Notes spanning of the cellular membrane, cell movement, transport across the membrane, homeostasis, cells and organelles. Also information on the mitochondria, endoplasmic reticulum and the endomembrane system. Cytoskeletons, micro/intermediate filaments, skeletal muscle contraction as well as the...
Studying Cells
● 1600s started experiments (microscopes) started cell theory.
● 1665 Robert Hook magnified by 30x, boxlike components observed (cellula-little rooms);
examined cork (dead plant cells). Lowest obj we use is 100x.
● 1670s, Antonie van Leeuwenhoek built a better microscope (300x resolving power).
Variety of samples, even single celled organisms! Looked at own sperm under
microscope. Draw what they see, send them in letters.
● 1830s now, compound microscope to see inside cells. 1831 Robert Brown found nucleus
in all plant cells (onions started). 1838 Matthias Schleiden suggested germ (cell) theory
for plants. 1839 Theodor Schwann proposed for animals too. Schwann cells-insulate
nerves.
● Cell Theory-All cells derive from a single cell. Cell is the basic unit of structure for all
organisms. All cells arise from pre-existing cells.
○ 20 years later, 3rd principle: Karl Nageli and Robert Remak and Rudolf Virchow
(based on cell division) all cells arise from pre-existing cells.
● (Know key names and what they are associated with. No exact dates needed).
● Before Schwann and co, in 1660s Francesco Redi challenged that life was not
spontaneously generated. Saw this with open jar vs gauze covered-spontaneous air let
in-vs sealed jar with flies, (maggots), and meat. Life only appeared in open jar with
peanut butter.
● Cell biology disciplines
○ Cytology-study cell structure and function.
○ Genetics-genes, heredity, and variation of organisms (Gregor Mendel proposed).
○ Biochemistry-chemical substances and processes within cells-Watson and Crick.
○ Today, more about communication, genes switching on and off, ect.
● Note diverse size, shape, and structure of cells.
○ Size-tiny (1 micron/micrometer=10^-6m=1000nm=0.001mm).
○ Components-mitochondria (organelles-they came from prokaryotic cells,
continued w/evolution; same with chloroplasts), ribosomes, membranes, nucleus,
microtubule, microfilament (cytoskeleton), and DNA helix.
○ See them with a light microscope-1 to 2 microns (100x obj needed). Limit of
resolution because of white light wavelength-20nm. Roughly see mitochondria.
○ Electron microscope-smaller specimens which uses electron (shorter)
wavelength, different than photons in light. Limit of resolution is ~0.05nm
now-can see items.
○ Resolution-distinguish between 2 points in an image; smaller resolution, the
greater the resolving power (desired). Limit of resolution=(0.61*0.52)/(numerical
aperture).
○ See membrane and nucleus with the stain for our practical today.
● Microscopy types-brightfield-need stained, fluorescence-can tag cells or protein; see real
time expression of genes, phase contrast, differential interference contrast, and confocal.
● Electron microscopy-scanning-metal coated cells, electrons fired and do not pass
through coat which generates picture on camera-and transmission-dye coats section of
, sample, electrons pass through some and not other sections, generate a picture. Need a
camera to take a picture for these. Disadv-$$, time consuming, must be dead specimen.
● Other techniques-centrifugation techniques, radioactive isotope labeled chemicals,
chromatography, protein/nucleic acid electrophoresis, and mass spectrometry.
● Model systems/organisms to study disease-not humans. Cell cycle proteins in yeast.
Can use mice, fruit flies, e. coli, s. cerevisiae due to basic immune system.
● Homework
○ Describe the differences between light microscopy and electron microscopy and
what types of cellular structures these techniques can be used to visualize.
Light microscopy and electron microscopy are very different from how they read
information to what cellular structures are visible. The light microscope uses a different set up
where you need only the substance to be analysed on a slide, where the electron microscope
has more prep where the substance to be analysed must be coated with metal.
Light microscopes work by shining white light onto the slide whilst electron microscopy
works by firing electrons at a metal coated sample. Light microscopy illuminates the background
of the slide; as for the electron microscope, a ray of electrons is diverted and focused by an
electromagnetic field. Because of this, the process for electron microscopy is time consuming,
and samples must be dead. With light microscopes, the specimen does not necessarily need to
be dead, unless it will be stained.
Light microscopes use the wavelength of white light whilst the electron microscope uses
the wavelength of electrons, which are much shorter. Electron microscopes have a much
smaller limit of resolution (2nm compared to 200nm for light microscope) so you can see smaller
molecules but also in greater detail. With a light microscope you can see the cell nucleus,
chloroplasts, and mitochondria; electron microscope you can see cell membrane, nucleus,
mitochondria, microtubules, microfilaments, ribosomes, proteins, viruses, DNA, lipids, and
various macromolecules.
These microscopy techniques are quite different, and they each have a specific purpose.
The light microscope is more for _, whilst the electron microscope should be used more for _.
Since the electron microscope is costly, the light microscope is used more often in science
laboratories where seeing the smallest parts of a cell is not necessary.
Cells and Organelles
Prokaryotes-bacteria and archaea-and
eukaryotes-plants, animals, fungi, algae, and
protozoa-yeast (1 cell). Virus-not cells! Usually
round or rod shaped bacteria. Plasma
membrane-bounded by cell wall. Can have things
on side-flagella.
Photosynthesis in cyanobacteria happen in the
compartmentalization.
TEM-useful for internal components. DNA is around
nucleus (whiter) in image. Compartments-close off
things for environmental control (lock away in
,membrane bound compartment when aerobic respiration-no affect other cells).
Prokaryotic-DNA in nucleoid; also twisted; binary fission. Euk-in chromosomes, tightly coiled;
mitosis and meiosis. HeLa-bigger nuc, lost control of cell division. No nucleus-not necessarily
prokaryotic. Ribosomal RNA (rRNA) sequence analysis-prokaryotic can be divided into
eubacteria and archaea.
Ribosomes-translation of messenger RNA into proteins.
Pro-70S, euk-80S-Svendberg unit-how quick sediment to
bottom. More biochemistry-large/small subunit, ect.
Archaea and euk-
chromosomal DNA
w/histone like proteins.
Translation initiation is
similar.
Cell size-SA is key-SA to V
is optimum-big (so material exchange and
environment is limiting). Theory 1000-small
bacteria 10x more efficient @exchange material
than 1 euk by factor of 10.
Increase SA w/fingerlike projections.
PLANTS→
Produce ATP-powerhouse of cell. Like bacterial
cells. Have own genome. Fingerlike projections-have protein (best SA). 2
membranes. Ribosomes same size as Pro. Site-high energy consumption
(like sperm-have 1 massive mitochondria). Endosymbiosis-early pro
engulfed each other to give us mitochondria and chloroplasts. Aerobic
respiration-good for early cells.
ER, golgi-membrane sacks in euk cells. Rough ER-large organelles,
ribosomes are diff in
smooth v rough.
Golgi-associated w/nuc.
, Hold digestive enzymes, later excreted from cell.
Cytoskeleton-network of proteins within euk cell.
Intro to Cell Membrane-surround cell and organelles
Selective permeability-osmosis. Membranes form
functional compartments.
Membrane functions-enable cell to pump things in/out
(transport), level of organisation, signal detection, and
cell to cell interactions (cells joined together). In
between cells joined, there are membrane of cells, and
in between that is the intercellular space (seen by
TEM). Unique compositions-different amounts of
proteins, lipids, and carbs. Nerve cells-lipid rich;
golgi-transport proteins.
Phosphate lipids-hydrophilic head and
hydrophobic tail. Hydrophilic things stay in cell,
but hydrophobic can go in and out; transport can
have certain things go in/out even if do not
follow this.
Lipid types: phospholipids, glycolipids, and
sterols.
Glycol lipid-like the 2nd one pictured
above, but has galactose instead of
choline and phosphate. Usually in
neurons-static regions. Saturation of
fatty acid-no C=C, but unsaturated has
1+. Affects ability of fatty acid tails to
pack together in bilayer. Can have straight
chains or clink (usually bc of C=C). FA
chains formed of 16-20 C, so length of
chain affects saturation, same w/C bond #.
Also affects transition temp-pt where lipid
converts from gel to fluid. More C, higher temp, less fluid. More C=C, dec TT, more fluid.
Butter-higher TT, olive oil-lower.
Sterol lipid-like cholesterol (controlling how fluid membrane is). Hydrophilic OH group on head.
Diff sterol in plants and bacteria. Cholesterol sits in each monolayer of membrane. Controls
fluidity by forming bonds with group sitting on the lipid (hydrogen bonding-stabilizes membrane).
Less fluid at higher temps by stabilizing PLs. Buffering system between cholesterol and FA
chains. More fluid at lower temps then.
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