A2.1 origins of cells (HL)

• 4.5 billion years old • been formed from a swirling mass of smaller particles that collided with one another and formed larger masses • no atmosphere • various objects from space impact the surface of earth causing temp to raise

• impacts on the Earth’s surface began to decrease • developing atmosphere at this time was thick with water vapour and other compounds being released by volcanic eruptions • regular Lightning -carbon dioxide and methane, which were present in higher concentrations than today, allowed ultraviolet light to penetrate the early atmosphere and retained heat, resulting in high surface temperature

• Methane • Ammonia • Water vapour • Carbon dioxide • Hydrogen sulfide • Hydrogen • Nitrogen

• CH4 • NH3 • H2O • CO2 • H2S • H2 • N2

• metabolism • growth • reproduction • response • homeostasis • nutrition • excretion

Metabolism includes all the chemical reactions that occur within the organism. As a result of metabolism, cells can convert energy from one form into another.

growth refers to the increase in size or mass of an organism, which can involve cell division, enlargement, and differentiatio

Reproduction involves hereditary molecules that can be passed to offspring.

Responding to stimuli (or survival and adaptation, involving behaviors, physiological changes) in the environment is essential for an organism to survive.

maintanance of a constant internal environment. ( to control fluctuating temperature and acid-base levels to create a constant internal environment)

Using a source of compounds with many chemical bonds that can be broken down to provide an organism with the energy necessary to maintain life is the basis of nutrition.

Excretion is essential to life because it enables those chemical compounds that an organism cannot use or that may be toxic or harmful to be released from the organism’s system.

• all organisms are composed of one or more cells • cells are the smallest units of life • all cells come from pre-existing cells.

in 1665, after looking at cork through a self-built microscope he first described cells

observed the first living cells and referred to them as “animalcules”, meaning little animals

1838, botanist Matthias Schleiden stated that plants are made of “independent, separate beings” called cells. Matthias Schleiden made a similar statement about animals.

louis Pasteur in the 1880s, have performed experiments to support the third principle. After sterilizing chicken broth (soup) by boiling it, Pasteur showed that living organisms would not “spontaneously” reappear. Only after exposure to pre-existing cells was life able to re-establish itself in the sterilized chicken broth.

• The synthesis of small carbon compounds from abiotic (non-living) molecules, such as demonstrated in the Miller-Urey experiment. • Small organic molecules joining to form large-chain molecules called polymers. • Polymers becoming contained by membranes, creating a protective homeostatic environment around the polymers, separate from their surroundings. • The development of self-replicating molecules so that inheritance and control can occur.

Enzymes are proteins that act as biological catalysts and accelerate chemical reactions. Enzymes are carbon compounds, which means they always contain the elements carbon and hydrogen, usually along with other elements.

Scientists have been able to produce polymers from simple compounds by exposing them to hot sand, clay or rock. This vapourizes water from the simple compounds, and molecule chains are formed, suggesting that polymers could have formed on early Earth even if no enzymes were present.

Inorganic compounds do not usually contain carbon (an exception is carbon dioxide, which is considered to be an inorganic compound).

Carbon compounds (often called organic compounds) contain carbon and can be quite complex. It is these more complex compounds or molecules that make life possible, thus the element carbon can be said to be the keystone element for life on Earth.

1953 stanley miller harold urey

• the apparatus is initially charged with the simple inorganic compounds CH4, NH3 and H2, representing Earth’s early atmosphere • heat is used to produce water vapour, which rises to the chamber containing the simple inorganic compounds • two electrodes in this chamber produce 7,500 volts at 30 amps of electricity, representing the lightning that existed on early Earth • cold water flows into the condenser to allow condensation of gaseous compounds from the chamber • a sample is collected in the collecting device for chemical analysis.