IB biology topic 2 cell structures

When was the earth formed?

Aböut 4.5 billion years ago

What were features of the early atmosphere?

Little oxygen so no ozone layer and so many harmful uv rays hit earth

Higher levels of methane and co2 (greenhouse gases) so hotter atmosphere

Volcanoes erupting and making islands of ash and lava

More frequent bombardment from asteroids

What did most of the oxygen do?

React with metals to make metal oxides

Where has evidence for this come from?

Fossils

What are protocells?

The first cells

What were key features of life that must’ve developed for the first cells to appear? And for what reason?

Catalysis- so certain chemical reactions could happen

Self replication of molecules- so there could be inheritance and evolution of useful characteristics

Self assembly- spontaneous building of macromolecules essential for life formed from monomers

Compartmentalisation- to separate the ordered interior of the cell from the les ordered environment

What are macromolecules?

Large, complex organic molecules essential for life formed from monomers.

Give 2 examples of macromolecules

Proteins

Carbohydrates