What is Life?

ASTR 4: Life in the Universe

Discussion Topics

• Three Domains of Life

• Basic Cell Structure

• Macro-molecules

• Properties of Life

Three Domains of Life

Basic Cell Structure

Basic Prokaryotic Cell Structure

Basic Eukaryotic Cell Structure

Macro-molecules

• Proteins• Nucleic Acids• Carbohydrates• Lipids

Proteins

Proteins

Proteins

Proteins

Nucleic Acids

Nucleic Acids

Nucleic Acids

Carbohydrates (C:H:O=1:2:1)

Lipids

Chirality

Properties of Life

• Order

• Metabolism (Energy Utilization)

• Reproduction (Growth)

• Differentiation (Development)

• Communication

• Movement (Response to the Environment)

• Evolution

More Questions…

• How about Viruses, Viroids & Prions?

• Carbon-based Only?• Closed System Only?• What is the minimal

definition of life?

Human Coronavirus -- SARS

Prion – Mad Cow Disease