What Are Cells? (The Cell Theory)

Summary

This video introduces the concept of cells and the cell theory. It explains that all living things are made of cells, which serve both structural and functional roles. The four main points of cell theory are discussed: all living things consist of one or more cells, cells carry out life processes, new cells arise from pre-existing cells, and cells contain hereditary material (DNA). The video also touches on the six characteristics of living things, emphasizing that cells are the smallest independent units of life capable of meeting all these characteristics.

Takeaways

• 🔬 Cells are the basic units of structure and function in all living organisms.
• 🌱 All living things, including plants, animals, bacteria, and fungi, are made up of cells.
• 🧱 Cells contribute to both the structure and function of living organisms, unlike bricks in a wall, which only serve a structural role.
• 🔄 New cells arise from pre-existing cells through the process of cell division.
• 🧬 Cells contain hereditary material, specifically DNA, which controls cell activities and is passed from one generation of cells to the next.
• 💡 Cells are the smallest independent units of life that can meet all the characteristics of living things.
• ⚙️ Cells perform life processes, such as taking in energy, responding to stimuli, reproducing, and growing.
• 🧪 Cells are complex and organized, able to maintain their identity, grow, and develop.
• 🦠 Eukaryotic cells contain membrane-bound organelles, while prokaryotic cells do not, and these organelles perform specific functions in the cell.
• 🧩 All cells have a basic structure, including a cell membrane (or plasma membrane) and cytoplasm.

Q & A

What is the primary definition of a cell according to the script?

Cells are the units of structure and function in living things. They are present in all living organisms, including plants, animals, bacteria, and fungi.

What are the four main points of the cell theory mentioned in the script?

The four main points of the cell theory are: 1) All living things are made of one or more cells. 2) Cells carry out the life processes of organisms. 3) Cells arise from pre-existing cells through cell division. 4) Cells contain hereditary material (DNA) that is passed on during cell division.

How do cells differ from bricks in a wall, as per the analogy in the script?

While both cells and bricks contribute to structure (like bricks in a wall), cells also perform functions. Cells carry out life processes, unlike bricks, which only serve structural purposes.

What does it mean when the script says 'cells arise from pre-existing cells'?

This means that new cells are formed through the process of cell division, where an existing cell divides to produce new cells.

What is hereditary material in cells, and why is it important?

Hereditary material refers to DNA, which contains the instructions for all cell activities and is passed on from one cell to the next during cell division.

What are the six characteristics of living things mentioned in the script?

The six characteristics of living things are: 1) They are complex and organized. 2) They take in energy. 3) They maintain their own identity. 4) They respond to stimuli. 5) They reproduce. 6) They grow and develop.

Why are cells considered the smallest independent units of life?

Cells are considered the smallest independent units of life because they can meet all six characteristics of living things. Anything smaller than a cell, such as the components inside it, cannot fulfill all these characteristics.

What is the cell membrane, and what role does it play in the cell?

The cell membrane, also called the plasma membrane, is the structure that encases the cell, separating its internal components from the outside environment and regulating what enters and leaves the cell.

What is cytoplasm, and where is it found?

Cytoplasm is the fluid inside the cell that fills the space within the cell membrane. It is where many cellular processes occur, and it supports the organelles within the cell.

What are membrane-bound organelles, and which type of cells contain them?

Membrane-bound organelles are specialized structures within eukaryotic cells that carry out specific functions, much like organs in the human body. Examples include the nucleus, mitochondria, and endoplasmic reticulum.

Outlines

00:00

🔬 Introduction to Cells and Cell Theory

The paragraph begins by introducing a fundamental question in biology: what are cells? It explains that cells are the units of structure and function in all living things, including plants, animals, bacteria, and fungi. Examples of different cell types are provided, such as nerve cells, red blood cells, and plant cells. The paragraph then highlights the four key points of the cell theory: (1) all living things are made of one or more cells, (2) cells contribute to both the structure and function of organisms, (3) new cells arise from pre-existing cells, and (4) cells contain hereditary material (DNA) that controls the cell’s activities and is passed on during cell division.

05:02

🧬 Characteristics of Living Things and Cells

This paragraph discusses the six characteristics of living things that cells meet, which makes them the smallest independent units of life. These characteristics include being complex and organized, taking in energy, maintaining identity, responding to stimuli, reproducing through cell division, and growing and developing. The paragraph emphasizes that while cells fulfill all six characteristics, any component smaller than a cell cannot meet all of them, thus reinforcing the concept that cells are the smallest independent unit of life.

Keywords

💡Cells

Cells are the basic units of structure and function in living organisms. In the video, they are described as the building blocks of life, just like bricks in a wall contribute to the structure of a building. All living things, such as plants, animals, and bacteria, are made of cells.

💡Cell Theory

The cell theory is a fundamental concept in biology that explains the properties of cells. The video outlines four key points: all living things are made of cells, cells are the basic units of structure and function, new cells arise from pre-existing cells, and cells contain hereditary material. These principles help explain how life is organized at the cellular level.

💡Hereditary Material

Hereditary material refers to the DNA found within cells, which contains the genetic information passed from one cell to another during cell division. In the video, this concept is introduced when discussing how cells arise from pre-existing cells and how DNA controls cellular functions.

💡Eukaryotic Cells

Eukaryotic cells are complex cells that have membrane-bound organelles, including a nucleus. The video mentions eukaryotic cells when discussing basic cell structures and highlights their importance in more complex organisms like plants and animals.

💡Prokaryotic Cells

Prokaryotic cells are simpler cells without a nucleus or other membrane-bound organelles. The video contrasts prokaryotic cells with eukaryotic cells, emphasizing the structural differences and providing a foundation for understanding cellular diversity across living organisms.

💡Cell Membrane

The cell membrane, also called the plasma membrane, surrounds the cell and controls the movement of substances in and out of it. The video describes the cell membrane as a crucial part of all cells, providing structure and protection while maintaining the cell’s internal environment.

💡Cytoplasm

Cytoplasm is the gel-like fluid inside the cell, where the organelles are suspended. In the video, it is mentioned as a shared feature of all cells, acting as the medium in which life processes occur and supporting the cell’s internal structure.

💡Organelles

Organelles are specialized structures within eukaryotic cells that perform specific functions, much like organs in the body. The video compares organelles to organs and explains how they contribute to the overall function of the cell, with an invitation to explore them in more detail in a separate video.

💡Cell Division

Cell division is the process by which a cell divides to form two new cells. The video introduces this concept when discussing how new cells arise from pre-existing cells, emphasizing the role of cell division in growth, reproduction, and the transmission of hereditary material.

💡Characteristics of Living Things

The characteristics of living things include complexity, energy intake, maintaining identity, response to stimuli, reproduction, and growth. The video explains that cells are the smallest units of life capable of exhibiting all six characteristics, which defines them as living entities.

Highlights

Cells are the basic units of structure and function in all living things.

Plants, animals, bacteria, and fungi are all made of cells.

Cells carry out life processes, contributing to both the structure and function of organisms.

Cell theory states that all living things are made of one or more cells.

New cells arise from pre-existing cells through cell division.

Cells contain hereditary material (DNA), which is passed from one cell to the next.

Cells are the smallest independent units of life, capable of performing all life functions.

Living organisms must exhibit complexity and organization, take in energy, maintain their identity, respond to stimuli, reproduce, grow, and develop.

Cells meet all six characteristics of living things.

Sub-cellular structures cannot perform all six characteristics of life, making cells the smallest units of life.

All cells have a basic structure consisting of a cell membrane and cytoplasm.

Eukaryotic cells contain membrane-bound organelles, which carry out specific functions.

The plasma membrane (or cell membrane) surrounds the cell and controls the movement of substances in and out.

The cytoplasm is the fluid inside the cell where cellular processes occur.

For more information, videos on cell structure and the differences between prokaryotic and eukaryotic cells are available.

Transcripts

what ourselves well that's one of the

very first questions you should be

asking as a biology student and that's

what we're going to look at today an

introduction to cells and something

called the cell theory so let's get

stuck into it so cells are units of

structure and function in living things

if it's a living thing it contains cells

plants animals bacteria fungi all

contain cells and are made of cells just

bring in a few different pictures here

of some different cells so for example

we've got a nerve cell some onion cells

red blood cells some other plant cells

here and just a couple of general

eukaryotic cells here so you can see

cells are everywhere if it's a living

thing that you're talking about it is

made of cells and as this point States

cells are the units of structure and

function in living things so let's have

a look at the cell theory so there's

four main points to the cell theory

number one is that all living things are

made of one or more cells and that's how

cells contribute to the structure of

living things

imagine a brick wall each of those

bricks is contributing to the overall

structure of that wall and each of those

bricks in this analogy could be like a

cell so I for example are made of

billions of cells just like this brick

wall is made of many many bricks

that's how cells contribute to the

structure of living things but remember

they also contribute to the function so

we can see here cells carry out the life

processes of organisms

living things living things organisms

different words meaning the same thing

cells carry out life processes of

organisms and that's how they contribute

to functions so that's where they differ

from bricks in a brick wall bricks in a

brick wall are purely carrying out a

structural role but cells also serve a

functional role inside of those cells

life processes are occurring and that's

why cells are structural and also

functional the next point stated in the

cell theory is that cells arise from

pre-existing cells meaning new cells

come from old cells through cell

division here's an example here of one

cell dividing into two new cells so

cells arise from pre-existing cells and

because of that the fourth point comes

about in that cells contain hereditary

material hereditary material means

material that is passed on from one cell

to the next

and the hereditary material we're

talking about is DNA which is a very

important molecule in cells there's a

big large image of DNA there obviously

it's been enlarged many many times

because if it was from this cell here

for example it's obviously much much

bigger but we find DNA inside of cells

and that DNA contains the information

and instructions that controls all of

the cell's activities and it's passed on

from one cell to the next that's why we

call it hereditary material so there the

four main points of the cell theory

cells are referred to as the smallest

independent units of life that means

they are the smallest possible thing

that can be classified as living to be

classified as living it needs to

meet all of the characteristics of

living things I'm going to show you six

characteristics of living things and

cells are the smallest unit of life that

can meet all six of those

characteristics the characteristics of

living things are that they are firstly

complex and organized they take in

energy they can maintain their own

identity so you can distinguish where

they begin and where they end they

respond to stimuli they're able to

reproduce which we've already seen when

we looked at cell division just before

and of course to be living they need to

be able to grow and develop

now again cells are the smallest

possible independent units of life so

they are able to meet all six of these

characteristics of living things but if

we went any smaller than a cell and

looked at something inside of a cell as

an example they would not be able to

meet these six characteristics and

that's why we say that cells are the

smallest independent units of life so to

finish off I've just brought back a

simple cell here because all cells have

a basic cell structure in my video on

cell structure you'll see more

information about each of the different

components inside of cells and there's

also a video about the difference

between prokaryotic and eukaryotic cells

so follow the links for both of those

but the basic cell structure and what

all cells have in common is around the

outside of the cell encasing the cell is

what we call the cell membrane so I'll

just put an arrow there pointing to this

cell membrane there's a label there it's

also sometimes referred to as the plasma

membrane to words with the same

meaning now remember with our cell here

this is a cell that's been we've taken a

cross-section so that means we've got a

three-dimensional cell that we've cut

across the middle and we're looking in

like so so the cell membrane is around

the outside and then inside just this

pink area here we have the fluid inside

of a cell we call that the cytoplasm and

that's what all cells have in common if

the cell is like this one and it is a

eukaryotic cell remember to check out

the video prokaryotic cells and

eukaryotic cells to see the difference

but in a eukaryotic cell we have these

things called

membrane bound organelles we call those

organelles they're smaller components

within the cell that carry out specific

functions very much like the organs in

our bodies and for more information on

those I want you to go and check out the

video called cell structure it's about

the organelles and I go through each one

of them and talk about their structure

and function so that's been this lesson

on the cell theory answering your

question what ourselves and hopefully

showing you a bit about them and why we

consider them to be the smallest

possible unit of life hope you've

enjoyed it it's been a pleasure as

always and we'll catch you next time