BIOL 2020 - Lecture 1: Cell Theory

Cell theory

All living things are made of cells, and every cell arises only from a pre-existing cell by division

Cell (definition)

A membrane-enclosed compartment filled with a concentrated, organized solution of chemicals that can grow and copy itself

1650-80

Robert Hooke and Anton van Leeuwenhoek described the cellular structure of plants, blood, and insects

1839

Schleiden and Schwann observed that plants and animals are made of cells and proposed cell theory

Heredity (shared cell feature)

Genetic information is stored in genes made of DNA, using the same genetic code across all life

Central dogma

DNA is transcribed into RNA, which is translated into protein by ribosomes

Proteins (shared cell feature)

Catalyze reactions (enzymes), build structures, transport cargo, and send signals

Metabolism (shared cell feature)

Cells extract energy from surroundings and use it, largely via ATP, to power biosynthesis and movement

Compartmentalization (shared cell feature)

A plasma membrane (phospholipid bilayer) encloses the cell and controls what enters and exits

Prokaryotes

Bacteria and Archaea; no nucleus, no membrane-bound organelles, mostly single-celled

Eukaryotes

Protists, fungi, plants, animals; have a true nucleus plus internal membrane-bound organelles

Three domains of life

Bacteria, Archaea, and Eukarya, all descending from a last universal common ancestor (LUCA)

Endosymbiotic theory

Mitochondria and chloroplasts were once free-living bacteria engulfed by an ancestral eukaryotic cell about 1.5 billion years ago

Evidence for endosymbiotic theory

Mitochondria/chloroplasts have their own DNA and ribosomes, are enclosed by a double membrane, and divide independently of the rest of the cell

Model organisms

E. coli, budding yeast (Saccharomyces cerevisiae), Arabidopsis thaliana, C. elegans, Drosophila melanogaster, zebrafish, mouse