Abstract Oxyanions of arsenic and selenium can be used in microbial anaerobic respiration as terminal electron acceptors. The detection of arsenate and selenate respiring bacteria in numerous pristine and contaminated environments and their rapid appearance in enrichment culture suggest that they are widespread and metabolically active in nature. Although the bacterial species that have been isolated and characterized are still few in number, they are scattered throughout the bacterial domain and include Gram-positive bacteria, beta, gamma and epsilon Proteobacteria and the sole member of a deeply branching lineage of the bacteria, Chrysiogenes arsenatus. The oxidation of a number of organic substrates (i.e. acetate, lactate, pyruvate, glycerol, ethanol) or hydrogen can be coupled to the reduction of arsenate and selenate, but the actual donor used varies from species to species. Both periplasmic and membrane-associated arsenate and selenate reductases have been characterized. Although the number of subunits and molecular masses differs, they all contain molybdenum. The extent of the environmental impact on the transformation and mobilization of arsenic and selenium by microbial dissimilatory processes is only now being fully appreciated.
Thursday, August 26, 2010
Anaerobic respiration
In biology, anaerobic respiration is a way for an organism to produce usable energy, in the form of adenosine triphosphate, or ATP, without the involvement of oxygen; it is respiration without oxygen. This process is mainly used by prokaryotic organisms (bacteria) that live in environments devoid of oxygen. Although oxygen is not used, the process is still called respiration because the basic three steps of respiration are all used, namely glycolysis, the citric acid cycle, and the respiratory chain, or electron transport chain. It is the use of the third and final step that defines the process as respiration. In order for the electron transport chain to function, a final electron acceptor must be present to take the electron away from the system after it is used. In aerobic organisms, this final electron acceptor is oxygen. Oxygen is a highly electronegative atom and therefore is an excellent candidate for the job. In anaerobes, the chain still functions, but oxygen is not used as the final electron acceptor. Other less electronegative substances such as sulfate (SO4), nitrate (NO3), and sulfur (S) are used. Oftentimes, anaerobic organisms are obligate anaerobes, meaning they can only respire using anaerobic compounds and can actually die in the presence of oxygen.
GREEN MACHINES
What will happen if photosynthesis stops?
Have you ever wondered what will happen if photosynthesis stops?Firstly there will be a lot of carbon dioxide in the air around us.Due to the green house effect, global warming will occur.If global warming happens, all the ice in the North pole will be melted.This indirectly causes sea level to rise.When the sea level rises, there will be high tides and heavy floods or tsunamis will happen.This natural disasters will claim the lives of innocent people and houses will be destroyed.Secondly there will be no oxygen in the air because without photosynthesis, plants cannot produce oxygen.Obviously all living things will die because of the lack of oxygen.If the humans die,the plants will also die because they will not be able to receive oxygen.The gaseous exchange cycle will be broken.Now you might be wondering what on earth is photosynthesis.No need to worry because I will explain the meaning of photosynthesis.
What is the meaning of photosynthesis?
Photosynthesis is is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria.In plants and algae photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product.Some of the glucose produced by photosynthesis is used to provide food for the plant.Excess glucose is changed into starch and stored in the leaves as the main product of photosynthesis.Excess oxygen is released into the air through tiny pores called stomata found mainly on the underside of leaves.
A picture of stomata.
Why are leaves green?
Chlorophyll makes leaves green and is located in the cellof the leaf.As light bounces off it it projects the green shades into our eyes and that is what we see.In conclusion, if there is no photosynthesis, there will be no lives.
Aerobic Respiration
Aerobic respiration is a process of cellular respiration that uses oxygen in order to break down molecules, which then release electrons and creating energy. In the process, aerobic respiration creates a substance known as adenosine triphosphate (ATP). This is responsible for storing and carrying most of the energy to other body cells, thus making life as we know it possible. The other type of cellular respiration is known as anaerobic respiration.
When an animal eats food or when a plant makes its own energy through photosynthesis, that food is broken down into its most basic form of sugars. Those sugars are useless to the body in that form, however. Therefore, a process of releasing the sugars contained in the food is needed in order to be used as energy by a cell. While oxygen may not be needed at the beginning of this process, in aerobic respiration it will be needed so that the process can be completed.
There are two main byproducts of aerobic respiration. Because cellular structures are being changed with the transfer of electrons, there are chemical changes that go along with cellular respiration. The two main products coming from such respiration are water and carbon dioxide.
Aerobic respiration is often described as being broken down into three main stages, though depending on how detailed one wants to get, there could be many more. The first major stage is called glycolysis. It is at this point ATP is created, as are carbon molecules, called pyruvate or pyruvic acid, and some molecules known as NADH.
The second stage is known as Kreb's cycle. This takes some of the carbon not used in the first stage and puts them through another series of complex chemical reactions, creating more NADH and molecules known as FADH2. The third step is a process known as electron transport phosphorylation. This creates even more ATP for use by converting those other molecules for that purpose. Along the way, as NADH is produced, carbon dioxide is created as a waste product.
Oxygen is used as a receptor for electrons in aerobic respiration, as it makes a good receptor for electrons. Once the oxygen receives the electrons, it then converts them into water. This is done so that electrons do not build up in the ATP, which could cause problems. For cells that use anaerobic respiration instead of aerobic respiration, lactic acid is produced in the place of water.
When an animal eats food or when a plant makes its own energy through photosynthesis, that food is broken down into its most basic form of sugars. Those sugars are useless to the body in that form, however. Therefore, a process of releasing the sugars contained in the food is needed in order to be used as energy by a cell. While oxygen may not be needed at the beginning of this process, in aerobic respiration it will be needed so that the process can be completed.
There are two main byproducts of aerobic respiration. Because cellular structures are being changed with the transfer of electrons, there are chemical changes that go along with cellular respiration. The two main products coming from such respiration are water and carbon dioxide.
Aerobic respiration is often described as being broken down into three main stages, though depending on how detailed one wants to get, there could be many more. The first major stage is called glycolysis. It is at this point ATP is created, as are carbon molecules, called pyruvate or pyruvic acid, and some molecules known as NADH.
The second stage is known as Kreb's cycle. This takes some of the carbon not used in the first stage and puts them through another series of complex chemical reactions, creating more NADH and molecules known as FADH2. The third step is a process known as electron transport phosphorylation. This creates even more ATP for use by converting those other molecules for that purpose. Along the way, as NADH is produced, carbon dioxide is created as a waste product.
Oxygen is used as a receptor for electrons in aerobic respiration, as it makes a good receptor for electrons. Once the oxygen receives the electrons, it then converts them into water. This is done so that electrons do not build up in the ATP, which could cause problems. For cells that use anaerobic respiration instead of aerobic respiration, lactic acid is produced in the place of water.
our science experiment
This experiment served to determine the affects of light intensity on the rate of photosynthesis in the underwater plant elodea. It was found that the rate of photosynthesis in the plant was accelerated when placed in
closer proximity to a constant light source. The rate of photosynthesis was measured by counting the amount of oxygen, a product of photosynthesis, generated by the plant. When the plant placed closer to the light source in a given time it generated more bubbles than when it was placed farther away from the light source.
Introduction:
Purpose: to determine the effects of light intensity to rate of photosynthesis.
Photosynthesis can be described by the following chemical reaction
Light + 6CO2 + 6 H2O -> Glucose + 6O2
With this in mind, the efficiency of photosynthesis during a specified time period can be calculated by measuring the amount of product formed from the above reaction. The plants tested in this experiment were underwater plants (Elodea) and the rate of photosynthesis was measured by the amount of oxygen produced by the plant through photosynthesis. The amount of oxygen produced was measured by counting of the number of bubbles that formed and floated to the surface from the submerged plant. The affects of different light intensities was determined by the amount of bubbles produced from various intensities of light.
Hypothesis: If photosynthesis is more efficient in stronger light, then more products will be formed faster in photosynthetic reactions.
Materials
1) Aquatic plant (Elodea)
2) Test tubes
3) Watch
4) Water (at room temperature)
5) Lamp (light source)
6) Knife/Scissors
7) Ruler
Procedure:
1) A segment of plant of approximately 8cm was cut with scissors.
2) The end of the stem at the site of incision was gently crushed.
3) The plant was fully submerged into a test tube filled with room temperature water.
4) That tube was set on a test tube stand.
5) A light source was placed 50 cm away facing the test tube.
6) The light source was powered on and observations were made.
closer proximity to a constant light source. The rate of photosynthesis was measured by counting the amount of oxygen, a product of photosynthesis, generated by the plant. When the plant placed closer to the light source in a given time it generated more bubbles than when it was placed farther away from the light source.
Introduction:
Purpose: to determine the effects of light intensity to rate of photosynthesis.
Photosynthesis can be described by the following chemical reaction
Light + 6CO2 + 6 H2O -> Glucose + 6O2
With this in mind, the efficiency of photosynthesis during a specified time period can be calculated by measuring the amount of product formed from the above reaction. The plants tested in this experiment were underwater plants (Elodea) and the rate of photosynthesis was measured by the amount of oxygen produced by the plant through photosynthesis. The amount of oxygen produced was measured by counting of the number of bubbles that formed and floated to the surface from the submerged plant. The affects of different light intensities was determined by the amount of bubbles produced from various intensities of light.
Hypothesis: If photosynthesis is more efficient in stronger light, then more products will be formed faster in photosynthetic reactions.
Materials
1) Aquatic plant (Elodea)
2) Test tubes
3) Watch
4) Water (at room temperature)
5) Lamp (light source)
6) Knife/Scissors
7) Ruler
Procedure:
1) A segment of plant of approximately 8cm was cut with scissors.
2) The end of the stem at the site of incision was gently crushed.
3) The plant was fully submerged into a test tube filled with room temperature water.
4) That tube was set on a test tube stand.
5) A light source was placed 50 cm away facing the test tube.
6) The light source was powered on and observations were made.
What is photosynthesis and respiration?
What is photosynthesis and respiration?
This are our theories about photosynthesis and respiration.
1)Phototosynthesis and respiration are both chemical reactions.There is an exchange of gases and energy is involved.The definiton of photosynthesis is the process in which green plants use raw materials- carbon dioxide and water- to produce simple sugars and oxygen using sunlight trapped by chlorophyll.The definition of respiration is a chemical process in which glucose is broken down into carbon dioxide and water,together with a release of energy,
So what does photosynthesis and respiration have to do about living things?
During the day plants breathes in carbon dioxide and gives out oxygen.At night, the opposite happens.This is what you call photosynthesis.To ensure that there is not too much or too little carbon dioxide in the air, animals breathe in oxygen and gives out carbon dioxide.This is where respiration comes into the picture.
Why do plants photosynthesize?
To obtain the food they need, plants undergo photosynthesis.To do this, plants need the light energy from the Sun.The light energy is then trapped by the green pigment called chlorophyll contained in chloroplasts which can be found in the cells of the green leaves.Other than light carbon dioxide and water is needed.The formula is shown below.
carbon dioxide + water chlorophyll
→→→→→→→→
light energy glucose+oxygen Respiration on the other hand is necessary for the survival of all living things. At night only the green plants will take in oxygen as there is no sunlight for photosynthesis.When plants respire ,instead of taking in CO2 and releasing O2, the opposite will happen.The formula is shown below.
glucose+oxygen=water+carbon dioxide+energy
What will happen if there are no plants?
Since humans and animals cannot make food because there is no chloroplasts in their cells,plants are the only source of oxygen.Humans also do not have the green colour of the plant's green leaves.
,
In conclusion, we have learned that without photosynthesis and respiration living on earth is totally impossible.
This are our theories about photosynthesis and respiration.
1)Phototosynthesis and respiration are both chemical reactions.There is an exchange of gases and energy is involved.The definiton of photosynthesis is the process in which green plants use raw materials- carbon dioxide and water- to produce simple sugars and oxygen using sunlight trapped by chlorophyll.The definition of respiration is a chemical process in which glucose is broken down into carbon dioxide and water,together with a release of energy,
So what does photosynthesis and respiration have to do about living things?
During the day plants breathes in carbon dioxide and gives out oxygen.At night, the opposite happens.This is what you call photosynthesis.To ensure that there is not too much or too little carbon dioxide in the air, animals breathe in oxygen and gives out carbon dioxide.This is where respiration comes into the picture.
Why do plants photosynthesize?
To obtain the food they need, plants undergo photosynthesis.To do this, plants need the light energy from the Sun.The light energy is then trapped by the green pigment called chlorophyll contained in chloroplasts which can be found in the cells of the green leaves.Other than light carbon dioxide and water is needed.The formula is shown below.
→→→→→→→→
light energy
glucose+oxygen=water+carbon dioxide+energy
What will happen if there are no plants?
Since humans and animals cannot make food because there is no chloroplasts in their cells,plants are the only source of oxygen.Humans also do not have the green colour of the plant's green leaves.
,
In conclusion, we have learned that without photosynthesis and respiration living on earth is totally impossible.
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