4.3 Carbon cycling Flashcards
Describe the heaviness of CO2
Carbon dioxide, CO2, is a gas that is heavier than other components found in the atmosphere, so it will accumulate at the bottom of a room.
How does the sinking of CO2 affect heterotrophs? (reword)
-In nature, it will slowly diffuse to the lower layers of a forest or canyon, which could pose a problem for heterotrophs since CO2 is a waste product from respiration and they need to take in oxygen for survival.
-However, CO2 can be mixed in the air due to temperature changes and wind patterns.
-Since CO2 tends to sink, it is readily available to photosynthesisers and can be trapped in water.
Describe the solubility of carbon dioxide
-Carbon dioxide solubility is quite low ranging from 0.88 cm3 to 0.65 cm3 of CO2 per gram of water, with temperatures of 20 °C to 30 °C.
-However, the solubility of CO2 increases as pressure increases.
-So, if CO2 sinks, it is at a higher pressure at the water’s surface and, with waves or turbulence, can dissolve into the water to be available for aquatic plants.
-Large amounts of CO2 can be dissolved in sparkling water using pressure.
-Once you have opened a bottle of sparkling water, pressure drops and the carbon dioxide forms bubbles and escapes from the water.
How can carbonic acid be made and what are its properties?
-Carbon dioxide can combine with water to form carbonic acid (H2CO3).
-This molecule is unstable and dissociates easily in water into hydrogen ions (H+) and hydrogen carbonate ions (HCO3-).
-The H+ that are released during this dissociation lowers the pH of the water (makes it more acidic).
-This is also important when discussing the CO2 that dissolves in blood plasma.
-When CO2 combines with the water in blood it lowers the pH.
-This is detected by the brain which sends a signal for you to breathe.
Key info about carbonic acid
-Carbonic acid – H2CO3 – is the molecule that forms when CO2 combines with water.
-This molecule is unstable and dissociates easily in water into hydrogen ions (H+) and hydrogen carbonate ions (HCO3-).
-The H+ that are released in this dissociation lower the pH of the water (makes it more acidic).
Diagram showing how CO2 can accumulate above water, then dissolve due to pressure. It may then become carbonic acid and break down to H+ making the water more acidic
Hydrogen carbonate ions are also known as ___
Bicarbonate ions
In aquatic ecosystems, carbon is present both as ___
Dissolved carbon dioxide and hydrogen carbonate ions
In what form do aquatic plants and other autotrophs living in water require carbon and for what?
They require carbon in the form of dissolved carbon dioxide and hydrogen carbonate ions to produce more complex carbon compounds.
How do land plants and aquatic plants take up CO2 and what effect does this have?
- Land plants take up carbon dioxide as a gas through their stomata, which are pores found in their leaves.
- In aquatic plants, dissolved carbon dioxide diffuses into the leaves from the environment.
- In both cases, in water and on land, the carbon dioxide is used in the Calvin cycle to make carbohydrates and more complex carbon compounds.
- This lowers the concentration of carbon dioxide in the plant, setting up a concentration gradient that helps the carbon dioxide diffuse into the autotrophs.
What are stomata?
Pores found on the underside of leaves which allow for gas exchange.
Stomata on aquatic plants
Aquatic plants are adapted to have stomata on the upper side of their leaves for gas exchange.
Diagram of how CO2 diffuses from the atmosphere or water into autotrophs
Picture of stomata
Diagram showing what happens to carbon dioxide during photosynthesis and its interaction with heterotrophs
Taking in and release of CO2 in autotrophs and heterotrophs
-Autotrophs take up carbon dioxide and give off oxygen during photosynthesis.
-Heterotrophs can exist because of this process.
-However, both heterotrophs and autotrophs respire and produce carbon dioxide.
What process takes place in cells to produce CO2?
Cellular respiration takes place in cells to produce carbon dioxide, just like in all heterotrophs.
What organelles do plants have for photosynthesis and respiration and how do they use these?
-Plant cells contain chloroplasts, used for photosynthesis, as well as mitochondria, used for respiration.
-When plant cells perform aerobic respiration, mitochondria use oxygen and produce carbon dioxide.
How do plants use carbon dioxide during the day?
-During the day, carbon dioxide from respiration can be used directly by the chloroplasts for photosynthesis.
-In this case, carbon dioxide is not released from the leaves, as photosynthesis mainly occurs here.
-Carbon dioxide produced during respiration is a waste product of metabolism and diffuses out of the plant into the atmosphere or water.
-Carbon dioxide is also produced in anaerobic conditions where there is no oxygen available.
What are anaerobic conditions?
-Environmental conditions that lack oxygen for aerobic respiration.
-Also, known as anoxic conditions.
Diagram showing how CO2 is produced by both aerobic and anaerobic respiration
Describe the seasonal changes in CO2 concentration in Earth’s atmosphere
-In the northern hemisphere during the winter months, most plants are dormant because they lose many of their leaves which absorb CO2; producing little oxygen and taking up little carbon dioxide.
-So, during the cold winter season, the carbon dioxide concentration in the atmosphere increases due to less absorption from plants.
-More fuel is burnt to heat houses and the heterotrophs are still respiring.
-During spring and summer, trees will grow more leaves, which are able to absorb the atmospheric CO2, so the concentration in the atmosphere will drop.
The following graph shows variation in the concentration of CO2 in the atmosphere as measured at Mauna Loa in Hawaii. The small inset graph shows the variations in CO2 during the year.
Why does the concentration of CO2 decrease between April and August? Please take into account that Hawaii is located in the northern hemisphere.
The rate of photosynthesis in the northern hemisphere plants increases due to the summer season.
In aquatic ecosystems, carbon is present as ___
Dissolved CO2 and bicarbonate ions (hydrogen carbonate)
Which type of organisms convert atmospheric carbon dioxide into carbon compounds passed through the food chain?
Autotrophs
What is methane?
Methane – CH4 – is a carbon molecule that is produced in anaerobic/anoxic conditions and can oxidize into carbon dioxide and water.
Picture of marsh gas formations on a swamp in the Volta region in Ghana.
Marsh gas is a mix of methane and carbon dioxide.
How is methane produced?
-From organic matter under anaerobic conditions (meaning organisms that live without oxygen) by methanogenic archaeans (single-celled prokaryotes).
-These bacteria are found in several anoxic (without oxygen) environments, for example, wetlands, such as swamps, marshes, and bogs, as well as lake beds, the guts of ruminants, termites, and landfill sites.
What can happen to methane once it’s formed?
It may either diffuse into the atmosphere or accumulate in the ground.
What are methanogenic archeans?
Bacteria that are found in several anoxic environments and produce methane as part of the carbon cycle.
What are ruminants?
-Mammals that have a mutualistic relationship with methanogenic archaeans that help them to digest cellulose from the cell walls in the plants they eat.
-This creates methane, which is released as gas from the mammal.
Diagram of the chemical structure of methane
How is methane produced in ruminants?
The gut bacteria in ruminants and other herbivores produce vast amounts of methane, which is released into the atmosphere.
Diagram of methane production in herbivores
What are the types of organic matter that can be used for methane production?
-These include manure from farm animals and cellulose from plants.
-These are converted successively by several groups of bacteria.
Describe the process in which manure from farm animals and cellulose from plants is converted successively by several groups of bacteria (final step is methanogenesis)
-Ruminants chew on plants, breaking down the molecules, such as some carbohydrates, into smaller monomers (using their saliva) by the process of hydrolysis.
-Organic matter is first changed to organic acids and alcohol, such as ethanol, by a group of bacteria in a process called acidogenesis.
-Other bacteria then convert these organic acids and alcohol into acetate (through acetogenesis), carbon dioxide and hydrogen.
-Finally, methanogenic bacteria can produce methane either through the reaction of carbon dioxide and hydrogen (1) or through the breakdown of acetate (2), also known as methanogenesis.
-Methane can accumulate in the ground or diffuse into the atmosphere
-Methane does not build up to high levels in the atmosphere, as it is oxidized to form carbon dioxide and water
Chemical equations to show how methanogenic bacteria can produce methane either through the reaction of carbon dioxide and hydrogen (1) or through the breakdown of acetate (2), also known as methanogenesis
What is hydrolysis?
The chemical process of breaking large polymers into dimers or monomers using water.
Picture of a peat-forming area
Diagram of the carbon cycle
Diagram showing an example of the carbon flux
The annual carbon flux on Earth.
As is the case with models, they are simplified versions of rather complex processes, but they give a good idea of what happens to the carbon on our planet.
Graph showing historic atmospheric CO 2 concentrations
Graph showing mean CO2 concentration at Mauna Loa from 1958 to 2015.
Diagram of the carbon cycle (OSC)
Estimate global carbon fluxes in the carbon cycle (check what is needed for exam)
