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Biology Labs, Activities, Videos, and Study Guides About Cells (Photosynthesis, Mitosis, Cell Organelles, and More)

Photosynthesis lab

Photosynthesis lab

High School Cell Biology Labs And Videos

Biology is the study of living things, including plants, animals, and microorganisms, such as bacteria, fungi, and protists. During a class in biology, students are usually taught about cells, tissues, organs, organisms, genetics, ecology, animal behavior, and many other topics.

I, and one other teacher at our homeschool co-op, co-taught a high school level biology class to ten homeschooled teens during the 2011-2012 school year. The first unit we explored was cell biology. Cell Biology refers to the study of cells. This includes the properties of cells, their structures, their interactions with the environment, how they divide, osmosis and diffusion, photosynthesis, etc.

On this webpage, I've included some of the cell biology labs, activities, and you-tubes we used to supplement our Holt Biology text and enrich our biology experiences. I've also provided several free study guides of important information about cell biology for your use.

Students read from the text, "Holt Biology," answered chapter review questions, and watched various biology you-tubes at home, while engaging in a variety of labs and hands-on activities at our co-op. (Students who purchased the optional "Biology For Every Kid" book also enjoyed doing additional hands-on activities at home. In my opinion, hands-on activities and labs greatly enrich anyone's study of science!)

About This Webpage

I created this page for the students in my biology class. Although there are many references to the textbook that we used, many of the resources on this page can be used without having a copy of that book. Even if you're not one of my students, please feel free to have a look around and see if something here might be of interest or benefit to you!

If you have a different textbook, just look for the sections on this page (and on the other biology pages I've created) for whatever material you are currently studying. Most biology textbooks are very similar in terms of the type of information they cover, although some do go deeper into various topics than others. But just about all high school or college biology textbooks are going to cover ATP, for example. You'll find a youtube on ATP below!

If you don't have a textbook at all, you can still watch the youtubes, do the labs, read the study guides, and visit the many links to other websites.

Have fun!

Holt Biology - This is the primary book we used in our biology class

Holt Biology is full of colorful photographs and drawings. Most chapters also offer one or more labs to go along with the text.

The link will taken to a page which shows the different formats (and prices) of this Biology textbook. For example, if you prefer it on CD, that's one of the options!

101 Easy Experiments

Additional Biology Resources

Some of the labs mentioned in this unit on cell biology, as well as throughout the remainder of the course, will come from this book. The materials in the labs are easy to acquire and the labs are interesting and fun!

Labs DVD

This DVD is designed to accompany the hands-on labs mentioned in the Holt Biology textbook. It goes through the labs step by step, showing the student what he or she should be doing/seeing. Closeups of what the student is seeing in the microscope are provided for many of the labs.
Although the vast majority of our weekly labs consisted of real hands-on labs (including many not mentioned in the text), we did use this DVD a few times as a substitute for a lab when we were unable to acquire the needed materials to complete the lab on our own.

500x Power Microscope

This is the microscope my son has. It's worked quite well for him! He enjoys using it, not just for formal lab assignments, but also for looking at a variety of other things in magnification!

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Biology And You

The three sections in this chapter in the Holt Biology textbook cover the seven properties that all living organisms have in common, how achievements in biology impact the world, and the scientific method.

Themes of Biology

Do you know how to tell if something is a living thing or not? What qualities do living things have?

1. For a very brief overview, read this short description of the 7 Properties of Life.

2. Watch the two youtubes below on the 7 properties of life. (If you are short on time, just watch the second video.)

3. Read "Themes of Biology" in the Holt Biology text.

4. Answer the Section 1 review questions found within the text.

YouTube Videos On the 7 Properties of Life

On the first youtube below, we are shown a chart with biology terms on it. As you watch the video, notice the order the terms have been placed in on the chart. We start with the smallest particles within an atom (subatomic particles, such as proteins and electrons) and build up larger and larger until we are at the level of the world. This increasing organization as we move from level to level - from subatomic particles to atoms to molecules and so on up to the biosphere - is part of what the first you-tube below is trying to get across to the viewer. Another main point within the video is that key to life can be found somewhere between the level of molecules, and the level of cells.

The second you-tube moves on to a discussion of the 7 properties of life.

What are the characteristics of all living things?

The 7 properties of life

The Impact of Biology On The World

Does the study of biology make any difference in our lives? Can science help solve current problems the world is experiencing?

The field of conservation biology is working towards preserving our environment. They try to make the best uses of the earth's resources, reduce waste, and protect plant and animal species and their habitats.

In 2003, biologists completed mapping the genes of the human body. This information may be used in medical research in the future. AIDS, cancer, hereditary disorders, and a variety of diseases are all currently being researched.

1. Read Section 2 in your text.

2. Answer the Section 2 review questions found within the text.

Scientific Method

Scientific Method

Scientific Processes

What methods do scientists follow when doing an experiment?

The Scientific Method

Ask a Question.

Make Observations.

Create a Hypothesis.


Analyze the Results.

Share the Results.

1. For an overview of the scientific method, watch this

Animated Video On the Scientific Method

2. Read Section 3 in Holt Biology (or other text) on the Scientific Method.

3. Answer the review questions.

Biology Labs for Chapter 1

1. This lab goes along with the theme of the characteristics of life: What life characteristics can be observed in a pill bug?

While discussing the components of the Scientific Method, Holt Biology refers to a scientific study involving frogs and acid rain. Below are two labs which closely resemble those given in the text, but which use clearly stated and easy-to-find materials.

2. Lab: Determining the pH of Common Substances

3. Lab: Effects of Acid Rain On Seeds

(To view the directions for this lab, copy and paste the url above into your browser.)


This chapter covers a brief overview of chemistry, including atoms, elements, covalent bonds, and ionic bonds. Also covered are the properties of water, acids and bases, polarity, cell chemistry, chemical reactions, and enzymes.

The Nature of Matter

Iconic bonds are ones in which one atom loses an electron to another atom. Covalent bonds are ones in which two or more atoms share electrons.

1. View this graphic of Iconic and Covalent bonds. (Click on the image on the website in order to enlarge it. Note: Even if a box pops up asking for your email, don't worry. There's a link within the box that will take you directly to the graphic, without your having to give them your email.)

2. Read Section 1 on the "Nature of Matter" in Holt Biology.

3. Answer the section 1 review questions found within the text.

4. Watch the you-tube below on iconic and covalent bonds.

Ionic and Covalent Bonds

Water and Solutions

1. Watch the you tube below on the properties of water.

2. Read Section 2 on Water and Solutions in your biology textbook.

3. Answer the review questions for section 2.

Properties of water

Chemistry of Cells

This section is about organic compounds. Organic compounds are substances which contain carbon which has bonded to hydrogen, oxygen, or other elements.

Did you know that graphite (in pencils) and diamonds are both carbon? Think about how different graphite, which is very soft and easily rubs off onto paper or your skin, is from a diamond, which is very hard and doesn't rub off at all. The Math And Science Activity Center gives a short explanation as to why they are so different, even though they are both the same element.

A Few Photos of Carbon

Our text discusses the organic compounds: carbohydrates, lipids, proteins, and nucleic acids.

Also covered in the text is ATP. ATP is something in cells which stores energy. compares ATP to a rechargeable battery and explains that ATP is created by the mitochondria of cells.

1. Read my brief introduction to the chapter above, and check out the links I've provided if you'd like.

2. Watch the you tube on carbohydrates, lipids, proteins, and nucleic acids below.

3. Read "Chemistry of Cells" in the text.

4. Answer the review questions in the text.

Carbohydrates, Lipids, and Proteins

Energy and Chemical Reactions

Enzymes are things which speed up chemical reactions.

1. Read: What Are Enzymes and Why Do We Use Them In Laundry Detergents?

2. Watch one or both of the you-tubes belows on enzymes.

3. Read "Energy and Chemical Reactions" in our text.

4. Answer the review questions in the text.

Enzyme Basics

Labs on Enzymes

Lab: How Do Enzymes Work?

This lab demonstrates how enzymes in pineapple and detergent can break down the proteins in gelatin.

Lab: Do detergents with enzymes perform better than those without enzymes?

Cohesion allowed a drop of water to form on this Hibiscus flower.

Cohesion allowed a drop of water to form on this Hibiscus flower.

Biology Study Guide

Study guide on enzymes, properties of water, covalent and ionic bonds, acids and bases.

Types of Chemical Bonds

Covalent bonds occur where two or more atoms share electrons. (Both atoms use the electron.)

Ionic bonds occur where one atom gives one or more of it's electrons to another atom. Iconic bonds create ions. An ion is an atom or molecule which no longer have the same number of electrons as they have protons, because they've either given an electron away, or gained an electron from another atom. (An atom normally has the same number of electrons as protons.)

Qualities of Water

Polar molecules are molecules that have positively and negatively charged sides, rather than being the same all the way around. Because water is a polar molecule, other things that are polar dissolve well in it. Salt is polar molecule and can easily be dissolved in water. Oil is not polar; that's why oil and water don't mix.

Since water is a polar molecule, it forms hydrogen bonds (a weak attraction) between the negatively charged oxygen atom of one molecule and one of the positively charged hydrogen atoms of another molecule.

Cohesion means "sticking together." In the case of water, cohesion is an attraction between water molecules. Cohesion allows water to form drops. It's caused by hydrogen bonds that are formed between molecules (in this case water molecules). Surface Tension is the effect of cohesion on the surface of the water. Cohesion allows water to support things that are heavier than it, such as a water strider bug, or a pin laid carefully on top of some water in a bowl.

Water also likes to stick to other things. This is called adhesion. Adhesion is what allows water to move up a plant stem. Adhesion also makes the surface of the water in a tube look somewhat bowl shaped, as the water sticks to the sides of the tube.

PH Scale

Solutions are measured on a scale of 1 to 14 on their level of acidity. Substances with low numbers (under 7), such as lemon and vinegar, are more acidic than substances with high numbers (above 7), like soap and ammonia. Acids are sour, are corrosive to metals, and have a high concentration of hydrogen ions. Bases are slippery and have a low concentration of hydrogen ions. Water is considered neutral and has a ph close to 7.

Carbon Compounds

Carbohydrates can be found in foods such as grains, fruits, and vegetables. Carbohydrates are made from monosaccharides, which are simple sugars. Glycogen and starch are two types of carbohydrates that store energy.

Lipids include things such as fats, steroids (including cholesterol), phospholipids, and waxes.

Proteins contain amino acids. There are 20 different amino acids in proteins.

Nucleic Acids can be found in all cells. Nucleic acids are made up of nucleotides. Nucleotides are molecules that join together to make up RNA and DNA. Nucleotides consists of phosphate group, a sugar, and a base.

ATP is like a rechargeable battery for a cell. It consists of a nucleotide with two extra phosphate groups.

Chemical Reactions

Chemical Reactions occur when atoms form new chemical bonds or break old ones with other atoms. The "stuff" you start with are called the reactants. The substance(s) you have after the chemical reaction is/are called product(s). To help you remember which is which, think about a factory that makes cloth. The cotton would be like the reactant. The machines that do something to the cotton would be the chemical reaction in our analogy, and the beautiful cloth would be the final product.

Activation energy is the energy that is needed to get a chemical reaction started. It's what gives the reaction a little push and gets the process going.



..... are usually proteins.

......increase the speed of a chemical reaction

......reduce the activation energy that is needed to start a chemical reaction organisms maintain homeostasis

.....are affected by temperature and ph

.....are added to laundry detergent to help break down stains

Some enzymes are used for digestion, but other enzymes are used for performing various chemical reactions in cells. Enzymes can be found in both plants and animals. We add enzymes to laundry detergent to help break down stains on our clothes.

A Substrate is the item being broken down by an enzyme. The substrate fits into the active site of an enzyme (the pockets in an enzyme) like a key fits a lock.

Cell Structure

This chapter introduces various types of microscopes, cell theory, structural features of cells, prokaryotes cells, eukaryote cells plant cells, and animal cells.

Looking at Cells: Microscopes


Compound Light Microscopes

Above is a photo of a compound light microscope. They are the type of microscope often used by middle school and high school students. This type of microscope uses glass slides to hold the specimum being studied. A light shines up through the slide.

Electron Microscope

Electron Microscope

Electron microscopes

Above is a photograph of an electron microscope. Electron microscopes magnify images up to 200,000 times their normal size. This type of microscope can be used to examine structures within cells. It doesn't work with living cells though, because the specimen must be placed in a vacuum chamber and cells can't live in a vacuum.

Scanning Electron Microscopes

Here is a photograph of a Scanning Electron Microscope. Scanning Electron microscopes show 3d images of cells! They can be used to look at living things.

This is an ant as seen through a scanning electron microscope.

This is an ant as seen through a scanning electron microscope.

Robert Hooke's Microscope

Robert Hooke's Microscope

Robert Hooke's Microscope

In 1665, Robert Hooke published a book describing microscopic and telescopic observations. His book was titled: Micrographia. To make the microscope observations, he used the microscope shown here. The microscope was constructed by Christopher White. While looking at a tiny piece of cork under a microscope, Robert Hooked identified the little "compartments" that he saw as "cells." He was the first one to use the term "cells" to identify microscopic structures.

Cell Features

Prokaryotes do not have a nucleus, but Eukaryotic cells do. Eukaryotic cells have compartmentalization. According to the you-tube below, "Compartmentalization allows specialization."

1. Watch the you-tube below on the cell membrane, the compartmentalization of Eurkaryotic cells, and why the ratio between the surface area and the volume of a cell is important. (But watch out for giant amoebas!)

2. Read "Cell Features" in the text. As you read about the characteristics of Prokaryotes and Eukaryotes in the text, you may find it helpful to create a chart. Label one column: Prokaryotes, and the other Eukaryotes, and add their characteristics under each as you read.

3. Answer the questions in the text.

Plant and Animal Cells

Cell Organelles

1. Watch the first you-tube below on the Endoplasmic Reticulum.

2. Read the section "Cell Organelles" in the text.

3. Answer the questions in the text.

4. Optional: If you enjoy watching and learning from youtubes, you may also want to view this one: A Tour Of The Cell

5. Optional: Watch one or two of the other you-tubes below (look for the thumbnails below the large you-tube) and try to identify the various organelles as they are shown.

(Note that there is no narration to these last two videos, so learn about the various cell organelles before you watch them!)

Endoplasmic Reticulum

Animal Cell

Biology Labs On Plant and Animal Cells

Lab: Do the lab on page 70 in the Holt Biology textbook (using an elodea plant from a petstore) or do a lab with cheek cells and onion cells. Here's one: Plant and Animal Cell lab

Optional Activity: Create a 3 dimensional model of a cell using candy and gelatin (in a ziplock bag), or using playdough or other items. Here's one I found that uses icing and candy: Edible Animal Cell Cake. Many others can be found via google.

Prepared Microscope Slides

This set of 100 glass slides of plant parts, insect parts, animal tissues, etc. comes in a nice wooden box.

Here are just a few of the slides that are included in this set: Bee Wings, Earthworm, Euglena, Frog Lung, Human Hair, Human blood, Penicillium, Mosquito Mouth Parts, and Mitosis in an Onion Root Tip.

Slide Making Kit

Want To Make Your Own Slides?

This kit comes with slides, cover slips, Methylene Blue (which is mentioned in the onion cell lab I recommended above.) and a few other things.

Blank Slides and Cover Glass

This comes with both the slides and the cover slips that you'll sandwich your specimen between. The cover slips prevent your microscope lens from accidentally dipping down into your specimen as you focus.

Robert Hooke's Microscope

Robert Hooke's Microscope

Biology Study Guide

on Cell Structure and Microscopes

In addition to studying the information below, this video: A Tour Of The Cell, will provide you with an excellent review of the information in chapter 3 of Holt Biology.

* Robert Hooke used an early version of a microscope and noticed a "lot of little boxes" in cork. The boxes he saw were cells.

* Anton van Leeuwenhoek used a microscope to examine pond water. He named the living creatures he saw, "animalcules."

Information about Microscopes

* The magnification of something describes how much bigger it appears.

* Resolution measures how clearly you can see something.

* Compound Light Microscopes use two lenses and can have a magnification up to 2000X.

* Electron Microscopes can magnify things up to 200,000X, but can not be used to view living things (because living things can't survive in the vacuum that's used in an electron microscope.)

---*Transmission Electron Microscopes uses electrons that produce an image on a screen. The specimens are stained with metal ions. The images are in black and white, but color can be added with a computer.

---*Scanning Electron Microscopes show 3D images of cells. The specimens are coated with a thin layer of metal. As with the transmission electron microscope, the images are in black and white but can be colorized with a computer.

* A Scanning Tunneling Microscope also creates a 3d image, but unlike the scanning electron microscope, a scanning tunneling microscope can be used to examine living things.

Cell Theory

1. All living things are made of cells.

2. Cells are the basic units of organisms.

3. Cells come from other cells.

Size of Cells

Smaller cells do better than larger ones. Larger cells have a low surface area to volume ratio and are unable to take in enough nutrients through their cell membrane to support the large cell. (Remember the giant amoeba story in the you tube? Also remember the tissues that are folded inside the box in order to provide greater surface area?)

Types of Cells

*Prokaryotes are simple one celled organisms that do not have a nucleus. Prokaryotes do not have compartmentalization. The loop of DNA can usually be found near the center of the cell. The enzymes and ribosomes are lose in the cytoplasm. Many prokaryotes have flagella which are long string like "arms" which help the organism move. Bacteria is an example of a prokaryote.

*Eukaryotic cells have a nucleus. They have various compartments, or organelles, each with their own job.

Parts of a Eukaryotic Cell

*The Nucleus of the cell contains the DNA.

*Ribosomes make enzyme proteins (including digestive enzymes). Some ribosomes are found in the cytoplasm and others are found on the Rough ER.

*The Endoplasmic Reticulum (ER) is a system of membranes that move proteins and other things through the cell. The Rough ER contains ribosomes. The Smooth ER does not contain ribosomes.

*Proteins that are made by the ribosomes are put into a "sac" (vesicle) by the endoplasmic reticulum and are then moved to the Golgi Apparatus. In the Golgi Apparatus, they are processed and packaged into vesicles again before moving on.

*The Mitochondria make ATP, which is like a rechargeable battery for the cell.

*The Cytoskeleton is a web of fibers which help hold the cell together and provide it with a frame, much like a skeleton. Some parts of the cytoskeleton also act as a highway for getting information from the nucleus to the other parts of the cell. There are three types of cytoskeleton fibers: long actin fibers, microtubules (hollow tubes), and intermediate fibers (like ropes).

*The Cytoplasm is the interior of the cell.

*A Cell Membrane can be found in all cells, including both plant and animal cells. Cell membranes separate the cell from it's surroundings and also controls what goes into and out of the cell.

What's Only in Plant Cells?

*A Cell Wall is only found in plants. It helps support the cell and make it be more firm.

*Chloroplasts use light energy (from the sun) to make carbohydrates (food) for the plant. You'll learn more about chloroplasts in a later chapter.

*Central Vacuole is a large space in a plant cell that stores water and other things. It helps a plant cell be more rigid.

Cells And Their Environment

This chapter on cells covers movement of substances across the cell membrane. This includes the passive transport methods of osmosis and diffusion, as well as active transport methods of crossing the cell membrane. Passive transport means that energy is not needed for the substance to cross the cell membrane. In active transport, energy is needed.

Passive Transport

1. Watch the two you-tubes below on diffusion and osmosis.

2. Read this short definition and example of a concentration gradient.

3. Read "Passive Transport" in the text.

4. Answer the review questions in the text.


Osmosis Demonstration

Active Transport

1. Watch the youtube video below on active and passive transport.

2. Read "Active Transport" in the text.

3. Answer the review questions in the text.

Active and Passive Transport

Biology Labs On Osmosis and Diffusion

Lab: Do the egg lab that's shown in the osmosis you-tube video above.

Note: To prepare the egg for the lab, soak it in vinegar for a day or two before using it in the activity.

Lab: Gummy Bear Osmosis Lab or the Fluffy Raisins lab on page 12 of "Biology for Every Kid."

Limp Spuds on page 10 and In But Not Out on page 144 of "Biology for Every Kid" are also about osmosis.

Spicy Escape on page 8 of "Biology for Every Kid" is about diffusion.

Biology Study Guide on active and passive transport

To review for your test, you may want to watch this excellent video: Transport Across Cell Membranes.

Passive Transport

Passive transport is the movement of a substance across a cell membrane without any energy being used. Diffusion, osmosis, the ion channel, and facilitated diffusion are four types of passive transport.

1. Diffusion is the movement of something from an area of high concentration to an area of low concentration by the random motion of the particles in the substance. The cell membrane is picky about what it will allow to cross through it, turning away ions and most polar molecules, but allowing most small or nonpolar molecules to move through it.

*****Imagine the aroma of dinner cooking, starting inside the pot and spreading throughout the kitchen and possibly even throughout the house. That's what diffusion is like.*****

Equilibrium is when the substance is evenly distributed.

2. Osmosis involves water moving across the cell membrane. In osmosis, water can move out of the cell or into the cell.

a.) Fluids often contain various types of dissolved particles in them. If the fluid outside the cell has more of a particular type of particle in it than the fluid inside the cell, the cell moves water out of itself in order to dilute the more concentrated fluid outside it. A solution that causes water to move out of a cell via osmosis, thus causing the cell to shrink, is called a hypertonic solution. (Remember the corn syrup and the egg at the beginning of the experiment on the youtube?)

b.) If the fluid inside the cell has more of the particles in it than the fluid outside, water moves into the cell in order to dilute the particles more. A solution that causes water to move into a cell via osmosis, causing the cell to grow bigger, is called a hypotonic solution. (Remember the water that made the egg get bigger?)

c.) An isotonic solution is one that doesn't change the volume of the cell at all. In this case, water moves into and out of the cell at about the same rate. This occurs when the dissolved particles have the same concentration both inside and outside the cell.

3. Ions won't fit through the cell membrane unaided, but can cross it using an ion channel. An ion channel is a protein in the cell wall with a hole or channel in it. The ion can pass through the channel, thus crossing the cell membrane. Ion channels are "selectively permeable" which means they can control what passes through them. Some ion channels are always open, while others have a gate which can open and close as needed.

*****Imagine a tunnel through the mountains. For some reason, the tunnel has a guard that only allows certain types of vehicles through. That's a little similar to what an ion channel is like.*****

4. Facilitated diffusion is another type of passive transport that allows things to cross the cell membrane. Molecules move into and attach to the inside of carrier proteins. Once they've attached inside the carrier protein, the protein changes shape, allowing the molecule to be released on the other side.

*****Imagine a lock on a canal. The boat moves into the lock. The lock "changes shape" and opens on the other side, allowing the boat to pass on through. That's similar to facilitated diffusion.*****

Active Transport

Like passive transport, active transport moves things across the cell wall. Unlike passive transport, active transport requires the cell to use energy ( usually ATP) to do so. Passive transport only works when moving from a higher concentration to a lower one (down the concentration gradient), but active transport works the other way...moving things from an area of lower concentration to an area of higher concentration. (Active transport works "against" the concentration gradient.)

*****Passive transport is a little like distributing money equally among everyone (creating equilibrium). Active transport is more like "the rich get richer."*****

Passive transport works "down" the concentration gradient, and therefore doesn't need energy.

*****Think about floating easily "down" a relaxing river on a raft or tube. The current carries you "down" the river without you having to paddle. That's like passive transport.*****

Active transport works "against" the concentration gradient, and therefore DOES need energy.

*****Think about having to paddle your canoe "against" the current of the river (to go upstream). It takes a lot of energy! That's like active transport.*****

The sodium potassium pump, endocytosis, and exocytosis are three types of active transport.

a.) The sodium potassium pump works with only sodium and potassium. It moves 3 sodium (Na) ions out of a cell, and allows 2 potassium (K) ions into the cell. Because there is already usually more sodium outside the cell, and the pump continues to move more sodium outside the cell, the sodium potassium pump works against the concentration gradient, meaning "the rich get richer."

Here's how it works: Sodium ions inside the cell move into the pump. ATP donates some energy (thus becoming ADP). The pump changes shape and opens on the other side, allowing the sodium to pass out of the cell. While the pump is still open to the outside of the cell, potassium moves into the pump, the pump changes shape again - opening back up on the inside of the cell, and the potassium passes into the cell.

b.) Endocytosis is another way of moving things into the cell. A substance moves into a pocket on the cell membrane. The pocket closes. Then the pocket moves further into the cell, taking the substance with it.

c.) Exocytosis is almost exactly the same as endocytosis, but does the process in reverse, moving things (such as wastes) out of the cell.

*****To remember which is which, think about "en" means things move in to the cell. "Ex" means things exit the cell.*****

Communication Between Cells

Signal molecules, such as hormones carry messages from one cell to another. Receptor proteins, which are usually located in the cell membrane, bind to the signal molecules, transfer information to the cell, and allow the cell to respond to the signal molecule (by changing in some way).

*****Think about phones or walkie talkies. A "receptor" is like a receiver. The "signal" goes to the "receptor." So signal molecules work with receptor proteins to transmit information to the cell.*****

Photosynthesis and Cellular Respiration

Photosynthesis is the process by which a plant makes it's own food. Cellular Respiration is the process of getting usable energy out of food. Both processes occur in plants. Cellular Respiration also occurs in animals.

For a short introduction to photosynthesis, watch the short video Illuminating Photosynthesis.

Energy And Living Things

The energy in the food we eat, whether plants or animals, can be traced back to the sun. In fact, sunlight is the source of energy for almost all life.

Organisms that get their energy directly from the sunlight are called autotrophs. They use the energy to make organic compounds. There are some autotrophs, such as the organisms that live in complete darkness near underwater volcanic vents, that get their energy from chemicals.

Photosynthesis is the process by which most autotrophs change light energy into chemical energy.

Heterotrophs are organisms that get their energy from food.

Cellular respiration is the process in which the energy in food is changed into ATP. Cells use ATP for various things, including active transport across the cell membrane as we learned in the last chapter. Remember that both plants and animals use cellular respiration.

1. Find out (via the following link) what a reactant and a product are (if you don't remember from chapter 2).

2. Read ATP and Energy Storage in which ATP is compared to a rechargeable battery.

3. Read "Energy and Living Things" in the text. Watch the you tube below on ATP, along with the section of the chapter entitled, "ATP."

4. Answer the review questions in the text.

What is ATP? How does it work?

How Living Things Obtain Energy (Consumers and Producers)


Photosynthesis is the process in which energy from the sun is turned into food (chemical energy) by plants, algae, and some bacteria. The sun's energy is then passed on to almost all living things, because almost all food can be eventually traced back to plants. (For example, an owl eats mice, but the mice eat plants, thus the owl gets energy from the sun via it's food.)

During photosynthesis, carbon dioxide from the air, water taken into the plant primarily by the roots, and light from the sun work together to create sugar for the plant to use and oxygen which the plants gives off.

1st Stage of Photosynthesis: Absorption of Light and Creation of ATP and NADPH

In the first stage of photosynthesis, a plant leaf absorbs light from the sun. The stuff that absorbs the light is called a pigment. Chlorophyll is the main pigment used in photosynthesis. Chlorophyll absorbs blue and red light, while reflecting back yellow and green light. (That's why most plants look green to us. We see the light that is reflected back to us.) Chlorophyll is located in the chloroplasts (an organelle in plant cells). Within the chloroplasts are some disk shaped objects (thylakoids) which contain clusters of pigment, as well as a water splitting enzyme.

When light hits the pigment in a thylakoid, some of the sun's energy is transferred to the electrons in the pigment. The energy "excites" the electrons, which then begin jumping around and are passed down what's called the electron transport chain. Water is split into oxygen and hydrogen ions and the plant gives off the oxygen. The electrons that are freed when the water is split take the place of those bouncing down the electron transport chain. As the excited electrons pass through a protein along the electron transport chain, they power a pump which pumps even more hydrogen ions into the thylakoid. When the concentration of hydrogen ions builds ups greater inside the thylakoid than outside it, some of the hydrogen ions leave the thylakoid through carrier proteins. This begins a reaction in which ATP (a "rechargeable battery" that holds energy for the cell) is formed from ADP. Meanwhile, the excited electrons that are passing along the electron transport chain make NADPH.

Both the NADPH and the ATP created in this stage of photosynthesis, are used in the next stage of photosynthesis: The Calvin Cycle.

2nd Stage of Photosynthesis: The Calvin Cycle

The first part of photosynthesis (sometimes referred to as the first two parts) involves light, and is therefore referred to as light-dependent reactions. The Calvin Cycle, which comes after the light dependent reactions, is not light dependent, since it doesn't use light. The Calvin Cycle is the most common form of carbon dioxide fixation, which means changing C02 into organic compounds (sugar).

During the Calvin Cycle, CO2 (carbon dioxide) is changed into glucose (three-carbon sugar molecules). The NADPH and ATP created in the previous stage are used to power this reaction.

1. Watch the youtubes, "Photosynthesis," and "Learn About Plants - Photosynthesis," below.

2. Read section 2 carefully, studying the diagrams in the book as you read.

3. Watch the youtube below on Photosynthesis (by Bozemanbiology). Use the pause button to slow it down if you want to take notes or even just have a moment to absorb what he's saying. Also, remember you can easily replay parts (as many times as you want) by dragging the bar back a little. Take your time listening to this video.

4. Answer the review questions in the text book.

Note: After reading the text up until stage 3, and watching Bozemanbiology's video, if you're still having trouble understanding photosynthesis, watch this additional movie on photosynthesis and cellular respiration (but feel free to stop the movie when he gets to cellular respiration, as we'll cover that in the next section!).

As you are reading the chapter in the text, remember that a neutrally charged atom of hydrogen has one proton and one electron. When it gives it's electron away, it becomes a positively charged ion. For more about ions, please refer to section 1 of chapter 2 in your text.


Learn About Plants - Photosynthesis

Cellular Respiration

Cellular Respiration is the process we use to convert energy from food into ATP (a "rechargeable battery" for storing energy). During cellular respiration, glucose (sugar) and oxygen become CO2, water, and ATP.

Stage 1 of Cellular Respiration: Glycolysis

Glycolysis takes place in the cytoplasm of the cell. During this process, a 6 carbon molecule of glucose is broken down into two 3 carbon pyruvate ions. NADPH and ATP are also formed. When oxygen is present, we get several things, including a 2 carbon acetyl group which is attached to coenzyme A, thus becoming acetyl-CoA.

Stage 2 of Cellular Respiriation: Krebs Cycle (Citric Acid Cycle)

In the Krebs Cycle, which takes place in the matrix of the mitochondria, two main things happen. Carbon from the pyruvate created during glycolysis is given off as carbon dioxide, and energy from the pyrurate is stored as NADH and FADH2.

Stage 3 of Cellular Respiriation: Electron Transport Chain

The electron transport chain is located in the inner membranes of mitochondria. Electrons given off by the NADH and FADH2 pass along the electron transport chain, causing hydrogen ions to be pumped outside the inner membrane (to the space between the inner and outer membranes). As a positive charge from the hydrogen ions builds up in this outer area, the ions begin to flow back through a carrier protein into the inner compartment, making ATP in the process. This ATP stores energy for the organism (whether a plant or an animal), releasing it as it's needed. Meanwhile, the electron passing along the electron transport chain combines with oxygen and hydrogen to make H20.

1. Watch the youtube below. I recommend watching it slowly, pushing the pause button as needed, and/or dragging the bar back some to replay portions. Take notes, and try to fully grasp what he's saying before you move on.

2. Read "Cellular Respiration" in your Holt textbook. (If you feel you really understand it well from the youtubes, feel free to skip parts of the text.)

3. Answer the review questions in the text.

Photosynthesis and Respiration

Biology Labs On Photosynthesis and Cellular Respiration

Labs on Photosynthesis and Cellular Respiration

Labs on Photosynthesis and Cellular Respiration

This photo shows two of our labs. One is on photosynthesis, and the other is on cellular respiration.

Photosynthesis Lab

To observe photosynthesis, we put sprigs of elodea in test tubes of water. We placed some of the test tubes in front of a bright light, others farther down the table away from the light, and a few others were covered with foil so that they received no light at all. After about 30 minutes, the test tubes in the bright light had bubbles of oxygen at the top. These plants were undergoing photosynthesis! The other two groups did not have bubbles.

Cellular Respiration Lab

Inside the empty soda bottle the youth placed 2 packages of yeast, 6 spoons of sugar, and warm tap water. Next they placed a balloon over the opening in the bottle. It didn't take long for the balloon to stand up as it filled with carbon dioxide, showing us that the yeast were eating the sugar (engaging in cellular respiration) and giving off carbon dioxide.

More Labs on Photosynthesis and Cellular Respiration

There are several great labs in "Biology For Every Kid" that go along with photosynthesis and cellular respiration.

1. What happens to a plant that doesn't receive any light? --Darkness Below. (p 56)

2. Would you like to see the starch in leaves? --Food Producers. (p 28)

3. During cellular respiriation, plants give off carbon dioxide. - Plants Breathe. (p 36)

4. Want to learn more about pigments in leaves? -- Leaf Colors. (p 38)

5. In "Independence," you'll see signs of respiration. (p 40)

Here are a few other labs that can be found online:

Photosynthesis Lab which uses Bromthymol blue and a sprig of Elodea.

Measuring the rate of photosynthesis lab

Here are some unique teaching strategies for teaching about the electron transport chain, and how ADP becomes ATP, etc.: Photosynthesis and Respiration Demos

Photosynthesis in action! See the bubbles of oxygen?

Photosynthesis in action! See the bubbles of oxygen?

Biology Study Guide

Photosynthesis and Respiration

The sun is the main source of energy for all life on Earth. Plants get their energy directly from the sun. Animals get their energy from plants, or from other animals which eat plants.

Photosynthesis is the process of changing energy from light into chemical energy (food). Autotrophs are organisms that use the sun (or sometimes chemicals from their environment) to make their own organic compounds (food). Organisms that have to look for food, rather than make it themselves, are called heterotrophs.

*****To help you remember autotrophs and heterortrophs, think: The "auto" in autotrophs means they do it automatically. But the "he" in heterotrophs, means "he" has to hunt for his food.*****

Pigments absorb light. Plants contain both chlorophyll (a green pigment) and cartenoids (orange and yellow pigments, etc.). The main pigment in photosynthesis is chlorophyll. Chlorophyll can be found inside the thylakoid membrane in the chloroplasts which are in the cells of the leaves.

Oxygen, the air that animals breathe, is given off as a by-product of photosynthesis. This takes place at the beginning of the electron transport chain as water molecules are split into hydrogen ions and oxygen, thus providing electrons and hydrogen ions (both of which are needed in photosynthesis), and releasing oxygen into the air. When light is absorbed by the chlorophyll, the electrons in the chlorophyll become "excited" and begin moving down the electron transport chain. This is what starts the process of photosynthesis.

The Calvin Cycle comes next in the process of photosynthesis. Carbon dioxide fixation means changing carbon dioxide into food (organic compounds), and this is exactly what the Calvin Cycle does. During the Calvin Cycle, carbon dioxide is changed into three-carbon sugar molecules (food).

The rate of photosynthesis is affected by several environmental conditions, such as temperature, light, and concentration of carbon dioxide.

Using the photos in your book, see if you can trace the steps in photosynthesis. If you need help, refer to my notes in section 5.2 above, and/or watch Mr. Anderson's youtube on photosynthesis again.

Cellular Respiration is the process of getting energy from food. While only autotrophs do photosynthesis, both autotrophs and heterotrophs use cellular respiration to convert food into energy they can use. The energy is stored in the form of ATP. This energy is then available for use by the cell. Oxygen aids in the production of ATP, although ATP can be made without oxygen as well. Aerobic processes are ones that use oxygen. Anaerobic processes do not need oxygen.

There are three stages in cellular respiration: Glycolysis (the breaking down of glucose), the Kreb's Cycle (also sometimes called the Citric Acid Cycle), and the Electron Transport Chain. The end products of cellular respiration are ATP (energy) and water.


In order for living things to be able to grow, heal wounds,