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Lesson 4 Cells

Site: MoodleHUB.ca 🍁
Course: Science 10 [5 cr] - AB Ed copy 1
Book: Lesson 4 Cells
Printed by: Guest user
Date: Sunday, 7 September 2025, 6:46 PM

Table of contents

  Introduction


How do single-celled organisms carry out life functions?

AS2.1 Single-celled organism called Amoeba
How single-celled organisms carry out life functions is an excellent question and one that scientists have been studying for years. Just when we think we know everything there is to know about a cell, we find a new function or a new type of cell to study. Cells are fascinating structures and scientists are constantly amazed by them.

In this section, we will look at the different structures inside of a cell (called organelles) and the functions they perform. We will also look at the differences between plant and animal cells, as well as the reason behind the size of cells. Then we will discuss how this knowledge has impacted society.

  Targets


By the end of this section, you will be able to

AS2.2 Paramecium and the food it has eaten (coloured)
AS2.3 Plant vs. animal cell
AS2.4 Diagram of the cell Membrane
© CNX OpenStax, via Wikimedia Commons
AS2.5 Relative cell sizes
AS2. 6 Medical research


  1. describe the cell as an open system
  1. identify the structures and functions in plant and animal cells and the difference between those cells
  1. describe the role of the cell membrane in moving particles into and out of the cell and understand the different kinds of passive transport and active transport
  1. describe cell size and shape as they relate to the surface area to volume ratio and explain how that ratio limits cell size
  1. identify how microscopic research and knowledge about the cell membrane has affected society


  Introduction

What are the different parts of a cell?



A4.1 Some organelles we will study
Single-celled organisms exchange gases, eat, and create waste, just like larger, multicellular organisms, such as humans. But how do they do this? They don’t have a stomach or a mouth like humans do. They also don’t have lungs or a bladder, so how can they perform these functions? The answer lies in the structures found inside a cell called organelles.

By the end of this lesson, you will be able to name the general structures within a cell and explain their functions. This is not an inclusive list of all the structures that can be found in a cell, but it does contain the ones that are seen in most cells. You will also look at cells under a microscope in order to see the different structures in real life.

  Did You Know?
A4.2 Human organs

The structures inside of a cell are called organelles because they have similar functions to our organs. They help the cell perform life functions, so they are like small organs inside the cell.

  Targets

By the end of this lesson, you will be able to
  • describe the cell as a functioning open system that gains nutrients, removes waste, and exchanges matter and energy with its environment
  • identify the structure and function of the cell membrane, nucleus, lysosome, vacuole, mitochondrion, endoplasmic reticulum, Golgi apparatus, ribosome, chloroplast, and cell wall (where present) of plant and animal cells
  • prepare a wet mount for a microscope

  Watch This


Studying Cells


Watch this video for an introduction to plant and animal cells, as well as some of the organelles found within them. https://adlc.wistia.com/medias/6zd2bwuh1k
 

  Cells Are an Open System

There are two types of systems we discuss in biology: an open system and a closed system.



A4.3 Deer gaining nutrients through eating

  Did You Know?



A4.5 A Blue Thermos
 

There is a third kind of system called an isolated system. An isolated system does not exchange energy or matter with its environment. A great example of an isolated system is a thermos. When the lid is on a thermos, it does not exchange matter or energy with its surroundings. It is not a perfectly isolated system, as eventually the energy will leave the thermos and the contents inside will get cold—but it takes a very long time for this to happen!
An open system is one that is open to its environment. This means it gains nutrients from and exchanges energy and matter with the surrounding environment. Most animals are open systems since they eat what’s around them (gaining nutrients), get rid of waste, and decompose when they die (exchanging energy and matter).

A closed system is one that does not interact with its environment, except to exchange energy. One such example is Earth. Earth exchanges energy with space in the form of the sun’s rays. The materials of Earth cycle around the different layers of the earth, but most are rarely exchanged with space.

Cells are considered to be an open system because they are constantly interacting with the environment surrounding them. Just like an animal, they eat what’s around them, they get rid of waste, and they decompose when they die. Through this cycle, they are exchanging energy with their surrounding environment as well.

A4.4 Earth from space

  Read This

Please read pages 266 to 267 (not including Table C2.1) in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the definition of an open system and how a cell meets that definition. Remember, if you have any questions or you do not understand something, ask your teacher!

  Practice Questions


Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. What is the difference between an open system and a closed system?
An open system interacts with its environment to exchange energy and matter, excrete waste, and gain nutrients. A closed system does not interact with its environment, except to exchange energy.

  1. Provide an example of why a cell is an open system.
Any of the following are correct. You may think of other examples as well. Cells find food in their environment, gaining nutrients. Cells send their waste into the environment. Cells decompose, providing food and energy to the environment, exchanging both energy and matter.

  Parts of an Animal Cell

The different structures within a cell are called organelles.


 Each organelle has a specialized function that helps cells carry out the processes of life. An animal cell contains 10 organelles you need to know.

 

A4.6 Labelled diagram of an animal cell
 


A4.7 Cell Membrane Structure
This is a protective barrier around the cell that separates the inside of the cell from its environment. Similar to the shell of an egg, this protective barrier makes sure that the cell is safe. It allows materials that are needed to enter the cell, and it allows waste products to leave the cell. The cell membrane keeps out materials that are not needed or that may harm the cell. It also helps cells communicate with each other and recognize each other and other molecules.


A4.8 Cytoplasm is found within the cell membranes.
The cytoplasm is not technically an organelle but rather the substance all the organelles and nutrients are suspended in. All the “empty” spaces in a cell are actually the cytoplasm, and it is held in a general shape by the cell membrane. Cytoplasm has a jelly-like texture that the other organelles can move around in (similar to water in a fish tank).

  Digging Deeper

Organelles do not float freely around in the cytoplasm. The cytoplasm contains a network of strong tubes and strings that hold all the organelles in place or move them where they need to go. This network is called the cytoskeleton because it has a similar function to our skeleton.

Learn More

A4.9 Image of cancer cell, cytoskeleton in purple


A4.10 The Nucleus surrounded by the nuclear envelope
The nucleus is the organelle that contains DNA and tells the rest of the cell and its organelles what to do. It is like the manager of a store or the brain of an animal. It is surrounded by a barrier called the nuclear envelope that acts in a similar way to the cell membrane. It allows needed particles into the nucleus but keeps out unwanted particles.


A4.11 A Lysosome
Lysosomes are sacs that are surrounded by a membrane. This is where the food the cell eats gets broken down into nutrients, similar to our digestive system’s function. They can also help with the defence of the cell, as they can digest molecules that are not supposed to be in the cell, such as invading bacteria. Lysosomes will also break down organelles that are broken or are not needed anymore.

  Digging Deeper

Lysosomes play a part in cell death as well. They will break open and digest the cell they are housed in. This is called apoptosis and it occurs constantly in our bodies. The most common reason for this is controlling the number of cells present, and getting rid of cells that have something wrong. https://quick.adlc.ca/lysosomes

Learn More

© National institute on alcohol abuse and alcoholism, via Wikimedia Commons
A4.12 Necrosis vs Apoptosis


A4.13 Onion cells with blue vacuoles
Vacuoles are also called vesicles, depending on the function they are performing. These are sacs or pockets of cytoplasm surrounded by their own membrane within the cell. Vacuoles are used for storage of things like nutrients, water, fats, or needed materials; while vesicles are used to transport these around the cell. Plant cells use vacuoles to control the amount of water within the cell.

A4.14 A mitochondrion
Mitochondria are organelles that look a lot like sticks or rods. They are long and thin. This is where nutrients are converted into energy for the cell to use through a process called cellular respiration. Mitochondria have an inner and outer membrane to assist in cellular respiration

  Did You Know?

Mitochondria have their own set of DNA (mtDNA) that is passed down from mother to child. It is thought that mitochondria were once single-celled organisms that were eaten by larger cells. They evolved to become part of the larger cell. https://quick.adlc.ca/mitochondria

Learn More

A4.15 Mothers pass mtDNA to their children

A4.16 The endoplasmic reticulum
The endoplasmic reticulum is a series of small tubes that extend from the nuclear envelope that are used to move materials from the nucleus around the cell. There are two kinds of endoplasmic reticulum: the rough endoplasmic reticulum and the smooth endoplasmic reticulum.

The rough endoplasmic reticulum has ribosomes attached to it. This version of the endoplasmic reticulum is used for protein synthesis. The nucleus makes copies of sections of DNA called messenger RNA that then pass through the nuclear envelope into the rough endoplasmic reticulum where they are read like a recipe to make proteins.

The smooth endoplasmic reticulum does not contain ribosomes and helps the cell create lipids (fats and oils).

Within both the rough and smooth endoplasmic reticulum, the products made are then packaged into vesicles and transported to the rest of the cell, usually to the cell membrane or the Golgi apparatus.

A4.17 A ribosome
Ribosomes are tiny particles that can be attached to the rough endoplasmic reticulum or that are floating freely in the cytoplasm. This is the place where the messenger RNA is read to produce proteins.

A4.18 The Golgi apparatus
The Golgi apparatus receives the materials made in the endoplasmic reticulum and processes them. This means the Golgi finishes the materials off so they are fully functional. It then sorts and repackages the materials into vesicles to be sent to the rest of the cell or the cell membrane. It is made up of flat, disc-shaped sacs.

  Read This

Please read pages 267 to 270 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the different organelles we have covered and their functions. Remember, if you have any questions or you do not understand something, ask your teacher!

  Practice Questions


Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. Draw your own diagram of an animal cell. Label each of the 10 structures described in the lesson.

A4.6 Labelled diagram of an animal cell
 

  1. Create a diagram or write a short paragraph that shows how the organelles are connected to each other.    
Your answer should be a variation of the following: You can get more detailed than this. (You can also start with the cell membrane allowing materials to enter the cell.) The nucleus releases messenger RNA to the rough endoplasmic reticulum where ribosomes create proteins using energy from the mitochondria. The mitochondria produce energy from the nutrients that are digested in the lysosomes. The proteins that are made in the rough endoplasmic reticulum are then packed into vesicles or stored in vacuoles. The vesicles travel through the cytoplasm to the Golgi apparatus where the proteins are processed and repackaged into the vesicles. These vesicles then travel through the cytoplasm to other parts of the cell or to the cell membrane to be released outside of the cell.

  Parts of a Plant Cell

Plant cells have two extra organelles that animal cells do not.


The extra organelles plants have are important to how plants get their food, as they perform photosynthesis rather than eating other organisms.

 

A4.19 Labeled plant cell
 


A4.20 Chloroplasts in a moss leaf cell
The chloroplast is where the process of photosynthesis occurs. Photosynthesis produces the glucose the mitochondria use to make energy. Chloroplasts contain chlorophyll, which produces a green substance. This is what makes most plant leaves green!

  Digging Deeper


© NOAA MESA Project, via Wikimedia Commons
A4.22 A phytoplankton
Phytoplankton is a unique class of organisms. They can be a variety of different kinds of organisms (bacteria, protists, or plants), but they can all photosynthesize.

Learn More

  Did You Know?


A4.21 Green leaves

Plants are green because chloroplasts absorb the other colours of light. The green light is reflected off the chloroplasts, so that is the colour we see.


A4.23 Plant cell with cell wall
This is a hard frame around the cell that holds it in a specific shape. It provides strength and support to the cells and to the plant as a whole.


  Read This

Please read pages 267 to 270 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the two organelles unique to plants that we have covered and their function. Remember, if you have any questions or you do not understand something, ask your teacher!

  Watch This!

Introduction to Cells: The Grand Cell Tour © YouTube Amoeba Sisters  


This video will take you on a virtual tour of the cell and its organelles. It will go through all the organelles we have discussed. This video discusses prokaryotes (do not have a nucleus) vs. eukaryotes (have a nucleus). In this course, we focus on eukaryotes.


  Practice Questions


Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. Draw a diagram of a plant cell and label the 11 organelles that were discussed.


A4.19 Labeled plant cell
 

  1. Add these two organelles to your short paragraph or diagram from the previous page that shows how all the organelles are connected.    
Your answer should be a variation of the following. You can get more detailed than this. (You can also start with the cell membrane allowing materials to enter the cell.) The nucleus releases messenger RNA to the rough endoplasmic reticulum where ribosomes create proteins using energy from the mitochondria. The mitochondria produce energy from the nutrients that are digested in the lysosomes. The chloroplasts produce the food that is then digested and used in the mitochondria.

The proteins that are made in the rough endoplasmic reticulum are then packed into vesicles or stored in vacuoles. The vesicles travel through the cytoplasm to the Golgi apparatus where the proteins are processed and repackaged into the vesicles. These vesicles then travel through the cytoplasm to other parts of the cell or to the cell membrane to be released outside of the cell through the cell wall.

  Watch This

Studying Cell Preparation

https://adlc.wistia.com/medias/pd7cjlek96


This video will show you how to prepare a slide for viewing under a microscope, from sample collection to the preparation of a wet mount. There will be questions on this process on your assessments, so make sure you pay close attention and take notes!
 

  Read This

Please read page 480 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the steps involved in creating a wet mount and staining a specimen. Remember, if you have any questions or you do not understand something, ask your teacher!

  Virtual Lab


Microscope Lab - Cell Structure and Function


Background Information:

This lab will let you see the organelles we have discussed in a real-life setting. Some organelles are too small to be seen with a compound light microscope, so we will be focusing on the nucleus, cell membrane, cell wall, cytoplasm, chloroplasts, and vacuoles. You may have to look at different cells on the slide to see all the parts.

If you need a refresher on how to use the virtual microscope, please review Exercise 1 under Lab 1.  This microscope has an ocular lens magnification of 10x.


  1. Click on the play icon to open the virtual lab. Print students can access the Virtual Microscope in the Online Resources for Print Students section of their online course.
  2. Click on Exercise 2 under Lab 1.
  3. Click on the procedures tab on the right side of your screen to open the procedures.
  4. Follow the directions found in the procedures. You will need to complete both procedures found in this lab. Remember, finding these tiny structures can take time. Some are very difficult to see, so try not to get frustrated! It is OK if you cannot find a structure or do not understand what you are seeing. Diagrams and real cells are very different things.
  5. Please return to the top of this page and click on analysis to complete the analysis questions.
  1. Include the images or drawings you took of your cells from Procedure 1 in your notes to study from at a later date.  For more information on how to draw scientific diagrams, see page 481 in your textbook. 


Total Magnification Used = 400x.  The ocular lens has a magnification of 10x and the 40x objective lens was used.

  1. Include the images or drawings you took of your cells from Procedure 2 in your notes to study from at a later date.  For more information on how to draw scientific diagrams, see page 481 in your textbook.


Total Magnification Used = 400x.  The ocular lens has a magnification of 10x and the 40x objective lens was used.
The paramecium is approximately 0.5 mm long and 0.2 mm wide.

  1. Compare the shape of the cells that did and did not have cell walls.  What effect does the cell wall have on the shape of the cell?

The cells in the leaf cross-section slide contained cell walls.  These cells had a more square or rectangle shape compared with the paramecium that does not have a cell wall.  The cell wall gives the cell more structure so that it can better hold its shape.

  1. Where in your leaf does photosynthesis occur?  How do you know?

Photosynthesis occurs in the long cells.  We know this because that is where the chloroplasts are and photosynthesis occurs in the chloroplasts.

  1. Why do you think the paramecium contains 1 cell while the leaf cross-section contains many?

The paramecium is a single-celled organism, meaning that it completes all life functions using one cell.  The leaf is part of a multi-cellular organism, meaning that different types of cells have different specialized functions.  You will learn more about multi-cellular organisms and how they work in section 3.


  The Cell Is an Open System

Cells interact with their environment to get food, get rid of waste, and exchange energy and matter.

A4.1 Some organelles we studied
The different organelles within a cell help the cell to perform the basic life functions, as well as being an open system. The vacuoles and vesicles help get food, waste, and materials into and out of the cell through the cell membrane. The nucleus, ER, Golgi apparatus, ribosomes, and lysosomes help to create or break down the material being exchanged; and the mitochondria create the energy needed for all these functions.

In the next two lessons, we will look even closer at the structure of the cell and how it performs the basic life functions.

  Interactive Activity


Organelle Cell Model © CELLS alive.com https://quick.adlc.ca/cells-alive


Explore this interactive to review the different organelles in both plants and animal cells and their functions. This interactive contains a few organelles that we did not cover such as microtubules and centrioles.

Begin by clicking on “Animal cell” or “Plant Cell” under the interactive window. Once you have chosen a type of cell, you can either hover over an organelle to see the name or hover over the name to see the location. To see more information about that organelle, click on the name or the organelle.