lecture 2 Flashcards
compound microscopes
-multiple lenses
-commonly used
-ocular lens (fixed magnification)
-objective lens (variable magnification)
light microscopy
light passes through a cell and undergoes little change in amplitude but phase of light is changed
–> visible differences
incident white light in light microscopy
shows change of phase of waves
if you stain a cell… (light microscopy)
waves will be out of phase
–> some stains localize to different cellular components
How to prepare samples for light microscopy
- prepare thin sections
- fixation
-preserves cell
-formalin, glutaraldehyde are used to cross-link proteins to DNA - staining
-adds colour for contrast
- can bind to particular molecules in a cell
Dye charges
cations bind to - charge groups on proteins, nucleic acids
anions bind to + charges on proteins, phospholipids
fluorescence microscopy
light is absorbed at one wavelength and emitted at longer wavelengths!!!
ex.
absorption max of 358 nm
emission max of 461 nm
What are the two filters that fluorescence microscopes have?
- filters light before hitting the specimen
- blocks all light except wavelength of the light emitted by the excited fluorescent dye
immunofluorescence microscopy
fluorochromes (fluorescent dyes) can be attached to specific antibodies
what is the problem w fluorescence microscopy?
blurry. volume image– overlaps
–> use confocal fluorescence microscopy
confocal microscopy
volume of image is a lot smaller/thinner
focal lens
3D structures can be constructed using
multiple 2D images taken at diff planes of focus
resolving power
ability of an imaging device to separate points of an object that are located at a small angular distance
Light microscope induces
bright-field, phase and fluorescence
Electron microscope induces
transmission electron microscopy
Transmission electron microscope (TEM)
operates under a similar principle to light microscopy except a beam of electrons is used instead of light. 2D image.
Scanning electron microscope (SEM)
scatters electrons off the surface of the sample. 3D image.
Cells will have (3)
- Nucleus (or nucleoid)
- Cytoplasm
- Plasma membrane
Nucleoid
contains most of the cell’s genetic material
NOT surrounded by a membrane
Nucleus
membrane enclosed
contains cell’s genetic material
Prokaryotes
- No membrane bound
organelles - Smaller
- Nucleoid
- Single circular
chromosome - Cytoplasm bound by
plasma membrane
Eukaryotes
- Membrane bound
organelles - Larger
- Nucleus
- Multiple linear
chromosomes - Plasma membrane bound
by plasma membrane
and nuclear membrane
2 membranes in nuclear envelope
inner nuclear membrane
outer nuclear membrane
Nucleolus (in the nucleus– organelle)
large structure in the
nucleus where ribosomoal RNA
is transcribed and ribosomal
subunits are assembled
Why does the nucleus have pores?
lets things in and out
Mitochondria (organelle)
have their own DNA, reproduce by division
inner and outer membrane
generates ATP: ATP is “loose” once expelled from mitochondria
–> for ETC and oxidative phosphorylation
Mitochondria and chloroplast origins
evolved from engulfed bacteria
Endoplasmic reticulum (organelle)
major site of protein, membrane lipid and oligosaccharide synthesis
ribosomes attached to the ER translate RNA to proteins
golgi apparatus (organelle)
stacks of flattened membrane-enclosed sacs
modifies and packages molecules made in ER to be secreted/sent to another compartment
exchange of material by transport vesicles!
lysosome (organelle)
v acidic
contain hydrolytic enzymes that are activated by proteolytic cleavage in an acidic envmnt
recycles things by breaking down macromolecules–> amino acids, sugars, nucleotides
proteins are broken down in acid
lysosomal membranes contain transport proteins that…
carry products of macromolecule digestion to the cytosol for reuse or excretion
Peroxisomes (organelle)
membrane enclosed vesicles
carry out oxidation rxns that lead to the production of H2O2 (hydrogen peroxide)
H2O2 is used to inactivate toxic molecules
difference between cytosol and cytoplasm
cytosol= aq part of cytoplasm
cytoplasm includes aq portion, the suspended particles and the organelles!!!
cytoskeleton (organelle)
network of protein filaments in the cytoplasm that are involved in strength organization, mvmnt, shape and cell division
components of the cytoskeleton
actin filaments (for example; in muscle cells)
microtubules (ex; seen in chromosone separation)
intermediate filaments
major components of cell membrane (3)
lipids
proteins
carbohydrates
membrane functions (4)
- integrity of cells/organelles
- highly selective permeability barrier
- controls flow of info between organelles and surrounding envmnt
- site of energy transformation
-mitochondrial membrane performs oxidative phosphorylation
homologous genes
genes from diff organisms w v similar sequences
the bulk of our DNA does not
code for proteins
