Cell cycle phases | Cells | MCAT | Khan Academy 

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

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

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.

LOOK OUT HARVARD I'M COMING FOR

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!!!

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

5 feet and 2m have a huge difference

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

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!!!

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

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

The way you explained this was pure love!

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

That synthesis phase was wrong...i guess because your chromosome number remains constant whereas your dna duplicates🤷

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

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

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.

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 !

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

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?

wait, 2meters tall? a person? I'm only 150cm tall....

Hi I am surian you mast proffesor

Average person’s height is a little less than 2 meters? I think you meant like 30 cm less

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

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

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?

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

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 😎

awesome man, have a look at my channel, let me know what you think, i've just started

5 feet is not 'about 2 metres' hahahaha. It's just over 1.5m ... 0:04

Khan academy is so wordy.

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.

Heyy...isn't the S phase wrong🤔..meaning to say ..the chromosome number Remains The Same and the DNA replicates???

I wanted to ask why you wrote 46 pairs of chromosomes in the S phase when the number of chromosomes in the S phase remains the same just the amount of DNA gets doubled. I am confused.

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.

The average person is little less than 2 meters tall?? No, 1.65 cm is average. A little less than 2 m is a tall person. Just throwing this there before I continue the video

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

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

How it can be 46 pairs chromosomes in S phase ?? Only amount of Dna doubles not chromosomes ..number

When someone said you can't explain 2 hours shit in just five minutes, this dear teacher said- you bet?

Hi, I am preparing for medical school. Anyone wanna be friends so we can group study?

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

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

I don't know why all the comments are full of mistake of 2m why dont you clear your concept rather than talking about mistake made by him😞😡😡

neurons do divide! Remember that.

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

Thank you. Gid bless this institution.

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

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.

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

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

2 METERS IS THE AVERAGE HEIGHT OF A HUMAN??? LeBron James height is 2 meters.

Medicine students do not have much time to listen unnecessary discussion please get quickly to the topic in your next videos.

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

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

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

thank you sooo sound and understandable!

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

Wait why In my book that making protein in (s period )not (g period )?! Now I’m confused

when ur lowkey learning this as a freshman in bio honors lol

You probably should have said "diameter" instead of "size" at 43 seconds

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

You should keep it up (:

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

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

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!)

oh my god this is so much easier to understand 😭

ap bio final tomorrow and im ready to fail ha

What phase of chromatin can I see 30 nm fiber in the cell cycle?

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

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

is it bad that i giggled when he said "ur mom"

An avarage persen is not "littleless than 2m tall"

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

A 2-meter female is pretty hard to find.

A two meter "average" human is very tall !!! 6'8'' .......

Who else is here due to COVID canceling their classes?

during mitosis, what is interphase doing?

Most confusing diagram ive ever seen...

Doesnt M-Phase consist of mitosis and cytokinesis? not just mitosis?

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

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

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

I don't get how he converted to get 1/1,000,000

Avarage person 2 m Me: don’t cry, don’t cry donttt

2 metres is 6 and a half foot ... not "just over 5ft"

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

The mitotic phase and mitosis are not the same, my friend.

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

You have skipped cytokinesis😔

*tinder logic* is a little over 5 feet or about 2 meters tall

it's called the mitotic phase, mitosis is just the nucleus

i have two books both explaining completely different cell cycle , wtf to do know

Sal said a little LESS than 2m and not exactly 2m.

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.

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

5ft isnt 2m and an average person isnt 2m height.

you sound like sal khan a little bit.

did he say 5 feet is 2 m bro i WISH

in what world is the average human 2 meters tall