L2: Cells & Organelles Flashcards
cells vary dramatically in size
bacteria (~1 micrometer)
ostrich egg (~.1 m = 100,000 micrometers)
typical human cell is about 10-50 micrometers in diameter
cells vary dramatically in shape
size scales relevant to cell biology
1 meter = —- mm/micrometers/nm
resolving power (resolution) definition
the ability to distinguish two close objects
maximum RP depends on the wavelength of the illumination
visible light has a wavelength of
400-700nm and can resolve objects about 200 nm apart
size scales relevant to cell biology
.2 mm = minimum resolvable
200nm = minimum resolvable by light icroscope
.2nm = minimum resolvable by electron microscope
cells have thousands of different proteins. how to find just one?
- indirect immunofluorescence
- GFP
indirect immunofluorescence
- specificity - uses an antibody to your protein of interest, the “antigen”
- sensitivity - fluorescence - a molecule is fluorescent if it absorbs light of one wavelength and
then emits light of a different (longer) wavelength – very sensitive
can only be done by killing the cells!
how does IF use antibodies to tag antigens?
First steps: ‘Fix’ cell (chemical cross-linking) and make cell permeable to antibodies using a detergent to dissolve the plasma membrane
green fluorescent protein (GFP)
- Sensitivity - uses GFP fluorescence
- Specificity - GFP protein “fusion”
transmission electron microscopes (TEM)
pros and cons to electron microscopy
EM pro: Much better resolution than light microscopy (more detail)
EM con: Much more effort to get 3D view of the cell (“tomography”)
More difficult to label specific proteins
Cannot be used on live cells (imaging is done in a vacuum)
Highest resolution is tricky because of damage to sample caused by electrons
nucleus
Contains the ‘genome’ (most of the cellular DNA)
Darker regions are the “nucleolus” – this is where ribosomes are assembled.
plasma membrane
separates the cell from the environment
endoplasmic reticulum
Primary site for synthesis of lipids, membrane proteins, and secreted proteins
Sections of ER with ribosomes bound are called “rough ER”
golgi complex/apparatus
Performs modifications on secretory proteins
Central sorting station for vesicle trafficking
mitochondria
have 2 membranes + their own genome + ribosomes
more closely related to bacterial genomes and ribosomes than to the Eukaryotic nuclear genome and ribosomes in the cytosol
major site of ATP production
consumes and produces many metabolites
not bean-shaped, form dynamic tubular networks
chloroplasts
responsible for photosynthesis
have their own genome + ribosomes
more closely related to bacterial genomes and ribosomes than to the eukaryotic nuclear genome and ribosomes in the cytosol
cytoplasm vs. cytosol
cytoplasm = all the stuff in between the plasma membrane and the nucleus
cytosol = the soluble portion of the cytoplasm
why do eukaryotes contain internal membranes
Allows compartmentalization of function
-cells perform many competing reactions that need to be separated (ie. protein synthesis and protein degradation
Allows more membrane surface per cell volume
-many reactions are carried out on membranes
-larger cells have smaller ratio of cell surface to volume
