PHOTOSYNTHESIS - AQA A LEVEL BIOLOGY + EXAM QUESTIONS RUN THROUGH
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- Опубліковано 18 сер 2020
- In this video explain ALL the content required for the "Photosynthesis" section for AQA A Level Biology. This includes: the light-dependent reaction, light-independent reaction and limiting factors of photosynthesis.
Time stamps are in the comments.
The content crosses over with other exam boards too.
I also go through some exam questions and explain the mark schemes.
Please comment if you have any questions, I'll be more than happy to answer them! :)
00:49 = Light-dependent reaction
06:32 = Light-independent reaction (Calvin Cycle)
08:35 = Limiting factors of photosynthesis
10:28 = Exam questions and mark schemes
This was soooo helpful! especially in the times impacted by coronavirus, we need all the help we can get! :)
9:43 ... that first plant picture seems very suspicious
.... 🏃🏾♀️🏃🏾♀️
Thankyou, this video was so helpful. Really condensed as well so saves a lot of time.
Absolutely brilliant channel love the exam practice at the end so good and just straight to point earned a subscribe
great vid, tyvm. Keep it up :)
thankkk youuu just what i was looking for!!!! the exam Qs really help
Thank you!
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This is so helpful thank you!!
Glad I could help :)
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Thank you
Hello, I love your videos, but photosystems are not mentioned in the book or the AQA spec.
Hi!! Thank you so much!! These videos are amazing. Just wondering for Q2) part b) why is light intensity controlled? If they’re measuring the light wavelengths wouldn’t that mean different intensities?
And for part c) why are we talking about co2 when we’re focusing on the light dependent reaction?
Thanks a lot!!
Hi, so light intensity and light wavelengths are actually slightly different things! Light intensity is the amplitude (i.e. distance of light source from apparatus) of light with the same wavelength, so that needs to be kept constant. As for part c, the light-independent reaction is still occurring as it uses products from the light dependent. You need to assume this as the main text of the question doesn't highlight that it is just the light dependent reaction, it just says "photosynthesis". Hope this makes sense :)
Thank you for the video, had a question. At 21:14 I thought light intensity is the independent variable that we are manipulating to see how much O2 is produced then how are we supposed to keep it constant throughout the investigation? Don't we keep control variables constant?
i think it means that even tho yes you manipulate it eg doing high or low light intensity, when you do high you keep it high throughout the testing, and if you do low keep it low, dont like move the lamp or anything, i think that's what it means, cause if it said control variable then you wouldn't mention light, but it doesn't specify what type of variable so you don't have to worry about that
For question 4 part c, how can we tell that there is a faster production of ATP and NADPH from the graph?
yah ,i was wondering the same thing
@Fazzy22 understand why she said that it is because in the light dependent reaction the products are reduced NADP(she is calling it NADPH) and ATP so it would be obvious that there would be an increase in both of them ,the products go on to be used in the light independent reaction during reduction of GP to TP
we can't lol, we're expected to just learn the mark scheme🙂
Hi, sorry for such a late reply. As you can see from the graph, the mutant plants in both light intensities have a higher rate of oxygen production. Oxygen is produced in the light-dependent reaction, implying that the light-dependent reaction is occurring at a faster rate. ATP and NADPH are also produced in this reaction, implying that they're produced faster too. Hope this helps!
How/when is oxygen produced in the LDR?
Hi, it's during the photolysis of water. Two water molecules (I know I only showed one in the video but let's ignore that haha), are split by light into protons, electrons and oxygen. The formula should be 2H2O (+photons) = 4H+ + 4e- + O2. Hope this helps!!
Maita basa zviro kwazvo
At 10:33 for the second mark point can we say The higher the rate of oxygen produced the quicker the light dependent reaction will happen?
Yes I think that would get you the marks!
@@AlevelBiologyHelp Thank you
10:12 but doesn't the CO2 get assimilated by the plants anyway?
It does, but as there is excess, a greenhouse effect is created. :)
In the maths question about how much oxygen is produced, why do you divide by 4?
Because if there is a difference of 140 in 15 minutes, that wont get smaller after an hour, surely you times by four as you are scaling up the time and thus scaling up the amount? Like why do you divide by four I dont understand.
Yeh I don't understand how the amount produced would decrease over the next 45 minutes
Hi, good question. If you read the question carefully, it says that the Scientists only collected the oxygen for 15 minutes, so they didn't keep on collecting any after that. This means that you have to kind of assume that no gas is formed after that if that makes sense? This means that you divide by four. It's a very tricky question - I find it quite confusing myself
Hello what about C4 and C3 Plants?
Hi, C4 and C3 is not on the specification (at least for AQA) , so you don't need to worry about that! :)
@@AlevelBiologyHelp actually i’m from Pakistan and my exam variant is 42.. so C4 and C3 plants are included in my syllabus sadly. Also thank you very much for replying. Can you please suggest me any other channel to study C4 plants? Also This video helped a lot :)
i dont understand why the ph increases, where is co2 being removed from and how does this relate to ph
CO2 + H20 = H2CO3 = H+ + HCO3-
CO2 reacts with water to produce hydrogen carbonate. This then splits to produce Hplus ions and hydogen carbonate ions. As I'm sure you're aware that H+ ions are what makes things acidic. So more H+ ions = more acidic and less H+ ions = less acidic. To answer your question - Photosynthesis uses up C02 in the Calvin Cycle. Less C02 = less H+ = less acidic = more more alkili = high pH value.
@@Limitless-vx8jd Thank you that's what I was going to say!
My lecturer never mentioned the photosystems 1&2… should I be concerned?
You are required to know about them to learn the process of light dependent photosynthesis :)
It makes me wonder what other areas I may be missing out on… It’s just as well that I’ve found your channel! Thanks so much😊
i dont understand why we divide 15mins by 4 wouldnt it be multiply