Cell Cycle | Biology MCAT

Summary

This educational video delves into the cell cycle, distinguishing between prokaryotes and eukaryotes, and detailing the three categories of mammals: placental, marsupial, and monotreme. It explores DNA structure, the nucleus's role, and the significance of chromosomes and genes. The script explains the difference between somatic and germ cells, the process of DNA replication, and the transcription and translation into proteins. It breaks down the cell cycle into phases: G0, G1, S, G2, and M, highlighting the importance of each phase and the types of cells (permanent, stable, and labile). The video also touches on the clinical implications of the cell cycle, such as the effects of chemotherapy on rapidly dividing cells.

Takeaways

• 🌟 Organisms are categorized into prokaryotes and eukaryotes, with eukaryotes further divided into placental mammals, marsupials, and monotremes.
• 🧬 DNA, found in the nucleus, is a double helix composed of a sugar backbone, phosphate group, and nitrogenous bases.
• 🔬 The human body is organized into systems, organs, tissues, and cells, each containing a nucleus with 46 chromosomes in somatic cells and 23 in germ cells.
• 🧬 Chromosomes contain genes, segments of DNA, which are essential for genetic inheritance.
• 👶 Determining sex involves analyzing the presence of XX (female) or XY (male) chromosomes.
• 🧬 Germ cells are either 22+X (ovum) or 22+Y (sperm), combining to form either a male (XY) or female (XX).
• 📚 Transcription is the process of DNA being made into RNA, and translation is the process of RNA being made into proteins.
• 🔄 The cell cycle is divided into interphase (G0, G1, S, G2) and the M phase (mitosis), with interphase including growth, DNA replication, and preparation for mitosis.
• 🌱 G0 is a resting phase where cells are not dividing, while G1, S, and G2 are active phases of the cell cycle leading to cell division.
• 💊 Chemotherapy drugs work by inhibiting the cell cycle, affecting rapidly dividing cells, which can lead to side effects like hair loss and gastrointestinal issues.

Q & A

What are the two main categories of living organisms based on their cellular structure?

The two main categories of living organisms are prokaryotes and eukaryotes.

How are eukaryotes subdivided in terms of mammals?

Eukaryotes are subdivided into three categories: placental, marsupial, and monotreme.

What is the difference between a placental and a marsupial in terms of fetal development?

In placental mammals, the fetus develops inside the mother's uterus until a late stage, whereas in marsupials, the early fetus develops in the uterus and then moves to a pouch (marsupium) where it continues to develop.

What is the unique feature of monotreme reproduction?

Monotremes are unique because they lay eggs, and the young hatch from the eggs with underdeveloped features, often entering a pouch for further development.

What is the role of the nucleus in a cell?

The nucleus serves as the 'house' of the cell, containing the DNA, which is essential for the cell's genetic information and functions.

How is the DNA structure described in the script?

DNA is described as a double helix made up of a sugar backbone, phosphate group, and nitrogenous bases.

What are the two types of cells in the human body, and how do their chromosome numbers differ?

The two types of cells in the human body are somatic cells and germ cells. Somatic cells have 46 chromosomes (diploid), while germ cells have 23 chromosomes (haploid).

What is the significance of the Barr body in determining the sex of an individual?

The Barr body is an inactive X chromosome found in females. The presence of a Barr body indicates a female, while the absence indicates a male, as males have only one active X chromosome.

What is the process called when DNA is transcribed into RNA, and what is the subsequent process when RNA is made into proteins?

The process of transcribing DNA into RNA is called transcription, and the process of making proteins from RNA is called translation.

What are the phases of the cell cycle, and what do the letters G, S, and M stand for?

The phases of the cell cycle are G0, G1, S, G2, and M. G stands for growth, S stands for synthesis (DNA replication), and M stands for mitosis (cell division).

How do chemotherapeutic agents affect cancer cells and why might patients undergoing chemotherapy lose their hair?

Chemotherapeutic agents are replication inhibitors that target rapidly dividing cells. They affect cancer cells by preventing them from dividing, which is beneficial. However, the side effect is that other rapidly dividing cells, like hair follicle cells, are also affected, leading to hair loss.

What are the three types of cells mentioned in the script, and how do they differ in terms of cell division?

The three types of cells mentioned are permanent, stable, and labile cells. Permanent cells remain in G0 and do not divide, like neurons. Stable cells are quiescent in G0 but can divide when necessary, like hepatocytes. Labile cells are constantly dividing with little to no rest in G0, like hair follicle cells and bone marrow stem cells.

Outlines

00:00

🧬 Introduction to the Cell Cycle and Eukaryotes

The script begins with an introduction to the cell cycle, highlighting the distinction between prokaryotes and eukaryotes, with a focus on eukaryotes such as mammals. It delves into the classification of mammals into three categories: placental, marsupial, and monotreme, with descriptions of their reproductive and developmental characteristics. The script then transitions into a discussion about the nucleus and DNA, explaining the structure of DNA, its role in the nucleus, and the significance of chromosomes and genes. It also touches on the difference between somatic and germ cells, the process of determining sex through genetic testing, and the presence of a bar body in female cells. The paragraph concludes with an overview of the processes of transcription and translation, emphasizing the importance of proteins in the body's functions.

05:01

🔬 Understanding the Cell Cycle Phases and Cell Types

This paragraph delves deeper into the cell cycle, dividing it into the interphase and M phase. It explains the stages of interphase, including G0 (resting phase), G1 (growth phase), S (synthesis phase for DNA replication), and G2 (preparation for mitosis). The paragraph clarifies the purpose of each phase and the processes that occur within them. It also introduces the concept of permanent, stable, and labile cells, providing examples for each type and explaining their division behavior. The paragraph further discusses the M phase of the cell cycle, which includes prophase, metaphase, anaphase, and telophase, and touches on the clinical implications of cell cycle understanding in chemotherapy and the effects of chemotherapeutic agents on rapidly dividing cells.

10:02

🛑 Clinical Implications of the Cell Cycle and Pharmacology

The final paragraph focuses on the clinical applications of the cell cycle, particularly in the context of chemotherapy. It discusses the objectives and mechanisms of action of chemotherapeutic drugs, which are designed to inhibit the cell cycle and prevent cell division, thereby affecting rapidly dividing cancer cells. The paragraph also addresses the side effects of chemotherapy, such as hair loss and gastrointestinal issues, which are a result of the drugs' impact on normal, rapidly dividing cells in the body. The script concludes with a reminder of the importance of understanding these biological concepts in a clinical setting and invites viewers to follow the speaker's website and social media for more educational content.

Keywords

💡Prokaryotes

Prokaryotes are unicellular organisms that lack a nucleus and membrane-bound organelles. In the video, they are mentioned in contrast to eukaryotes, which include more complex organisms like mammals. The distinction is important for understanding the basic biological classification and the differences in cellular structure.

💡Eukaryotes

Eukaryotes are organisms whose cells have a nucleus enclosed within membranes. They include a vast array of life forms, from plants and animals to fungi and protists. The video discusses eukaryotes in the context of their cellular organization and how they are subdivided into categories like placental mammals, marsupials, and monotremes.

💡Placental

Placental refers to a type of mammal where the fetus develops inside the mother's body and is nourished through a placenta. The video uses this term to describe one of the categories of eukaryotes, specifically mammals, and contrasts it with marsupials and monotremes, highlighting the different reproductive strategies among mammals.

💡Marsupials

Marsupials are mammals that give birth to relatively undeveloped young, which then continue to develop outside the womb, often in a pouch. The video mentions marsupials as a category of eukaryotes, specifically mammals, and uses the example of kangaroos to illustrate the unique characteristics of this group.

💡Monotremes

Monotremes are a unique group of mammals that lay eggs instead of giving birth to live young. The video discusses monotremes in the context of their reproductive strategy, mentioning that they have a cloaca, a single opening for the urinary, intestinal, and reproductive systems.

💡DNA

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms. In the video, DNA is described as being housed in the nucleus of eukaryotic cells and is essential for understanding the genetic basis of life.

💡Chromosomes

Chromosomes are structures within cells that contain DNA. They are made up of segments called genes. The video explains that human somatic cells have 46 chromosomes, which are divided into 23 pairs, and that these chromosomes play a crucial role in cell division and the transmission of genetic information.

💡Cell Cycle

The cell cycle is the series of events that take place in a cell, leading to its division and duplication. The video discusses the cell cycle in detail, explaining its phases (G0, G1, S, G2, M) and the processes that occur during each phase, such as DNA replication and cell division.

💡Germ Cells

Germ cells are the reproductive cells in organisms that undergo meiosis to produce gametes. The video distinguishes germ cells from somatic cells, noting that germ cells have 23 chromosomes (haploid) compared to the 46 chromosomes (diploid) in somatic cells. This distinction is crucial for understanding the process of sexual reproduction.

💡Transcription

Transcription is the process by which the genetic information in DNA is copied into RNA. The video mentions transcription in the context of gene expression, explaining that it is the first step in the production of proteins, which are essential for the functioning of all living cells.

💡Translation

Translation is the process by which the information in RNA is used to synthesize proteins. The video emphasizes the importance of translation in the context of protein synthesis, noting that all active components in the body, such as enzymes and receptors, are proteins.

Highlights

Introduction to the cell cycle, a fundamental concept in biology.

Differentiation between prokaryotes and eukaryotes, with a focus on eukaryotes including mammals.

Subdivision of mammals into three categories: placental, marsupial, and monotreme.

Explanation of the nucleus as the 'house of DNA' and its role in cell structure.

Description of DNA structure as a double helix composed of sugar, phosphate, and nitrogenous bases.

The significance of chromosomes and genes within the nucleus and their role in heredity.

Difference between somatic and germ cells in terms of chromosome count and function.

The process of sex determination in humans through the examination of XX or XY chromosomes.

The concept of transcription and translation from DNA to RNA and then to proteins.

Importance of proteins in all active biological processes within the body.

Division of the cell cycle into interphase (G0, G1, S, G2) and the M phase (mitosis).

Detailed explanation of the G1 phase, including cell growth and protein production.

The role of the S phase in DNA replication and formation of sister chromatids.

G2 phase's function in preparing the cell for mitosis, including mismatch repair and cell growth.

M phase of the cell cycle involving prophase, metaphase, anaphase, and telophase.

Types of cells based on their division cycle: permanent, stable, and labile cells.

Clinical implications of the cell cycle, including the effects of chemotherapy on rapidly dividing cells.

Explanation of how chemotherapeutic agents work as replication inhibitors affecting cancer cells and normal cells.

Common side effects of chemotherapy, such as hair loss and gastrointestinal issues.

Upcoming discussion on cell cycle checkpoints in the next video.

Transcripts

hey guys it's médicos whisper friction

elsewhere medicine makes perfect sense

let's continue our biology playlist and

they'll talk about an introduction to

the cell cycle so let's get started we

divide living organisms into prokaryotes

and eukaryotes eukaryotes include

bazillion things including mammals also

known as mammalian and they are

subdivided to three categories the first

one is Pleasant area

the second was is the marsupial yeah and

the third one is the Monod Shri Mata

meaning one whole which sounds slightly

inappropriate for a biology lecture

let's talk about Pleasant alien the

fetus is scared inside theatres of its

mother until a late stage of development

example here is humans marsupial Ian's

early the fetus is in the eros late the

fetus is carried in this pouch called

dimmer Suqian how about the monotreme

otter they have the one hold the one

hole here is that cloaca if you do not

know what the cloaca is there is no hope

for you in one of my previous videos in

this playlist called biology MCAT we

have talked about the DNA which is in

the nucleus as you know the DNA is a

double helix made up a sugar backbone

phosphate group and a nitrogenous base

also we have talked about the nucleus

before the nucleus is the house of the

DNA if you take your human body it has

many systems if you take one system it

has many organs if you take one organ it

has many tissues if you take one tissue

it has many cell if you dissect one cell

you will find a nucleus if you go deeper

into the nucleus you will find about 46

chromosomes if here if we are talking

about a somatic cell each chromosome has

segments these segments are called genes

each genes is if you just like unwrapped

them you'll find heterochromatin like

this and then you'll find this you

chromatin as we have mentioned before

and then this you chromatin has the

famous double helix which we call the

DNA the deoxyribonucleic acid when one

cell divides into

two cells you know what happens yes the

DNA is being divided into two copies so

that each cell of the new cell will have

an equal amount of the DNA as the parent

cell human cells are divided into

somatic cells and germ cells most of the

cells in your body are somatic cells

they have 46 chromosomes each we call

this deployed dye means 2 2 times 23

happens to be 46 at least where I grew

up but the germ cells have only 23

chromosomes we call them haploid just

one so 23 that's why we call those n but

those ones 2 n which means deployed if

you would like to determine the sex of

the subject here is what you do easy

open your mouth sweetheart and you

introduce a nice thin swab you take a

sample from the buccal mucosa and you

send it to the lab if you see 44 X X

female 44 XY male thank you so much

sometimes they do it by something called

the bar body what the flip is a bar

buddy here is the rule if you have 2x

one of them will be active one of them

will be inactive the inactive is the bar

body how about if I'm a boy and I have

only one X since you only have one X it

has to be active because X is essential

for life therefore you have no inactive

X therefore you do not have a bar body

so if you see a bar body female if you

see no bar body male thank you so much

the germ cells are different

you're either 22 plus X which happens to

be 23 in total and this is the nice ovum

and the sperm is different here look at

this 22 plus y 22 plus X when your

parents were having fun by the way if

they had sex

3 seconds earlier or 3 seconds later you

wouldn't be here right now watching

YouTube so at least be grateful if this

ovum combines with the sperm to 2 plus y

this will be 44 plus X Y this is a male

that's me 22 plus X

and if it combines with this ovum you

get 44 plus X X that's a beautiful girl

look at you if you have been with me for

a while you know that when we take DNA

template and we make it into RNA this

process is called transcription when we

take the same RNA and make it into

proteins this is called translation

everything in your body everything

active in your body is protein if it's

active its protein take it to the bank

enzymes are active they are freaking

proteins channels are active they're

freakin proteins receptors are active

they are dead gum proteins pumps are

active they are proteins now let's talk

about the cell cycle which happens to be

today's topic we divide the cell cycle

into the interface and the M phase so

here is the M phase right here

everything else is a freaking interface

the interface includes g0 g1 s and g2 G

stands for growth S stands for synthesis

and M stands for mitosis cell cycle g0

g1 s g2 m thank you so much M is divided

into Pro meta ANATEL oj1 is the growth

and this is preparing for the S let's

talk about the g1 we start with

cycling's we stimulate them and then

they become cycling D kindnesses and

then transcription translation we end up

with proteins such as the enzymes the

cell grows in size that's why we call it

growth increase energy and protein

production thank you so much and

increase organelle formation that's why

we call it growth so this is the g1

thank you so much

what is the g0 the g0 is resting if the

cell is not dividing the cell is resting

in the zero phase in the cell decides to

divide it will leave the g0 phase enter

into the g1 phase s g2 M thank you so

much I've replicated successfully and

now instead of having one cell we have

two cells we are done with g0 and g1

suck about s s s for synthesis what do

you mean by synthesis I mean DNA

replication what do you mean by DNA

replication instead of having the single

chromatid called chromosome now we have

double or sister chromatids also known

as chromosome this is called chromosome

this is called chroma I mean what else

are you going to stitute to call it it's

still a chromosome we are done with s

thank you so much this talk about G 2 G

2 is the same freaking thing G 2 you

have the indu nucleus and this will help

us with the mismatch repair what does

that mean we repair the mismatch no duh

the cell increases in size and increased

energy and protein production do not get

confused G 2 is preparing for the

ultimate phase the M phase the mitosis

phase which is subdivide into prophase

metaphase anaphase and telophase I have

a video on my channel called cell types

we have talked about three cell types

permanent stable and labile stable is

the same thing as quietened what is a

permanent cell a permanent cell is a

cell that just remains in g0 at just

permanent it's not gonna divide it's

over like your neuron or nerve cell it's

like once you mature your nerve cell do

not divide ya your neuroglia or

neuroglial cells divide but they are

supportive cells they are not the actual

freaking neurons the neurons themselves

do not divide as far as we know that was

the permanent cell how about the stable

cell the stable cell is quiescent it's

here in g0 most of the time but

sometimes it decides to divide so it

leaves the g0 jumps to the g1 s g2 M

thank you so much now we have two cells

give me an example of a cell that's

stable the hepatocyte the liver cell

normally your liver does not divide but

let's say that a surgeon cut 1/4 of your

liver

oh now the lever Oh danger danger we

need to divide guys we need to divide

leave the T 0 jump into the g1 s g2 m

and before you know it your liver will

be complete again this 1/4 of your liver

will have been regenerated ok medicos is

how about the third type the labile cell

the labile cell is freakin crazy

it's always dividing g1 s g2 and it

barely stops at the g0 it's always

dividing always divine give me an

example your hair cell yeah like your

hair yeah your hair follicle always

regenerate when you shave you're like

your hair you always get it back quickly

that's a freaking labile cell want

another one how about your bone marrow

stem cells they are always vomiting out

red blood cells white blood cells and

platelets in millions and thousands and

ten thousands we have talked about this

before so I'm not gonna repeat myself

cell cycle is g0 g1 s g2 em what happens

in mm4 mitosis so karyokinesis and

cytokinesis now let me give you some

nuggets of Medicine DNA replication

takes place exclusively in the S phase

yes as for synthesis cancer is nothing

but uncontrolled replication due to

errors and/or mutations chemotherapeutic

agents are nothing but replication

inhibitors also some antibacterial and

antivirals inhibit the replication of

the bacteria and/or the virus

respectively I'm not concerned with

theories I'm actually more concerned

with flesh-and-blood patients so let's

actually take it clinical let's talk

about pharmacology maybe chemotherapy

what is the objective they are

anti-cancer drugs okay what's the

mechanism of action they inhibit the

cell cycle

so the interfere with cell division is

not going to happen

therefore rapidly dividing cells are the

one most affected I don't understand

okay why do you think people who have

cancer lose their hair

most people say oh it's because of the

cancer shut up it's not because of the

cancer it's because of the chemotherapy

what do you mean I mean the chemotherapy

is an anti-cancer drug what do you mean

I mean they do this like

chemotherapeutic drug inhibits the cell

cycle interferes with so division so of

good news kind of bad news what are the

good news the cancer cells won't be able

to divide and eventually they will

yah-hoo wonderful but there are no

solutions in life there are only

trade-offs as dr. Thomas soul said the

cons your own cells won't be able to

divide eventually your cells will die

and the rapidly dividing cells of yours

are the most affected

what are those rapidly dividing so hair

cells GI cells that's why with any

chemotherapeutic agent you're probably

are going to lose your hair and you'll

get diarrhea because we are sloughing

off the epithelium of your GI tract this

is medicine as it should be not your

fake biology professor in the next video

we'll talk about checkpoints of the cell

cycle so please save this playlist

called biology here is my website you

can go to my website to download these

biology lectures until this lecture they

are free they are PDFs they are the

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I'm honored as always be safe stay happy

and study hard

this is medicos is perfection Ellis or

medicine makes perfect sense