BI-220 Cell Theory

theory

explanation of something that’s based on scientific data

• developing and testing multiple hypotheses

tenets of cell theory

• all living organisms composed of 1+ cells

• cell most basic unit of life

• all cells arise only from preexisting cells

what experiment proved cells come from preexisting cells

Louis Pasteur

• swan neck flasks

  • Add Broth: Pasteur put meat broth inside his custom swan-neck flasks

  • Boil the Liquid: He boiled the broth hard to kill all living germs and microbes already inside.

  • Expose to Air: The long, curved neck let fresh air flow freely into the flask, but it trapped floating dust and microscopic germs in the bend.

  • Wait and Observe: The broth stayed completely clear and fresh for a long time because germs could not pass the curve.

  • Break the Neck: When Pasteur tilted the flask so the broth touched the trapped dust, or broke the neck off entirely, the broth quickly turned cloudy with microbes.

features of all cells

• plasma membrane

• cytosol

• ribosomes

• chromosomes

how does the plasma membrane correlate to cell theory

all living organisms composed of 1+ cell

how does cytosol correlate to cell theory

cell

how do ribosomes correlate to cell theory

basic unit of life; pre-existing cells

how do chromosomes correlate to cell theory

all cells arise

is a virus alive

no

• requires host to reproduce

  • lacks ribosomes

shared cell similarities

allows for study of cell structure and function

model organism

non-human species studied to understand fundamental biological processes

• short life spans

• breed quickly and largely

• easy to take care of

• simple

examples of model organisms

• zebrafish

• drosophila (fruit fly)

• mus musculus (house mouse)

• S. cerealisiae (yeast)

homologous genes

genes shared by different species because they were inherited from common ancestor

difference between prokaryotes and eukaryotes

• presence/absence of nucleus

• presence/absence of membrane bound organelles

domains of prokaryotes

• bacteria

• archaea

bacteria kingdom

eubacteria

archaea kingdom

archaea

domains of eukaryotes

eukarya

kingdoms of eukaryotes

• protista

• fungi

• plantae

• animalia

characteristics of prokaryotes

• no membrane bound nuclear region or organelles

• contains singular circular chromosome and plasmids

• smaller in size

plasmids

small, independently replicating circular pieces of DNA

• antibiotic resistance, mating, virulence

characteristics of eukaryotes

• membrane bound nuclear region and organelles

• multiple linear chromosomes

• larger in size

  • nucleus size → cell size

endosymbiotic theory

ancient cell swallowed prokaryotic “mitochondrion” then prokaryotic “chloroplast” to create eukaryotic cells