A2.2 Flashcards
Cell Structure (29 cards)
Microscopy
What is Cytology?
- Specific branch of biology that is focused on study of the cell and all aspects related to cellular structure and function.
- Relies on microscopes to provide understanding.
Microscopy
What is Magnification?
Magnification:
- The increase in an object’s image size compared to its actual size. (how many times larger is the viewed image that the object itself.
- Can be calculated by dividing size of the image by actual size of the object.
Actual Image: Image size/ mag
Mag: image size/ actual image
Image Size: Actual x Mag
Microscopy
What is meant by resolution
Minimal distance between two points/ objects at which they can still be distinguished as two.
— INDICATOR OR CLARITY (high res, higher clarity)
- Relationship between resolution and mag = inverse, as mag gets higher, resolution gets lower.
Microscopy
What is a micrograph?
A photo taken through a microscope to reveal the view of the microscope.
- Can be done from a light microscope but the ones of organelles are from an electron microscope.
- Often black and white
Microscopy
What does it mean to freeze fracture?
A technique that aids in viewing internal structures with an electron microscope.
1) specimen is rapidly frozen, then broken apart (fractured) creating a plane through the cell that can be observed.
2) Ice can be vaporized off and then a carbon/ patinum vapor is used to etch the surface and examine that etching under microscope.
Microscopy
What is a fluorescent stain?
Dyes that combine only with specific cellular components.
- When samples are irritated with UV/ violet blue light, those parts that it combines with will fluoresce and product visable colours to highlight those cellular components.
- Special microscopes have been nuilty that use high power LEDs to produce bright images.
Microscopy
What is immunofluorescence?
A more recent development in visibility enhancement.
- Makes use of antibodies that have dyes combined with them.
- Antibiodies are matched to identify/ bind to certain target molecules, often protiens.
- Antibiody binds to the target molecule —> creates a coloured glow.
- Used to detect viral proteins inside of cells.
Microscopy
Micrometre vs Centimetre
Micro –> 10^6 metres, would be 10^4 centimetres or 10^3 mm.
1 Micrometre = 0.001 mm.
Microscopy
Benefits of a Light Microscope
- Can pass light through organisms and are able to be used with both living/dead specimens.
- Affordable, safe, provide quality images at lower magnifications + visable colour
Microscopy
Benefits of an Electron Microscope
- Use beams of electrons
- Short wavelength of electrons preserves resolution at higher magnifications
- can magnify up to 1,000,000 times.
- can not be used with living species/ always black and white
Microscopy
Coarse Focus vs Fine Focus
COARSE - makes larger adjustments bring objects into focus. Used first.
FINE - Adds sharpness and clarity.
Microscopy
To calculate actual size
Magnification=image size/actual size.
- Use scale bar to find the first determine the magnification.
Microscopy
Scanning Electron Mciroscpoe vs Transmission
SEM - (scanning electron microscope): uses a beam of electrons to scane the outer surface of the specimen –> provides detailed images of the exteriors.
TEM - (transmission electron microscope): beams electrons through a thin section of the specimen to allow internal structures to be viewed.
Microscopy
Cryogenic Electron Mircosopy
(Cryo-EM), used for researching protein structure.
- protein solution is applied to a grid, this layer is flash frozen (like with liquid ethane)
- frozen protein gird is placed in an electron microscope, the pattern the electrons are transmitted by the protein is recorded, the computer uses the pattern to create a theorised 3D protein structure image.
Microscopy
Benefits of Flurorescent Stains
- stains bind to specific structures, help them to stand out from surrounding structures.
- special fluroescent microscopes are useful at creating imgaes that clearly show the placement of key cellular structures.
Prokaryotes and Eukaryotes
What is a prokaryotic cell?
- Simple unicellular organisms, primarily bacteria.
- Prokayotic cells are small and simple, lacking in complex organelles.
- Term means “before nucleus”, they’re ancesteral organisms, before evolution of nucelus.
What is a eularyotic Cell?
- Eukaryotic cells are larger, more complex, make up plans and animals and fungi and protists
- Term means “true nucelus”, the DNA of their cells contain nucelus.
- also contain other membrane bound (structurall complex) specialised organelles carrying out unique functions.
Prokaryotes and Eukaryotes
What is peptidoglycan?
- The make up of fungi, plants, and prokaryotic cell’s cell walls unique from other organisms and is usually comprised of a carbohydrate and protein polymer called peptidoglycan.
- Can be found in the cell membranes of all bacteria.
- another type of prokaryotes called archae, and they don’t usually have peptidoglycan.
Prokaryotes and Eukaryotes
Features common to all cells
- A cell membrane (phospholipid bilayer) to allow transport into and out of cells.
- DNA to provide the isntructions for the production of protiens.
- Ribosomes to make proteins
- Cytoplasm as the inside component of the cell.
Prokaryotes and Eukaryotes
(some) Bacterial Cell Structure: Capsule
An additional thick layer outside of the cell wall.
- Made up of polysaccharides and is used to help the bacteria adhere to structures in other organisms (teeth, skin - fruits/ vegtables.)
Prokaryotes and Eukaryotes
(some) Bacterial Cell Structure: Pili
Small hair structures on the outside of the cell wall.
- Can be used to attatch onto other organisms but also have a uniqe function in reproduction.
- Have two bateria cells to join together and exchange DNA to facilitate a form of sexual reproduction.
Prokaryotes and Eukaryotes
(some) Baterial Cell Structure: Flagella
A Whip-like tail called a flagellum (singular) or multiple flagella.
- Longer than pili, help the cell to move.
Prokaryotes and Eukaryotes
(some) Bacterial Cell Structure: Plasmids
A single long continuous circule thread of DNA. (in prokarotes)
- Bacteria also can contain smalle rings of DNA that are not connected to the main chromosome –> seperately replicate, do not contain essential DNA for survival but often have helpful adaptive genes, like antibiotic resistance.
- Bacteria can transfer plasmids to one another and share adaptive genes.
Prokaryotes and Eukaryotes
Gram Positive vs Gram Negative Bacteria
Divided into Pos or Neg based of their cell membrane.
GRAM-POS: they have a thick layer of peptidoglycan as their cell wall.
GRAM-NEG: also have a peptidoglycan, but a thin layer underneath an additional outer membrane.
