IB Biology Unit 1

Cell theory

• All living organisms are made of cells

  • Multi or unicellular

• Basic unit of life

• Come from pre-existing cells

Light microscope

• can view live and dead specimens

• poor surface view

• uses light rays to illuminate specimens

• low magnification (1500x)

electron microscope

• views only dead specimens

• good surface view and internal details

• uses beam of electrons to view specimens

• high magnification (1,000,000x)

Staining

• improve visibility

• uses dye or iodine

Immunofluorescence

• made antibodies that bind to target areas and make them more visible

Freeze fracturing

Freeze the specimen using liquid nitrogen, causing it to crack, exposing the insides of the specimen. Able to reform it.

Cryogenic electron microscopy

• Able to see the 3D structure of proteins

• electron gun shoots electrons through the sample

• high-tech camera catches the image and projects it

• Specimen can be moving

Calculating magnification

• Scale bar=μm, so convert ruler to μm

• 1mm = 1000 μm so 20mm = 20,000 μm

• To calculate magnification

  • scale bar measurement/scale bar label = 20,000 μm/ 10μm

  • magnification = 2,000 times

Calculating actual size

• measure the part of the image you are instructed to and divide it by the magnification

• convert to the most appropriate units

• measured length/magnification

• ex: 80mm/90,000 = 8.9 × 10^-4mm OR 0.00089mm

  • converts to 0.89μm

prokaryotic cells