ASTR-3040: Astrobiology Day 11 The Nature of Life on Earth Chapter 5.
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Transcript of ASTR-3040: Astrobiology Day 11 The Nature of Life on Earth Chapter 5.
ASTR-3040: Astrobiology
Day 11
The Nature of Life on Earth
Chapter 5
Homework - 4
Due Tues. Feb. 22
Chapter 5: 4, 6, 14, 20, 25, 27, 33, 37, 42, 47, 48, 49, 51
Molecular Components
Carbohydrates – energy sources Sugars and starches
Lipids – energy stores, barriers Fats
Nucleic Acids – DNA and RNA
Molecular Components Proteins – structure & chemistry
Structural materials
Enzymes – catalysts for reactions
Amino Acids (20 used in most life forms)
Left-handed in biological entities.
Major Groupings
Leeuwenhoek – 1674 – microscope
5 Kingdoms Plants
Animals
Protista
Monera
Fungi
Is there a biochemical classification?
Microscopic Life Plants and Animals are different
Cell walls (plants)
Cell Nucleus Prokaryotes
Eukaryotes
All prokaryotes are
single celled. They
lack a cell nucleus.
Eukaryotes – single or multi-celled.
Domains of Life
Based on biochemistry and genetics:
Bacteria
Archaea
Eukarya
Tree of life.
Kingdom – Phylum – Class – Order – Family – Genus – Species
The Tree of Life
Extremely valuable organizational tool.
3 key ideas 1. Domains based on biochemistry & genetics is
fundamentally different from the older KPCOFGS based on structural & physiological differences.
2. New and fundamentally different view of microbes - lipid structure of cell membranes.
3. True diversity almost entirely in microbes.
Metabolism: Chemistry of Life
Metabolic needs: 1. Source of raw materials.
2. Source of energy.
ATP: adenosine triphosphate Used by every living cell for internal energy.
Outside energy needed only to produce ATP.
Carbon sources – form basic materials.
Energy sources – run the metabolism.
Classification by Metabolism
To obtain carbon:
1. Heterotrophs: Consume preexisting organic compounds (i.e. eating).
2. Autotrophs: Direct uptake from the environment (self-feeding, plants)
Classification by Metabolism
To obtain energy:
1. Photosynthesis: sunlight
2. chemosynthesis: chemical energy Ingested food
Inorganic reactions
4 Metabolic Classifications
Based on energy and carbon acquisition.
1. Photoautotrophs
2. Chemoautotrophs
3. Photoheterotrophs
4. Chemoheterotrophs
Liquid Water on Earth
All living cells on Earth depend on liquid water because metabolism requires:
1. Organic chemicals are readily available for reactions.
2. A means of transporting chemicals to and within cells; waste products away.
3. Water plays a role in many of the reactions.
DNA and Heredity
3 key features of life on Earth 1. structural units – cells
2. metabolic processes – energy production
3. owner's manual – data storage for how a cell is constructed, how it works, and how to build another one, and pass it on to the next generation - heredity.
DNA Structure
Double helix
DNA bases – 4 Adenine
Guanine
Thymine
Cytosine
Pair as AT & CG
Replication
Unzip & each strand acts as a template.
Use RNA in the rebuild process.
Genome Humans have ~3 X 10^9 bases
46 chromosomes (23 pairs)
Sequences for individual instructions are called genes.
Most of DNA is “noncoding” (junk 95%)
Complete sequence – genome.
Some bacteria – 10^5 bases, few 10^2 genes
Humans – 20,000 – 25,000 genes
Rice – 37,000 genes (smaller DNA sequence)
Genetic Code
Words consist of 3 DNA bases.
Sequence has a start and stop word.
Used to build proteins.
Redundancy (64 codes, 20 amino acids)
Most amino acids are coded with the first 2 base letters only (16). Does this give a clue to evolution of complex organisms?
Nearly all living organisms have mostly similar genetic code.
RNA
Uses ACG & Uracil
mRNA – transcription (carries the instr.)
tRNA – transfer (gathers the AAs)
rRNA – backbone of building structure.
Mutations - <1:10^9, but can have dramatic consequences.
Provide the basis for evolution.
Genetic Engineering.
RNA was probable precursor.
Extreme Life - Extremophiles
Thermophiles – heat lovers
Hyperthermophiles Black smokers (350˚C)
Hot springs
Extreme Life - Extremophiles
Psychrophiles – cold lovers Antarctica ice pack (-20˚C)
Also very dry
Radiation hardened
Extreme Life - Extremophiles
Endoliths – within rocks Up to several km below ground
Endospores (resting) – found on moon Could these survive interplanetary journeys?