IB HL Biology: Origins of Cells

Questions and Answers

What is believed to have performed both the functions of genetic storage and catalysing chemical reactions in early cells?

RNA

What are the roles that DNA and proteins (enzymes) took over from RNA as life evolved?

DNA took over genetic storage, while proteins (enzymes) became biological catalysts.

What is an example of RNA's enzymatic properties in modern cells?

Ribozymes catalysing the formation of peptide bonds

What is the significance of ribose being formed from methanal, a product of the Miller-Urey experiment?

It suggests RNA may have been present before DNA. Signup and view all the answers

What is necessary for the evolution of early cells, as mentioned in the exam tip?

Catalysis, self-replication of molecules, self-assembly, and compartmentalisation of cell parts Signup and view all the answers

What can RNA do spontaneously from nucleotides?

Assemble Signup and view all the answers

What is the process by which deoxyribose in DNA is produced from ribose in RNA?

Enzyme-catalysed reaction Signup and view all the answers

What can ribozymes join together to form proteins from an RNA template?

Amino acids Signup and view all the answers

What is the possible site for the evolution of LUCA?

Hydrothermal vents deep in the ocean Signup and view all the answers

What process do organisms near hydrothermal vents use to generate energy?

Chemosynthesis Signup and view all the answers

Where were fossilised structures similar to those produced by modern prokaryotes found?

Near deep-sea hydrothermal vents in Quebec, Canada Signup and view all the answers

What is the approximate age of the fossilised structures found near hydrothermal vents?

At least 3.77 billion years old, but could be more than 4 billion years old Signup and view all the answers

What type of organisms are thought to have produced the fossilised structures found near hydrothermal vents?

Prokaryotes Signup and view all the answers

What is the significance of the fossilised structures found near hydrothermal vents?

They provide evidence for the evolution of life near hydrothermal vents Signup and view all the answers

What role do membranes play in cells?

Membranes separate genetic material and biochemical processes inside the cell from the outside environment, facilitating compartmentalisation. Signup and view all the answers

Why is the amphipathic nature of fatty acids significant in membrane formation?

The amphipathic nature allows fatty acids to arrange themselves into bilayers, with polar parts facing outward and non-polar parts inward. Signup and view all the answers

Describe how lipid molecules behave when placed in water.

Lipid molecules initially form a monolayer at the water's surface, with polar parts in the water and non-polar parts protruding. Signup and view all the answers

What might the spontaneous formation of bilayers lead to?

The formation of bilayers can lead to the spontaneous creation of microspheres or small vesicles. Signup and view all the answers

How could triglycerides have evolved during the development of membranes?

Fatty acids may have combined with glycerol through condensation reactions, forming triglycerides as membranes evolved. Signup and view all the answers

What initial composition was likely present in the membranes of the first cells?

The membranes of the first cells were likely composed of fatty acids. Signup and view all the answers

What is the significance of the coalescence of fatty acids in the context of cellular origins?

The coalescence of fatty acids is theorized to have formed spherical lipid bilayers that could encase early cells. Signup and view all the answers

How do the properties of fatty acids contribute to the formation of cellular membranes?

The amphipathic properties of fatty acids drive their self-assembly into bilayers, essential for creating cellular membranes. Signup and view all the answers

What role did methane and carbon dioxide play in the early Earth's atmosphere?

They were powerful greenhouse gases that trapped infrared radiation, raising surface temperatures on Earth. Signup and view all the answers

How did the absence of free oxygen affect the early Earth's atmosphere?

It prevented the formation of ozone, allowing UV radiation to penetrate the surface and cause DNA damage. Signup and view all the answers

What hypothesis did Alexander Oparin and JBS Haldane propose regarding the origin of life?

They proposed the 'primordial soup' hypothesis, suggesting that organic molecules formed spontaneously under early Earth conditions. Signup and view all the answers

Which process may have led to the formation of organic molecules such as amino acids on early Earth?

Adding energy through heat or UV radiation to a mixture of early atmospheric gases could have facilitated this formation. Signup and view all the answers

What was the significance of the higher temperatures on early Earth?

Higher temperatures contributed to the greenhouse effect, creating a more suitable environment for chemical reactions necessary for life. Signup and view all the answers

What compounds are thought to have been formed as a result of early Earth conditions?

Organic molecules such as amino acids, simple sugars, nucleotides, and fatty acids. Signup and view all the answers

In what way did UV radiation impact the formation of biological molecules on early Earth?

UV radiation could have catalyzed the formation of larger polymers from simpler organic molecules. Signup and view all the answers

What is the greenhouse effect in the context of early Earth's atmosphere?

It is the trapping of infrared radiation by greenhouse gases, leading to increased surface temperatures on Earth. Signup and view all the answers

Why is the absence of ozone significant for early Earth conditions?

The absence of ozone allowed harmful UV radiation to penetrate the atmosphere, risking DNA integrity and promoting mutations. Signup and view all the answers

What are the building blocks of early cells thought to be formed during early Earth conditions?

The building blocks include amino acids, simple sugars, nucleotides, and fatty acids. Signup and view all the answers

What was the primary goal of the Miller-Urey experiment?

To recreate the conditions of early Earth and synthesize organic molecules. Signup and view all the answers

Which gases were used in the Miller-Urey experiment to replicate the early atmosphere?

Methane, hydrogen, and ammonia. Signup and view all the answers

How did Miller and Urey simulate lightning in their experiment?

By adding electrical discharges to the mixture of gases. Signup and view all the answers

What type of molecules did Miller and Urey find in their condensed mixture after the experiment?

Simple organic molecules, including amino acids. Signup and view all the answers

What role did boiling water play in the Miller-Urey experiment?

It produced steam to imitate the primordial soup of early Earth. Signup and view all the answers

What process did Miller and Urey use to cool their gaseous mixture?

They cooled the mixture to represent the condensation of water in the atmosphere. Signup and view all the answers

Why is the Miller-Urey experiment considered significant in the study of the origin of life?

It provided evidence that organic compounds could form in conditions similar to those on early Earth. Signup and view all the answers

What are the implications of synthesizing simple organic molecules from inorganic ones?

It suggests a possible pathway for the origin of life on Earth. Signup and view all the answers

Study Notes

Origins of Cells

Conditions on early Earth were instrumental in the origin of biological compounds that made life possible
- Higher atmospheric temperatures due to higher levels of carbon dioxide and methane, leading to the greenhouse effect
- Lack of free oxygen, preventing ozone formation, and allowing UV radiation to penetrate to the surface
The spontaneous formation of carbon compounds by chemical processes may have occurred due to these conditions
- Adding energy, such as heat or UV radiation, to the mixture of gases in the early atmosphere could have led to the formation of organic molecules
- These organic molecules would have formed the building blocks of early cells, as proposed by Alexander Oparin and JBS Haldane in the 'primordial soup' hypothesis

Formation of Carbon Compounds: Evidence

The Miller-Urey experiment recreated the conditions thought to have existed on Earth prior to life
- The experiment used a specific apparatus to boil water, mix with gases, add electrical discharges, and cool the mixture
- After a week, the condensed mixture was found to contain traces of simple organic molecules, including amino acids
The spontaneous formation of vesicles may have occurred due to the amphipathic nature of fatty acids
- Fatty acids are major components of lipids, which can form bilayers with polar parts facing outward and non-polar parts facing inward
- These bilayers can spontaneously form microspheres, or small vesicles, which could have formed the membranes of early cells

The First Cells: RNA

RNA may have performed both genetic storage and enzymatic functions in early cells, as proposed by the RNA world hypothesis
- RNA can store genetic information and have enzymatic properties
- RNA can assemble spontaneously from nucleotides, replicate itself, and control the rate of chemical reactions
Evidence for the RNA world hypothesis includes
- Ribose can be formed from methanal, a product of the Miller-Urey experiment
- Deoxyribose in DNA is produced from ribose in an enzyme-catalysed reaction
- Ribozymes are able to join amino acids together to form proteins from an RNA template

Evolution of Life: Hydrothermal Vents

It is possible that LUCA (Last Universal Common Ancestor) evolved in hydrothermal vents deep in the ocean
- The conditions near hydrothermal vents provide opportunities for organisms to generate energy by chemosynthesis
Fossilised structures found in sedimentary rocks near deep-sea hydrothermal vents in Quebec, Canada, may be evidence of early life
- The structures are similar to those produced by modern prokaryotes found near hydrothermal vents
- The fossils are at least 3.77 billion years old, but could be more than 4 billion years old

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Description

Revision notes on the origins of cells, covering formation of carbon compounds, evolution of cells, and evidence for evolution of life.