Ch 2 Microscopy Flashcards
What were the first microscopes like?
They were simple microscopes that allowed people to see microorganisms. Through these microscopes, light was passed through only one lens.
What types of things could be seen with the first microscopes?
microbes like bacteria, protozoa, and single-celled organisms.
What does resolution mean?
ability to differentiate that 2 points are separate.
What factors determine resolution?
wavelength and numerical aperture
How does wavelength affect resolution?
shorter wavelengths have a greater resolving power, allowing people to see smaller objects.
How does numerical aperture affect resolution?
measures the ability of a lens to gather light; the higher it is, the better the resolution of an object is
Why is immersion oil important?
It enhances resolution by collecting more light to strike the lens.
What size range are “typical” eukaryotic cells?
Around 10 µm to 100 µm
What size range are “typical” prokaryotic cells?
About 1 µm
What size range are “typical” viruses?
Roughly 100 nm
What is Bright field microscopy?
A compound microscope that is one of the most used types of microscope. It produces dark images of an organism on a white field. It uses staining to increase the contrast and resolution of a specimen.
What is Dark field microscopy?
produces an image of a light organism on a dark field
- it does not need stains to create a high contrast and resolution image of a specimen
Which specimen does dark field microscopy examine?
live, unstained specimens.
What is phase contrast microscopy?
utilizes refraction and interference caused by the structures in an organism. Refraction and interference allow the production of high-resolution and contrast images.
- images are created by the alteration of wavelengths of light rays that pass through the organism
Which specimen does phase contrast microscopy examine?
live specimens
Ex: endospores in prokaryotic cells and organelles in eukaryotic cells
What is fluorescence microscopy?
Uses fluorochromes that absorb energy from a light source and emit it as visible light. Fluorescent probes bind to specific cell types or type of structure to create an image of an organism in bright colors against a dark field.
Which specimen does flourescence microscopy examine?
spot and pinpoint disease-causing microorganisms (immunofluorescence).
What is confocal microscopy?
lasers scan numerous z-planes, to create multiple high-resolution, 2-D images at a variety of depths
- These images can be used to create a three-dimensional image using a computer. Fluorescent stains increase the resolution and contrast of the images.
Which specimen does confocal microscopy examine?
thick specimens both unfixed and alive
What is electron microscopy?
increase the magnification and resolution of an image by using short-wavelength electron beams. They have very short wavelengths of 0.005nm with a very high resolution of 1nm. With these microscopes, people can see subcellular structures. This type of microscopy cannot be used on living material.
What is scanning electron microscopy?
used to view surfaces of specimens
- a beam of electrons is used to knock electrons off the surface of the microorganism
- three-dimensional, highly detailed images
What is transmission electron microscopy?
Electron beams that pass through an organism are used to examine small images. The specimens have to be extremely thin and dehydrated to see the internal structures of the specimen.
What is probe microscopy?
Very short and sharp probes that are passed over the surface of the specimen and directly interact with it are used. This type of microscopy does not use light or electrons. It can be used to view atoms and surfaces.
What is scanning tunneling probe microscopy?
Pictures the structure of surfaces at a resolution where atoms can be seen. The process involves moving a probe horizontally above a surface and measuring the variations in the current. This type of microscopy works best with conducting materials
What is atomic force microscopy?
It has a constant current, but it measures variations in the height of the thin probe tip as it is passed just above the specimen. With a resolution at the atomic level, images of the surface of the specimen are produced. Atomic force microscopy is easier to use with nonconducting specimens.
What microbes/structures can we NOT see with our brightfield microscopes?
Viruses
