This was so helpful! I feel like I've got a much better understanding of this topic as I found it so difficult before, thank you for all the effort you put in to it because it's certainly helping me and lots of others in the comment section too! :)
I've been looking for a you tube channel for detailed notes on topics since the start of the year. glad i found your channel. your videos are amazing very helpfull. thank you!
THANKS, GREAT EXPLANATION I'm interested in to know more about how sucrose transforms from the companion cell to the phloem. Please link me to the better vision ;)
Haven't seen any of your other videos but this one really makes this topic easy to understand, I'll definitely be checking out your other ones, Thank you!
I just have one question, Why is it that at the Source, there is co-transport with the H+ ions to move the sucrose into the sieve tube elements whereas at the sink it seems to be just active transport?
I have a question for u when the sucrose is unloaded from phloem to companion cell it is from high to low concentration , isn`t it ? then why active transpot using atp it should be faciliated diffusion.
@@GabijaS18 water is a smaller molecule and can pass through channel protein(aquaporins)no atp is required or directly through the phospholipid bilayer , whereas sucrose is a big molecule and should pass through carrier protein and it requires energy(from atp) so this is an active process
@@souhaylahabdoolraheem5301 but the thing he pointed out was why isnt it the same(facilitated diffusion through protein pump) when the sucrose is unloaded from phloem to companion cell(high to low concentration) as it is when sucrose is downloaded into companion cell from the palisade cell(which, is again, high to low concentration and still uses facilitated diffusion). So the size of the molecule shouldnt matter? because it is the same context just the solution with which the plant came is different and i dont understand why.
@@sea5205 I put that specific question in order for someone who does know the answer to point it out for me, or to explain how it does nt make sense. You just telling me it makes no sense, without showing me where, does not help anybody with anything.
My biology aqa student book contains information on the co-transport of hydrogen ions and the teacher has told us we need to know this. Please maybe make an updated video, including this section as it is the bit i am most unsure of.
Will try and do a few more...more likely exam technique soon though. Most of my old spec videos still apply though; if in doubt, refer to the specification!
Hello, I really like your videos, thank you. Could you please go through some of the Experimental questions in AQA Biol-1 to Biol5 please (e.g. say from the June 2015 papers)? I really want to understand how to tackle them. If you have time to do a few then please could you go through some of the BIOL4/5 papers ( mainly the experimental questions which are usually towards the end). I have seen some of the other videos that you have done but could you please do a few more particularity explaining how to do the How science works and all the data questions, please. E.g. questions which tell you to 'evaluate' 'explain the graph' 'use the table/graph and explain why this happens' ' suggest why this was done in the experiment' etc... I would really appreciate it :)
sucrose doesn't move into the sieve tube element by facilitated diffusion because facilitated diffusion doesn't involve the use of ATP (as it's passive transport) and also facilitated diffusion is the movement of substances from an area of high to low concentration. So it moves by active transport.
Sieve plates are to maintain the gradient between the source and the sink. Without the sieve plate to provide resistance and obstruct the flow of sucrose by translocation,sucrose will be transported too fast and this will cause the high hydrostatic pressure at the source to disappear. Its like there must be a "balance" between for the rate of translocation.It cant be too fast or too slow
Just one question, how is Sucrose transported to the companion cells through channel protein, i thought channel proteins are used for water soluble ions, shouldn't it be through a carrier protein
In the first part from source to companion cell it is by facilitated diffusion which can be with protien channels since sucrose is still soluble however in the second part at the sink cell it is through active transport so yes will only be via carrier proteins.
My understanding is that H+ is actively transported from companion cells into the space within cell walls. The solute (eg, sucrose) is then co-transported from the companion cell into the sieve tube elemnt along with the H+. My quesiton is, if the H+ is in the cell wall, and the solute is in the companion cell, how can they interact to be co-transported together?
It sounds like active transport to me the movement of sucrose into the phloem. If you could quickly message me with some detail of why it is not active transport that would be great. To allow me to get a better picture of the process.
I was just lying in the Park, thinking about a procedural algorithm to let digital plants for Virtual Reality in real time depending on how much light each leave gets and wondered how the energy flows back down the plant. Your Videos answered it concise, I got it the first time. Thank you. PS: How do plants defend against parasites? I know about poison, but to the have some like an immun system that detects cell infected by bacteria or viruses?
That's some deep thinking Tristan! This article from nature details the plants immune response...www.nature.com/nature/journal/v444/n7117/full/nature05286.html
+Utopic its got quite a few differences (apoplast/symplast pathway, root pressure, casparian strip) and I'm not sure what exactly I need to know for my spec
Dan Ghafoor oh okay, well I didn't watch the video myself as the stuff required for that topic in the new spec is quite simple, but the things you mentioned are definitely not required this year
Please could you put a link up to explain that the movement of molecules from the companion cell into the sieve elements and why it's not exactly active transport. Thank you, this was very helpful :)
Thanks for the video it was really useful. Im unsure however why at the sink end of the phloem, why are the solutes removed out from the phloem into the companion cells by active diffusion. Why would the solutes be going against their concentration gradient as it thought the phloem had more solutes in than the companion cells anyway (esspecially at the sink end??
Sir ,thank you so much. I have a confusion. I had read that food made at the mesophyll cell then it's move to bundle sheath cell then pholem parenchyma then companion cell and then seive tube .so where is palisade cell . Is mesophyll cell is palisade cell. Or what I had read is wrong.
Hi Mr Pollock. Thanks for the great video. Just one small issue. At 8:28 you say that some water moves out of the phloem back into xylem. I am unsure of why this is the case since the water potential of the xylem is higher than that of the phloem. Why would the water move against the concentration gradient.
Don't worry too much about it. In reality, the plant actively transports some mineral ions into the xylem in the roots to enable water to move in...but that's not on your spec :)
Sometimes nature just amazes you, how can a process like this evolve naturally? It looks so unnatural just by its complicated process~ XD (Tq for the video, my teacher went through this chapter in online class, which isn't that good... but after watching this, I can clearly remember the concept now~)
Hi, at 7:56 you say sucrose moves out of the phloem into the companion cell by active transport? I don't get how, as there is a lower solute conc in the companion cell and a higher sucrose conc in the phloem? Surely thats high to low? Thank you!!
Hajra Batt active transport works against the gradient to transport the remaining 50% of the sucrose that's left once equilibrium has been reached, idk if that answers your question but hope it helps a bit
Why is sucrose actively transported from the sieve tube elements into sink cells when the sucrose concentration in the sink cells are lower? Would they diffuse down the concentration gradient?
Also, when the sucrose moves down the phloem is that due to the different hydrostatic pressure or due to the difference in concentration on the sink and source end of the phloem ??? URGENT
I have a question about phisiology I was reading today from campbell biology,It said that medulla ablongata controls breathing and pons balances!I wanna what it means by balancing and how it's done
Correct me if I'm wrong, but from what i understand sucrose is transported to the companion cells from the source by co-transport (via facilitated diffusion) using a co-transport carrier protein and down a conc gradient, created by actively transporting H+ ions out for the companion cell. Sucrose then is transported into the phloem sieve cell by co-transport again with H+ ions and while sucrose is going against its conc gradient the H+ ions are going down its conc gradient because there's a higher conc of H+ ions in the companion cell than there are in the sieve element? I get the rest, but could you clarify this part please^?
Hiya, here are the steps: 1) sucrose in source moves down conc grad from source to companion cell by FACILITATED DIFFUSION. 2) H+ ACTIVELY TRANSPORT against conc grad from companion cells into spaces within cell wall using ATP. 3) H+ and sucrose diffuse down conc grad by CO-TRANSPORT. Hope that helps :)
+Zoey M yh thanks. Question: is there a different between facilitated diffusion and Co transport aren't the two the same thing because facilitated diffusion involves carried and channel protein and Co transport uses Co transport carrier protein to transport the H+ ions and sucrose into the sieve element?
+Aaron Owusu no, they aren't the same. Similarly, active transport also requires a carrier protein. Co-transport (specific to translocation) is when the sucrose is drawn out to the cells along with H+ that have been actively transported out. This is also know as an indirect form of active transport. It is the H+ conc gradient that powers the movement of the sucrose into the sieve tube. I would recommend looking at the sodium-potassium pump (especially since its on the spec), it will really help you in understanding co-transport :)
+Mr Pollock you know the 6 required practicals which we need to know about as they make up 15% of the papers (something like that, can't remember exactly). Just a general video explaining the concepts or good exam questions they could ask us. Any important details about the practicals :)
Thanks for the amazing explanation but I had a small confusion. How does the phkoem already have a concentrated solution of sucrose. I mean where does it come from
From the leaves that make glucose in photosynthesis(water + carbon dioxide -> oxygen + glucose). This is then turned in to sucrose which travels via the phloem.
For low levels of Oxygen medulla oblongata effects only rate,but for high Co2 both rate and depth! in page 1160 of campbell biology it didn't say only!but it hasn't written whether for low levels of O2 has an effect on depth too?! if not Why
Same thing. There are difference places where active loading is used for a different purpose, but here active loading results in the loading of the phloem so we can use the terms interchangeably.
