1.5: Origin of Cells

Question 1

1.5.U1 Discuss two implications of all cells being formed from pre-existing cells.

Answer 1

There must have been an original cell.

All cells are related (if even distantly)

Question 2

1.5.U2 Outline the 4 processes needed for the spontaneous origin of cells on Earth.

Answer 2

1. The synthesis of simple organic molecules from inorganic compounds
2. The assembly of these organic molecules into polymers
3. Packaging of molecules into membranes with an internal chemistry different from the surroundings
4. The formation of a polymer that can self-replicate

Question 3

1.5.U2 Outline the experiments of Miller and Urey into the origin of organic compounds.

Answer 3

Miller and Urey created a model of early Earth’s hypothesized conditions. Their conclusion was that organic molecules can form under the hypothesized conditions of early Earth.

Question 4

1.5.U2 Define polymerization, monomer and polymer.

Answer 4

Polymerization - A chemical reaction in which two or more molecules (monomers) combine to form larger molecules (polymers)

Monomer - “one part”, the single building block unit of a polymer

Polymer - “many parts” A large molecule composed of many monomer subunits

Question 5

1.5.U2 Outline two properties of RNA that would have allowed it to play a role in the origin of life

Answer 5

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1. RNA can self-replicate
2. RNA can act as a catalyst

Question 6

1.5.U3 State the endosymbiotic theory

Answer 6

Theory that states that mitochondria and chloroplasts evolved from free-living prokaryotic cells that were engulfed (not digested) by early eukaryotic cells. The mitochondria and chloroplasts evolved as symbiotic parts of these cells.

Question 8

define spontaneous generation

Answer 8

the theory of spontaneous generation held that living creatures could arise from nonliving matter and that such processes were commonplace and regular.

Question 9

historical thinking about spontaneous generation

Answer 9

Aristotle: insects are generated spontaneously

Paracelsus: produces small animals from herbs

Jan Baptist van Helmont: placed his dirty shirt in wheat and “mice appeared”

Question 10

summarize the Redi experiment

Answer 10

Redi placed meat in 3 different jars. One jar was left open; two were covered. Later the open jar contained maggots, whereas the covered jars contained no maggots. Successfully demonstrated that the maggots came from fly eggs and were not spontaneously generated

Question 11

Summarize the Spllanzani experiment

Answer 11

put broth in a flask, sealed the flask so that no air could get in, and boiled it. No organisms grew in the flask. This suggested that microbes were introduced into these flasks from the air