Microscopy Flashcards
development of microscopy
Robert Hooke (1665) constructed the first LM, observed dead cork tissue and other plant and animal tissue - introduced the term “cell” from monk cells
magnification
- number of times an object is magnified
- how much smaller/larger is the image than the real specimen
resolution
- the ability of a microscope to show two close objects separately
- depends on the wavelength of the rays that pass through the spectrum (e- have much shorter wavelength so EM has much higher resolution)
LM vs EM
- what passes through specimen?
- FOV (field of view)?
- magnification?
- resolution?
- colors?
- type of specimen?
- beam of light/beam of electrons
- larger/smaller
- up to 500x/up to 500 000x
- 0.25 microm apart/0.25 nanom apart
- visible/black-white
- alive/dead
- as magnification increases, FOV…
…decreases
magnification =
image size/actual size
scale bar
- a line added to the micrograph to show the actual size of the structure
freeze-fracture EM
- physically breaking apart frozen biological sample through the weakest piint of the cell
- structural details exposed by the fracture plane is visualized by deposition of Pt-C to make a replica for examination in the EM
cryogenic EM
- structures of proteins, nucleic acids and other biomolecules
- studying how they move around and change as they perform their functions (alive)
cell theory
1) cells are the basic units of life (nothing smaller than the cell can survive independently)
2) all living things consist of cells
3) new cells come from pre-existing cells by the process of cell division
1) cells are the basic units of life (nothing smaller than the cell can survive independently) - evidence
- sub-cellular components have never been seen to perform functions of life whereas full cells have
2) all living things consist of cells - evidence
- biologists examined tissues from all kingdoms, each specimen had at least one cell
3) new cells come from pre-existing cells by the process of cell division - evidence
- we have observed cells coming from other cells but never observed spontaneous generation
discrepancies (exceptions) to the cell theory
1) Striated (skeletal) muscles
- more than 1 nucleus per cell
- long cells, around 30 mm
2) Giant algae, Actabularia
- single-celled organism but up to 20 cm long
3) Aseptate Funghi
- fungal hyphae (narrow thread-like structures) are made up of rows of cells usually separated with septa but some funghi lack this septa -> each hyphae is a continuous multinucleated tube-like structure
unicellular organisms…
(example)
…carry out all functions of life. Amoeba
functions of life
1) metabolism
2) response
3) nutrition
4) excretion
5) reproduction
6) growth
7) homeostasis
8) movement
metabolism
all chemical reactions in a cell (catalyzed)
response
ability to react to stimuli from the environment
nutrition
obtaining food to get energy
excretion
removal of waste products
reproduction
production of offspring sexually or asexually
growth
irreversible increase in size
homeostasis
regulating internal conditions (keeping them within limits)
all cells (prokaryotic and eukaryotic) have some basic features in common:
- plasma membrane
- cytoplasm
- DNA
- present ribosomes
differences between euk. and pro.
- size (pro - 0.2-10 microm, euk - 10-100 microm)
- complexity - eukaryotic cells are compartmentalized (many differences arise from this fact like type of cell division, DNA structure…)
pro, eu, karyon
before, real, nucleus
TEM and SEM
transmission electron microscope (for the interior) and scanning electron microscope (for the surface)
structure of a cell seen from a microscope
ultrastructure of cells
anucleate cells vs multinucleate cells
don’t have a nucleus - cannot transcribe DNA to make mRNA and synthesized proteins - red blood cytes (erythrocytes)
have multiple nuclei (more mRNA and proteins) - skeletal muscle/aseptate fungi
