IA Chapter 1 Origin Of Life Flashcards

Question

What is the top-down strategy for the origins of life on Earth?

Answer 1

This strategy looks at present-day biology and extrapolates backwards towards the simplest living entities.

Answer 2

This approach focuses on a collection of inanimate elements, molecules and minerals from the past with known properties and attempts to figure out how they may have become combined to create a living organism.

Answer 3

These are organic molecules that consist of a six-carbon ring held together by alternating single and double-carbon bonds.

Answer 4

Organic molecules can be produced in candle flames, from burning coal, from stars and in interstellar molecular clouds.

Answer 5

The temperatures are so low in molecular clouds that any element heavier than H or He will stick to the surface of any dust grains it comes into contact with. Chemical reactions between organic compounds are catalyzed by the grain surface. Then they are further processed by UV and cosmic rays. The products of grain mantle chemistry may take part in further organic chemistry when they are incorporated into the warm (200/400 K) and dense areas of gas around recently formed stars.

Answer 6

These are the hot dense molecular clouds around newly formed stars which are the most-chemically diverse regions of the universe. Various interesting chemical compounds are produced when icy grain mantles are heated in hot cores. Radiation evaporates the ice and organic compound return to a gaseous state.

Answer 7

Hot cores become **solar nebula** which eventually become a new solar system containing all the new organic molecules.

Answer 8

It could have felled chemical reactions that synthasised organic matter in the early solar system and sustained primitive life.

Answer 9

- Solar radiation would have been the most prominent - geothermal heat flow - electrical discharges (lightning) - cosmic rays - shockwaves (atmospheric waves)

Answer 10

Millers experiment replicated the oceans and atmosphere of the early earth. He boiled the solution and subjected the 'atmosphereʼ to a continuous electric current. After a week his experiment showed that organic compounds, specifically amino acids were easily produced and were likely very abundant in the universe. This experiment showed organic compounds could be produced in the hydrosphere of a planet.

Answer 11

The murchison meteorite feel in Australia in 1969.it was a rare type of **carbonaceous chondrite** that was found to contain many organic molecules, including amino acids. The amino acids found in the meteorite are both similar in type and abundance to those formed in the miller Urey experiment.

Answer 12

The miller Urey experiment relys on a reducing atmosphere, however methane and ammonia both break down in the presence of UV radiation. Therefore it is believed that earths early atmosphere consisted of carbon dioxide, nitrogen and water which were less favourable for producing amino acid in the experiment.

Answer 13

- Shock waves from impacts may have forced gas to combine, producing organic matter. - impactors may vaporise rock on impact allowing organic molecules to form as gasses recombine.

Answer 14

This refers to how some molecules can have an identical chemical structure, but differ in their structural arrangements. These molecules are known as **isomers**. **Chiral** molecules are molecules that when reflected, could not be superimposed on its mirror image. **Achiral** molecules are molecules that would be superimposeable on their mirror image.

Answer 15

They are usually carbon bonded to 4 different groups.

Answer 16

- Right landed forms are abbreviated to D (dextro). - left handed forms are abbreviated to L (levo).

Answer 17

This is a mixture that has an equal number of left and right handed molecules. These mixtures are typically created in the absence of life.

Answer 18

All protein can only be made from left handed amino acids apart from glycine which is achiral. A mix of left and right handed amino acids in protein would hinder the proteins from performing their biological functions.

Answer 19

This is a type of starlight where in electric field direction rotates along the beam. This rotation con occur in a left or right handed direction. Chiral molecules have different absorption intensities for left and right UVCPL, therefore UVCPL destroys one form of the molecules more readily than the other.

Answer 20

Meteorites contain mainly left handed molecules. This could be due to: -UVCPL destroying right handed variety's. - the chirality may have been inherited by molecules that grew on certain surfaces such as magnetite.

Answer 21

This is a theory that suggests that microbes can be carried between interstellar bodies via comets and meteors.

Answer 22

1. Marginal marine environments such as lagoons and tide pools. Evaporation increases concentrations in residual liquids. 2. Freezing an aqueous solution increases the concentration of any organic molecules as the water freezes first. 3. The surfaces of days and other minerals provide sites for trapping organic matter.

Answer 23

They are important for providing enough localised raw material for the creation of primitive living systems.

Answer 24

These are formed by either two -OH groups undergoing a condensation reaction, or a -NH2 group reacting with a -COOH group. These processes would allow single monomer sugars and amino acids to form larger organic molecules, although water is destructive to polymers.

Answer 25

They are single molecules that process both a **hydrophilic head** and **hydrophobic tails**. The hydrophilic head has a small charge, making it soluble in polar solvents, such as water. The hydrophobic tails have no charge making them insoluble. (phospholipids)

Answer 26

If a solution containing amphiphilic molecules is shaken, the amphiphilic molecules group together and form spheres with the soluble heads outside and the insoluble tails inside called **micelles**.

Answer 27

This is when there are enough anphiphilic molecules to form a bilayer with water on both the outside and inside. All the **biylayer vesicles** and **micelles** can form organically.

Answer 28

When proteins are dropped in water they group together into droplets called **coacervates**. Many substances when added to coacervate preparation can become incorporated into the coacervates. This is potentially how prebiotic chemical factories were made.

Answer 29

Amino acids were dry heated to cause polymerisation by condensation reaction. These polymers resembled proteins so were named **proteinoids**. These proteinoids were then introduced into hot water and allowed to cool. The proteinoids formed small spheres 2 microns in diameter that had a double wall resembling a biological membrane. These spheres could expand and contrast depending on the salt concentration of the water and were coined **microspheres**. When left microspheres absorbed more proteinoids over time.

Answer 30

- Small pockets in mineral may have provided protection from dispersion and destruction for early chemical systems. - mineral may have acted as catalysts for chemical processes. - minerals could have acted as support structures to support molecules and allow them to accumulate. - certain minerals such as calcite ham a mirrored structure so when bonding with amino side can produce protein like structures that are inherently left or right handed.

Answer 31

RNA can store genetic information and can have some of the catalytic properties of enzymes therefore, may have predated DNA and proteins. Arguments to support this: - nucleotides in RNA are more easily synthesised than nucleotides in DNA. - its easy to imagine DNA evolving from RNA, given DNA 's greater stability. - RNA likely evolved before proteins as it is not believed that proteins can replicate in the absence of RNA.

Answer 32

These are organisms that use photosynthesis or chemosynthesis (chemical energy) to generate energy and use for metabolic reactions.

Answer 33

This is a form of metabolism where the carbohydrate glucose (C6H12O6) is transformed into CO2 and ethanol (CH3CH2OH) or lactic acid (C3H6O3) for a net gain equivalent to that stored in two phosphate bonds.

Answer 34

This is where glucose reacts with oxygen from the earths atmosphere to form carbon dioxide and water with a net gain equivalent to 36 phosphate bonds, far better than fermentation.

Answer 35

These are organisms that gain their energy from consuming other organisms such as autotrophs.

Answer 36

By comparing the ribosomal RNA of many organisms we can put together a tree that represents how closely related different organisms are.

Answer 37

By comparing ribosomal RNA we can hypothesise that our last common ancestor may have been heat loving chemosynthetic organisms that populate hydrothermal vents today. This does not however suggest these were the first organisms on earth.