Cell cycle phases | Cells | MCAT | Khan Academy

[@rhiamy4087]

My lecturer went over this for a whole hour and I didn’t get it, you spent 5 minutes and it was perfect! Thanks

[@legohead23432]

Rhi Amy and who says the internet is bad?

[@christiangustavo9223]

Preach!

[@vaibhavpagare7250]

@@legohead23432 🙏

[@drhabelhazari1729]

Well you probably understood this so satisfactorily because your mind was already primed by the lecturer.. You just needed a fine polishing..

[@emilylaramore5873]

Who else understood this a lot better than their 3 hour lecture?

[@christiangustavo9223]

Emily Laramore 🙋🏼‍♂️

[@_xiowa9617]

Literally me

[@garrettfleming1636]

lol you got a 3 hour lecture? Lucky you, I get a 50min one.

[@crystinamarie1]

Lol, right? Idk what is going on with teachers. Always gotta make stuff like this hard to understand when Khan can break it down so simply.

[@abdim3375]

Littaraly in 7th grade

[@V4nd44ll]

SORTING OUT THE PARTS: PROPHASE As the first active phase of mitosis, prophase is when structures in the cell’s nucleus begin to disappear, including the nuclear membrane (or envelope), nucleoplasm, and nucleoli. The two centrosomes, duplicated in the synthesis process during interphase and each containing two centrioles, push apart to opposite ends of the nucleus, forming poles. The centrioles produce protein filaments that form mitotic spindles between the poles as well as asters (or astral rays) that radiate from the poles into the cytoplasm. At the same time, the chromatin threads (or chromonemata) shorten and coil, forming visible chromosomes. The chromosomes divide into chromatids that remain attached at an area called the centromere, which produces microtubules called kinetochore fibers. These interact with the mitotic spindles to assure that each daughter cell ultimately has a full set of chromosomes. The chromatids start to migrate toward the equatorial plane, an imaginary line between the poles. DIVIDING AT THE EQUATOR: METAPHASE After the chromosomes are lined up and attached along the cell’s newly formed equator, metaphase officially debuts. The nucleus itself is gone. The chromatids line up exactly along the centerline of the cell (or the equatorial plane), attaching to the mitotic spindles by the centromeres. The centromere also is attached by microtubules (spindles) to opposite poles in the cell. PACKING UP TO MOVE OUT: ANAPHASE In anaphase, the centromeres split, separating the duplicate chromatids and forming two chromosomes. The spindles attached to the divided centromeres shorten, pulling the chromosomes toward the opposite poles. The cell begins to elongate. In late anaphase, as the chromosomes approach the poles, a slight furrow develops in the cytoplasm, showing where cytokinesis will eventually take place. PINCHING OFF: TELOPHASE Telophase occurs as the chromosomes reach the poles and the cell nears the end of division. The spindles and asters of early mitosis disappear, and each newly forming cell begins to synthesize its own structure. New nuclear membranes enclose the separated chromosomes. The coiled chromosomes unwind, becoming chromonemata once again. There’s a more pronounced pinching, or furrowing, of the cytoplasm into two separate bodies, but there continues to be only one cell. SPLITTING UP: CYTOKINESIS Cytokinesis means it’s time for the big breakup. The furrow, formed by a contractile ring that will divide the newly formed sister nuclei, migrates inward until it cleaves the single, altered cell into two new cells. Each new cell is smaller and contains less cytoplasm than the mother cell, but the daughter cells are genetically identical to each other and to the original mother cell, and will grow to normal size during interphase.

[@ieatglitter828]

thank you so much

[@_SumbulAnsari]

Omg thank you sooo much 😭😭

[@boom350ph]

This explain so much than my teachers presentation

[@angelidez13]

I'm trying SOOOO hard to understand everything in Campbell's Biology book but after the first few sections of a chapter I just can't focus anymore, it all just goes WA WA WA WA WAAAAAH, WA WA WAAA WA....this helps tremendously thank you Khan academy!!!

[@pradipchaterjee9576]

Bro just chill out campbel is too much for High school 😭

[@niyealwinter6064]

i struggled with understanding the phases since elementary school, and now it seems way more simple in 5 minutes (i now graduated college)

[@kaykanysha]

The way you explained this was pure love!

[@darcihasselbach4125]

you already know I have a test in pre-ap bio in 5 minutes so im cramming super quick

[@wisdaviniel2349]

How did your test go?

[@Hamzahaisha-fu7mf]

This is the voice I need to have in my pdfs while using read aloud effect in Microsoft edge ❤

[@vpcreationsunlimited]

Perfect explanation ......better than a 3 hours lecture !!

[@HamnaAzhar7]

Perfect introductory explanation! I'm continuing zoology after a two years of break. Thank you Khan academy

[@LumiGhost]

thank you so much for this simple explanation, I understood this a lot better than the 2hour lecture my professor gave

[@rosaliaibarra9090]

I love your hand writing, literally the biggest reason why I stayed to watch the video and subscribed lol

[@linostoe]

[@irwincrook567]

5 feet and 2m have a huge difference

[@Studads3]

Irwin Crook thanks Irwin

[@agentsus9681]

It's about 1.6m so I guess he rounded up.

[@riittasutinen2970]

I was too distracted by "the average person being 2 m tall" to listen to any of it. A young person that tall have basketball coaches approaching them left and right

[@slampest]

@@agentsus9681 rounded up? Thats not how that works. Its like rounding up from 5.5 to 6 feet. We are not 2 meters tall in avarage lmao

[@YunqJamesGetsMoney]

LOOK OUT HARVARD I'M COMING FOR

[@FattestKidEvvverr]

+James Soria for... the end of your sentence?

[@nefsa84]

*you*

[@corpsmanyt8516]

You wanna go to Harvard but you can’t finish a sentence. 😂

[@张小歆-q3m]

James Soria wow god luck

[@madwolf0966]

How was the entrance exam?

[@belfagor80]

wow, great video!!! So clear and straightforward! Congrats!

[@lailaalmalki6517]

I can finally ACE my FINALS! Thank you so much!

[@usurper5045]

Laila Almaliki بالتوفيق

[@demetriawilson4893]

Thank you. Gid bless this institution.

[@mansisharma7486]

best explanation video for non science background people despite the fact its a really difficult concept

[@simontinashemakuzha]

I like this guy's voice, he sounds dedicated and very clear lecture

[@cramegg]

Humans aren't about 2M. 2M is about 6.5 feet.

[@skyangelnaruto]

+cramegg hahahah same thought here

[@TheColormemad]

Lol I was thinking the same thing...

[@soumyadey4889]

cramegg is true , nothing can be done if you are a dwarf

[@Casandratraselviento]

I was going to write the same... Average can be 1,60-70 for women and 1,80 for men. Juan Martín Del Potro is 2 metres tall. That's not normal!

[@anemari5809]

I bet you're asian

[@malaknahari6105]

well done khan I understood it from you more than our professor

[@b-agent5153]

Very short and simple... Thanks... Have a test on it tomorrow 😌

[@alexanderclaidemorgadez5946]

i love how i can understand this 5 min more than a 1 hour lesson

[@everydayfun9531]

Ugh the teacher torched me and put this on the quiz i didn't study for this nor I had the materials wow..............

[@doubles3511]

im from egypt and i thank you for your explain is very good

[@user-zy3mj6fs6q]

simply uh-mazing!!! fricking easy to understand :)

[@uswahhassan6617]

Thank u sooo sooo much Sir This literally helped so much :)

[@erintiffany4938]

Thank you so much for this video I needed this ❤️❤️

[@nickolausafon5458]

I am here for two reasons, really. I need to prep for a cell division and inheritance test. Additionally, I need more science for my Fiction stories.

[@rust5427]

So underrated deserves more views subs and likes 😦

[@angelaxuswl5994]

This sounds so simple yet my textbook and my teacher makes it seem so complicated

[@himanshisharma4558]

What grade are u in?

[@darragiarfawiassala6027]

I don't think an average person is 2m tall .... or maybe I'm too short :(

[@ksokso8204]

Darragi Arfawi Assala I thought 2m is like 6"2 -not an average height

[@AI_Overlord]

you're off by almost 6 inches

[@inescerqueira8985]

no its not

[@TheyyLuvvAjj_]

Let’s be short together 😔✊

[@natiman55]

the Republic of short people

[@victoriagoetz9002]

Love the comparison to seasons and the pictures. Thank you

[@robiulahmed]

Excellent breakdown.

[@Ray-h1v]

Perfect ❤

[@imarun1152]

I admired ur way of explanation..have a blessed life sir

[@backstreetfan2887]

thank you khan academy

[@KinGamerBoy568]

Tell me a better lecturer than this narrator.🙌🏽 Thanks bro.

[@demetriawilson4893]

thank you sooo sound and understandable!

[@gracesharples6228]

This video made things clearer thank you!

[@kiabog_]

oh my god this is so much easier to understand 😭

[@hikpopbyestudiesmuah4067]

Thanks so much !!!!!!

[@marikuna750]

Very helpful! Thanks

[@0279644401]

simple illustration. Good job

[@khairunnizam4294]

very very well explained... thanks so much

[@michel-angemoravia9838]

Good explanation for an AP Bio student

[@jeff-freehoke8012]

I enjoyed your video on interphase. I look forward to watching your videos on mitosis.

[@sawalsawal7968]

THANK YOU!!!! This video helped me a lot on my TEST (

[@김하은-p4p]

thank you for the good video!

[@DatCerealYT]

amazing.

[@acegibbs3850]

Thanks for the lecture. It helped a lot👍🏾

[@MtMtGaming]

Great work, mister!

[@flamebows5814]

Why does he lowkey sound like the actual Khan? the repeating of a word while struggling to find a new color lol ..we found the IMPOSTER!!!

[@rehnumachowdhury3629]

U r a legend😘

[@sylvester8004]

This is awesome

[@jakobtorel3165]

Thanks a lot !

[@ronasli]

Thank you🥲

[@roxyroller120]

So helpful

[@laura8397]

thank you khan academy for this information. ,

[@maramnasagain]

i didn't get the part of synthesis like from 23 pairs to 46 pairs? it's always 23 pairs i thought with the number of chromatids and not chromosomes duplicated. i also found in many french biology material that once a cell enters G1 it doesn't get back to G0 instead it's stuck in G1 in case of neurons for example. i wonder if that's true. other than this couple of remarks , i love this platform and i'm grateful that it exists. i study in french but i find it easy to understand you. merciiiii infiniment

[@psksl7]

Nice 🙂

[@mylesgoldman9219]

This is great

[@Ali-wl9tj]

You didn't mention the most important thing about cells division which is it how many times the one cell will dividing during the human life. and how long stay as a one cell particulary before dividing 😎

[@nirvana152]

Thank you :) I think there is a small mistake, the cell has 46 chromosomes in the nucleus, they come in 23 pairs and not 46 pairs !

[@shadowhunterrachel5732]

imene ben but he said after replication

[@rezaayoubi9147]

Exactly. Human cells have 46 chromosomes both before and after replication. The only thing that changes is that they become sister chromatids after they are replicated.

[@brightolonilua717]

You guys ammuse me with your knowledge but it is actually 2 pairs of 23 chrmosomes which becomes 46. An average adult has a total of 23 chromosomes whereas an embryo is started with 46 chromosomes

[@OtakuLuoluo]

@@michigan1085 still 23 PAIRS. Each pair just has 4 chromatids (2 chromatids per chromosome in each pair that are joined at a centromere so they look like 2 "x" side by side)

[@9a_17_ektachauhan7]

Daam right

[@faizzzo]

Thanx a lot brothr!

[@cartinemwanafunzi2584]

👍 👌 video but i have one question if the neurons stop dividing when they mature why are there older patients with brain tumors?

[@emiliolopez8796]

Nice video!!!!

[@hammedtukur]

Great

[@maariatalha4810]

😀thanks

[@hardeepko8efrc]

During the S phase, It's the number of chromatids that double not chromosomes.

[@adh_roshan]

Its chromosomes actually. But its the same thing. Like 2 chromatids make a chromosome right?

[@Its_BlackRock]

thx sir

[@shrivaishnaviv-1672]

awesome

[@sawalsawal7968]

You should keep it up (:

[@adama7926]

Thanks for this I have a test fore this in 10/23/2019

[@lvx_4eterna]

how did it go?

[@illuminateme8182]

Can anyone point me towards some independent cancer research publications? I've only found official publications from institutes of higher learning but I've never seen anyone actually independently work on this subject enough to correctly explain the science behind their research.

[@hrijewelraj4837]

Super

[@talha.tunahanergul4778]

Hi I am surian you mast proffesor

[@MsHelene2009]

most cells go through the Go phase. Some cells stay there permanently and others continue to the S phase but it's part of the cycle for all cells.

[@nahidabano1615]

NICE

[@kaylanicole7956]

love the video and explination..how long is the process...does this happen in seconds..minutes..hours..days...weeks ect. ? @khanacademymedicine

[@bernardoferreira8271]

since a cell's diameter measures 100 micrometers and a micrometer is 10^-6 of a meter... at 1:40 shouldn't it be 1/10 000 of the human size?

[@CarlosBenito28]

Neurons do divide, if you don't drink alcohol and if you don't eat carbohydrates. Read Dr David Perlmutter's Grain Brain

[@scienceblossom6197]

Does the S phase only happen to sex cells (gametes) or all cells experience it? The video explains "many" cells go in that direction but I thought it's only about sex cells. (Thanks superb clear explanation video!)

[@YouYou-sg6ll]

It occurs prior to mitosis and mitosis occurs in all cells

[@redeyedfairy]

how does the cell know that it needs to go into the next phase? why does the cycle not move backwards? how does the cell know?

[@goat1462]

there are different checkpoint during cell cycle where all the necessary stuff required for cell division check , if cell full all needs then it send to next step of cell division . also there are different type of protein , enzymes and other things which act as regulator during cell division . you should search for cell cycle regulation at google does that help?

[@lilacehakoun818]

thank you!

[@chandanaupreti5951]

Correction: the number of chromosomes does not double in S phase, that's just fundamentally wrong. In the S phase the DNA replicates itself and each chromosome splits into 2 sister chromatids but the no. of chromosomes remains the same.

[@asiandiana6257]

If chromosomes replicates itself, how the number of chromosomes do not get doubled? 🤔

[@dicknock3711]

@@asiandiana6257 When a chromosome is said to be "replicated" that doesn't mean it doubled in number, it means that the chromatid has been doubled. Look, a chromosome can either have 1 chromatid or 2 chromatids, during cell replication, chromatids double so that they form for us a chromosome consisting of 2 chromatids.

[@felmrngstr]

How about Cytokinesis? The cytoplasm division? Isn't it included in the cell cycle?

[@letscreatesomething6969]

Sir. As FROM THIS DEFINITION ;THE INTERPHASE IS THE INTERVAL BETWEEN TWO SUCCESSIVE DIVISIONS .🤔🤔🤔🤔🤔 Sir what are the names of these two successive divisions please let me know I am very confused

[@treasurexteumestv8145]

during mitosis, what is interphase doing?

[@pawansrivastava5846]

Cell phases is 1. Interphase 2. Growth cell 3. DNA 4. Meiosis 5. Mitosis 6. ?

[@SALTYCHOCOCAKE]

How do you know when a cell dose to the GNot Phase?

[@tayyabsohail2932]

How is inter and G1 both phases a place were cells spend most of the time?

[@randdnar7392]

interphase is the place were cells spend most of the time compared to M phase ...and G1 is the place were cells spend most of the time compared to S and G2 phases of interphase .

[@angelafarah7714]

Why can the cell in G0 back to G2? And what is the different inside the cell that in G0 and G1?

[@honeypatel1465]

I had paid a lot to my institute teacher to know what I can learn for absolutely free

[@Zetsuke4]

All of these are in IB Biology, while others study this in universities.. :(

[@Zetsuke4]

This is probably the most basic and core topics in Med University exams.

[@rahulrahul-lv6qi]

Zetsuke4 there's no way this stuff is ib for you. This is easy as shit.

[@Zetsuke4]

Rahul Bargujar we review it for like 15 minutes and it's a very little part of all the thingfs we have to know you idiot.

[@rahulrahul-lv6qi]

ha i'm the idiot

[@Me-to5zw]

Zetsuke4 I study this in high school.. I'm a senior

[@jkovenski]

Khan academy is so wordy.

[@mandalorian4620]

Dude, 5 feet = 2 meters hahaha For reference, 2 meters are about 6 ft 6 or 6 ft 7. I got a heart attack when you said the average person is 2 meters tall :D

[@nivedithapraisy6032]

even I got an attack when he said avg person is 2 meters coz I'm not even 1 meter and I thought... what the hell I'm not even a human or what?😂

[@aniyolki2595]

@@nivedithapraisy6032 1 meter is 3'4" or 100 centimeters... There's no way you're shorter than that.

[@Scientomics]

At 3:51 second its wrong from 23 pairs to 46 pairs after dna replication ok Even after dna replication its still 23 pairs but each chromosome or to be precise chromatin in every pairs has copy of dna.

[@languageandmana9255]

🙏🙏✨

[@gabrielagomes1447]

neurons do divide! Remember that.