Cells and Microscopes Flashcards
Light microscopes use, advantages and disadvantages
Allows scientists to see biological structures in more detail.
Adv
- Cheap
- Small and portable
- Sample dead or alive
- Natural colour of sample seen
- Vacuum not required
- Simple preperation
Disadv
- Low resolution- o.25um
- Low magnification- x1500
- Stain needed to see important features
- Sample has to be thin
- 2D image
SEM use, advantages disadvantages
Allows scientists to see 3-dimensional structure of cells.
Adv
- 3D image
- High resolution 5-50nm
- High magnification x200,000
Disadv
- Expensive
- Large and static
- Black and white or false colour
- Samples must be in dead
- Vacuum required
TEM use
Allows scientists to see subcellular structures in more detail.
Adv
- High resolution 0.05-2nm
- High magnification x500,000
- Detailed image
Disadv
- Expensive
-Large and static
- Images black and white or false colour
- 2D images
- Samples must be dead
- Vacuum required
Laser Scanning confocal microscopy
- How it works
- Image formed
- Specimen features
Uses laser beams to scan a specimen that has been tagged with fluorescent dye. Laser causes dye to fluoresce, which is then focused into a pinhole into a detector, which generates an image onto a computer.
Pinhole aperture is so light from outside focal plane is blocked, reducing blurriness.
Form 3D by scanning multiple layers of a specimen and stacking together to form 3D image.
- In colour
- 2D/3D
- Lower resolution than electron microscopes
- Live specimen
Definition of:
Resolution
Magnification
Resolution- Smallest distance at which 2 separate structures can be distinguished from one another
Magnification- How many times larger an image is compared to its real size.
Stain uses
Differential staining
- Contrast
- Higher resolution
- X organelles more visible
Differential staining- when multiple stains are used and each binds to different structures.
M–>mm–>um–>nm
Microscope slides
Artefact meaning
Wet mount- Specimens are suspended in a liquid such as water or immersion oil, and cover slip placed at an angle (aquatic samples)
Dry mount- Dry sample viewed whole in sections and cover slip placed on top (muscle tissue, plants)
Smear slide- Edge of slide used to spread sample across another slide, creating even coating (blood)
Artefact- structural detail caused by *processing the specimen** and not a feature of the specimen (bubbles)
Preparing light microscope
- Clip slide containing specime onto stage.
- Select lowest powered lens and use coarse adjustment to bring stage up to below objective lens.
- Using course adjustment, move stage downwards to focus image
Use fine adjustment knob to get clear image of the specimen
How to calibrate eyepiece graticule
- Eye eyepiece graticule
- Calibrate using stage micrometre/find length of 1epu
- Measure diamtere of nucleus in epu
- Take repeat measurements and calculate mean (in epu)
- Use calibrated epu to find diametre (in um)
Eyepiece- scale inside eyepiece lens. Units are arbitrary (unknown)
Stage micrometre- scale in coverslip.
- Whole is 1mm long
- 100 divisions
- eac division is 0.01mm long
Eukaryote and Prokaryote difference
Eukaryote
- multicellular
- membrane bound organelles
- 80S ribosomes
- linear DNA (with histones)
- Nucleus
- Flagella made of microtubules in 9+2 arrangement
- Cellulose cell wall
Prokaryote
- unicellular
- no membrane bound organelles
- 70 S ribosomes
- Circular DNA (plasmids and nucleoid)
- no nucleus
- Flagella made of flagellin and helix structure
- Cell wall made of peptidoglycan
Nucleus structure and function
Nuclear envelope- double membrane
Nuclear pore- allows substances to exit or enter nucleus (ribosomes and mRNA)
Chromatin- DNA wrapped around histone proteins
Nucleolus- packed with DNA and protein, makes ribosomes
Ribosomes structure and function
- 2 subunits 60S and 40S
- made of ribosomal RNA and protein
- site of translation
SER structure and function
- network of cisternae
- no ribosomes
- storage and synthesising lipids and carbohydrates
RER structure and function
- Network of cisternae
- Ribosomes
- continuous with the nuclear membrane
- Folds and processes proteins
Golgi Apparatus structure and function
- Network of cisternae and vesicles
- no ribosomes
- Processes and packages proteins and new lipids
- also makes lysosomes
Vesicles structure and function
- single membrane
- transport substances in and out of cells and between organelles
Lysosomes structure and function
- type of single membrane vesicle
- break down waste materials in cell
- Break down pathogens in phagocytosis
Chloroplasts structure and function
- Double membrane
- thylakoids in stacks called granum (many granum are grana)
- Connected by membrane called lamellae
- fluid called stroma
- site of photosynthesis
Mitochondria structure and function
- Double membrane
- Cristae in fluid called matrix
- Site of cellular respiration
Plasma membrane structure and function
- Double membrane
- Controls what enters and exits cell
Centrioles structure and function
- Made of microtubules
- 2 form centrosomes
- involved in spindle fibre arrangement
Cell wall structure and function
- Made of cellulose
- supports cell
Flagella structure and function
- Made of microtubules in a 9+2 arrangement
- helps propel through liquids
Cilia structure and function
- Made of microtubules in a 9+2 arrangement
- allows substances to move across cell surface
Plasmodesmata structure and function
Narrow thread of cytoplasm that passes between cell walls of adjacent plant cells
- allows communication and exchange of substances
Protein synthesis
1) Proteins synthesised on ribosomes on RER
2) They then pass through cisternae and packaged into transport vesicles
3) Vesicles move proteins to cis face of golgi via transport function of cytoskeleton
4) Proteins are structurally modified before leaving golgi apparatus via trans face
5) Secretory vesicles carry proteins to cell membrane and fuses, releasing proteins by exocytosis.
