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AP BIOLOGY

Emergence of Organic Molecules

www.njctl.org

Summer 2013

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Emergence of Organic Molecules

· The Early Universe & Earth

· Organic Compounds

· Development of Life

Click on the topic to go to that section

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The Early Universe & Earth

Return toTable ofContents

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The Beginning...Many scientists have provided evidence of an event called the "Big Bang".

This event is said to have occurred about 14 billion years ago.

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Big Bang TheoryThis theory states that all of the mass in the universe was once compacted into one small point.

The universe was then created by a massive explosion and it has been expanding ever since.

photo: NASA

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Big Bang Theory

Every piece of matter in the universe came from this one point ... this one explosion.

Since everything is made of matter, this means that the material that makes up everything in the universe came from this one point in time.

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Evidence Supporting the Big Bang TheoryIf no one was around 14 billion years ago, then how did this theory come about?

In the early 1900's, an astronomer* named Edwin Hubble, discovered that various galaxies were spreading apart by measuring their location in the sky.

Due to this finding, he concluded the entire universe must be expanding.

*astronomer: a scientist who studies planets, stars, and galaxies

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Evidence Supporting the Big Bang Theory

Scientists explain this phenomenon by claiming that the universe expanded from a single point.

To visualize this, think of a stone that hits the surface of the water...

The water will ripple out from that one point and expand larger and larger.

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Our Expanding Universe

The universe will continue to expand, as it always has since the Big Bang occurred.

Stephen Hawking is one of the most famous physicists in the world today. He has researched and spoken on the expanding universe.

Click here to hear Stephen Hawking talk about this idea, the expanding universe

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1 The Big Bang Theory...

A created all the elements on the periodic table

B expanded all matter in the universe from a single point

C states that the universe is expanding linearly

D is just a tv show

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2When closely examined the universe appears red. This is due to...

A the short wavelength of red light

B the high frequency of red light

C the doppler effect as the universe expands

D the high percentage of red giant stars

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The age of the universe is about 14 billion years.

The age of Earth is about 4.6 billion years.

The early universe was almost completely made of hydrogen (H2) and helium (He).

None of the heavier elements (above helium) existed at the dawn of the universe.

The Early Universe

Click here to see David Christian's explanation of the formation of the

Universe

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Earth formed about 10 billion years after the start of the universe, about 4.6 billion years ago.

In those 10 billion years, generations of stars were born, and died.

All the heavier atoms on the periodic table were created by nuclear fusion inside those stars, or when they exploded.

The Early Universe

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When the early stars died explosively (novae and supernovae), those heavier elements were scattered into space.

When Earth, and its solar system, formed, it was in a cloud of matter which included all the naturally occurring elements in the periodic table.

No new elements have been created since Earth formed.

This means that all the atoms in you and your world, other than hydrogen and helium, were once inside a star, long ago.

The Early Universe

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3 Which came first?

A atoms

B electromagnetic force

C neutrons

D quarks

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4 Where did all the elements heavier than hydrogen and helium come from?

A the Big Bang

B the sun

C stars that we see at night

D stars that exploded long ago

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5 Carbon was formed in nuclear fusion reactions such as...

A 2H + He C

B He + He + He C

C He + Li C

D 2H + Li C

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The most prevelant were:

· water vapor (H2O), · carbon dioxide (CO2), · nitrogen (N2), · hydrogen sulfide (H2S), · methane (CH4), and · ammonia (NH3).

Early EarthStudies of volcanos suggest the early atmosphere of Earth was composed of a mix of chemical compounds.

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Earth was also subject to intense lightning and ultraviolet radiation.

It is ironic that life arose under conditions that included bombardment by UV radiation -

Today, depletion of the ozone layer that protects us from this radiation is a major environmental concern!

UV Radiation

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Early Earth atmosphere contained practically no oxygen, as this gas is not expelled during volcanic eruptions.

Oxygen gas first entered the atmosphere as a byproduct of photosynthesis. Initial oxygen production reacted with iron, producing banded iron formations. These geological formations have been used to date the evolution of photosynthesis to approximately 2.45 billion years ago.

Oxygen in the Atmosphere

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As Earth's crust cooled and solidified, water vapor condensed to create oceans.

Water is thought to have been brought to Earth by comets in the early solar system.

Early Earth's Oceans

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6 Scientists hypothesize that Earth's early atmosphere contained substances such as:

A oxygen, carbon dioxide and hydrogen gas

B nitrogen, oxygen, and water vapor

C water vapor, methane, and oxygen

D ammonia, water vapor, and hydrogen gas

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7 What is believed to have been the source of water for Earth?

A nuclear fission

B chemical reactions on Earth

C electrolysis

D comets

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Three-quarters of Earth’s surface is submerged in water.

The abundance of water is the main reason the Earth is habitable.

The Blue Planet

image courtesy NASA

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A water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom.

The more electronegative oxygen atom pulls the electrons from the hydrogen atoms toward it, resulting in an uneven distribution of charge.

Water Molecules

Slight Positive Charge

Slight Negative Charge

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Water: Polar Molecule

Since a water molecule has a positive end and a negative end it is called a polar molecule.

This property of water causes it to act like a magnet, attracting other molecules that have positive and negative poles.

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Properties of Water

The polarity of water gives it several important properties that allowed life to emerge on Earth:

· Ability to moderate temperature

· Versatility as a solvent

· Cohesive behavior

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Moderate Temperature

Water has a very high specific heat. This means that a great amount of energy is needed to raise the temperature of water even a few degrees. Because of this, temperature on the Earth's surface can undergo extreme variations - between night and day, or between seasons - without its water freezing or boiling away.

Why is this important in the development of life on Earth?

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Universal Solvent

A solution is a homogeneous mixture of substances.

An aqueous solution has water as the solvent. Water is sometimes referred to as the "universal solvent" because of its ability to dissolve most compounds.

Life's chemical reactions need to occur in solution. In water, nutrients can dissolve and chemical reactions can occur.

Solute SolventSolvent dissolves solute in solution

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HydrogenBonds

Cohesive BehaviorThe polarity of water molecules causes them to be attracted to each other.

Weak hydrogen bonds form between the hydrogens on one water molecule and the oxygen atoms on another to form liquid water.

Attraction between water molecules is termed cohesion. Attraction between a water and a non-water molecule is termed adhesion.

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Cohesive Behavior

This property allows:

· plants to pull water up through their roots

· small insects to walk on water

· and most importantly, water to bend carbon (organic) molecules into 3-D shapes.

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8 In a water molecule, hydrogen and oxygen are bonded together by:

A Ionic bonds

B Covalent bonds

C Hydrogen bonds

D Van der waals forces

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9 Which of the following best describes a hydrogen bond?

Aformed through an electrostatic attraction between two oppositely charged ions

Bformed by the equal sharing of electrons between to atoms

C the attractive force between neutral molecules

Dthe attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule

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10 Which property of water accounts for the other properties?

A cohesion

B adhesionC polarity

D high specific heat

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Organic Compounds

Return toTable ofContents

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Organic Monomers Formed

Three of the four organic molecules necessary for life to form are polymers, chains of monomers linked together by covalent bonds.

Monomers are highlighted in blue

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Organic Monomers Review

Can you name the 3 organic molecules that are polymers?

Nucleic Acids (DNA/RNA) - Proteins - Carbohydrates

Can you name the monomers for each of these?

Nucleotides - Amino Acids - Monosaccharides (sugars)

Can you name the organic molecule that is not a polymer?

Lipids/Fats

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Source of Organic Monomers

There are two theories for the source of organic monomers.

Which of these theories do you think is true?

How would you go about proving one of these theories?

· Arrival on Earth from space

· Creation on Earth through chemical reaction

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Organic Monomers from Space

The dust in the solar system, from which Earth formed, was rich in organic chemicals.

Meteorites striking Earth would have hit with lower velocity since the atmosphere was thicker; organic components would have survived.

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Organic Monomers from Space

We find organic chemicals in old meteorites discovered even today, such as this one.

Also, it's estimated that several million kg* (5,000,000 pounds) of organic chemicals fall as cosmic dust to Earth each year.

*The Story of Life , Richard Stockton, 2003, pg. 11

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In the 1920's, two scientists (Oparin and Haldane) proposed that organic chemistry could have evolved in the early Earth's atmosphere because it contained no oxygen.

The oxygen-rich atmosphere of today is corrosive and breaks molecular bonds.

Organic Monomers From Reactions

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In 1953, Stanley Miller used Oparin and Haldane's original idea and tested a hypothesis involving an artificial mixture of inorganic molecules. In his experiment, he stimulated the conditions thought to be found on primitive Earth.

Within days, the experiment produced some of the 20 amino acids presently found in organisms, as well as other organicmolecules.

Organic Monomers From Reactions

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Stanley Miller's Experiment

the primeval sea

the early atmosphere

lightning

rain

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Recent experiments, improving on Miller's, have produced most of the naturally occurring organic molecules including:

Organic Monomers From Reactions

· amino acids· sugars· lipids· nucleotides

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Absence of Oxygen in the atmosphere - O2 would have broken down any large organic molecules by accepting electrons.

High energy input - at that point in time, the sun was producing massive amounts of ultraviolet radiation

Micromolecules- the inorganic molecules had to be in the atmosphere and primitive oceans

Time - adequate time had to pass to give the molecules a chance to form, react, and reform.

Four Conditions Required for Chemical Evolution

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11 Miller and other scientists have shown that

A simple cells can be produced in a laboratory

B amino acids and sugars could be produced from inorganic molecules

C cells survived in the primitive atomosphere

D life on early earth required material from space

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12 Which of the following is not a condition for the formation of organic molecules?

A a long period of time

B inorganic micromolecules in the system

C presence of oxygen in the atmosphere

D high energy input

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13 Some evidence supports the theory that organic molecules and life arose deep in the oceans on or near hydrothermal vents. These vents would replace which variable in Miller experiment?

A atmosphereB rain

C lightning

D primeval sea

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Organic Monomers Combined to Form Polymers

Polymers are formed through a process called dehydration synthesis

Dehydration the process of removing water from a compound

or molecule

Synthesisthe combining of

separate parts to make a new whole

word breakdown

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The process of chemical evolution relies on molecules reacting with one another to form new molecules.

Reacting together also involves breaking molecules apart.

This process is called Hydrolysis:

Hydro (water) Lysis (splitting)

Hydrolysis

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14 Which is true about dehydration synthesis?

A one monomer loses a hydrogen atom, the other loses a hydroxyl group

B electrons are shared between the joined monomers

C water is formed when monomers join

D covalent bonds are formed between monomers

E all of the above are true

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15 The results of dehydration synthesis can be reversed by

A condensation

B hydrolysis

C polymerization

D adding an amino group

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16 The following equation is an example of:

A dehydration synthesis

B hydrolysis

C5H12 + H2O C3H7OH + C2H6

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17 The following equation is an example of:

A dehydration synthesis

B hydrolysis

C5H12 + C3H7OH C8H18 + H2O

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Hydrocarbons form the framework from which the 4 different classes of macromolecules (large molecules) have been derived.

Biological Macromolecules

· Carbohydrates· Nucleic Acids· Proteins· Lipids

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The general formula for a carbohydrate is

CxH2xOx

Some possible formulas for carbohydrates are:

Formula for Carbohydrates

Carbohydrates have equal amounts of carbon and oxygen atoms, but twice as many hydrogen atoms.

· C6H12O6

· C8H16O8

· C9H18O9

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The simplest sugars. Examples include glucose and fructose.

In solution, they form ring-shaped molecules.

The basic roles of simple sugars are as:- fuel to do work, - the raw materials for carbon backbones- the monomers from which larger carbohydrates are synthesized.

Monosaccharides

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Sugars all have several hydroxyl (OH-) groups in their structure that makes them soluble in water.

C

Glucose Fructose

(monosaccharides)

Carbohydrate Solubility

Note: the names of sugars typically end in "ose".

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Cells link 2 simple sugars together to form disaccharides

Disaccharide formation is another example of a dehydration reaction, the same reaction used to create proteins

The most common disaccharide is sucrose (glucose + fructose)

Disaccharides

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18 Which of the following is an example of a monosaccharide?

A sucrose

B glucose

C fructoseD B & C

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19 Saccharides are soluble in water because...

A They are nonpolar molecules

B They can form hydrogen bonds

C Carbon is highly electronegative

D They are unsaturated

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20 What is another name for simple carbohydrates?

A sugarsB saccharidesC monosaccharidesD all of the above

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Polysaccharides are polymers of glucose.

Different organisms link monosaccharides together, using dehydration reactions, to form several different polysaccharides.

The most important 3 are starch, glycogen, and cellulose.

Polysaccharides

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Polysaccharides: Starch

Starch is used for long term energy storage in plants.

Can be branched or unbranched.

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Polysaccharides: Glycogen

Glycogen has the same kind of bond between monomers as starch but it is always highly branched.

It is used for long term energy storage in animals.It's used in muscles to provide a local supply of energy when needed.

Glycogen is broken down to obtain glucose.

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Polysaccharides: Cellulose

Cellulose has a different kind of bond between monomers, forming chains that are cross-linked by hydrogen bonds.

Cellulose is a carbohydrate used to make cell walls in plants.

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In order for cells to obtain energy from polysaccharides, they must be first broken down into monosaccharides.

Hydrolysis occurs, breaking the polysaccharide into glucose molecules.

Getting Energy

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21 The fundamental unit of polysaccharides is

A fructose

B glucose

C sucrose

D A and B

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22 Starch and glycogen are both used for energy storage. Which of the following is not true of these two polysaccharides?

A breakdown of these molecules produces carbon dioxide

B they contain easily hydrolyzed bonds

C they are products of photosynthesis

D synthesis of these molecules is endergonic

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23 Cellulose is found in plants but not animals, because...

A It is produced by chloroplasts

B It is the structural molecule of cell walls

C It requires more energy to produce; plants receive unlimited energy from sunlight

D It provides the green coloration to plants

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Nucleic acids are compounds consisting of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

Nucleic Acids

The two main types of nucleic acids are DNA and RNA

Nucleic acids are chains of nucleotides linked together by phosphodiester bonds.

nucleotide nucleotide nucleotide

Nucleic Acid

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Nucleotides have three parts:

a sugara base (a nitrogen compound)

a phosphate

Parts of a Nucleotide

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Sugars

Ribonucleic Acid (RNA) uses the sugar ribose, while Deoxyribonucleic Acid (DNA) uses the sugar deoxyribose.

Here's the difference.

Ribose Deoxyribose

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Each strand is unique due to its sequence of bases. In this way, genetic information is stored in the sequence of nucleotides.

Since the bases are not part of the sugar or the bond, the base sequence is independent of them. Any base sequence is possible.

Nucleotides

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24 The creation of a phosphodiester bond involves the removal of ____ from the nucleotides:

A phosphates

B glucose

C water

D nucleic acids

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25 Which of the following is not a component of a nucleotide?

A phosphate group

B nitrogenous base

C 5-carbon sugar

D glucose

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26 Which base is found in RNA but not DNA?

A Cytosine

B Uracil

C Guanine

D Adenine

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27 Adenine would be characterized as a purine.

True

False

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29 Pyrimidines are bases with single carbon rings.

True

False

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30 Guanine and adenine do not pair because...

A They create different numbers of hydrogen bonds

B They are both purines

C They are not found in the same nucleic acid

D They both have a single ring

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RNA

RNA is usually single stranded. As a result, it can take on many different shapes.

Hydrogen bonds form between different bases, and between bases and water. These bonds cause RNA to form different shapes.

Different sequence of bases = different shapes

A UC G

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RNA World HypothesisThe RNA world hypothesis proposes that self-replicating RNA molecules were the precursors to early life. Evidence to support this hypothesis includes the observation that many of the most critical components of cells, are composed of RNA or substances closely related to RNA.

In early life, RNA is believed to have played many roles that have now been taken over by more specific molecules. RNA's role is still essential, but more limited than it once was.

Function Then Now

cata lyze reactions

RNA Prote ins

store energy RNA's phosphate group

ATP

store genetic information

RNA DNA

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DNA is double-stranded.

It only forms one shape: the double-helix.

Pair bonding between nucleotides still occurs, but in DNA it is between guanine (G) and cytosine (C) and between adenine (A) and thymine (T)

DNA

Adenine

Thymine

Cytosine

Guanine

A TC G

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Proteins are compounds consisting of carbon, hydrogen and oxygen, nitrogen, and sometimes sulfur.

Proteins also called peptides also called polypeptides.

Proteins

Proteins are chains of amino acids linked together by peptide bonds.

There are 20 amino acids used to construct the vast majority of proteins. While there are a few others that are sometimes used, these 20 are the "standard" amino acids.

All life on Earth uses virtually the same set of amino acids to construct its proteins.

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amine group (NH3)

side chain

carboxyl group (COOH)

Amino Acids always include an amine group (NH3), a carboxyl group (COOH) and a side chain that is unique to each amino acid.

Components of Amino Acids

The side chain (sometimes called the R-group) determines the unique properties of each amino acid. Here it is symbolized by the letter "R".

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The 3 in the light blue box are basic ("amine" group in the side chain).

The 2 in the magenta box are acidic ("carboxyl" group in the side chain).

The 8 amino acids in orange are nonpolar and hydrophobic.The others are polar and hydrophilic.

The unique side chains are shown in blue.

The common "amine" group (NH3) and "carboxyl" group (COOH) are shown in black.

http://www.bioss .ac.uk/~dirk/genomeOdyssey/go_1955_to_66.html

Amino Acids

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31 Glucose molecules are to starch as ___________ are to proteins.

A oils

B fatty acids

C amino acids

D waxes

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32 Which component of amino acids varies between the 20 different kinds?

A Amine group

B Carboxyl group

C Hydroxyl group

D R-group

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33 Which of the following statements is best supported by the chart?

A The DNA sequence of horses and donkeys are identical for the cytochrome c gene.

BPenguins have an increase number of hydrophillic amino acids in their cytochrom c protein.

C Snakes and horses use entirely different amino acids in their cytochrome c structure

DThe gene for cytochrome c protein is snakes is most similiar to the gene for this protein in penguins

Horse Donkey Chicken Penguin Snake

Horse 0 1 11 13 21

Donkey 1 0 10 12 20

Chicken 11 10 0 3 18

Penguin 13 12 3 0 17

Snake 21 20 18 17 0

Ans

wer

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Protein Shape and Structure

Shape is critical to the function of a protein. A protein's shape depends on four levels of structure:

· Primary · Secondary · Tertiary · Quaternary

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The primary structure of a protein is the sequence of amino acids that comprise it.

Each protein consists of a unique sequence.

Proteins: Primary Structure

Alanine Lysine

Valine

Leucine Serine

Leucine Leucine Alanine

Lysine Alanine Serine Lysine

or

or

or...

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Secondary Structure

Secondary Structure is a result of hydrogen bond formation between amine and carboxyl groups of amino acids in each polypeptide chain.

Depending on where the groups are relative to one another, the secondary structure takes the shape of an alpha helix or a pleated sheet.

Note: R-groups do not play a role in secondary structure.

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alpha helix

pleatedsheets

Secondary Structure

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Tertiary Structure

Tertiary Structure is the overall 3-D shape of the polypeptide. This 3-D shape determines the protein's function.

It results from the clustering of hydrophobic and hydrophilic R-groups and bonds between them along the helices and pleats.

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Denaturation

Changes in heat, pH, and salinity can cause proteins to unfold and lose their functionality, known as denaturation.

This egg's protein has undergone denaturation and loss of solubility, caused by the high rise in the temperature of the egg during the cooking process.

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Quaternary Structure

Some proteins have a Quaternary Structure.

Quaternary structure consists of more than one polypeptide chain interacting with each other through hydrogen bonds and hydrophobic/hydrophilic interactions.

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34 The tertiary structure of a protein refers to:

A its size

B the presence of pleated sheets

C its over all 3D structure

D the number of R-groups it contains

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35 The __________ structure of a protein consists of a chain of amino acids assembled in a specific order.

A primary

B secondary

C tertiary

D quaternary

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36 Scientists alter a valine molecule to prevent hydrogren bonding of atoms in the R group. This would not effect ____________ of a protein.A the secondary structure

B the tertiary structure

C the quaternary structure

D it would effect all the structural levels

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Structure Summary

Level Structure Notes

Primary bonds between amino acids

s ingle chain of amino acids

Secondaryhydrogen bonds between amine and carboxyl groups

alpha he lix, pleated sheet

Tertiaryclustering of hydrophobic or hydrophilic R groups

disulfide bonds

Quaternaryattractions between multiple peptide chains

not present in a ll prote ins

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Types of Proteins

Structural hair, cell cytoskeleton

Contractile as part of muscle and other motile cells

Storage sources of amino acids

Defense antibodies, membrane proteins

Transport hemoglobin, membrane proteins

Signaling hormones, membrane proteins

Enzymatic regulate speeds of chemical reactions

Type Function

Proteins have 7 different roles in an organism.

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37 Hormones are an example of what class of protein?

A structural

B defense

C transport

D signaling

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38 Hemoglobin is an example of what class of proteins?

A Transport

B Signaling

C Enzymatic

D Structural

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Lipids are the one class of large biological molecules that do not consist of polymers.

Lipids

Main functions of lipids include

· energy storage· the major component of cell membrane· involved with metabolic activities

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Lipids are either hydrophobic or amphiphilic.

Amphiphilic

hydrophobic

hydrophilic

Amphiphilic molecules have a hydrophobic "tail" and a hydrophilic "head". So one of its ends is attracted to water, while the other end is repelled.

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Triglicerides are hydrophobic. They are constructed from two types of smaller molecules: a single glycerol and three fatty acids

Fatty acids are carboxylic acids with a very long chain of carbon atoms. They vary in the length and the number and locations of double bonds they contain

Triglicerides: Hydrophobic Lipids

a fatty acid

CH2OH

CH2OH

CH2OH

glycerol

C C C CC

H H H H

HH

H

HHHC C C COOHC

H H H

H H H

H

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3 fatty acids added to glycerol produce a trigliceride

Triglicerides

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Phospholipids have 2 fatty acids and 1 phosphate group.

The phosphate end is polar and hydrogen bonds with water. The fatty acids are made of long chains of carbon and hydrogen, making them non-polar.

As a result, the phosphate end is hydrophilic and the fatty-acid end is hydrophobic. Overall, phospholipids are amphiphilic.

Phospholipids: Amphiphilic Lipids

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Steroids are lipids with backbones which form rings. Cholesterol is an important steroid as are the male and female sex hormones, testosterone and estrogen.

Steroids

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39 Lipids can be _____.

A hydrophobicB hydrophilicC amphiphilicD hydrophobic and amphiphilic

E hydrophilic and amphiphilic

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40 A phospholipid is an example of a/an _____.

A hydrophobic molecule

B hydrophilic molecule

C amphiphilic molecule

D hydrophobic and amphiphilic molecule

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Development of Life

Return toTable ofContents

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The chemical reactions in early protobionts would eventually create sugars, and then ribonucleic acid (RNA). RNA has been shown to be capable of some of the key functions enabling life:

· replication: making identical copies of itself

· metabolism: storing energy for chemical reactions

· catalyzation: dramatically speeding up favored chemical reactions

Once these three functions were developed, evolution accelerated.

From Micromolecules to Macromolecules

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Abiogenesis is the study of how biological life could arise from organic molecules through natural processes.

In particular, the term usually refers to the processes by which life on Earth may have arisen.

Abiogenesis

3.5 Billion year old cyanobacteria are the oldest and simplest life forms ever discovered.

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This topic is outside the scope of the AP test, but if you need further evidence for the formation of living things from chemical components, you can view the work of Jack W. Szostak who has shown ways in which organic molecules could have assembled into a complex sphere capable of self replication and producing energy.

Abiogenesis

Jack SzostakHarvard Medical SchoolNobel Prize for Physiology 2009

Click here to see Szostak Lab's animations that show the steps in

forming a pre-biotic complex sphere

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Membranes are an arrangement of phospholipids that gather together and make a closed shape. Membranes act as a wall or a barrier separating the outside and the inside of the closed shape.

This is the natural condition of phospholipids when placed in aqueous solution.

Primitive Cells: The Start of Animated Earth

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This occurs because of the unique chemical properties of phospholipids. They are amphiphilic : containing a portion that is hydrophobic and a portion that is hydrophilic.

Primitive Cells: The Start of Animated Earth

Polar head that will attract water

Non-polar hydrocarbon tail that will repel water

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Primitive Cells: The Start of Animated Earth

Within an enclosed volume, more complex chemistry can proceed; leading to protobionts: the precursors to life.

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Within the inner environment of the protobiont, the processes of chemistry created ever more complex:

· Proteins· Carbohydrates· Lipids· Nucleic Acids

Simple metabolism evolved to increasingly complex levels based on the principles of organic chemistry.

From Micromolecules to Macromolecules

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Last Universal Common Ancestor (LUCA)

Protobionts became ever more complex until they included all the large biological molecules, including both RNA and DNA and the enzymes needed to maintain and use them.

This led to what is called Last Universal Common Ancestor (LUCA). As you'll learn throughout this course, the common features of life on Earth are so profound that all life must have evolved from a single ancestor.

"A universal common ancestor is at least 102860 times more probable than having multiple ancestors…"

Saey, Tina (5 June 2010). "Life has common ancestral source". Science News 177 (12): 12. doi:10.1038/465168a

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LUCASome of the common features of all life on Earth that make a universal ancestor a logical necessity includes the following:

ALL LIFE on Earth uses the IDENTICAL:

· Universal Genetic code that makes all life's structures possible· Base pair coding in DNA (ATCG)and RNA (AUCG) · DNA and RNA polymerases, enzymes that make polymers· mRNA for sending genetic messages · tRNA for gathering amino acids· Ribosomes for assembling proteins · L-isomers of amino acids· 20 Amino acids that are used to build all proteins· Glucose as the ultimate energy source (very few exceptions

exist)· Lipid bilayer for making cell membranes· Cellular division for growth· Sodium and Potassium ion pumps for creating potential· ATP as the "currency" of energy to power all their systems· ATP Synthase to power the production of ATP

AND MANY, MANY MORE SIMILARITIES!

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LUCANone of these features of life on Earth had to be exactly this way. There are alternative ways to solve each problem.

Question: How would it come to be that all life uses all these common features if there was not a universal ancestor?

Take a moment and come up with an alternate theory to LUCA.

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LUCA

Earth is 4.6 billion years old+

The environment is too hostile for life until 3.9 bya+

The earliest fossil evidence for life is 3.5 bya

= The evolution of LUCA occurred between 3.9 and 3.5 bya.

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Cells

Fossilized stromatolites (layered rocks that form when certain prokaryotes bind thin layers of sediment together) provide evidence that the first organisms on Earth were prokaryotic cells. The earliest stromatolites have been dated to 3.5 BYA.

These cells were/are very limited in their capabilities to perform the functions of life.

http://www.life.umd.edu/classroom/bsci124/img/bacteria.jpg

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Cells

Early prokaryotic cells are the simplest packet of chemicals capable of doing all the functions that define life.

Life is defined as a set of conditions that separate abiotic (non-life) from the biotic (living).

There are 7 conditions. Can you name them?

·Organization/Order: Composed of units/cells·Adaptations: Populations evolving to their environment·Response to the environment: Individual response to stimuli·Regulation: Mantaining an internal condition (homeostasis)·Energy processing: Using energy from environment·Growth and development: Immature to mature form·Reproduction: Producing offspring, heredity

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41 The creation of membranes from phospholipids __________________.

A allowed for a more complex chemistry

B allowed bacteria to flourish

C allowed lipids to make glycoproteins

D allowed more amino acids to form

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42 Evidence for a last universal common ancestor among life on Earth is:

A they all rely on photosynthetic reactions for energy

B they all utilize ATP

C they all reproduce through mitosisD they are all aerobic

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