Lac operon 

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can not believe how much more helpful you are than my professor. god.

you just compressed 3 of my agonizing lectures into 11 minutes and now i've understood it all. You are my hero.

This helps me understand the LAC OPERON very well without bordering reading whole Campbell 10th edition textbook.

I used to watch your videos in high school/mcat. Now im months away from my usmle step 1 in final year of medical school and youre still helping me. Thankyou

I referred your videos for taking a biology seminar at my school and i got an A+, thank you khan academy.

I decided to take Microbiology over the summer, for the 6 week term. I don't even bother listening to my lectures anymore because they are so confusing and overly complicated. I just use my book along with Khan Academy. I will be making a donation!

I am a MS2. This video still teaches it better than my biochem or microbio prof. Thank you!

Thanks for this video! Great explanation! One thing to add for those who are curious is that when glucose levels are high the RNA-polymerase will bind to a promoter (not the same promoter) and transcribe a gene that codes for a repressor so that in turn can bind to the operator and stop transcription of the beta-galactosidase (LacZ) since we don't need to metabolize lactose.

I love this guy. Whoever is the narrator. Amazing explanation. He just made lipincott so easy. Khan Academy is the best. Always listen to it literally for every topic

My professor spent two lectures trying to explain this and we were all still blank at the end of it. Thank you so much

SO GOOD, EXPLAINS BETTER THAN ANYONE ELSE COULD

Thank You Khan Academy, What took Hours of Learning you taught in 11 minutes, Thanks!

Why can't professors explain this as easily?

best 11 minutes of my life

thank you very much SIR the way you explain the topic makes it very clear i understood very well THANK YOU AGAIN

Amazing set of videos... easy to understand and very helpful...

this video is just perfect to understand ! just amazing ! hope you'll continue these kind of videos thank you so much

this sounded so complicated when my teacher taught it ! tysm !

To sum up, when there is no glucose and lactose is present, the catabolite activator protein with high cAMP will bind to the CAP site, therefore enabling transcription(the body needs energy) while if there is glucose and lactose, the system prefers glucose over lactose and will not transcribe. The catabolite activator protein will not bind since it already has a lot of cAMP, here the lac operon acts as an regulatory sequence of gene responsible for protein synthesis. The glucose inhibits the production of cAMP(cAMP are derivatives of ATP) which makes sense since there is already a lot of energy.

thank you I'm studying for Micro final and this helped a lot

Wish i had known about this guy when i was still in high school

OMG. Thank you so much! I can't believe how much better you are explaining that then my uni lecturer! I mean even in english (I am from Germany) I can easily understand what u are talking about. You saved me. Hopefully trp will be as good as this video. =) Keep going'! Best Regards

I love Khan Academy, but it drives me batsh!t when Sal sounds out what he's writing.

Khan da real MVP

I think I’ve watched this video minimum ten times over the course of my degree

god bless u. ur saving me from vandy bio

THIS. IS. AMAZING!!!!!!!!!!!

sir there are no words to say for your effortless work I have so much respect fr u KEEP INSPIRING !!

You are seriously the best!!!

Learned more in 1 video than an entire week of class

This is so much better than trying to read from the Lehninger Principles of Biochemistry textbook. I read every word about the lac operon, but did not understand any of it until this video. THANK YOU

superb, I m Ms genetics student and having this topic in molecular genetics, very impressive. Stay blessed

So you lack the lac operon

Thank you very much! It's really helpful!!!

Super helpful as always!

You cracking up made this a very enjoyable learning experience for me. Thanks

I would like to point out that the Operon is activated when glucose is absent and lactose is present. If glucose and lactose are present, the repressor would still remain bound

this guy sounds like Dave Smith, AND is also a good teacher. lol, awesome

How do you literally know everything?

Seriously u are heavenly teachinggg... thank u so so so very much ! All the best ,keep helping us ]

Thanks a lot for this video and also the one on tryptophan. I was understanding nothing about this genetic expression regulation systems, and you made it very clear, I feel I completely got it. You explain very well and the video also helps So thanks and keep it up :DD

thank you so much for this video!

Unbelievably helpful, took a concept that I wasn't understanding from lecture and made it make so much sense

thx very much salman khan even you are a star man

Thanks a lot

This is crazy!!! Now I wonder is my professor simply what to make my life miserable 😒 Btw small question at 4:32 the picture in my book actually shows that it is lactose instead of allolactose that bind to the repressor? But I think your video makes more sense😂

Would have been useful about 7 hours ago before my exam, haha great video as always!

Thank you so much Sir !

As a suggestion I think you should have a quiz after every lecture

thank you so much

Wow! I've skipped over this many times. Thanks for making is so easy to understand!

So Sal lacs the operon......

Thankyou sooo much..!! You're a legend ⭐

My microbio professor warned me not to use this video as a resource to study, she says its wrong. Khan academy is a good resource but this particular video may not match some undergrad classes. Viewer beware!

This is the first time I actually completely understood the chapter of molecular inheritance, thank you so much khan academy

i will ace this question ,in my exam tomorrow,all thanks to you

Omg so helpful! Thank you!

Especially that you explained the cAMP was very helpful. I'm german and I didn't find anything about it in german videos. Thank you!

This means if you are lactose intolerant and still want to drink milk, do it when you have'nt eaten anything all day.

you did not mention lac I (regulatory gene). Youhave confused me.

This is SAVING my life. Thank you so much.

Sal you are a life saver.

thanks you so much !

this is AMAZING ! thank you so much and keep please don't stop posting vedioes

In today's episode, Sal battles words.... LOL

One hour study in 10 min!! thank you!!

Is this academy same as KSG ( Khan Study Group)????

This was one of the best explanations of the lac operon I've heard

FINALLY!!! I really needed to understand this, thank you!!!!

This saved me, thanks!

if the promoter region is located further upstream (closer to 5' cap) from the structural gene and since the RNA polymerase starts at the promoter region and moves towards the structural gene, how come we say that mRNA is transcribed in a 5' to 3' direction if it is technically reading in a 3' to 5' direction here

I'm assuming CAP is the same/similar to cAMP receptor protein (CRP)?

Nice ...

"catabolater" made me laugh, thankyou now this can finally stay in my brain 😭

If lactose cannot cross the cell membrane without permease (lac y) and if lactose is needed to code for permease then how can lactose cross the cell membrane? This is classic case of what came first the chicken or the egg?

awesome!

I’ve been trying to understand this for weeks 😂 thank you

if we take glucose and no lactose what will be trnscription of lac structural genes

my professor said lac operon is not turned on in presense of glucose until glucose has been used up?

What kind of application is he using for drawing?

I think school/Uni Bio should just be replaced by RU-vid creators. They just explain stuff better with their animations. I mean it's pretty sad that if I want to understand something from my bio class I have to turn to yt...

But prokaryotic cells do not have CAP sites in their operons? Isn't it only found in eukaryotic genes?

Where does Lac l fit into this diagram?

Great explanation. You just saved my life❤

what if there's no lactose but there is glucose?

by reading the comments, most of the people here are in college. whereas they tech this stuff in highschool biotechnology

Love you guys! Paying a fortune for MD school to come here post lecture to learn the material : ))))

will lac operon transcription still occur if glucose and lactose are present in the media? The operon prefers glucose as their energy source so wouldn't the lac operon be repressed? Can anyone confirm?

Seriously, u are the best...💪

so the LacY is responsible to transport lactose through cell membrane, its an inducible system, and LacY protein itself cant transcribe if there is no lactose, so how come lactose entered first time when there is no LacY protein. is there any other protein that pumps the lactose inside cells (initially)?

where does the allolactose come from?

The explanation is very good. It helps me a lot nunderstanding the topic correctly. Thanks Khan Academy

SHORT and SWEET, thanks prof

The RNA polymerase binds to the operon not the promoter

Amazing explanation❤

Theresa Skyway

gosh it's just so much more useful than my teacher

U r saving me everytime😌no other videos satisfies me in studying