes & Protein Synthesis <ul><li>Many ribosomes can read the same mRNA strand to create many copies of the polypeptide at the same time </li></ul>
    86. 89. Generalised Plant Cell
    87. 90. Chloroplasts Structure – Double membrane - chloroplast envelope; inside is the fluid stroma and granum (stacks of thylakoids) Function - site of photosynthesis
    88. 91. Chloroplasts Large surface area for light absorption
    89. 92. Chloroplasts SEM TEM Starch grain
    90. 93. Thylakoid – contains chlorophyll
    91. 94. Centrioles
    92. 95. Centrioles <ul><li>Structure – two short bundles of microtubules positioned at right angles to each other; located just outside nucleus in clear area of cytoplasm called the centrosome; wall of each centriole is made up of nine triplets of microtubules </li></ul><ul><li>Function – during cell division, they migrate to opposite poles of the cell where they produced the spindle to assist movement of chromosomes </li></ul>
    93. 96. Vacuole <ul><li>Structure - Plant cells have a large, permanent vacuole bounded by a membrane called the tonoplast </li></ul><ul><li>Vacuole contains cell sap – a solution of sugars, amino acids, mineral salts & waste chemicals </li></ul>
    94. 97. Vacuoles <ul><li>Function – act as food stores; accumulate waste products; contain pigments which give colour to parts of plant eg. petals; help maintain turgidity </li></ul>
    95. 98. Electron micrograph of plant cell
    96. 99. TASKS <ul><li>“ Cell Apprentice” – make a 30-60 second elevator pitch to explain why your organelle shouldn’t be fired from the cell </li></ul><ul><li>Cut & Paste – Create the generalised animal cell </li></ul>
    97. 100. 2.3 Eukaryotic Cells Learning Objectives <ul><li>4. Compare prokaryotic and eukaryotic cells </li></ul><ul><li>5. State 3 differences between plant and animal cells </li></ul><ul><li>6. Outline the roles of extracellular components (including cell wall in plants and glycoprotein's in animals) </li></ul>
    98. 101. Prokaryotes vs Eukaryotes Prokaryotes Eukaryotes Average diameter 0.5-5um Up to 40um diameter – often 1000x10 000 times volume of prokaryotic cells DNA is circular & free in cytoplasm DNA is linear, within nucleus – nuclear “envelope” = 2 membranes DNA is naked DNA associated with protein, forming chromosomes Smaller ribosomes -18nm Larger ribosomes – 22nm No ER present ER present, to which ribosomes may be attached Very few organelles – none membrane-bound Many cell organelles present – many single or double membranes Cell wall present Cell wall sometimes present eg. In plants
    99. 102. Protein Synthesis TASK: Use the diagram to compare & contrast protein synthesis in prokaryotes and eukaryotes
    100. 103. Prokaryotes Eukaryotes Where transcription occurs Cytoplasm – because no nucleus Nucleus RNA Processing? No - because no introns Yes Where translation occurs Cytoplasm – simultaneously with transcription Cytoplasm How many genes transcribed? Usually several related genes = operon Usually only one