Unit 1: Microscopy Flashcards Preview

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Flashcards in Unit 1: Microscopy Deck (31):

What is Microscopy?

Ratio of image size to object size


What is Resolution?

The ability of distinguish between 2 objects that are close together


Magnification Formula

Magnification (M) = Image size (I) ÷ Actual size (A)


What are the 4 types of microscopes?

Light, Scanning Electron (SEM), Transmission Electron (TEM) and Laser Scanning Confocal


Light Microscope Facts

Magnification 1000-2000x, Resolution 50-200nm and used for viewing tissues and cells


Scanning Electron Microscope (SEM) Facts

Magnification 50000-500000x, Resolution 0.4-20nm and used for viewing surfaces of cells and organelles in 3D images


Transmission Electron Microscope (TEM) Facts

Magnification 300000-1000000x, Resolution 0.05-1.0nm and used for detailing organelles - ultrastructure


Laser Scanning Confocal Microscope Facts

Magnification 1000-2000x, Resolution 50-200nm and used to provide 3D images with good depth selection


Advantages and Disadvantages of LM

+ Cheap and easy to use
+ Allows us to see living things
- Limited resolution


Advantages and Disadvantages of SEM & TEM

+ Better resolution than LM and therefore clearer, more detailed images
+ SEM is 3D and is good for viewing surfaces
- Very large and expensive which require trained operatives
- Cannot view living organisms
- Images are black and white (colour added through false colour electron micrographs)


Advantages and Disadvantages of LSCM

+ Specimens can be living
+ Can be focused at specific depths
- Relies on computers to create image, which is made from dots of light created by lasers - the image is more of an interpretation


What is staining?

Application of coloured stains to the tissues or cells


What is the purpose of staining?

Most cell components are colourless and hard to see, therefore staining makes them visible under LM, increases the contrast between organelles and is often specific to each tissue or organelle


Examples of stains

Acetic Orcein: Chromosomes - Dark red
Eosin: Cytoplasm
Sudan Red: Lipids
Iodine (from Potassium Iodide): Cellulose - Yellow, Starch Grains - Blue/Black

In an electron microscope, stains are typically heavy metals that reflect/absorb electrons


What are cells?

The basic component of living organisms


Cell wall

Cellulose cell wall surround plant cells



1. Involved in the organisation of the microtubules that make up the cytoskeleton
2. Form spindle fibres to move chromosomes in nuclear division



Site of photosynthesis



1. Small hair-like extensions of cell surface membrane containing microtubules
2. Large numbers work in synchronised fashion
3. Able to move whole organisms or to move fluid (mucus) across a surface



1. Network of microtubules and microfilaments
2. Provides mechanical strength, support and structure for the cell
3. Maintains the cell shape and is used in some cells to change the shape of the cell
4. Enables movement of organelles inside the cell
5. Enables movement of the whole cell



1. Large extension of cell-surface membrane containing microtubules (in eukaryotes)
2. Able to beat to enable locomotion or move fluids


Golgi apparatus

1. Modifies proteins made in the ribosomes
2. Often adds a carbohydrate group
3. Repackages proteins into vesicles for secretion



Small vacuoles containing hydrolytic or lytic enzymes



Site of aerobic respiration


Nucleus, Nucleolus and Nuclear Envelope

1. Contains the genetic material (chromosomes)
2. Controls the cell activities
3. The nuclear envelope separates the genetic material from the cytoplasm
4. The nuclear pores allow molecules of mRNA to pass from the nucleus to the ribosomes in the cytoplasm
5. The nucleolus assembles the ribosomes



Site of protein synthesis


Rough Endoplasmic Reticulum (RER)

1. Holds many of the ribosomes
2. Provides a large surface area for protein synthesis


Smooth Endoplasmic Reticulum (SER)

Associated with the synthesis, storage and transport of lipids and carbohydrates


Production and Secretion of Proteins

1. mRNA leaves nucleus via nuclear pores
2. It is used by the ribosomes in the RER to construct a protein
3. This protein travel to the golgi in a vesicle
4. The vesicle is moved by the cytoskeleton
5. The golgi modifies the protein, often by adding on a carbohydrate group and repackages it into a vesicle
6. The vesicle is moved into the cell surface (plasma) membrane
7. The vesicle fuses with the membrane to release the protein from the cell


Prokaryotic Cells

1. Smaller than eukaryotes - 10um long and 1-2um wide
2. No nucleus
3. No membrane-bound organelles
4. 18nm sized ribosomes
5. Single loop of DNA; no histones
6. Some cells have a flagellum, and generally have a very different structure


Eukaryotic Cells

1. Larger than prokaryotes - 10um diameter
2. Has a nucleus
3. Has membrane-bound organelles
4. 22nm sized ribosomes
5. DNA associated with proteins (histones)
6. Some cells have a flagellum with '9+2' structure of microtubules