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Biology 1140 Lecture Notes
Introduction to Cell Biology
What is a Cell?
Fundamental unit of life.
Robert Hooke invented the microscope in the mid 1600s (1670).
Every organism is a cell or a collection of cells.
Key points to describe a cell: organelles, plants/animals, cytoplasm, network,
membrane, walls, compartments, nucleus, power, regulate internal environment,
contain genetic information, bounded by a membrane and exert control of what
enters and leaves, respond to environment, able to replicate (cells give rise to
other cells), evolve, communicate with each other (respond to other cells around
them), mutate, carry out metabolic processes by using nutrients, energy transfer,
transfer energy with ATP, cytoplasm (semi-liquid consisting of salts and organic
matter) is the structural unit.
oAll organisms consist of one or more cells
oThe cell is the basic unit of structure for all organisms
Schwann 1839 (Zoologist) and Schleiden (Botanist)
oAll cells arise only from pre-existing cells (i.e. the cell is the basic unit of
(Rudolf Virchow 1855)
The cell is enormous, and diverse.
They vary in shape to very complex structures (retinal cells).
Highly proliferated membrane, better for transportation, can carry out more
An ostrich egg is an example of a cell; it’s a coyesent cell (non-active cell).
Lots of diversity in cell function: some are unicellular, and some are multicellular
(you can have cells that are highly specialized for a single function, such as
information transmission, or hormone production).
They have a common chemistry, made out of same molecules, lipid membranes,
same basic types of lipids. Proteins, same collection of 20 or so amino acids.
DNA is pretty much the same, in terms of basic chemistry. Metabolism, energy
transfer, uses common currency across all cell types in the form of ATP.
Muscle cells are a good choice to study ATP.
To work on chloroplasts, use plants.
Internal Organelles do not affect the surface to volume ratio.
Most of the things that we will measure are in micron (1x10-6m) and a nanometer
Refer to slide for more information…
Nucleus – 0.006mm
Ribosome – 30nm
Microfilament – 0.007 micrometer
Giraffe Axon – 1x106 micrometer
Mitochondrion – 3x10-6m
Why are Cells Small?
Surface area to volume ratio.
Larger volume, more nutrients, more wastes to get rid of.
Have to easily transport nutrients and wastes across cell surface.
Length = L
oSA:V is 6:1
Length = 2L
oSA:V is 3:1
SA to V provides a limitation to cell size.
Second limitation comes from the rate of diffusion. They way molecules move
around the cell is by diffusion. It is only fast over very short distances, longer
distance the longer it takes.
Concentrations of substrates need to be high for reactions to take place.
Larger cell needs 8 times as many molecules that the smaller cell to get the same
Third limitation is the need to achieve these adequate concentrations. You can
overcome this with respect to SA:V Ratio, large organism made up of many small
cells. To overcome this problem, contain reaction in a smaller space, such as
organelles in mitochondria.
Eukaryotic vs. Prokaryotic
oTypically small, 1-area 5 microns.
oConstrained by all the factors we discussed.
oSmall simple organisms
oCell membrane, and inside cytoplasm, you’ll find ribosomes, nucleoid
(DNA) which is free flowing.
oBecause of their simplicity, constrained by factors we discussed, therefore
oBacteria (thousands of species, we only now a few, primarily the ones that
cause human disease) and Archaea (Extremophiles are included in this
group), two groups of organisms that have prokaryotic cells.
oA typical eukaryote cell is 10 to 30 microns.
oA lot of membranes present, a key characteristic.
oInside of the cell is divided up into compartments by a series of
membranes. One of the way these cells become large, by breaking up
interior into compartments.
oTransport systems, can move solutes around, without relying on diffusion,
another reason they can become bigger than prokaryotes.
oFour groups to look at:
The protists, single celled eukaryotes. Such as amoeba and
paramecium. A protist has a nucleus and PROKARYOTES DO
Fungi – Yeast, bakers or brewers, commonly used for lab research,
model fungus, grows easily in a lab, small, grows in large vats,
easy to work on, for bread and beer, and although its simple, shows
many characteristics of more complex fungi.
Plants – Arabidopsis, is a plant that is commonly used in research,
small genome, grows easily like growth cabinets in a lab, short
generation time, grows to maturity in a few months.
– A fruit fly is a model organism. Geneticists used them for a long
time. A lot of mutants that are easily distinguished.
– A mouse is a popular choice for biomedical research, relatively
small, happy living in sawdust, eat rodent chow, reproduce quickly,
three months generation time; mammals, basic physiology similar
– Zebra Fish, external fertilizers, and eggs are clear which is a
tremendous advantage, early stages of development take place over
48 hours, only a few centimeters long, reproduce really easily,
have some traits that we are interested in figuring out, their heart
muscle can heal itself, attractable and easy to keep.
Cytosol is the aqueous solution, and the cytoplasm is the cytosol plus what you
find in it, the ribosomes, etc…
Cytosol the same in prokaryotes and eukaryotes, but the cytoplasm is
DIFFERENT, prokaryotes lac the organelles.
Non-membrane Bound Organelles
oFound in eukaryotic cells.