SIG 1
1. From what and to what values have the CO2 concentration and the CH4 concentration increased in the last 800 000 years?
CO2: 200-426 ppm
CH4: 400-1935 ppb
Which part of the world used the most energy in 2011?
The OECD countries used the most right about 2000 Mtoe.
How does the concept of global energy use differ from swedish?
Globally, the source of energy is majorly fossil, about 80%. Swedish source of energy is more distributed between fossil (30%), nuclear (30%) and about 20% from renewable energy like wind, solar and hydro. NOTE that source of nuclear is far from the usage of nuclear, since the efficiency is really low.
Give three examples of renewable energy sources that are used today.
There are way more than three, but hydro, wind and solar is three of them.
How much sunlight energy does the sun provide to the earth in one hour?
The sun intensity is about 120 000TW, i.e. in one hour it will provide 120 000 TWh of energy.
Where and how does the plant convert solar energy to chemical energy?
In the chloroplast, over the thylakoid membrane. The sun beams on the plant and the antennas receive and absorb the energy from the sunlight. This energy then is transported from the antennas to the PS2. When the energy reaches the PS2, it excites an electron, this electron origins from splitting water. When this electron is excited, it obtains a higher potential and therefore it is able to transport its electron all the way to PS1 through some complexes. All this way it pumps protons over from the stroma to the lumen. When the electron reaches PS1, it is excited again and then transported to the complex that produces NADPH from NADP+, obviously the pumped protons plays a role here. The rest of the protons is pumped through the ATP-synthase which then produce ATP form ADP, this ATP is considered chemical energy.
Describe the water splitting reaction.
The water is splitted in the PS2, in the Mn-cluster, and releases an electron to the electron transport chain. The water is split in five steps in the KOK cycle, S0-S4, where two water is needed and four electrons is released during one cycle. The water is able to be split because PS2 is such a great oxidizing agent, otherwise oxygen is really hard to oxidize.
Describe the KOK cycle.
The water is splitted in the Mn-cluster, using the KOK-cycle. The KOK- cycle has 5 steps, S0-S4, where electrons is released between all of the steps, hydrogen is released between all steps except S1-S2, and water is splitted between steps S2-S3 and S4-S0.
Why is the photosynthesis so inefficient?
There are three different factors determining the efficiency of the photosynthesis, quantum yield, light harvesting yield and fractional energy yield. The quantum yield is how much of the light intensity is absorbed, this is about 90% at optimal intensity. Light harvesting yield is about wavelengths, the antennas , chlorophylls and cartenoids absorbs light at certain wavelength and therefore the light harvesting yield is about 32%. Fractional energy yield is due to losses in chemical reactions, mostly due to the required time differences, it usually is about 50%. This ends the total synthesis to be about 0,2-2%
Mention four ways in which we can use photosynthesis or principles of photosynthesis to produce efficient solar fuels.
Green cell factories, Photocatalythic, PV+ electrolysis, Biohybrid approaches
Describe one example of green cell factories.
The production of hydrogen when in photosynthesis, where water is split to release electrons and protons, this creates H2 which then can be used to power any type of electrical process. When the H2 then is used, water is released, and the process can be repeated.
Give an example of a photocatalytic approach.
To replace the Mn-cluster with something more efficient to make the water splitting reaction more efficient.