The Nature & Origin of Life

Transcription

1 The Nature & Origin of Life OCN 201 Biology Section Lecture 1 Grieg Steward Oceanography Department grieg@hawaii.edu

2 What is Life? 2

3 What is Life? General Defining Features Of Life: Self-replication Maintenance of order Requires controlled collection and transformation of matter and energy for replication and repair 3

4 What is the essential defining element of life (as we know it)? A: Nitrogen B: Sulfur C: Iron D: Carbon (Organic!) E: Hydrogen

5 Features of Life as We Know it Life adheres to - The principles of organic chemistry - The laws of thermodynamics 5

6 Life is amazing... Despite the astonishing diversity of life there is considerable underlying unity but not miraculous! 6

7 Features of Life as We Know it Life on earth today: Based on cells as the fundamental unit Carbon-based Water-dependent Building blocks: Carbohydrates, DNA, RNA, Protein, Lipid 7

8 Cell Building Blocks Lipids DNA and RNA Proteins Carbohydrates 8

9 The Elements of Life sugars (carbohydrates) H, C, O Energy Functions: Structure Glucose Cellulose

10 The Elements of Life nucleic acids H, C, O, N, P DNA and RNA are built from nucleotides O O Nucleotide O O

11 Function: Information

12 The Elements of Life amino acids (proteins) H, C, O, N, S H H H C H S H

13 Catalytic Structural Collagen Hexokinase

14 The Elements of Life sugars (carbohydrates) H, C, O nucleic acids H, C, O, N, P amino acids H, C, O, N, S lipids H, C, O, P, N, S Energy/Structure

15 Cell Membranes

16 The Elements of Life sugars (carbohydrates) H, C, O nucleic acids H, C, O, N, P amino acids H, C, O, N, S lipids H, C, O, P, N, S

17 Relative Mass of Elements in a Bacterium Element Atomic number Percentage Role Carbon 6 50 basis of organic molecules Oxygen 8 20 cellular respiration, component of water Nitrogen 7 14 component of all proteins and nucleic acids Hydrogen 1 8 component of water & most organic molecules, electron carrier Phosphorous 15 3 component of nucleic acids, important in energy transfer Sulfur 16 1 component of most proteins Sodium 11 1 main positive ion inside cells Potassium 19 1 main positive ion outside cells Magnesium essential component of many energy-transferring enzymes Chlorine main negative ion outside cells Calcium cell structure, motility, and intracellular signalling Iron Redox reactions enzyme co-factor other trace 0.3

18 Chopra et al. 2010, Australian Space Science Conference Series

19 Which element is not a component of living cells? A: Hydrogen B: Helium C: Phosphorus D: Carbon E: Copper

20 Origin of Life on Earth Panspermia Divine Creation Chemical Evolution (abiogenesis)

21 How Do You Think Life Began on Earth? A: Divine creation of all types of life all at once B: Divine creation of a simple form of life that has evolved into more complex forms C: Arose on earth from organic molecules by chemical processes D: Transported here from elsewhere in the universe E: I d rather not say or just don t have an opinion

22 Origin of Life on Earth Difficult task! Must combine knowledge of: Chemical nature of life History of conditions on early earth to make logical inferences about what happened in the very (very) distant past Step 1: macromolecules; the building blocks of life

23 The Miller-Urey Experiment SPARK Gas (Atmosphere) H2O Methane Ammonia Hydrogen COOL Water (Ocean) HEAT Amino Acids & other organic Compounds

24 Murchison Meteorite Up to a two line subtitle, generally Samples used to from describe Comet the Wild takeaway 2 for the slide simple organics compounds 90 amino acids and other organic compunds 24

25 What is the Lesson from Miller-Urey Experiment and the Murchison Meteorite? A: Life began on earth B: Life could not have originated on earth C: Life came to earth on a meteorite D: The organic building blocks of life are unique to early earth E: The organic building blocks of life are common in the universe

26 Many building blocks of life are easy to make Many variations on Miller-Urey experiment have had similar results Meteorites and comets found to contain organic compounds similar to those produced in the Miller experiment Wild 2

27 Molecules to Life Large gap to overcome from organic molecules to self-replicating entities Life forms today are complicated machines Copyright M.W. Davidson and Florida State University Research Foundation

28 Chicken and Egg Problem Lipid In modern Cells all components are Interdependent RNA DNA RNA PROTEIN

29 autocatalysis Lipid The Central Dogma RNA RNA DNA RNA PROTEIN

30 RNA World hypothesis RNA may have been the first self-replicating precursor to cellular life information content structural enzymatic activity

31 Origin Theories Common themes RNA probably came before DNA Life probably began in the sea: Water is essential Many unanswered questions. Still an active, fascinating area of research! No matter how it came about, the first replicating form would be acted upon by NATURAL SELECTION

32 The Nature of Life Life adheres to the laws of thermodynamics and follows the principles of organic chemistry Life is the capture of energy and material by an entity and the direction of these toward selfreplication Increasing complexity in this process over time is driven by evolution by natural selection