A-Level Biology OCR Notes: Cell Structure

2.1.1 Cell Structure

Types of Microscopes
- Light Microscope
  - Uses a light beam
  - Provides 2D images
  - Max Magnification: X1,500
  - Max Resolution: 200 nm
- Scanning Electron Microscope (SEM)
  - Uses an electron beam
  - Provides 3D images
  - Max Magnification: X200,000
  - Max Resolution: 20 nm
- Transmission Electron Microscope (TEM)
  - Uses an electron beam
  - Provides 2D images
  - Max Magnification: X2,000,000
  - Max Resolution: 0.1 nm
Magnification and Resolution
- Magnification: Size of image compared to original object
- Formula: Magnification = (size of image)/(size of object)
- Resolution: Ability to distinguish between two close points
Preparing Slides for Light Microscopy
- Dehydrate specimen
- Embed in wax and section
- Stain specimen
- Mount specimen
Staining
- Used to increase contrast
- Binds to molecules or cell structures
- Differential staining helps identify cell components

Organisms: Animals, plants, fungi
Organelles Present in Eukaryotic Cells:
- Detailed images in provided diagrams
Additional Organelles in Plants, Algae, Fungi:
- Detailed images in provided diagrams
Cytoskeleton
- Complex protein network in cytoplasm
- Microfilaments
  - Made of actin
  - Maintain cell shape and mechanical strength
- Microtubules
  - Made of tubulin
  - Involved in movement of organelles and substances
- Intermediate Fibres
  - Interlocking protein fibres
  - Anchor nucleus, stabilize tissues
Specialization
- Eukaryotic cells specialize for functions
- Organized into tissues, organs, systems