Chapter 2: The Cell
Eyes contain many small photoreceptor cells. Ocellus is common in a number of insects, arthropods, and
molluscs. The Vertebrate eye (human eye) is very similar in structure and function to the eye of certain
molluscs (squids and octopi).
Light sets the biological clock, but circadian rhythms aren’t a direct result of changes in the light
- All organisms are composed of 1 or more cells
- The cell is the functional unit of life
- Cells only arise from pre-existing cells.
Cells were first observed by Robert Hooke in 1600s and by anton van Leeuwenhoek.
Hook coined the term cellulae, Van Lee described bacteria and protists as animalcules.
Robert Brown first to observe nucleus in 1800s. Mathias Schleden: plants are made of cells and nucleus
is important for development. Theodor Schwann: all animals are made up of cells. Rudolf Virchaw: cells
only arise from pre-existing cells.
Synthetic cells first reported on 2010
Mycoplasma- has one of the smallest genomes. They chemically synthesizes this gene in a lab. They also
worked with bacteria that is very similar to mycoplasma. The DNA used was chemically synthesized.
They placed this edited genome inside an empty cell and it worked naturally while creating daughter
cells in the form of mycoplasma.
Typical animal cell: 5 – 30mm Typical bacterial cell: 0.5 – 5mm
Micrometers are written an 10 to the -6 which is the light microscopy range. A typical membrane is 7 to
8 nm. Cells are small because of the surface area to volume ratio. Volume determines capacity for
chemical activity. Surface area determines amount of transport in and out. Volume increases much
faster than surface area
Synthetic cells were constructed from chemically-synthesized DNA inserted into “empty” host cell with
its DNA. Prokaryotes/ Eukaryotes
All forms of life are based on these two distinct types of cells.
Prokaryotes: Pro cells lack a nucleus. Pro = before which means they came before Euk cells. Prokaryotes
make up 2 of the 3 domains of life: Bacteria and Archaea. Nucleoid is the chromosome and is the only
piece of DNA which is basically free floating, it’s a circular molecule.
Eukaryotes: included nucleus. Plants, animals fungi algae protozoa
Archea looks very similar to Bacteria branch, however it is more evolutionarily similar to Euks.
-plasma membrane - cytoskeleton - ETC
- cytosol - DNA organized into chromosomes - Transcription and Translation
- Organelles - Basic cellular processes
More differences: (All in Euk)
-Seperation of DNA and cytosol by nuclear envelope
- presence of membrane bound compartments with specialized funtions: Mitochondria, chloroplasts, ER,
- highly specialized motor proteins
What do cells of all living organisms have in common?
Chromosomes, plasma membrane and Ribosomes.
Have nucleus. Organelles – many are found only in Euk cells like mitochondria
Organelles are why Eukaryotes are evolutionarily advanced, however some Pro cells have organelles.
Organelles allow for specific chemical pathways that are concentrated and segregated. This
concentration allows great efficiency. Segregation is good because it disallows competition between
organelles. Nuclear Pore Complex: made up of many proteins
- they create pores on nucleus t