A2 Biology - Selective reabsorption (OCR A Chapter 15.5)

[@muhammadjawad4808]

I have watched every single video and its absolutely amazing how everything is done win a proper order of OCR A book. I would deffinately recommend everyone every OCR A student to watch each video :)

[@BioRach]

Thank you, I'm glad you found the videos helped! I'm a bit particular with how they are organised, as it makes it clear what has been covered and what hasn't. Thanks for watching and sharing with others! :D

[@muhammadjawad4808]

@@BioRach is it possible of you could do a video on pancreas explaining about pancreas please!?

[@BioRach]

On my list! :)

[@yohansa333]

i hate this topic so much but you made it so understandable thank you so much for all your videos they’re so helpful and they’re the neatest ones I’ve seen by far :))) ur the reason I’ll pass a level biology in a few weeks💟

[@seanhill3488]

I finished my A levels 5 years ago I'm just watching this to remind myself what I used to know 😅

[@user-wy6lm5zp3p]

BioRach I love you so much! Especially because of all the broken up teaching, advanced info and whatnot - a real lifesaver. I have paper 1 and 2 this time 2 weeks!!

[@hellershelsby81]

Covering homeostasis in biology for my health and social care diploma. This video has absolutely saved my bacon so a huge THANKYOU for posting this. I've been away for 14 days & missed 3 full days of biology, so I'm having to teach myself what I've missed and this has been perfect for my assignment questions on nephron structure & ultra-filtration. Thanks again from Cornwall in the UK.

[@BioRach]

Glad to be of help! :)

[@viclate428]

Thank you so much! I hope you know how helpful and valuable you are to us. You are the reason my grades have improved xx

[@sophielee7495]

This is such a great well-explained video, so glad I found your channel! Perfect and so useful, thank you!

[@zohamudassar5906]

hands down... will definetly recommend it to my friends!

[@BioRach]

Thank you for watching and sharing! I'm glad you find it useful! :D

[@nzakamebonse1195]

Nice tutorial

[@jasminehaqq6536]

soo helpful, defo better than my teacher and rly articulate thanks so much :)

[@BioRach]

Aww glad you find it helpful! Thanks for watching :)

[@katysmith7220]

AMAZING video thank you so much so grateful for people like you who can actually teach well

[@theoneh5249]

Thank you, this was so clear. I do AQA but these vids are extremely helpful. Please keep up the great work!

[@AA-fo8hw]

Omg Rach I’m so grateful for this video Thankyou so much it has helped me a lot , very Clear and simple.

[@BioRach]

Haha I'm glad the video helped! This bit can be a bit confusing... Thanks for watching! :)

[@imaneelk7064]

You explain things so so well!!! Thank you so much

[@BioRach]

Haha glad you found it helpful, thanks for watching! :D

[@hopepauline5767]

thank you so much this has helped summarise this topic.. could you please make a video for urine analysis and how guard cells work

[@eshalshoaib5923]

Amazing video! I love the representation and the vivid explanation. Thank you!

[@11hbashir]

really great videos!! really concise yet detailed video!!

[@BioRach]

Glad they're helpful! :)

[@masiieeh]

shuuuuush

[@bharathsomani5091]

tomorrow i have finals and i am sure i will definitely attempt this question if it occurs...thank u so much

[@BioRach]

Glad to be of help! Thanks for watching :)

[@radika9363]

That was sooo important thank u for ur explanation. OMG that was amazing better than my teacher❤️

[@bangtaesty4256]

1:30 why are the arrows for water leaving and glucose being reabsorbed the same?

[@nataliepritchard784]

These are really useful videos, thank you so much!

[@georgenelson8857]

Great video but just wondering why is Cl- reabsorbed by diffusion instead of active transport in the distal convoluted tubule? Especially since it was being reabsorbed by AT in the ascending limb of the LoH but now it's by diffusion (unlike Na+ which is still absorbed by AT in the DCT)?

[@hasanyt1277]

Because water leaves by osmosis just before that which creates high concentration and low water potential in the DCT so it leaves by diffusion down the conc gradient

[@BioRach]

This! :)

[@sanulimummullage2476]

thank you for the clear explanation and you are a life saver!

[@bananamangoes01]

Thaaank you ... I was almost lost ✨❤ Subscribed 👌

[@Ghost-fo8kf]

So is the role of the loop of henle to lower the water potential of the medulla to create a concentration gradient between the filtrate and medulla allowing for water reabsorption back into the blood?

[@Ghost-fo8kf]

Also I’m confused what does the dct do to the dilute filtrate that enters the dct from ascending limb

[@rahh8222]

Please keep making videos !!

[@jammyjammy1769]

Excellent. Absolutely live this video.

[@BioRach]

Glad you found it helpful! Thanks for watching :)

[@mirzamanzoorhussain2191]

SUPER EXPLANATION IN A VERY SHORT TIME

[@BioRach]

Glad to be of help! Thanks for watching! :)

[@chloeb6093]

Is the only point of the counter current multiplier system in the loop of henle to make the water potential in the medulla super low for quick osmosis at the collecting duct?

[@BioRach]

Yes, and the countercurrent system maintains this constant concentration/water potential gradient!

[@chloeb6093]

@@BioRach thanks 😊 thought of your diagram for the adh osmoregulation 6 marker today haha, thanks so much

[@lumiinouss4744]

amazing video i would love if you could make sure when you cut/clip parts of the video your not cutting some bits out because i sometimes miss some info :)

[@BioRach]

Ah what info are you missing? If it is a question I can help answer in the comments then I'm happy to do so :)

[@lumiinouss4744]

BioRach it’s fine :) i was able to figure it out this video was really helpful I had my a level biology exam today and got a question on this thank so kich

[@musiimentaallen615]

Thank you for your clear explanation 🙏🙏

[@KamisatoElias]

Hi, I'm quite confused by the function of the ascending limb in the loop of Henle. Why do we want Na and Cl ions to be diffused/actively transported into the blood again? Is it simply so it can be absorbed back into the descending limb and allow more osmosis of water to happen, so water is continuously reabsorbed in the descending limb? Also, how do Na and Cl ions help water be reabsorbed? Surely at that point the, the Na/Cl ions will lower make the concentration of water in the loop of henle is lower than the outside, so it will just go back into the nephron and not be reabsorbed??

[@BioRach]

Few things to address: 1. Selective reabsorption is to allow the blood to take back useful substances. Na and Cl ions are important ions, so that's why they're reabsorbed. 2. The higher concentration of salts in the blood will help the reabsorption of water, as you said, since the blood will have a lower water potential than the filtrate. 3. Keep in mind that the descending and ascending loops have different permeability for water and salts, also they are a countercurrent system. This is why the water potential gradient is maintained throughout the process to allow continuous reabsorption of both water and salts, without worrying that water will leave by osmosis. Hope this makes sense!

[@softlilac]

Hello! I had a question on this- many different sources go into different amounts of detail for the kidney. Would we need to know about how sodium ions act as cotransporters? Or how sodium ions first are put into the tubule via the sodium potassium pump and cotransport all other solutes in, THEN when it is in high concentration in the proximal convoluted tubule they move out from high concentration to low concentration in the blood? I'm confused since the textbook doesn't go this much in depth, but my teachers and other sources online have

[@BioRach]

I wouldn't go into too much detail about the sodium potassium pumps and co-transport. I'd definitely remember that sodium ions are reabsorbed by active transport, which then creates a water potential gradient to allow efficient water reabsorption.

[@aye75.]

Hi, i had a few questions 1. why is Na and Cl absorbed by diffusion in the loop of henle, in many resources i have read that it only is absorbed by active transport in the loop of henle (please correct me if im wrong?) 2. and for distal convoluted tubule in my book it says that the first part of it acts as ascending loop of henle, so how is it done? 3. and lastly why do chloride ions diffuse out?? and thanks alot for making these lovely videos, they are very helpful

[@Mujiboy]

Diffusion is passive, if there is lower concentration of the ions (Na+, Cl-) in the blood outside than the concentration of them travelling inside filtrate, OFC diffusion will occur. I am not sure I understand what you mean by the other questions.

[@BioRach]

@aye75. @Mujiboy Q1+3.) Na+ is absorbed by active transport. This affects the concentration gradient and water potential gradient, which in turns causes Cl- to be absorbed by diffusion. Q2.) The ascending limb of the loop of Henle connects immediately to the distal convoluted tubule, so it is no wonder the book says they act as if they are the same structure. Hope this makes sense :)

[@heersharma7010]

beautifully explained ❤

[@muniroloko3584]

This channel is amazing

[@abbasarshad380]

Miss can this be used for A level biology?A2 syllabus and answering style?

[@BioRach]

Yes, all my videos are based on the OCR A level spec :)

[@wilbanedome2245]

I'm really understanding😮😮😮😮

[@muhammadkamranmirza2783]

The music behind is soothing thankyou

[@rohanbarnes4349]

This really helped Thankyou 👍

[@paulapenades01]

Hi, i love you videos, Could you upload genetic technology videos

[@BioRach]

Ah yes that is on the list - will do soon! :D

[@masiieeh]

love u too

[@nala1269]

I love you biorach

[@Charlotte-hf5jz]

could you please make videos on the missing topics for chapter 15 and 16 as i’m really struggling in class :)

[@mithushas]

same lottie :)

[@Charlotte-hf5jz]

@@mithushas why are u on chapter 15 pls😭😭

[@CORNELIUSOWERE-le4lt]

Good and understood

[@Sara-zm1gp]

thank you so much, this is amazing

[@baqirshah326]

Ok the video is good and all but just wanted to fix the last bit Osmosis does not take place in the collecting duct rather ADH acts as a signal for water channels or aquaporins to open and water is taken in

[@BioRach]

Yes, but note that the movement of water through the aquaporins IS osmosis... :)

[@gennarocontursi6890]

Very good video

[@BioRach]

Glad to be of help! Thanks for watching :)

[@rangineechoudhury3755]

Very well explained. However, I have one suggestion. The arrows for reabsorption can point towards the nephron for clarity.

[@BioRach]

Thanks! :) Just to clarify - reabsorption refers to how the substances are reabsorbed from the nephron filtrate back into the blood which is in capillaries surrounding the nephron. This is why the arrows point OUT of the nephron to show them moving into the blood.

[@jeffo8520]

What happened to brush borders???

[@samihasyeda3786]

That's not in the OCR A spec. We just say that the Proximal Convoluted Tubule has microvilli on its membrane to increase surface area so there's a larger area for active transport.

[@imsunny3416]

The wtchae (water) being british hits

[@hamidas7890]

why would urea also be reabsorbed if it's toxic?

[@BioRach]

There may not be a reason at all! Remember we have observed that urea is reabsorbed, but that does not necessarily mean there's a reason for it to be reabsorbed. Having said that, we can think of how it may happen based on the physiology of it... Because of the selective reabsorption of everything else, the filtrate would have an increasingly high concentration of urea. Urea is a small molecule, so it could pass through the gaps of the nephron wall and capillary wall and back into the blood by just diffusion. This may explain how urea is reabsorbed, but there isn't necessarily a reason for it. And yes, it's not ideal for the human body that it is reabsorbed, but it does, and we are still technically removing at least half of it so it's fine. Hope this makes sense :)

[@Mortube2023]

Ndl

[@abdallahomer5463]

niko defence leauge

[@Mortube2023]

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[@fiyazrahuman6992]

I wonder why this video has 5 dislikes?

[@fariowascool]

SUIIII

[@zfaisal8800]

please remove the distractive music

[@isabelflynn8330]

Thank you so much for your help, you really make everything so much easier to understand!!! Just know that you have a bunch of fangirls in my class ahaha 🩷🩷

[@CORNELIUSOWERE-le4lt]

Good and understood