Lecture 4-7 Flashcards
Prokaryotic microorganism
bacteria and archaea
most bacteria have cell walls that contain…
peptidoglycan (polymer consisting of sugars and amino acids)
most archaea have cell walls that contain…
seudopeptidoglycan, differences in genetics, metabolic pathways, and the composition of membranes
Domain Eukarya (4):
Protists, fungi, plants, and animal
Algae (3)
- unicellular or multicellular
- cell walls made of cellulose
- Photosynthetic
Protozoa (3)
- very diverse
- move with cilia or flagella
- some are photosynthetic, parasitic, pathogenic
Fungi (3)
- Unicellular or multicellular
- Non-photosynthetic
- cell walls contain chitin rather than cellulose.
- Yeasts (3)
- unicellular
- Large impacts in food production & safety
- Can cause gonadal infections and oral thrush
- Molds / filamentous fungi (4)
- multicellular
- made up of long filaments (pl. hyphae) that form visible colonies
- play a critical role in decomposition and nutrient cycling
- have been used to make pharmaceuticals
viruses
Acellular microorganisms that consists of proteins and genetic material—either DNA or RNA, but never both
Light microscopy:
resolves images according to absorption of light
Electron microscopy:
uses beams of electrons to resolve smaller details (smaller than the wavelength of visible
light)
Atomic force microscopy:
uses intermolecular forces to map 3D-
topography of the cell
X-ray crystallography:
detects the interference patterns of X-rays entering the crystal lattice of a molecule
four types of light microscopy:
- Bright field microscopy
- Dark field microscopy
- Phase-contrast microscopy
- Fluorescence microscopy
Oil immersion lens/microscopy:
Putting a drop of oil between the lens and the object minimizes loss of refracted light at the
widest angles and sharpens image
Bright Field Microscopy
- Object appears as a dark silhouette blocking passage of light
- The limit of resolution is ~1000x
A simple stain adds…
dark colour specifically to cells, but not to the external medium or surrounding tissue
A differential stain stains…
one kind of cell but not another
Acid-fast staining can differentiate two
types of gram-positive cells:
those that have waxy mycolic acids in their cell walls, and those that do not.
Endospores are…
structures produced within certain bacterial cells that allow them to survive harsh conditions
Phase-contrast microscopy exploits…
differences in refractive index between the cytoplasm and the surrounding medium or between different organelles
In fluorescence microscopy:
specimen absorbs light of a defined wavelength and then emits light of lower energy (longer wavelength)
Autofluorescence:
some cell components naturally fluoresce under specific light wavelengths; no stain required!
Fluorophores:
fluorescent compounds or proteins that can fluoresce
immunofluorescence:
used to identify certain disease-causing microbes by observing whether antibodies bind to them
Electron Microscope (EM)
Uses beams of electrons instead of light in the visible spectrum for visualization
* Can produce a sharp image magnified up to
100,000X
Scanning Electron Microscope (SEM):
creates an image by detecting reflected electrons; topology (3D)
Transmission Electron Microscope (TEM):
uses electrons that are passing through thin sections of the sample (transmitted) to create an image (Electron-dense regions appear darker)
