What is the actual size of this?

1.1 Introduction to cells Nature of science: Understandings: Applications: Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae. Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism. Use of stem cells to treat Stargardt’s disease and one other named condition. Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues. Understanding: Understandings: According to the cell theory, living organisms are composed of cells. Organisms consisting of only one cell carry out all functions of life in that cell. Surface area to volume ratio is important in the limitation of cell size. Multicellular organisms have properties that emerge from the interaction of their cellular components. Specialized tissues can develop by cell differentiation in multicellular organisms. Differentiation involves the expression of some genes and not others in a cell’s genome. The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic Skills: Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) Nature of science: Looking for trends and discrepancies—although most organisms conform to cell theory, there are exceptions. (3.1) Ethical implications of research—research involving stem cells is growing in importance and raises ethical issues. (4.5)

Magnification Calculate true size, image size, and magnification Make unit conversions

Magnification Micrographs often have the magnification or scale bars to allow calculation of the actual size of specimens. x400 4.55μm

Magnification In this exercise you will calculate the magnification and/or true size of the following: 1 2 3 4 5 8 6 7 10 9

Before we begin: Note: Numbers written like this: 1.26 x 105 mean you move the decimal point to the right. In this case you move it 5 times: 1.26 x 105 = 126000.0 1.2 6 0 0 0 0 .

Before we begin: Note: Numbers written like this: 1.26 x 10-5 mean you move the decimal point to the left. In this case you move it 5 times: 1.26 x 10-5 = 0.0000126 0.0 0 0 0 1. 26

Have a go at these: 14500.0 1.45 x 104 = 0.37 x 107 = 86.41 x 10-3 = 3700000.0 0.08641 0.0265

Units Unit How many millimeters Millimeter (mm) 1 mm Micrometer (μm) Nanometer (nm) 0.000001 mm

Conversions mm into μm (x 1000) μm into nm (x 1000) 32.5 mm is how many μm? 32 500

Calculations… Size of image (I) True size (T) Magnification (M) Write the equations for each Size of image (I) True size (T) Magnification (M)

Figure 5.1 Paramecium caudatum Find the true size (T) x600

Figure 5.1 Paramecium caudatum Measured length = 142mm 142 ÷ 600 = 0.237mm 0.237mm = 237μm x600

Figure 5.2 chloroplasts x9000

Figure 5.2 chloroplasts Mean measured length of the four largest chloroplasts = 39.25mm 39.25 ÷ 9000 = 0.0044mm 0.0044mm = 4.4μm x9000

Figure 5.3a bacterium (actual size = 0.002mm) Calculate the magnification (M) Measured length = 128mm 128 ÷ 0.002mm = magnification Magnification = x64000

Figure 5.4 seven week human embryo

Figure 5.4 seven week human embryo If you have a scale bar… Measure the actual length of the scale bar (25mm) and divide by the length it represents Magnification = 25 ÷ 10 = x2.5

Figure 5.5 head of a fruit fly

Figure 5.5 head of a fruit fly A length of the scale bar - 12.5mm Magnification = 12.5 ÷ 0.2 = x62.5

Figure 5.6 pollen grain

Figure 5.6 pollen grain (a) Measure the actual length of the scale bar and divide by the length it represents Magnification = 25 ÷ 0.02 = x1250 (b) Image size = 47mm. What is the true size? (c) 47 ÷ 1250 = 0.0376mm 0.0376mm = 37.6μm

Figure 5.7 red blood cells in an arteriole

Figure 5.7 red blood cells in an arteriole Measured length of scale bar = 30mm Magnification = 30 ÷ 0.01 = x3000 Diameter = 25mm Actual diameter = 25 ÷ 3000 = 0.0083mm 0.0083mm = 8.3μm

Figure 5.8 a mitochondrion

Figure 5.8 a mitochondrion Measured length of scale bar = 30mm Magnification = 30 ÷ 0.002 = x15000 Measured width = 34mm Actual width = 34 ÷ 15000 = 0.0023mm 0.0023mm = 2.3μm

Figure 5.9 bacteriophage [a type of virus]

Figure 5.9 bacteriophage [a type of virus] Measured length of phage = 29mm Magnification = 29 ÷ 0.0002 = 145000 what about in standard form? Magnification = 1.45 x 105

Magnification The resolving power of the unaided eye is approximately 0.1mm The maximum useful magnification of light microscope is around x1500 Plant and animal cells typically measure around 20µm Many organelles are as small as 25nm – beyond the resolving power of the light microscope [wavelength of light is 500nm approx] Wavelength of electron beam is 0.005nm Maximum resolving power of the electron microscope is 0.2nm