Topic 1 Flashcards
What is a cell?
a vehicle for the hereditary information that defines a species
Who discovered the cell?
Z and H Janssen, Robert hook and Anton van Leeuwenhoek
H and Z Janssen
produced the first compound microscope
1590
What is a compound microscope
A microscope with multiple lenses
Robert Hooke
Used a compound microscope
described the chambers in Cork as cells
1665
Anton van Leeuwenhoek
first to observe living cells
made his own microscope
1673
what objective does van Leeuwenhoek microscope have
~300x
Who proposed the first two rules of the cell doctrine? what year 1839
Schleiden and Schwann
1839
Who proposed the third rule of cell doctrine and why was it added
Virchow
Added because ppl believed in spontaneous generation
The cell doctrine
- All life is made from one or more cells
- Cell is the basic unit of structure for all organisms
- All cells arise from pre-existing cell
Exception of rule 3 of the cell doctrine
viruses, liposome and artificial cells
J. Craig Venture institute
built a completely synthetic genome
What are the 10 most important universal features of cells
- All cells store their hereditary information in the same linear chemical code (DNA)
- All cells replicate their hereditary information by templated polymerization
- All cells transcribe portions of their hereditary information into the same intermediary form (RNA)
- All cells use proteins as catalysts
- All cells translate RNA into protein the same way
- The fragment of genetic information corresponding to one protein is one gene
- Life requires free energy
- All cells function as biochemical factories dealing with the same basic molecular building blocks
- All cells are enclosed in a plasma membrane across which nutrients and waste materials must pass
- A living cell can exist within fewer than 500 genes
What is Cell Biology
Combo of Biochemistry, Cytology and Genetics
Why can’t we see neurons/how long can they get
Neurons can be a meter long but too thin to see with naked eye
Resolution
The minimum distance between two objects where we can determine that they are distinctly separate
What is the resolution of a light microscope?
just under 200nm
What is the resolution of the human eye
Resolution for our eye is 100um
Definition for resolution of a light microscope (formula)
Resolution = 0.61 (lambda)/NA
How to get a better resolution
Larger angle and shorter wavelength (violet light (390))
Does a small distance make for better or worse resolution?
Small distance = higher or better resolution
what is the issue with trying to observe cells using wavelength? What can we do to solve this issue?
lots of cells are translucent
Can add stains to visualize
(may kill cell)
Violet light wavelength
390nm
electromagnetic wavelength
0.004nm
Types of microscopy (7 types)
- Brightfield microscopy
- Phase contrast microscopy
- Differential interference contrast microscopy (Nomarski)
- Fluorescent microscopy
- Confocal microscopy
- Transmission electron
microscopy (TEM) - Scanning electron microscopy (SEM)
Brightfield microscopy
Light is shone through the specimen and is blocked by material which creates a shadow
can increase contrast with stains
can use with living sample
Phase contrast microscopy
Uses phase and absorbed light
compare light that travelled through light that didn’t to get an image (constructive and destructive interference)
can be used on living samples
Constructive and destructive interference
Peak + peak =constructive
Peak +troft = destructive
Differential interference contrast microscopy (Nomarski)
Uses phase light and absorbed light and polarization of light
How does polarization work
Light can be oriented to travel in a sheet
When light hits the sample it shifts the plane of light
Blocks reflected light from travelling through (ie polarized sunglasses)
Fluorescent microscopy
Light is generated by fluorophores in the sample
fluorescent samples have an excitation and emission wavelength
Emmision wavlength is _____ and excitation is ______
longer
shorter
how do dichroic mirrors work in fluorescent microcopy?
Light is shone into the microscope which then reflects off the dichroic mirror down to the sample which then excites the fluorophores and light passes through the mirror and is detected at the top using imaging
Confocal microscopy
Uses Z stacking to create a 3D image
Can look specifically for fluorescence anywhere in an object
Z stacking
Using cross sections to create a 3D image
used with fluorescence
Transmission electron microscopy (TEM)
opposite of brightfield
x-rays that are focused with magnets are sent through the sample and look at where they are blocked
done under vacuum conditions
samples are stained with heavy metals
cant use for living samples
Resolution is 2nm
Scanning electron microscopy (SEM)
Samples are frozen or dried and then sprayed with a very thin layer of heavy metals
uusually gold bc its electron dense
Works in vacuum
Resolution ius about 10nm
Not compatible with living organisms
Green fluorescent protein (GFP)
originally isolated from a jellyfish
It fluoresces green
gene that makes this protein can be put into any organism to make them fluoresce
Green fluorescent protein (GFP) excitation and emission
Excitation: 465
Emission: 510
What doe the Green fluorescent protein (GFP) promoter do?
The promoter determines whether the gene is on or off
(acts as a lightswitch)
Why is cell size important
The larger the cell becomes the less efficient internal processes become
More energy costing
slower rates of diffusion
lower membrane volume with larger cells
Surface area to vlume ratio: More sides = ____ surface area and _____ volume
more
less
The three domains
Bacteria
Archae
Eucaryotes
prokaryotes
Bacteria and archae
Have no true nucleus
Generally lack internal membranes and compartments (organelles)
There are still some levels of organization
What does Prokaryote
Means pre-kernel (no true nucleus)
Eukaryotes
Have a nucleus
Have organelles
Are compartmentally organized
Everything inside the plasma membrane
cytoplsm
Everything inside the plasma membrane, apart from organelles
cytosol
T or F: Organisms can be unicellular or multicellular
True
If organisms are a single cell for most of their life we classify them as……
microbes!
Rank from highest to lowest number of genes in a genome:
Prokaryotes
Eukaryotes
Multicellular organisms
Prokaryotes > Eukaryotes > Multicellular organisms
Primary cell culture
Taken directly from the organism
Secondary culture
Subculture of a primary culture
Invetro
biological components removed from the cell
Invevo
within the same biological system
In silico
experiment done computationally (performed by computer)
How are cells typically grown?
Suspended in a liquid (pure liquid)
Suspended in a semi-solid
Plated on the surface of a semi-solid (agar)
Cells are grown in
Media
healthy animal cells are
anchorage-dependent for growth in media or else they undergo programmed cell death
Normal vs Transformed (animal cell culture)
Normal: Healthy, Anchorage-dependant, attached to a component of the extracellular matrix
growth factor dependant
contact inhibited
Transformed: Opp of normal cells, Anchorage-independent, Growth factor independent, Not contact inhibited
hayflick limit
amount of time a cell will divide before dying (normal cell: ~50-100 times), does not affect transformed cells
Eagles basal medium (1955) MORE DETAILS
Amino acids: There at 10 amino acids, we can make, the 10 we need from diet are called essential amino acids because we have to consume them
Vitamins: functional ground that certain proteins require to function that cant be produced by our body, function as components of coenzymes
Salts: Used for maintenance of tonicity and membrane potential as components of buffers, etc
Glucose: glucose is sugar, used by cells for energy
Penicillin and streptomycin are used to treat infection (don’t necesarily need)
Antibiotics: reduces the risk of bacterial contamination in this very rich medium
Phenol red: PH indicator, tells us PH of media by over time media changes from bright pink to yellow, once yellow it is called exhausted (don’t necessarily need)
Serum: the exogenous source of growth factors required by normal cells, there can be variation between serums (growth factors can also be provided directly)
Water: the most abundant component
Eagles basal medium (1955) (components)
Amino acids, Vitamins, salts, glucose, antibiotics, phenol red, serum, water
Hela cells
The first immortal human cell culture
cultured from Henrietta lacks aggressive cervical cancer
was used to develop the polio vaccine
Ethical issue surrounding
Hela cells
there was no consent to donate cell samples
and People made money off of it
Who discovered Hela cells? and where
George and Margaret Gey, Johns Hopkns (1951)
Subcategories of cryopreservation (3)
Cryobiology
Cryogenics
Cryonics
Cryobiology
looking at the effects of temperature on organisms or the use of cryopreservation
using low temps to preserve cells
Cryogenics
A branch of physics that studies low temps
Cryonics
Freezing ppls heads in the hopes of restoring life
Cryopreservation
Metabolically inactivates cells
Advantages of Cryopreservation of animal cells
Allows many repetitions of the same experiment
Cells can be stored for additional work at different stages of differentiation or after a variety of experimental treatments (metabolically suspended)
Cryoprotectants
prevent the formation water of crystals which destroy cells
