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Biochemistry of the Cell (Membrane (Structure, Function), Inside the Cell…
Biochemistry of the Cell
Membrane
Structure
Function
Inside the Cell
Microscopes
used to help scientist discover how the cell functions
there are a variety types
light microscope (LM)
has a visible light that passes through the specimen and glass lenses
those lenses then go on to refract the light
to where the image of the specimen is magnified
the first microscope used to be by
renaissance scientist
and in any laboratory
has fluorscent markers
which makes it possible to see structures with detail
specs
magnification
can magnify almost 1,000x
reso-lution
cannot resolve details finer about .2 micrometers or 200 nanometers
electron micro-scopes (EM)
types
scanning electron miscopy (SEM)
used for studying topography of specimens
through 3-D images
this is done by
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transmission electron microscope (TEM)
used to study the internal structure of cells
this is done by
aiming an electron beam through the very thin section of the specimen
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created to study the cells' structure in detail
improved resolution through
focusing on a beam of electrons through the specimen or onto its surface
wavelength of light used by microscopes
are shorter than visible light
specs
0.002 nm
still cannot resolve structures smaller than 2 nm across
resolution better than LM by 100x
has revealed many sub cellular structures
that were impossible to resolve with LM
killed specimens before viewing though
uses electro-magnets as lenses
to bend the paths of electrons
giving the microscope something to focus on
was invented during the the late 1500s
cell walls were first seen in 1665 by Robin Hooke
examined the dead cells from bark of an oak tree
then, refined through the addition of lenses
lenses created by antoni leeuwenhoek
gave the ability to visualize living cells
key parts in a microscope
magni-fication
the ratio of an object's image size to its real size
resolution
is the measure of clarity of an image
constrast
the difference in brightness between the light and dark areas of an image
cell fraction
is a technique used to study cell structure and function
which involves the separation of major organelles and other sub-cellular structures
it enables researchers
to prepare for cell components in bulk and identify their functions
equipment used
is the centrifuge
which spins test tubes
that is holding mixtures of disrupted cells
at a series of increasing speeds
each speed, the resulting force causes a subsets of the cell components to settle to the bottom of the tube
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Prokaryotic and Eukaryotic Cells
all cells has
chromo-somes
carries genes in the form of DNA
plasma membrane
is a selective barrier that bounds cells
it allows passage of enough
oxygen, nutrients, and wastes to service the entire cell
for each square micrometer of membrane
only a limited amount of a particular substance can cross per second
so the ratio of surface area to volume is critical
surface area vs volume ratio
as a cell increases in size
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smaller cell
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microvilli
increases surface area without greatly increasing the volume
cytosol
is a semifluid, jellylike substance
ribosomes
are tiny complexes that makes proteins
according to the instructions from the genes
prokaryotic cells
nucleoid
is where the DNA is concentrated in
and does not have a membrane
size
smaller of the two
mycoplasma
are bacteria that are the smallest cells
because they have 0.1 and 1.0 μm diameters
small enough to have DNA to program metabolism
and enough enzymes
and other cellular equipment to carry out the activities necessary for a cell to sustain itself and reproduce
eukaryotic cells
nucleus
contains the genes
and is 5 μm in diameter
surrounded by the nuclear envelope
which is a double membrane
each is a lipid bilayer with associate proteins
separated by a space of 20-40 nm
has a pore structure called
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separates the nucleus contents from the cytoplasm
chromosomes
are structures that carry genetic information
each one contains one long DNA molecule associated with many proteins
some of the proteins help coil the chromosomes
which reduces the length
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is made up of
chromatin
which are complex DNA and proteins
cytoplasm
is the interior of the cell
the region between the nucleus and plasma membrane
size
larger than prokaryotic cells
its size correlates with it's limit on multicellular metabolism
typically 10-100 μm in diameter
ribosomes
are complexes made of ribosomal RNAs and proteins
which carry out protein synthesis
they do this by
building proteins in two cytoplasmic locales
free ribosomes
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bound ribosomes
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endomembrane system
consists of
the nuclear envelope, the endoplasmic reticulum, the golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane
carries out a variety of tasks in the cell
including synthesis of proteins,
transport of proteins into membranes and organelles or out of the cells,
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endoplasmic reticulum (ER)
is an extensive network of membranes
that exists in the cytoplasm
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the network tubules and sacs are called cisternae
ER cavity
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golgi apparatus
is where proteins are modified and stored
then sent to other destinations
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a golgi stack
has a distinct structural directionality
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lysosomes
vacuoles