- Cell theory states that all living things are made of one or more cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells. - Evidence for cell theory includes that cells were first observed under microscopes, all organisms show metabolism and homeostasis, and cells can be isolated and grown in culture. - As cell size increases, surface area to volume ratio decreases, limiting nutrient exchange through the cell's surface. This constrains the maximum size of single-celled organisms.

1. Topic 2 : Cells

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

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

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. Comparing relative sizes of molecules

13. Calculations M = I /A I = M x A A = I /M X ÷ ÷ M A I

18. The importance of resolution Light Microscope, low resolution Electron Microscope, high resolution

19. The light microscope

20. The Electron Microscope

21. Chromosomes Light Microscope Scanning Electron Microscope

22. Light Microscope: Anaphase Animal Cell Plant Cell

23. TEM – Spindle Fibres

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

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)

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

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

39. Therapeutic Uses of Stem Cells

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. Stem Cells are found in adults, but the Most promising types of Stem Cells for Therapy are Embryonic Stem Cells

42. Embryonic Stem Cells The embryo is destroyed by separating it into individual cells for the collection of ICM cells.

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. 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?

48. Prokaryotes

49. Prokaryotic Features

50. Binary Fission

52. Prokaryotes vs Eukaryotes

54. Eukaryotes

57. Generalised Animal Cell

58. Plasma Membrane

60. Nucleus

61. Nuclear Envelope & Pores

66. Endoplasmic Reticulum (ER) Double membrane of RER Cisternae Chromatin Nucleolus Pore NUCLEUS Two membranes of nuclear envelope ROUGH ENDOPLASMIC RETICULUM Ribosomes

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

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

73. Golgi Apparatus

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

78. Cell Transport Transport vesicle from ER Rough ER Transport vesicle from Golgi Plasma membrane Vacuole Lysosome Golgi apparatus Nuclear envelope Smooth ER Nucleus

80. Mitochondria

81. Mitochondria – False colour SEM

82. Mitochondria - TEM

86. Ribosomes

89. Generalised Plant Cell

90. Chloroplasts Structure – Double membrane - chloroplast envelope; inside is the fluid stroma and granum (stacks of thylakoids) Function - site of photosynthesis

91. Chloroplasts Large surface area for light absorption

92. Chloroplasts SEM TEM Starch grain

93. Thylakoid – contains chlorophyll

94. Centrioles

98. Electron micrograph of plant cell

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

102. Protein Synthesis TASK: Use the diagram to compare & contrast protein synthesis in prokaryotes and eukaryotes

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