The Origin of Life

Question 1

What is monogamy?

Answer 1

The habit of having only one mate at a time.

Question 2

What is polygamy?

Answer 2

The habit of having more than one mate at a time

Question 3

Why are some animals polygamous or monogamous?

Answer 3

Gene for the protein Vasopressin receptor 1-alpha, making a hormone called vasopressin or antidiuretic hormone (ADH). The Prairie Vole (monogamous) brain has a mutation in this gene that leads to more protein being made

Question 4

What are the ‘‘model organisms’’ used for the investigation of the monogamous and polygamous nature of voles

Answer 4

• 2 types of vole studied:
• Meadow vole: totally polygamous
• Prairie vole: totally monogamous

Question 5

Vasopressin receptor 1-alpha can be surpressed by a substance, what?

Answer 5

It is surpressed by alcohol

Question 6

What is the general definition of life?

Answer 6

A multilevel system that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, sensitivity, nutrition, excretion, and continual change preceding death

Question 7

What did Erwin Schrodinger say about Entropy?

Answer 7

Erwin Schrödinger theorizes that life, contrary to the general tendency dictated by the Second law of thermodynamics (that the world as a whole is always in a state of positive entropy) decreases or maintains its entropy by feeding on negative entropy (Negative entropy means that something is becoming less disordered). Living systems defy Entropy (so they maintain structure/order)

Question 8

What is Negative and Positive Entropy

Answer 8

Entropy, also represented as the symbol S, is the measure of disorder of the particles in a thermodynamic system. The greater the disorder of the particles the more positive the change in entropy (∆S) will be. The less disorder results in more negative entropy

Question 9

Why is entropy change negative?

Answer 9

A negative change in entropy indicates that the disorder of an isolated system has decreased. For example, the reaction by which liquid water freezes into ice represents an isolated decrease in entropy because liquid particles are more disordered than solid particles

Question 10

What was Shrodingers Aperiodic Crystal?

Answer 10

Genetic Codescript: called an aperiodic (contains information) crystal (because it’s stable because each generation has it)

Question 11

Explain how evolution arises

Answer 11

Every time a cell divides gene are slightly different aka the proteins are different. The environment randomly changes and therefore there is ‘’survival of the fittest’’

Question 12

What are the characteristics which suggest if something is alive

Answer 12

Breathing Eating/drinking Energy utilisation 
Excreting 
Moving Growing/Developing
Reproducing 
Homeostasis is key (maintaining the system in spite of environment/keeping things stable) 
Response to environment
Order and complexity 
Evolution

Question 13

What is a cell?

Answer 13

The smallest structural and functional unit of an organism

Question 14

What did Van Leeuwenhoekcontribute to cell theory

Answer 14

First to see a microscopic world - He discovered “protozoa” - the single-celled organisms and he called them “animalcules”. He also improved the microscope and laid foundation for microbiology.

Question 15

What did Hooke contribute to the cell theory?

Answer 15

He discovered a honeycomb-like structure in a cork slice using a primitive compound microscope. He only saw cell walls as this was dead tissue. He coined the term “cell” for these individual compartments he saw.

Question 16

What does the Scheiden and Schwann cell theory state?

Answer 16

1. All creatures are made from cells
2. All cells arise from pre-existing cells
3. Cells can live alone (unicellular) or together (multicellular)

Question 17

What do the purines and pyramidines form?

Answer 17

Nucleotides such as : ATP (energy), GTP (communication)

Nucleic acids such as : DNA and RNA (information)

Question 18

What do Amino acids form?

Answer 18

Proteins (stuctures, enzymes, carriers, receptors, messengers)

Question 19

What is the function of Lipids?

Answer 19

Structure, Energy, Messengers

Question 20

How are Lipids messengers?

Answer 20

Since lipids are small molecules insoluble in water, they are excellent candidates for signalling, including ones that regulate inflammation and mood. The signalling lipids, in their esterified form can infiltrate membranes and are transported to carry signals to other cells.

Question 21

Explain the function of lipids in structure?

Answer 21

It is present in the cell membrane and its role is critical because its structural components provide the barrier that marks the boundaries of a cell.

Question 22

List the Lipids present in a living body

Answer 22

Fatty acids
Glycerides
Phospholipids 
Steroids
Cholesterol

Question 23

Name the sugar present in the body and its functions

Answer 23

Carbohydrates (structure, energy)

Question 24

List the combinations of complex chemicals in a living body and give their functions

Answer 24

Glycolipids : lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition
Glycoproteins : Important membrane proteins, where they play a role in cell–cell interaction and the mechanisms of infection by bacteria and viruses.
Lipoproteins : transport triglycerides and cholesterol in the blood between all the tissues of the body

Question 25

Why is carbon important?

Answer 25

Carbon forms the backbone of all the complex chemicals in our bodies such as carbohydrates, lipids, amino acids etc which carry out necessary functions in order to live. We are a carbon-based life-form

Question 26

What are the three most abundant elements in the living body

Answer 26

oxygen, carbon, hydrogen (nitrogen, calcium, and phosphorus)

Question 27

What does evidence suggest about the origin of life?

Answer 27

• Earth formed 4.5 billion years ago
• First sign of life: 4.2 billion years ago: chemical signature for life
• Oldest prokaryote: 3.5 billion years ago:

Question 28

Suggest a piece of evidence relating to the origin of life

Answer 28

Stromatolites
•Stromatolites are layered mounds of sedimentary rocks.
•They were formed by the growth of cyanobacteria, a single-celled photosynthesizing microbe
•Cyanobacteria were the only form of life on Earth for the first 2 billion years that life existed on Earth and were responsible for one of the most important “global changes” that the Earth has undergone. Being photosynthetic, cyanobacteria produce oxygen as a by product
•Photosynthesis is the only major source of free oxygen gas in the atmosphere. As stromatolites became more common 2.5 billion years ago, they gradually changed the Earth’s atmosphere from a carbon dioxide-rich mixture to the present-day oxygen-rich atmosphere.
•This major change paved the way for the next evolutionary step, the appearance of life based on the eukaryotic cell (cell with a nucleus).

Question 29

How did we get to the first cell?

Answer 29

• Prebiotic world was probably rich in organic building blocks
• Early conditions must have been correct to allow synthesis of complex biochemicals.
• Atmosphere was reducing (NB: no oxygen)
• UV light and electrochemical energy must have been present.

Question 30

What was the Miller-Urey experiment?

Answer 30

• The Miller–Urey experiment was a chemical experiment that simulated the conditions thought at the time to be present on the early Earth, and tested the chemical origin of life under those conditions.
• The experiment used water (H2O), methane (CH4), ammonia (NH3), and hydrogen (H2).
• Specifically, the experiment tested the hypothesis that conditions on the primitive Earth favored chemical reactions that synthesized organic compounds from inorganic precursors.

Question 31

What was the importance of the Miller-Urey experiment?

Answer 31

The Miller-Urey experiment was important because it showed that methane, ammonia, hydrogen, and water could be transformed into amino acids
Amino acids are the building blocks of proteins, and proteins are essential to life

Question 32

What did the Miller- Urey experiment attempt to prove?

Answer 32

The Miller-Urey experiment attempts to prove that organic compounds derive from inorganic materials in an idea called abiogenesis.

Question 33

What is the RNA world?

Answer 33

The RNA world is a hypothetical stage in the evolutionary history of life on Earth, in which self-replicating RNA molecules proliferated before the evolution of DNA and proteins.

Question 34

What discovery made it possible for the RNA World hypothesis to be considered?

Answer 34

Once it was discovered that RNA could both carry information and cause chemical reactions (like those that would be required to copy a molecule), RNA became the prime suspect for the earliest self-replicating molecule.

Question 35

Functions of RNA?

Answer 35

RNA can store genetic information
copy itself
perform basic metabolic functions
RNA can act as an informational polymer but also an enzyme to promote the replication

Question 36

What was the Primordial Soup Theory?

Answer 36

The Primordial Soup Theory suggests that life began from a series of chemical reactions in a warm pond on Earth’s surface, triggered by an external energy source such as lightning strike or ultraviolet (UV) light.

Question 37

'’We might not have come from primordial soup after all’’ Explain this statement

Answer 37

Recent research states that life arose deep in the ocean within warm, rocky structures called hydrothermal vents. due to the fact that the last common ancestor of all living cells fed on hydrogen gas in a hot iron-rich environment, much like that within the vents. Although the hypothesis may be controversial, it explains how living cells evolved the ability to obtain energy, in a way that just wouldn’t have been possible in a primordial soup.

Question 38

Describe the new theory of the origin of life

Answer 38

Sets of genes that were likely to have been present within the first living cells trace the origin of life back to deep-sea hydrothermal vents, which are porous geological structures produced by chemical reactions between solid rock and water. Alkaline fluids from the Earth’s crust flow up the vent towards the more acidic ocean water, creating natural proton concentration differences remarkably similar to those powering all living cells.
The studies suggest that in the earliest stages of life’s evolution, chemical reactions in primitive cells were likely driven by these non-biological proton gradients. Cells then later learned how to produce their own gradients and escaped the vents to colonise the rest of the ocean and eventually the planet.

Question 39

Why are hydrothermal vents used as the environment for the new theory emerging, disproving the Primordial Soup.

Answer 39

Deep-sea hydrothermal vents represent the only known environment that could have created complex organic molecules with the same kind of energy-harnessing machinery as modern cells

Question 40

Explain the Endosymbiotic Theory

Answer 40

Evolutionary theory which deals with the origins of mitochondria and chloroplasts, two eukaryotic organelles that have bacteria characteristics.

Question 41

How does the Endosymbiotic Theory explains the origin of mitochondria and chloroplasts

Answer 41

Mitochondria and chloroplasts are believed to have developed from symbiotic bacteria, specifically alpha-proteobacteria and cyanobacteria. The theory states that a prokaryotic cell was consumed or engulfed by a larger cell. However the prokaryotic organelle was not consumed, which would later lead to both cells forming a mutualism, receiving surviving benefits from each other. Over time, the newly combined organelle would develop into the complex eukaryotic cell of today.

Question 42

What prokaryotic similarties are there in mitochondria and chloroplasts

Answer 42

An enclosed double membrane, circular DNA, and bacteria-like ribosomes

Question 43

What evidence is there to support the Endosymbiotic Theory and explain

Answer 43

• Examining the DNA has led scientists to find similarities in the sequences to those of modern living bacteria. For example, each organelle in eukaryotes has a single, circular DNA that is more similar to prokaryotes than eukaryotes.
• Transfer RNA, ribosomes, and other molecules involved into transcription and translation processes were examined and compared with prokaryotes; it was discovered that they are similar in term of nucleotide sequence, size and even sensitivity to certain antibiotics.
• The existence of double membranes over many of these organelles suggests the possibility that the inner membrane may have belonged to the original prokaryote while the outer membrane may have formed from food vacuoles as the host cell devoured the prokaryote.

Question 44

How is each cell type defined and give examples?

Answer 44

Each cell type is defined by specific gene expression – all cells have all genes, but not all genes are expressed in all cells
Eg: B lymphocytes make antibodies, gut epithelial cells make digestive
enzymes