1. Cellular & Molecular Structure & Function Flashcards
(230 cards)
What is the approximate size of the nucleus?
5-10μm
What is the approximate size of a cell?
20-30μm
What is the approximate size of a RBC?
7μm
What is the smallest separation between two points that the eye can see?
0.1mm
Define a cell.
- A single unit or compartment enclosed by a border or membrane.
- Smallest metabolically functional unit of life.
Will extra magnification always help see the object in better detail?
No, because resolution depends on the wavelength of magnifying rays, so magnifying beyond a certain point will just “magnify the blur”.
Give an example of a biological scale marker.
Red blood cells - They are usually exactly 7μm, so they give a good comparison for size in a magnified image.
What are the two types of sample section?
- Transverse section (TS)
- Longitudinal section (LS)
Describe the difference between the two types of tissue section.
- Transverse section - Cross section of a long structure
- Longitudinal section - Cut parallel to long axis of structures inthe sample
What things give need for section preparation before observing it under a microscope?
- Tissue decay
- Loss of structural detail
- Autolysis (break down by own chemicals)
What is fixation?
The process by which tissue decay and degradation is stopped. It often involves cross-linking proteins to give additional rigidity.
What are the main steps of section preparation for observation under a light microscope?
Fixation, Sectioning, Staining
What are the two ways in which tissues being prepared for observation are stopped from decaying, autolysis and loss of structural detail?
- Chemical cross-binding
- Cryo (low temperature)
Describe how a sample may be sectioned.
- Embed in wax block
- Cut wax block into sections
What are the three routine staining techniques you need to know about?
- Histochemistry
- Immunohistochemistry (a.k.a. Immunocytochemistry)
- In situ hybridisation
What is histochemistry?
Staining of cells with specific chemicals (such as with a H&E stain).
What is another name for immunohistochemistry?
Immunocytochemistry
What is immunohistochemistry?
Localisation of specific tissue antigens using labelled antibodies.
What is in situ hybridisation?
Localisation of a specific nucleic acid sequence by adding a complementary strand of RNA or DNA, then adding a labelled molecule similar enough to bind with it.
What are the main types of microscope?
- Light microscope (LM)
- Electron microscope (EM) -> Transmission and scanning
- Fluorescence microscope (FM)
- (EXTRA) Confocal scanning laser microscope (CF)
Describe how a light microscope works.
Light from source:
- focussed by condenser lenses
- light passes through section
- section detail magnified by objective lens
- further magnified by eyepieces
- eyes see the contrast in the magnified image
Draw a diagram of how a light microscope works.
What is the resolution of a light microscope?
0.2µm
What is the significance of the resolution of light microscopy?
Can see:
- Bacteria
- Details within nucleated cells such as nuclei, mitochondria, ribosomes and storage ‘granules’.




