Chapter 4. Nucleic Acids and the Origin of Life

Question 1

Name the two types of nucleic acid

Answer 1

1. RNA
2. DNA

4.1 Nucleic Acid Structures Reflect Their Functions

Question 2

Nucleic acids are __________ composed of nucleotide ____________

Answer 2

polymers; monomers

4.1 Nucleic Acid Structures Reflect Their Functions

Question 3

Name the three components of a nucleotide

Answer 3

1. A nitrogenous base (nitrogenous just means a chemical substance that contains nitrogen)
2. A pentose sugar
3. One, two or three phosphate groups

4.1 Nucleic Acid Structures Reflect Their Functions

Question 4

Name the two components of a nucleoside and then think about the key difference between nucleotides and nucleosides

Answer 4

1. Nitrogenous base
2. Pentose sugar

The key difference between nucleosides and nucleotides: Nucleosides completely lack any phosphate groups.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 5

What are the two groups of bases?

Answer 5

Pyrimidines and purines

4.1 Nucleic Acid Structures Reflect Their Functions

Question 6

Which bases (ACTGU) are purines and which are pyrimidines?

Answer 6

Remember: Pure As Gold Purines: A G (“Pur” pronounced “pure” in this case)

CUT the Pyrimidine where “Py” is pronounced “Pie”

Question 7

Describe the structure of a purine and pyrimidine

Answer 7

Pyrimidines are 6 membered single rings. Purines have a fused double ring structure.

You could remember this by saying that Gold is strong and so must have a double fused ring rather than just a single ring.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 8

What is the name of the pentose sugar in DNA and what is the pentose sugar in RNA called? What is different about these two different pentose sugars?

Answer 8

DNA - Deoxyribose

RNA - Ribose

Main Difference between the two pentose sugars - deoxyribose has one less oxygen atom than ribose.

4.1 Nucleic Acid Structures Reflect Their Functions

Image found on google and not Life Book

Question 9

What are condensation reactions?

Answer 9

A condensation reaction is one in which two molecules combine to form a larger molecule at the same time eliminating a small molecule such as water.

4.1 Nucleic Acid Structures Reflect Their Functions

Image not found in Life Book

Question 10

What is the name of the bond formed between the sugar of the last nucleotide in the chain and the phosphate group of the incoming nucleotide?

Answer 10

Phosphodiester linkage

4.1 Nucleic Acid Structures Reflect Their Functions

Question 11

The formation of a phosphodiester bond and elimination of water is what kind of chemical reaction?

Answer 11

A condensation reaction

4.1 Nucleic Acid Structures Reflect Their Functions

Question 12

In which direction are nucleotides added to a growing nucleic acid (growing chain of nucleotides)?

Answer 12

5’ to 3’

NB: where ‘ = prime

4.1 Nucleic Acid Structures Reflect Their Functions

Question 13

Nucleotide chains (nucleic acids) can be short or very long in length. What are long and short nucleic acids called respectively?

Answer 13

Long nucleic acids = polynucleotides where “poly” means “many”

Short nucleic acids = oligonucleotides where “oligo” means “few”

4.1 Nucleic Acid Structures Reflect Their Functions

Question 14

Which bases (A, C, T, U, G) are found in DNA and which are found in RNA?

Answer 14

DNA - Adenine (A), Thymine (T), Guanine (G) and Cytosine (C)

RNA - Adenine (A), Uracil (U), Guanine (G) and Cytosine (C)

4.1 Nucleic Acid Structures Reflect Their Functions

Question 15

Which nucleic acid is double-stranded and which is single-stranded?

Answer 15

DNA - double-stranded

RNA - single-stranded

4.1 Nucleic Acid Structures Reflect Their Functions

Question 16

State the nucleosides of DNA and RNA

Answer 16

1. Adenosine
2. Guanosine
3. Cytidine
4. Uridine

4.1 Nucleic Acid Structures Reflect Their Functions

Question 17

Which bases in DNA always pair with each other

Answer 17

A with T and G with C

4.1 Nucleic Acid Structures Reflect Their Functions

Question 18

What type of bond forms between complementary base pairs

Answer 18

Hydrogen bonds

Question 19

How many hydrogen bonds are found between an A and T and G and C

Answer 19

Between A and T - 2 hydrogen bonds

Between G and C - 3 hydrogen bonds

To remember this just say that gold is strong so it needs 3 hydrogen bonds rather than 2.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 20

Are hydrogen bonds stronger than covalent bonds?

Answer 20

No

4.1 Nucleic Acid Structures Reflect Their Functions

Question 21

What kind of bonds are between N-H and C=O?

Answer 21

Polar Covalent bonds

Question 22

Can base-pairing occur in RNA molecules?

Answer 22

yes - Although RNA molecules are only single-stranded, portions of an RNA molecule can fold back and pair with other bases of the RNA molecule.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 23

Can ribonucleotides (A, C, U, G) pair with deoxyribonucleotides (A, C, T, G)

Answer 23

Yes

4.1 Nucleic Acid Structures Reflect Their Functions

Question 24

Predict what would happen if a folded RNA molecule was heated.

Answer 24

The hydrogen bonds of the base pairing between portions of the RNA molecule would break and the RNA molecule would arrange itself in another random position, losing its original folded shape.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 25

Which nucleic acid would you say can arrange itself in the most amount of different three-dimensional shapes?

Answer 25

RNA is a clear winner as there is an almost endless number of ways it can fold in on itself whilst DNA has only one uniform shape: that of a twisted ladder.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 26

What is the key difference between many different DNA molecules

Answer 26

The sequence of bases that make up the DNA molecules

4.1 Nucleic Acid Structures Reflect Their Functions

Question 27

If we compare DNA to a ladder what would be the rungs and side rails of the DNA ladder (ignore the anti-slip safety shoe/foot)?

Answer 27

Side rails - Pentose sugar and phosphate groups

Rungs - Nitrogenous bases

4.1 Nucleic Acid Structures Reflect Their Functions

Question 28

Name the two methods by which DNA can transmit its information

Answer 28

1. By DNA replication
2. By transcription to form mRNA and then translation of mRNA to form specific proteins. Transcription and translation together is called gene expression.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 29

Transcription involves usually _______ sequences of DNA whereas DNA replication involves replicating the ______ DNA molecule

Answer 29

short; whole

4.1 Nucleic Acid Structures Reflect Their Functions

Question 30

The sequences of DNA that are transcribed into RNA (mRNA) are called _______

Answer 30

genes!

4.1 Nucleic Acid Structures Reflect Their Functions

Question 31

What is meant by a genome

Answer 31

The complete set of DNA in a living organism

4.1 Nucleic Acid Structures Reflect Their Functions

Question 32

Transcription of specific genes…..

Answer 32

…..occur at different times and in different types of cells in the body of multicellular organisms.

For example, in humans, skin cells produce keratin which is the major protein found in hair but they do not express genes that code for proteins essential for muscles like muscle cells would. Muscle cells would never express keratin either.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 33

How much similarity would you expect to find in genomes of closely related organisms compared to less closely related organisms?

Answer 33

More similarity in genomes of closely related species than in genomes of less closely related organisms.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 34

Sequencing genomes is a powerful tool for elucidating evolutionary relationships between two or more organisms.

True or False?

Answer 34

True

Sequencing the genomes of humans and chimpanzees have confirmed that chimpanzees are our closest relatives. The similarity of their genome with human genomes is over 98%.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 35

Nucleotides are more than just the building blocks of nucleic acids they also serve other functions. Name these other functions and the nucleotides that perform these functions.

Answer 35

• ATP (adenosine triphosphate) acts as an agent of energy transfer in many biochemical reactions
• GTP (guanosine triphosphate) serves as an energy source, especially in protein synthesis. It also plays a role in the transfer of information from the environment to cells
• cAMP (cyclic adenosine monophosphate) is a special nucleotide with an additional bond between the sugar and the phosphate group. It is essential in many processes, including the actions of hormones and the transmission of information by the nervous system
• Nucleotides play roles as carriers in the synthesis and breakdown of carbohydrates and lipids.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 36

How is the width of DNA uniform throughout?

Answer 36

A whole stretch of DNA is the same width because a purine is always opposite a pyrimidine. The width of DNA would not be uniform if a purine was opposite another purine and a pyrimidine was opposite another pyrimidine.

4.1 Nucleic Acid Structures Reflect Their Functions

Question 37

Are living things composed of the same atoms as inanimate objects?

Answer 37

yes

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 38

When was the Renaissance?

Answer 38

The Renaissance period occurred in Europe between the 14th and 17 century. It saw the birth of modern science.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 39

What is meant by spontaneous generation?

Answer 39

Spontaneous generation is the idea that, under ordinary earth conditions, life could come from non-living materials.

For example, people once believed that mice came from sweaty clothes in dim light and frogs came from moist soil and flies came from rotting meat.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 40

What scientist performed the flies and the jars experiment?

Answer 40

Francesco Redi performed the experiment in 1668 to disprove the spontaneous generation idea.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 41

Predict what would happen in each of the jars below:

Answer 41

From left to right: There were flies inside and outside the jar as wells as eggs and larva on the rotting meat; there were only flies outside of the jar with the fine cloth over it; the same result as the jar with the fine cloth over it.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 42

Is it true that Louis Pasteur and Francesco Redi proved spontaneous generation will never occur?

Answer 42

Their experiments could not show that spontaneous generation could never occur. Their experiments could only show that spontaneous generation could not occur in present Earth conditions.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 43

Can bacteria can move in dust particles that float in the air?

Answer 43

yes

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 44

In summary, Redi and Pasteur showed that life can only come from ________

Answer 44

pre-existing life

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 45

It is estimated that the solar system formed _______ billion years ago

Answer 45

4.6

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 46

Describe what happened 4.6 billion years ago

Answer 46

A star exploded and collapsed to create the sun and about 500 small planetesimals. The 500 planetesimals collided with each other to form the inner planets including Mars and Earth. The inner planets are Mercury, Venus, Earth and Mars

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 47

What condition is essential for life?

Answer 47

The presence of water

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 48

How did Earth get water in the first place?

Answer 48

It has been said that comets collided with the Earth providing the Earth with water, nitrogen and carbon-containing molecules.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 49

If Earth along with the solar system was formed 4.6 billion years ago and the first signatures of life are approximately 4 billion years old then how long did it take for the Earth’s to become just right for life?

Answer 49

4.6*10^9 - 4.0*10^9 = 0.6*10^9

600 million years

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 50

What caused simple chemical reactions in Earth to take place, some believed to be the reactions that started life?

Answer 50

Chemicals from the Earth’s crust dissolving in the water initiated these simple but important reactions

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 51

What stopped life from starting even when those simple chemical reactions were taking place that was believed to have started life?

Answer 51

Collisions of comets and meteorites with Earth released enough heat energy to boil the waters killing any life but eventually, those collisions subsided and life could finally be left to develop.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 52

What are the two alternative theories for how life began on Earth?

Answer 52

1. That meteorites carrying living-organisms crashed on Earth
2. That life arose from chemical evolution

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 53

What is chemical evolution?

Answer 53

The theory that conditions on primitive Earth helped develop monomers and other simple molecules that would eventually form life.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 54

What evidence is there to suggest that primitive Earth’s atmosphere lacked oxygen gas?

Answer 54

presence of rare metals, Molybdenum and Rhenium, is directly proportional to the presence of oxygen. These rare metals were not discovered before 2.5 billion years ago when scientists believe that photosynthesis first evolved in unicellular organisms.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 55

What percentage of Earth’s present-day atmosphere is O₂?

Answer 55

21%

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 56

Which gases did Harold Urey and Stanley Miller believe were present in Earth’s early atmosphere?

Answer 56

1. Ammonia
2. Methane
3. Water vapour
4. Hydrogen gas

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 57

Describe the Urey-Miller experiment

Answer 57

1. A round-bottom flask containing simple chemicals was set up. This was called the oceanic compartment.
2. This flask was heated releasing H₂, NH₃, H₂O and CH₄ creating the “atmosphere” of early Earth.
3. Those gases moved to another flask that was assaulted with sparks to simulate lighting.
4. The atmosphere then moved through a condenser becoming artificial “rain” and was then allowed to move back into the oceanic compartment but some of this rain was sampled and tested to find new compounds.
5. The sampled “rain” contained amino acids, purines and pyrimidines which are absolutely essential to forming the biological polymers such as nucleic acids and proteins.
6. 2 The Small Molecules of Life Originated on Primitive Earth
   http: //www.life11e.com/animation0403.html

Question 58

What did Urey and Miller show through their famous experiment?

Answer 58

Miller and Urey demonstrated that the molecular building blocks (amino acids, purines and pyrimidines) necessary for life could have formed under the conditions thought to exist on primitive Earth.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 59

What role did the electrical sparks play in the Miller–Urey experiment?

Answer 59

The electrical sparks supplied a source of energy to allow bond breaking and new bond formation.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 60

What is the biggest criticism scientists have for the Urey-Miller experiment?

Answer 60

It relied on hypotheses about what conditions were like on early Earth that may not be accurate.

For example, some scientists believe earth’s early atmosphere was composed of N₂ H₂S, CO₂ and SO₂ .

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 61

What remarkable event other than the moon landings of Apollo 11 occurred in 1969?

Answer 61

Fragments of a meteorite fell to a town in Australia. In fragments of the meteorite, they found several of the molecules that are unique to life, including purines, pyrimidines, sugars, and ten amino acids.

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 62

What conditions existing on Earth today might preclude the origin of life from the prebiotic molecules Miller and Urey used?

Answer 62

The presence of O2 in the atmosphere produces an oxidizing condition that prevents the reduction reactions observed in the Miller–Urey experiment

4.2 The Small Molecules of Life Originated on Primitive Earth

Question 63

Why have hydrothermal vents sparked attention in regards to the production of proteins from amino acids in the early Earth?

Answer 63

Since hydrothermal vents lack oxygen and contain the metals Iron and Nickel that has been shown in the laboratory to catalyze the polymerization reaction of amino acids to form proteins in the absence of oxygen

4.3 The Large Molecules of Life Originated from Small Molecule

Question 64

Most biological reactions essential for maintaining life occur extremely _______ but are speeded up by _________ therefore __________ are essential to the origin of life.

Answer 64

Slowly; catalysts; catalysts

4.3 The Large Molecules of Life Originated from Small Molecule

Question 65

What came first: nucleic acid or proteins

Answer 65

Nucleic acid

4.3 The Large Molecules of Life Originated from Small Molecule

Question 66

Is it true that RNA can act only as a blueprint for protein synthesis like DNA

Answer 66

Nope

It is true that RNA can act as a blueprint for protein synthesis but it can also act as a catalyst.

4.3 The Large Molecules of Life Originated from Small Molecule

Question 67

What is the name we give to RNA molecules that can function as a catalyst?

Answer 67

Ribozymes. They can also be known as catalytic RNA or even RNAzyme

4.3 The Large Molecules of Life Originated from Small Molecule

Question 68

How can Ribozymes function as catalysts?

Answer 68

because they can fold in on itself creating many different 3D shapes

4.3 The Large Molecules of Life Originated from Small Molecule

Question 69

The RNA _______ hypothesis

Answer 69

world

4.3 The Large Molecules of Life Originated from Small Molecule

Question 70

What is the RNA world hypothesis?

Answer 70

The RNA world hypothesis is the hypothesis that early life relied on RNA to store its genetic information and catalyze its chemical reactions before proteins and DNA existed.

4.3 The Large Molecules of Life Originated from Small Molecule

Question 71

Who made the discovery of ribozymes and in what decade?

Answer 71

The discovery of ribozymes was made by Thomas Cech and Sidney Altman who were awarded a Nobel prize in chemistry in 1989.

http://exploringorigins.org/ribozymes.html

Probs don’t have to know this I just found it was interesting

Question 72

What evidence supports the idea that RNA could initiate the synthesis of proteins?

Answer 72

In present-day organisms, their ribozymes catalyze the formation of peptide bonds between amino acids.

4.3 The Large Molecules of Life Originated from Small Molecule

Question 73

What evidence is there to suggest that early organisms relied on RNA rather than DNA as its genetic storage molecule?

Answer 73

The fact that HIV has RNA inside its capsid rather than DNA.

4.3 The Large Molecules of Life Originated from Small Molecule

Question 74

What evidence is there to indicate that DNA could have evolved from RNA?

Answer 74

HIV has an enzyme called reverse transcriptase that can convert its viral RNA into viral DNA.

4.3 The Large Molecules of Life Originated from Small Molecule

Question 75

What evidence is there to suggest that RNA could catalyze its own replication?

Answer 75

An artificial ribozyme has been developed that can catalyze the assembly of short RNAs into a longer molecule that is an exact copy of itself.

Sorry I copied and pasted from life book 11th edition. Effort = 1/10

4.3 The Large Molecules of Life Originated from Small Molecule

Question 76

What is the role of a cell membrane?

Answer 76

It controls what goes into and out of the cell and so it helps the cell maintain an interior chemical environment that is different from the chemical environment outside of the cell. The role of the cell membrane could also be to keep the interior environment of the cell concentrated with the chemicals the cell needs for specific chemical reactions. These chemical reactions would probably proceed a lot faster if it was part of an environment that is concentrated with all the chemicals it needs.

4.4 Cells Originated from Their Molecular Building Blocks

Question 77

What does the term “amphipathic”?

Answer 77

It describes a chemical that has both hydrophobic and hydrophilic parts such as a phospholipid molecule.

4.4 Cells Originated from Their Molecular Building Blocks

Question 78

State what would happen if you add amphipathic​ fatty acids into a beaker of water.

Answer 78

The fatty acids would arrange themselves into a sort of sphere with a fatty acid membrane and a hollow interior. The fatty acid hydrophilic heads would face the water molecules in the beaker away from the interior of the sphere and the tails would face the interior of the sphere away from the water-rich environment outside the sphere.

4.4 Cells Originated from Their Molecular Building Blocks

Question 79

How could you form a bilayer?

Answer 79

Add water to the interior of the sphere of fatty acids. The structure formed is called a protocell. The image on this flashcard is a protocell.

4.4 Cells Originated from Their Molecular Building Blocks

Question 80

Fatty acid heads are _______ therefore they are attracted to _______. Fatty acid tails are ________ and therefore are not attracted to _______.

Answer 80

hydrophilic; water; hydrophobic; water

4.4 Cells Originated from Their Molecular Building Blocks

Question 81

What are some of the properties of protocells?

Answer 81

• Large molecules (like DNA or RNA) cannot pass through cell membrane but small molecules (like nucleotides and sugars) can pass through.
• Nucleic acids in the protocells can use nucleotides that pass through the membrane to initiate the nucleic acid’s own replication of itself.
• It can maintain an interior environment that is chemically different from the exterior environment.

4.4 Cells Originated from Their Molecular Building Blocks

Question 82

Just a useful simplified timeline of the origin of life. No questions on this flashcard.

Answer 82

4.4 Cells Originated from Their Molecular Building Blocks

Question 83

How old were the rocks that had imprints of fossilized early cells?

Answer 83

3.5 billion years old

4.4 Cells Originated from Their Molecular Building Blocks

Question 84

State the products of a similar reaction to the Urey-Miller experiment done by scientists who felt CO₂, N₂, H₂S, and SO₂ was a more accurate representation of the composition of early Earth’s atmosphere?

Answer 84

• All five bases that are present in DNA and RNA (i.e., A, T, C, G, and U)
• All of the 20 amino acids used in protein synthesis
• Many three- to six-carbon sugars
• Certain fatty acids
• Vitamin B6 (pantothenic acid, a component of coenzyme A)
• Nicotinamide (part of NAD, which is involved in energy metabolism)
• Carboxylic acids such as succinic and lactic acids (also involved in energy metabolism)