Origin of Cells

Cell Theories

• All living organisms are made of one or more cells.

• Cells are the smallest unit of life.

• All existing cells come from pre-existing cells.

Seven Functions of Life

• Mnemonic: H, hi Mr Green

  • H: Homeostasis

  • M: Metabolism

  • R: Response

  • G: Growth

  • R: Reproduction

  • E: Excretion

  • N: Nutrition

Louis Pasteur's Experiment

• Demonstrated that life does not arise spontaneously from non-living matter through sterilization of chicken broth.

Conditions for Cell Existence

• Carbon compounds are essential for cell formation.

• Organic molecules must be synthesized from abiotic (non-living) components.

• Smaller organic molecules must assemble into larger polymers (proteins).

• Enzymes are required to facilitate polymer formation.

• Membranes (vesicles) must enclose these molecules to create optimum growth conditions.

• Replication of molecules is necessary for inheritance (process involves RNA).

Origin of the First Cell

• Miller-Urey experiment simulating early Earth's atmosphere:

  • Included enzymes and other compounds to facilitate reactions.

  • Resulted in the formation of protocells from small organic molecules.

• Protocells are thought to have evolved into the first true cells.