Respiration: The Link Reaction | A-level Biology | OCR, AQA, Edexcel

Respiration: The Link Reaction in a Snap! Unlock the full A-level Biology course at bit.ly/2VZdKRC created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University.
The key points covered of this video include:
1. Pyruvate Transport for Aerobic Respiration
2. The Link Reaction
Pyruvate Transport for Aerobic Respiration
We previously saw that glycolysis occurs in the cytoplasm and produces pyruvate. This pyruvate has the potential to be broken down further to release more energy. The fate of pyruvate after glycolysis depends on whether or not oxygen is present. If oxygen is present aerobic respiration will take place and pyruvate must be transported into the mitochondrial matrix for the next stages of respiration. Pyruvate is actively transported across the mitochondrial envelope and into the matrix by a transport protein called the pyruvate-H+ symport.
The Link Reaction
The Link Reaction involves the conversion of pyruvate to a two carbon acetyl group and takes place in the mitochondrial matrix. In the Links reaction a carboxyl group and hydrogen atoms are removed from the pyruvate. When a carboxyl group is removed the process if called decarboxylation. When hydrogen atoms are removed the process is called dehydrogenation. The decarboxylation and dehydrogenation of pyruvate is catalysed by the large multi-enzyme complex pyruvate dehydrogenase. When the carboxyl group is removed, carbon dioxide is produced. When the hydrogen atoms are removed from pyruvate they are accepted by NAD, producing reduced NAD. This decarboxylation and dehydrogenation of pyruvate results in the formation of an acetyl group. Finally, this acetyl group combines with a molecule called coenzyme A (CoA) to form the compound acetylcoenzyme A (acetyl CoA).
Summary
In aerobic respiration, pyruvate formed in glycolysis must be transported to the mitochondrial matrix
Pyruvate is actively transported via the pyruvate-H+ symport
When it enters the matrix, pyruvate is decarboxylated and dehydrogenated by pyruvate dehydrogenase
This produces an acetyl group which combines with coenzyme A to form acetylcoenzyme A
The links reaction results in the formation of carbon dioxide, reduced NAD and acetylcoenzyme A

[@mollyclarke9987]

These videos are so helpful as I rarely know what is going on in class

[@alexyandfriends]

These videos help out a lot. Its much better than reading pages and pages of boring text

[@dalefernandez19]

Same for me bro
Smart Study

[@mintaexx2990]

I can't stress into words how helpful this video was.

[@jcn268]

explained it so well , i never thought this was possible

[@fatimaabualsell6219]

Very good explanation.I did not understand anything from my teacher but now I am fine thanks to you 👍👍👍👍👍

[@melaviia1929]

Thank you so much, this was very helpful!!!

[@ahmadcade55]

I understand this lesson really 💯🙏

[@nikkiwilliams1091]

Thank you, makes total sense then just reading it

[@mohammedalshare7685]

great video marcus

[@mustafakhalid8217]

Thanks alot...your video is really helpful

[@pooh2541]

May I know why is the hydrogen atom is still with the pyruvate? Isn't it was removed during glycolysis?

[@gauriupreti842]

such a very helpful video
love this from nepal
thank you

[@sunailamckenzie6584]

You guys are excellent

[@amerahmad7072]

Thank you 😊

[@JN-uz8wx]

Great video

[@damlayldz6629]

thank you so much

[@Afc20087]

My man Steve 🙌

[@maxwellteyjnr2125]

How come a pyruvate molecule still has a hydrogen atom. Because in the video on glycolysis we were told, during the oxidation reaction of the triose phosphate molecule the two hydrogen atoms are lost to NAD molecules to form reduced NAD molecules

[@abeersyed1250]

that is what i was asking

[@walidkhaled4542]

Glucose have 12 hydrogen atoms. In one pyruvate there will be 6 that if u don't remove any hydrogen

[@walidkhaled4542]

Cuz glucose is c6 h12 o6

[@Tailor14]

you're an abs legend

[@sellikgebrie8699]

Thankyou soooo much

[@sudhanshuraj437]

Love from India

[@fen5879]

im sorry, can i ask in glycolysis the hydrogen are removed by NAD..but how the hydrogen still have in the link reaction? where the hydrogen comes from?

[@xinyu663]

What about the Krebs cycle and Oxidative phosphorylation?

[@benfox422]

Vienna there’s one for Krebs cycle it’s just not in the playlist

[@mohamedghassenmahjoub6076]

idk if you still need it but here is it
Krebs cycle:
ua-cam.com/video/8IU9Ba7Ukpo/v-deo.html

[@rozhina1016]

[@syedmuska9921]

How are the 2 ATPS formed? I really can't understand

[@syedmuska9921]

@@-TheRealCozmik- thank you

[@ShahbazPanezai]

awwesomeeeeeeeeeee

[@aena5995]

Isnt it 4 ATP bein produced during glycolysis 2 from each triphosphate??

[@ujalgurung8420]

net ATP is 2 since 4 ATP is produced during glycolysis but 2 is used up in the process. 4-2= 2 net ATP

[@michaeljk6976]

2 ATP IS INVESTMENT DA

[@lology]

from each triose phosphate, 2 atp is produced but 1 atp is used to produce 1 triose phosphate (2 atp for the glucose molecule) so only 1 net atp is produced from each triose phosphate and 2 net atp from the whole glucose molecule.

[@nazishmallickanmol24786]

How oxygen is used in link reaction

[@LockurasEnVivo]

Hey, quick question. Should not be 4 molecules of ATP as a result of Glycolysis? If each triophosphates produce 2 molecules of ATP. According to the previous video. So, as a result, after glycolysis, we should have 4 molecules. If someone can clarify this, thank you very much! this content is super helpful

[@dominicawarrington9212]

2 ATP molecules are used therefore there is a NET production of 2 ATP

[@LockurasEnVivo]

@@dominicawarrington9212 yes I figured afterwards he talked about the net gains. Thank you!!

[@vijeta7792]

Sir can you tell me that link reaction is Oxygen dependent or oxygen independent process 🙏🙏🙏🙏????????

[@Potatoesandchaos]

It depends on oxygen in my understanding love. But just check maybe I'm wrong.

[@boundlessgaming6545]

Didnt we form 4 atp? 0:24

[@foolsgoldx28]

heyy yeah 4 atp are formed but 2 were used in the process, so the net yield of the atp is 2. (4-2) hope this helps xx

[@boundlessgaming6545]

@@foolsgoldx28 yea it helped, Thanks 🙏

[@foolsgoldx28]

@@boundlessgaming6545 no problem 😊

[@mohamedsalah5726]

hold up hold up hold up Isnt the hydrogen atom removed in Glycolysis?

[@jannat4585]

Yes. ONE hydrogen atom was removed but there are more than one hydrogen atoms present on the pyruvate

[@mohamedsalah5726]

@@jannat4585 yea i realised 10 mins after that lmao My bad but thats for replying tho

[@oscarmullan8237]

​@@jannat4585 There has to be 2 hydrogen atoms removed from each molecule of triose bisphosphate because otherwise the formula [NAD⁺ + 2H → NADH + H⁺] wouldn't work. He is wrong.
NAD⁺ needs a hydrogen atom to become NADH⁺, and then it needs an electron to reduce it to just NADH. This electron is gained from the second hydrogen atom.
If only one hydrogen atom was gained by the NAD⁺, you would be left with NADH⁺ only which is positively charged and therefore won't interact correctly with the molecules later on in respiration.
However, this means there is a hydrogen ion left - this is what is moved with pyruvate into the mitochondrial matrix.

[@foolsgoldx28]

@@oscarmullan8237 ohh so it’s like 2 hydrogen atoms were removed forming NADH and a hydrogen ion, which later attaches back to the pyruvate?