BIOL 2020 Lecture Notes - Lecture 1: Phagocytosis, Thermoproteus, Paramecium
Introduction and History of Cell Bio
o Most cells are beyond the visual range, the largest are single cell beings such as
paramecium and frog eggs
o Short distances to transfer materials both intercellular and intracellular
o Surface area to volume ratio is small
o So they can be productive and for their processes to happen quickly
o Slime mold have many nuclei, they have a single plasma membrane but they are fused
cells in reality
o Muscle cells are also multi nucleated - long thin and have many nuclei put
together
o The only big cells must have many nuclei - a cell must produce RNA from it's
DNA so if you only have one nucleus and the RNA has to get made, this is not
favourable
o Volume to nucleus ratio must stay small
o Consequences of cells being small
o Surface to volume ratio is maximized to promote exchange of gasees, ions,
nutrients with exterior
o Ensures that cytoplasm volume per nucleus is low ensure optimal production of
mRNA and proteins
o Cell has many parts but they are not random, they must have consistency and order so
things happen as they are supposed to, the cell has ways to correct events that are not
performing and producing as it is expected to
o Able to look at smaller details of cells - sub cellular structures
o First microscopes were like magnifying glasses
o They were made in the late 1500's and 1600's which was before they realized
that cells existed
o People who sold fabric used them - fabric's fine threads
o Anton's lenses were revolutionary because they showed 10x magnification and
resolution
o He started out as a textile merchant and started out looking at fabrics, nevertheless he
graduated from this and began looking at more interesting things such as pond water
o He was the first to describe many single cell organisms including protists and bacteria
o He was encouraged to bring his ideas to Hooke
o He was also the first to see sperm under a microscope
o Cell arising by only division from an existing cell originated from the idea of
spontaneous generation, which is clearly not correct
o Spontaneous generation is the idea that life can just appear from nothing
o Paslar used a "swan neck" experiment to prove this wrong
o He boiled broth
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o In one flask that was upright, material grew however in the swan neck, pointing
downward, nothing grew.
o This theory lead way to the fact that cells can only arise by the division of
existing cells
o This was in the mid 1800's
o According to fossils, the first cells originated 4.2 billion years ago
o These are exciting times for cell biology
o There are four different technologies that will severely alter society
1. Low cost for genome sequencing
o Moore's law - this is the rate of improvement we would have if the
cost of genome sequencing went down at the same rate that computer
chips improved
o Cost is now extremely low ($400.00) per genome when it originally
costed $100,000,000.00
o Is this ethical? - insurance, you have privileged information about
yourself
o This used to be almost impossible
o Synthetic biology - manipulating with the fundamental basis of life
o J.Craig Venter was one of the first people to sequence DNA and he sequenced his own
o The ultimate goal is to make life from scratch
o Alter genome in bacterium to develop unique characteristics
o Bacteria to make fuel to make other things such as vaccines or foods
o People have been able to engineer base pairs - they have been able to alter the genetic
code
o The Three tenets of Cell Theory are…
o All living things are made up of one or more cells
o The cell is the structural unit of life, it it's not a cell or more than one cell, it's not
alive
o All cells come from pre-existing cells
o Cells are complex and need order and consistency, therefore there is a very low
tolerance for errors
o Ex. When a cell wants to divide it must replicate it's DNA, when that happens
there is a DNA polymerase that does this and it's error rate is about 1 in 10
million base pairs. Even this is too much! This will amount for too many errors
to accumulate. However, we have a mechanism to correct this error
o Cells have a genetic program - it must have the means to interpret it's "recipe" and
make the needed proteins. If they don't have this, the cell will not be able to reproduce
anymore and it will kill itself #emo through apoptosis
o Cells can reproduce
o Cells acquire and utilize energy - commonly this comes from sunlight, however if this
is not the case, they can use heat
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