PTYS 214 – Spring2011

Homework #3 available for download on the class website DUE Thursday, Feb. 3

Tonight 7-8 pm at Centennial Hall: Guy Consolmagno "Cosmology: Making Sense of the Universe“ College of Science Lecture Series: Cosmic Origins

Class website: http://www.lpl.arizona.edu/undergrad/classes/spring2011/Pierazzo_214/

Useful Reading: class website “Reading Material” http://en.wikipedia.org/wiki/Energy http://hyperphysics.phy-astr.gsu.edu/hbase/therm/entrop.html http://en.wikipedia.org/wiki/Adenosine_triphosphate http://en.wikipedia.org/wiki/Photosynthesis

Announcements

Some articles in the most recent issue of Astrobiology

The Definition of Life: A Brief History of an Elusive Scientific Endeavor, by S. Tirard, M. Morange, A. Lazcano

Defining Life, by S. A. Benner Look at what scientists do to determine which definition of life they

can use to design missions to seek non-terran life, and what are universal biosignatures to identify life in the universe

Elucidation of an Iterative Process of Carbon-Carbon Bond Formation of Prebiotic Significance, by A. Loison, S. Dubant, P. Adam, P. Albrecht

Laboratory experiments of possible reactions that may have occurred in primitive deep-sea hydrothermal vents identify a process in which reduced metal species (Ni) appear to catalyze the formation of complex organic macromolecules

Quiz #2

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Homework #2

Total Students: 26

Class Average: 8

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Copying text without citing the source is plagiarism!Use your own words to explain a concept.

Some sentences may be taken verbatim from a source only if they are put in quotes and the source is listed.

Bottom-Up Approach: Summary

1. There are 3 sources of small organic carbon molecules (up to amino acids, sugars) in the prebiotic world

2. Small organic molecules must combine to form the basic sub-units of RNA

3. Polymerization allows for the formation of organic macromolecules

Dilution Problem The primordial soup was probably too dilute in simple

monomers to form very long molecules(a concentration mechanism is required)

The RNA World Short strands of RNA-like molecules were produced spontaneously (with some help, e.g.

minerals)

Eventually some of the RNA-like molecules were able to catalyze their own replication

Copying errors introduced mutations and therefore Darwinian-like evolution

CCU G

GGA C UGGA C U

CCU G A

Some lipids have hydrophilic head and hydrophobic tail (amphiphiles)

Example?

Soap!

In solution these lipids can form monolayers, bilayers and bilayer vesicles spontaneously → proto-cells

Bottom-Up Approach - Summary

4. Formation of the cell membrane=water-loving

Monolayer

Bilayer Bilayer vesicle

Micells

Cell Membrane

First DNA-based Life

Through natural selection life figured out that

a) DNA is a better way to store the hereditary information (better protected, less mistakes during replication) than RNA

b) Proteins are more efficient catalysts than RNA

Common sore spot for Top-Down and Bottom-Up approaches:

Simple organic

moleculesRNA world

Metabolism first?Replication first?

+Concentration

problem

Origin of Life on EARTH

Abiotic synthetic reactions on the early Earth

Prebiotic soup

Prebiotic polymers

Origin of lifeRNA world

DNA/RNA/proteinworld

Last Common Ancestor

Organics from space

Bada & Lazcano (Science, 2002)

Life Needs Energy

Energy

Widely used word:- Somebody is very energetic- Energy drinks, energy boosters- Clean Energy - Renewable Energy - Energy-efficient homes- Energy crisis

What is Energy? Energy causes things to happen around us…

Ability to accomplish changes

Energy = Ability to do work

Work (mechanical work): W = force x displacement = F x d

There are different kinds of Energy:

– Kinetic - energy of motion:

– Potential (gravitational): (h=height; g=gravitational acceleration)

– Thermal: random motion of particles (molecules/atoms)

– Chemical: “rearranging” electrons (chemical reactions)

– Nuclear: nuclear fusion, nuclear fission

– Electromagnetic: electromagnetic waves (light)

2vm2

1KE

hgmPE

Units of Energy & Work

JOULE (J): One Joule is the work done, or energy expended, by a force of one Newton (N) moving an object one meter along the direction of the force

1 Joule = 1 N × 1 meter = 1 kg×m/s2 × 1 m = 1 kgm2/s2

The force of Earth’s gravity on a 220 pounds human is about 1000 N

CALORIE (food energy, Cal): amount of energy required to raise the temperature of one kg of water by one degree Celsius

1 Cal = 4184 J

Power

Rate at which work is done (energy expenditure):

Units: Watts - One Watt is the power associated with the expenditure of one Joule of energy per second:

t

E

t

WP

s

JW

Energy Conversion

How many Joules are 2000 Calories?

Suppose we use 2000 Calories per day.

How many Watts do we use?

J108.3682000Cal 6

96.85W

Energy Example

An athlete lifted a barbell with weights (220 pounds) from the ground to 7 feet.

How many Joules did he use?

1 m = 3.3 ft

1 kg = 2.2 lb

g = 9.8 m/s2

How many Calories ?

2058 Joules

First Law of Thermodynamics:

Conservation of EnergyIn a closed (isolated) system the total amount of

energy is conserved

Energy cannot be created or destroyed, but it canchange from one form to another

KE + PE + W = Etot

Friction

Closed vs. Open Systems

Cup of hot coffee

Earth

Solar System

Universe

A closed (isolated) system is like an closed box: energy and matter cannot flow in and out

Not all kinds of energy are useful to life

So far, we have found no examples of life using gravitational, low frequency electromagnetic (radio), nuclear energy

EntropyMeasure of disorder in the physical system

Second law of thermodynamics

In the universe, or any isolated system, the degree of disorder (entropy) can only increase

…or

Heat cannot flow spontaneously from a cold object to a hot one

The most probable state is the most disordered

The movement towards a disordered state is a spontaneous process

Examples: - hot cake out of the oven- glass of ice cubes

Life produces order!

Life evolved from a primordial soup of random organic molecules to complex organisms (increased order)

Plants turn carbon dioxide and water into leaves and flowers (increased order)

A cell is not an isolated system: 1. it takes in energy from its environment to generate

order within itself 2. Part of the energy that the cell uses is converted into

heat 3. The heat is discharged into the cell's environment and

increases its disorder

Do Living Cells Obey the 2nd Law of Thermodynamics?

The total entropy increases

Photosynthesis

How does life take energy from the environment?

Photosynthesis

Find it on YouTube at: http://www.youtube.com/watch?v=pdgkuT12e14

Photosynthesis

A) Oxygenic (plants, algae):

CO2 + H2O + h (Energy) → CH2O + O2

B) Anoxygenic (purple bacteria, green sulfur bacteria, green gliding bacteria):

CO2 + 2H2S + h (Energy) → CH2O + 2S + H2O

In reality:

6CO2 + 6H2O + h (Energy) → C6H12O6 + 6O2

Glucose

Water

Hydrogen Sulfide

Life takes energy from the environment and stores it as chemical bonds

How does life extract the energy?

In the presence of oxygen:

Respiration (multicellular organisms)

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

Without oxygen:

Fermentation (some bacteria, yeast)(much less efficient!)

C6H12O6 → 2CO2 + 2C2H6O + Energy

Ethanol

ATPEvery living cell uses ATP (Adenosine TriPhosphate) to

transfer energy

Energy in Energy out

How does life utilizes energy?

Energy in terms of ATP

RespirationC6H12O6 + 6O2 → 6CO2 + 6H2O + 38ATP

Fermentation(much less efficient)

C6H12O6 → 2CO2 + 2C2H6O + 2ATP

There are ways to get energy without photosynthesis

Methanogenesis

CO2 + 4 H2 → CH4 + 2H2O + Energy

Sulfate reduction

4H2 + SO42- → S2- + 4H2O + Energy

Methanopyrus kandleriMethanopyrus kandleri

Green sulfur bacteria

Primary sources of energyfor life on Earth

Sun Earth’s Interior

What about fossil fuels?