What happens if we remove oxygen from a plant?

As plants respire aerobically , which is a form of respiration which requires oxygen , when oxygen is removed ,it may have to respire anaerobically to provide energy needed for its activities. However, while this may provide the plant with energy,it does not produce sufficient CO2 to carry out photosynthesis permanently. Without photosynthesis , the plant will not be able to produce food(glucose) , and it will eventually die. Other than that , the process of anaerobic respiration produces the toxic ethanol , in which excess of it may kill the plant as well.

Anaerobic respiration

Glucose = Ethanol + Carbon Dioxide + Energy
C6H12O6 = 2C2H5OH + 2CO2 + ATP

OR

Glucose = Energy + Lactic acid

C6H12O6 = ATP + C3h6O3

Less energy is produced during anaerobic respiration as oxygen is not involved. Oxygen is a highly electronegative atom , and hence is a good electron acceptor. During anaerobic respiration , other acceptors such as nitrate and sulfate are used , they have a smaller reduction rate , causing less energy to be released per oxidized molecule of primary electron donor.

Lactic Acid(C3h6O3)

The lactic acid system is capable of releasing energy that can resynthesise ATP without the involvement of oxygen and is called anaerobic glycolysis. Glycolysis (breakdown of carbohydrates) results in the formation of pyruvic acid and hydronium ions (H+). The pyruvic acid molecules undergo oxidation in the mitochondrion and the Krebs Cycle begins. A build-up of H+ will make the muscle cells acidic and interfere with their operation so carrier molecules, called nicotinamide adenine dinucleotide (NAD+), remove the H+. The NAD+ is reduced to NADH that deposit the H+ at the electron transport gate (ETC) in the mitrochondria to be combined with oxygen to form water (H2O).To prevent the rise in acidity, pyruvic acid accepts H+ forming lactic acid that then dissociates into lactate and H+. Excess lactate can be removed by conversion to glucose via gluconeogenesis in the liver and then released back into the circulation.

Ethanol(C2H5OH)

Better known as alcohol , it is formed by ethanol fermentation during anaerobic respiration , a biological process in which sugars such as glucose and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products. Yeast produce alcohol using ethanol fermentation and it is also responsible for the rising of bread dough. Yeast organisms consume sugars in the dough and produce ethanol and carbon dioxide as waste products.

Aerobic respiration

Glucose + Oxygen -> Carbon Dioxide + Water + Energy(Word Equation)

C6H12O6 + 6O2 -> 6CO2+ 6H2O+ ATP

As with all forms of cellular respiration , aerobic respiration begins with glycolysis , a metabolic pathway(a series of chemical reactions) that converts glucose (C6H12O6) into pyruvate(CH3COO− + H+).It is divided into 2 phases.

Glycolysis Phase 1

Glucose(C6H12O6) is broken down into 2 PGAL's(C₃H₇O₆P or G6P) , this reaction consumes 2 ATP and involves 2 enzymes , hexokinase and glucokinase. Hence , this phase is also known as the "preparatory" phase.

Glycolysis Phase 2

The 2 PGAL's are then converted to pyruvate(CH3COO− + H+) with the production of 4 equivalents of ATP and 2 equivalents of NADH. This process involves enzymes such as pyruvate kinase and enolase.As 2 ATPs are used in phase 1 , and 4 ATPs are gained in phase 2 , there is a net gain of 2 ATPs in the process of glycolysis.Hence , this face is also known as the "pay-off" phase.

Krebs Cycle

Following glycolysis , if oxygen is present(Oxygen is present during aerobic respiration , not present during anaerobic respiration) , it leads to the Krebs cycle or the citric acid cycle. The Krebs cycle produce carbon dioxide and ATP and takes place within the mitochondrion.One GTP (guanosine triphosphate) is produced which eventually donates a phosphate group to ADP to form one ATP; three molecules of NAD and one of FAD is reduced. the production of the reduced NAD and FAD are far more significant in the cell's energy-generating process. This is because NADH and FADH₂ donate their electrons to an electron transport chain that generates large amounts of energy by forming many molecules of ATP.

Simple Explanation of Photosynthesis(components)

1.Photosynthetic pigments

Photosynthetic pigments include chlorophylls, carotenoids and xanthophylls. These pigments are each sensitive to a particular range of light wavelengths.

2.Chloroplasts

Eukaryotic cells perform photosynthesis in a specialized, double-membraned structure called the chloroplast. The chloroplast contains a stacked series of membranes known as the thykaloid. Stack of thykaloids are called grana with the intermembrane space between thykaloids called the stroma.

3.Light Dependent Reactions

When light strikes photosensitive pigments such as chlorophyll, the electrons enter a high energy state. Through a series of electron transports, the energy from these excited electrons is utilized to create adenosine triphosphate (ATP) and nicotine adenine dinucleotide phosphate (NADPH). This process is known as photophosphorylation and occurs in the grana.

4.Light Independent Reactions

The high energy bonds produced during the light dependent reactions are used to create carbon-carbon bonds from carbon dioxide. This process, sometimes referred to as the Calvin Cycle, involves a multi-step series of enzymatic reactions to create a glucose sugar molecule from the addition of the carbon from a carbon dioxide molecule to a starter molecule called ribulose bisphosphate.

Photosynthesis Descriptions and Cycle

The process by which plants make food is called "photosynthesis". The word "photosynthesis" is made up of two words:

"photo" = light

"synthesis" = putting together

Plants take in carbon dioxide from the air and water from the soil; put them together (in the presence of light energy and chlorophyll) to produce sugar (glucose) and oxygen.

Chlorophyll is the green pigment found in plants. Both chlorophyll and light energy need to be present for photosynthesis to take place, but they are not used up in the process.

Thus, the process of photosynthesis can be represented as follows:

carbon dioxide + water →→→→→ sugar (glucose) + oxygen with the help of chlorophyll and light energy

Some of the sugar produced during photosynthesis is used by the plant for its life processes (such as growing and reproducing); the excess is converted mainly to starch and stored in various plant parts which may be used as food by animals and humans.

Oxygen produced during photosynthesis replenishes the oxygen that was used up by living things during respiration ... mouseover the above picture for more information on respiration.

This cycle of photosynthesis and respiration maintains the balance of carbon dioxide and oxygen on earth.

What is Cellular Respiration?

The release of chemical energy for use by cells.Once the energy that was in sunlight is changed into chemical energy by photosynthesis, an organism has to transform the chemical energy into a a form that can be used by the organism.This process is cellular respiration.

Making food without sunlight

In the 1970s, scientists discovered communities of living organisms thriving on the deep ocean bottom, too far down for sunlight to reach. Huge red worms living in tubes as well as new species of clams, jellyfish, crabs and other ocean animals were clustered around cracks or vents on the seafloor. This is where molten lava had oozed out from the depths of the planet, producing currents of heated water rich in dissolved minerals.
What were animals living on? There must be some food producers to support all these consumers. But how could food producers make food without a supply of sunlight energy?

Reseachers found that the food producers in these ocean vent communities are bacteria that are very different from those living at Earth surface. Instead of photosynthesis, they use a process called chemosynthesis to store energy in a special compound and convert chemicals to biochemicals used for food and building materials. Scientists classify these bacteria as lithotrophs [ rock eaters ]. They get energy by oxidizing minerals such as sulfates, nitrates and iron compounds as well as chemicals such as hydrogen sulfide and ammonia. These were chemicals that were plentiful on the ancient Earth before photosynthesis generated oxygen for the atmosphere.

Researchers believe that the bacteria that live by chemosynthesis are very ancient and perhaps the first living creatures that appeared on our planet. They have named them Archaebacteris or Archea from the Greek word for ' ancient '.