3 points of comparison between transmission electron microscopes and scanning electron microscopes
TEM:
- use electromagnets to focus beam of electrons
- high resolution images
- only used on thin specimens
SEM:
- scan beam of electrons across specimen to knock electrons from specimen
- lower resolution
- 3D images of surface
plasma membrane
-Found on surface of animal/plant cells
- regulates movement of substances in/out of cell
- receptor sites for proteins and hormones
- partially permeable
cell wall
- rigid
- supports plant cells/ gives it strength
- plants=cellulose
- fungi=chitin
nucleus
controls the cell’s activities
nucleolus
- most of genetic material kept
- makes ribosomes
nuclear pores
- regulates what goes in/out of cell
e. g mRNA
lysosome
-contains digestive enzymes:
- used to digest invading cells
- break down worn components of cell
ribosome
-site where proteins are made
- free in cytoplasm or:
- attached to RER
Rough Endoplasmic Reticulum
folds/processes proteins made in ribosomes
smooth endoplasmic reticulum
synthesises and processes lipids
vesicle
transports substances in and out of cell
fuse to cell membrane
Golgi apparatus
- processes and packages new lipids and proteins
- can make ribosomes
mitochondria
site of aerobic respiration where ATP is produced
- have a double membrane
- have a matrix
- cristae
chloroplast
the site where photosynthesis takes place
- have double membrane
- have grana-(stacked)
- have lamellae-(join grana)
centriole
involved with the separation of chromosomes during cell division
cytoskeleton
network of protein threads: arranged as microfilaments and microtubules
- support organelles
- strengthen
- transport
- movement
Protein Production
- Proteins made at ribosomes
- Free ribosomes and ribosomes on RER make protein.
- New proteins are folded and processed in RER
- Proteins transported from ER to Golgi apparatus in vesicles
- At Golgi apparatus, proteins undergo further processing
- Proteins enter more vesicles to be transported around the cell
Light microscopes
- 0.2μm resolution
- x1,500 magnification
- alive or dead specimens
- cheap
- colour through staining
- 2D
magnification
the degree to which the size of an image is larger than the object itself
resolution
the degree to which it is possible to distinguish two objects that are very close together
Transmission Electron Microscopes
- 0.0002μm resolution
- x500,000 magnification
- dead specimens
- expensive
- no colour
- 2D
Scanning Electron Microscopes
- 0.005μm resolution
- x100,000 magnification
- dead specimens
- expensive
- no colour
- 3D
staining
- put little drop of stain onto a cell or specimen
- some stains bind to specific cell structures so you can see those cell structures more clearly
sectioning
when specimens are embedded in wax in sections then cut without distorting the structure specimen
