Photosynthesis and Respiration can probably balance out ...

[Pages:28]Photosynthesis and Respiration can probably balance out the gases

necessary for life even in a small, sealed glass

container floating in outer space*.

*as long as it is kept from freezing.

Humans are falible. ^l

Biosphere 2

z Biosphere 2 was our attempt to design an ecosystem completely independent of Earth and live in it.

z It failed because the people ran low on breathable oxygen. z This proves that Biosphere 1 (Earth) is a complex system that we cannot yet

duplicate perfectly. z Let's attempt to understand why.

First some background info: Chemystery.

Elements of Life: (Earth, Air, Water)

H - Hydrogen

O - Oxygen C - Carbon N - Nitrogen P - Phosphorus

"Organic" elements form covalent bonds.

S - Sulfur

Ca - Calcium

Na - Sodium

K - Potassium Cl ? Chloride Mg ? Magnesium

Charged Ions or salts

Fe - Iron

and other trace elements...

z The greeks believed all matter is composed of 4 elements: earth, air, water and fire.

z They weren't too far off, but the first three elements are composed of ~92 chemical elements from stardust.

Energy for life: (Fire) Sunshine measured in joules or calories.

z The fire element represents the energy contained in the bonds between the elements.

Atoms have two different strategies to

deal with an incomplete set of electrons.

z Atoms may give or take an electron or two and become positive (electron poor) or negative (electron rich) ions.

z Atoms may share electrons in covalent bonds.

z Polar bonds are covalent bonds that have some characteristics of ionic bonds.

z Biochemicals are composed of covalent bonds.

What is a Calorie?

z 1000 calories = 1 food Calorie (kilocalorie)

z 1 calorie = 4.18 joules z A 100 watt light bulb uses 100

joules per second, or ___ Calories per second.

? Calories/ second ?

How long does it take the light bulb to burn a Calorie (kcal)?

Chemical reactions may store or release energy.

z Covalent bonds form when two atoms have a lower energy state when they are together, rather when they are apart.

z Each type of covalent bond stores a different amount of energy.

z The process by which covalent bonds form and break is called a chemical reaction.

z Reactants ---> Products

z Bonds broken ----> Bonds formed

z If there is energy released during a chemical reaction, it is because the bonds formed have a lower energy state than the bonds broken.

Respiration and Photosynthesis are the basic chemical reactions of life.

Photosynthesis: light from the sun + CO2 + H2O ----> CH2O + O2

Respiration:

CH2O + O2 ----> CO2 + H2O + cellular energy and/or heat

z During photosynthesis plants store energy from the sun in the bonds of carbohydrates.

z Energy stored in the chemical bonds of carbohydrates is released during respiration and used to do work in living cells.

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