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) z The greeks believed all H - Hydrogen matter is composed of 4 O - Oxygen “Organic” C - Carbon elements form elements: earth, air, N - Nitrogen covalent bonds. P - Phosphorus water and fire. S - Sulfur Ca - Calcium z They weren't too far off, Na - Sodium but the first three K - Potassium Charged Ions Cl – Chloride or salts elements are composed Mg – Magnesium of ~92 chemical Fe - Iron and other trace elements... elements from stardust.
z The fire element Energy for life: (Fire) Sunshine measured in joules or calories. 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. Q: How much energy is released during respiration?
Respiration: CH2O + O2 ----> CO2 + H2O + cellular energy and/or heat C-H bond: 99 kcal / mole C=O bond: 180 kcal/mole O=O bond: 119 kcal/mole O-H bond: 111 kcal/mole
Breaking bonds requires energy, forming bonds releases energy.
1 mole = 6.02 x 1023 atoms or molecules. 1 mole of hydrogen with an atomic mass of one is equal to one gram. Q: How long could 1 mole of CH2O (about 30 grams of sugar, or one soft- drink) power our 100 watt light bulb? Plants are made mostly of air!
z Plants create carbohydrates (sugar, wood) from carbon dioxide and water.
z Carbon dioxide is a CH O and O 2 2 - trace gas in air. CO2, H2O, NO3 , 3- PO4 , minerals, And other nutrients z This gas is a nutrient for plants.
z Other organic elements are also nutrients for plants. Nutrients feed plants which manufacture the building blocks of life.
Nutrient Carbon Nitrate in Phosphates dioxide gas water and in water and from air soil soil
(CO2) (NO3-) (PO43-) Cellular Carbohydrates Proteins DNA, RNA
“machine” (CH2O) and fats (CnH2n + 2) Cellular Energy Structure, “blueprint” function storage transport, for making locomotion proteins Plants and animals recycle each others waste products in the presence of sunshine. z Animals respire.
z Plants photosynthesize (and respire too).
z Sunshine is required to fuel the plants that feed Photosynthesis the animals.
z Animals inhale oxygen which plants release, and plants take up Respiration carbon dioxide which animals exhale. Ecosystems are living networks in which the only waste product is low-grade heat.
z Nutrients are constantly recycled as long as there is energy from sunshine.
z When there is an accumulation of wastes, an organism will invade or evolve to use the excess waste. Ecosystems are living networks in which the only waste product is low-grade heat.
z Nutrients are constantly recycled as long as there is energy from sunshine.
z When there is an accumulation of wastes, an organism will invade or evolve to use the excess waste. The first pollution on Earth was eventually used by other organisms.
z 1 billion years ago, the Earth was anaerobic (had no oxygen
gas - O2).
z Carbohydrates were created with a primitive photosynthesis that did not involve oxygen, and anaerobic life used fermentation to get energy from sugars.
z Cyanobacteria (blue-green algae) evolved to produce oxygen, and poisoned anaerobic life.
z Organisms eventually evolved to use oxygen (aerobic life). Respiration evolved because it is very energetically favorable.
z A fire needs three things: heat (initial energy input), fuel and oxygen.
z Respiration is very similar to combustion.
z All that must happen is to harness the “fire” and use it to drive mechanisms in the body and cells. Photosynthesis evolved once, it has been copied many, many times.
z All plants contain chloroplasts, an organelle which harvests sunlight.
z Chloroplasts store energy from sunshine in the chemical bonds of carbohydrates (sugars).
z Cyanobacteria are the ~1000X mag. ancestors of all chloroplasts.
z Basically, cyanobacterial cells are living within all plant cells! This is an example of symbiosis. Respiration also evolved sparingly.
z Respiration evolved to use oxygen.
z Mitochondria are organelles in animals (and plants too) that allow them to respire carbohydrates and gain cellular energy. picture of mitochondria z Mitochondria are also called the Mitochondria give energy to the “powerhouse” of the cell. ~1000x host cell in exchange for protection magnification z Mitochondria are descended from a and carbohydrates. bacterium that evolved to use oxygen very efficiently.
z Eukaryotic Cells provide protection and carbohydrate to the mitochondria, while the mitochondria provide cellular energy to the eukaryotic cells.
z They can afford this arrangement because there is SO much energy in oxygen vs. fermentation. Eventually respiration balanced photosynthesis.
z Equilibrium is the state in which all processes are in balance and there is no accumulation of wastes.
z Oxygen is maintained at a fairly O2 21 % stable 21% in our atmosphere, at higher concentrations, combustion proceeds more quickly and consumes oxygen. This is an
CO2 example of a negative feedback – Levels decreased a process that acts to cancel its (however they are Hypothetical concentrations own trigger. increasing currently)
Time (after cyanobacteria evolved) Gaia.
z The earth is a complex system which sustains the conditions necessary for life.
z James Lovelock pioneered the idea in 1970, and growing evidence supports his ideas. Negative and Positive feedbacks can influence Earth’s climate in important ways. Initial addition of carbon dioxide. Extra heat could cause more evaporation. The added water vapor could trap more heat. Or could clouds cause the sun’s rays to be reflected and cool the surface? What one is the positive and which one the negative feedback here? Can we balance photosynthesis and respiration in a sealed glass jar?
z You will get your very own ecosystem in a glass jar.
z How long can it survive on its own?
z What might prevent it from lasting forever? We can't yet duplicate Gaia.
z So let’s treat her well…