Integrated General Biology3. Develop a list of substances that a cell may need to move across the plasma membrane. These substances may be moving either into or out of the cell. Oxygen,

Integrated General Biology A Contextualized Approach

Active Learning Activities FIRST EDITION

Jason E. Banks

Julianna L. Johns

Diane K. Vorbroker, PhD

The Ins and Outs of Glucose Active Learning Activities

Transport Across Cell Membranes 2

Chapter 7 The Ins and Outs of Glucose

Section 7.1 Transport Across Cell Membranes Directions for the Student:

This lesson is designed for you to complete, on your own or in your study group. Use your notes and follow along in the text, as you find necessary.

Objectives: 1. Differentiate between passive and active transport. 2. Describe the various mechanisms for transporting material through the plasma

membrane. 3. Compare and contrast the similarities and differences between exocytosis and

endocytosis both as forms of transport mechanisms. 4. Define tonicity and explain its importance clinically.

Materials Required:

Cell membrane diagram from textbook

Food coloring, water, clear glass or jar

With a few exceptions, cells are very small—way too small to see with the unaided eye. Cells that stay

small have an advantage over large cells.

1. Remembering that the cell membrane is the gateway into and out of the cell, what benefit do small cells have over large cells?

Smaller cells have a greater surface area to volume ratio. This translates to a greater capacity for absorbing needed substances and releasing waste.

In a way, our bodies are similar to a cell—we have to take in things from the outside world and have to

get rid of things that we don’t want inside of us anymore.

2. Make a list of the things your body does to maintain a healthy internal environment in a day. What does your body take in and get rid of in a day?

We take in oxygen from the air, and release carbon dioxide to the air. We ingest food and water, and release metabolic wastes in our urine and other wastes in our feces.

Cells are often very active—growing, producing proteins, dividing, etc. To maintain relatively stable

internal conditions cells, must get useful materials in and waste materials out. Depending upon the

properties of the substance that needs to be transported across the membrane, a cell can use several

methods.

3. Develop a list of substances that a cell may need to move across the plasma membrane. These substances may be moving either into or out of the cell.

Oxygen, glucose, amino acids, hormones, water, lipids, carbon dioxide, proteins, ions, etc.

4. Do you think it will be easier to move smaller or larger molecules across the membrane?

Smaller molecules are easier to move.



5. The interior of the plasma membrane is composed largely of the hydrocarbon tails belonging to phospholipid molecules. Do you think that polar or nonpolar molecules will be able to move more freely through this region of nonpolar covalent bonds?

Nonpolar molecules will be able to move through this nonpolar area of the hydrocarbon tails.

Perform the following experiment.

1) Fill a clear jar or glass most of the way up with warm water. 2) Place a drop of food coloring into the glass. The diagram below shows a glass with a drop of

coloring just added to it.

6. Draw in the diagram the direction of the movement of food coloring, after it enters the water.

7. What does the distribution of the food coloring look like after a few minutes?

The food coloring is spread out, and the water is becoming evenly colored.

8. Did the coloring tend to move from regions of low coloring concentration to regions of high coloring concentration OR did it tend to move from regions of high coloring concentration to areas with low coloring concentration?

The food coloring drop moved from areas of HIGH concentration to areas of LOW concentration.

Now, use your imagination to visualize the direction that the water moved during this experiment. Go

back to the drawing of the jar and add different color arrows that show the movement of the water.

These arrows show the water’s motion relative to the food coloring.



9. After 10 minutes is the water more concentrated in certain areas or is the water spread out evenly through the mixture?

The water is spread out evenly throughout the glass.

10. Did the water tend to move from regions of low water concentration to regions of high water concentration OR did it tend to move from regions of high water concentration to areas with low water concentration?

The water also moved from areas of HIGH concentration to areas of LOW concentration.

Due to the random movement of particles in a solution, substances tend to spread out from regions of

relatively high concentration to regions of relatively low concentration. This does not require additional

energy; it happens all on its own.

11. What is the name of this process when particles move from HIGH to LOW concentrations?

Diffusion is when particles move from HIGH to LOW concentration.

Cells contain small channel proteins that allow water to diffuse freely from one side of the cell to the

other. The diffusion of water across a membrane is so important that it gets its own name! But, water

does not diffuse fast enough across the cell membrane by itself, so the cell membrane has special

proteins that help water diffuse into and out of the cell even faster.

12. What is the name of this diffusion of water across a membrane?

Osmosis is the diffusion of water across a membrane.

13. What is the name of the protein channel that allows for this easy diffusion of water?

Aquaporin is the name of the protein channel that allows for the diffusion of water.

Examine the beakers. Both contain a single cell in an aqueous (water) solution. The green dots represent

molecules of solute (a particle dissolved in water). The water can easily diffuse through the cell

membrane through the aquaporin protein channels, but the solute is too large and cannot easily diffuse.



14. Which of the cells has a higher concentration of solute particles inside the cell as compared to outside?

The cell in Beaker A has a higher concentration of solute particles inside the cell as compared to outside the cell.

15. Which of the cells has a lower concentration of SOLUTE particles inside the cell as compared to the outside?

The cell in Beaker B has a lower concentration of solute particles inside the cell as compared to outside the cell.

16. Which of the cells has a higher concentration of WATER inside the cell as compared to the outside?

The cell in Beaker B has a higher concentration of water inside the cell as compared to outside the cell.

17. Which of the cells has a lower concentration of WATER inside the cell as compared to the outside?

The cell in Beaker A has a lower concentration of water inside the cell as compared to outside the cell.

Remember, the solute particles are too big to move across the membrane, but water isn’t. The solute

particles cannot diffuse across the membrane, but the water can! This means that the water will move

from areas of HIGH concentration to areas of LOW concentration.

18. Which of the cells is in a hypertonic solution? The cell in Beaker B is in a hypertonic solution.

19. Which of the cells is in a hypotonic solution? The cell in Beaker A is in a hypotonic solution.

Draw arrows on both of the beakers showing the direction that water will move across the membrane.

Remember: Water will move from the side of the membrane that has the relatively higher concentration

of WATER to the side of the membrane that has the relatively lower concentration of WATER.

Substances in solution move from high to low concentration.

20. What will happen to the cell in Beaker A? Water will diffuse into the cell in Beaker A, and possibly burst the cell.

21. What will happen to the cell in Beaker B? The cell in Beaker B will lose water and shrink in size.

22. What will happen to a cell if it is put into a solution that has the same concentration of ions as the inside of the cell? Which term would we use to describe a solution that has the same concentration as the cell?

The cell would not change much. Approximately the same amount of water would go in and out of the cell.

This solution would be called isotonic.

Small solute particles, like glucose molecules, tend to move from high to low concentration across the

membrane. When the glucose concentration is higher outside the cell as compared to inside, the

tendency would be for glucose to go into the cell. There is a complication, however.



23. Is glucose polar or nonpolar? Glucose is a polar molecule.

24. Is the interior of the cell membrane polar or nonpolar?

The interior of the cell membrane is nonpolar.

25. Will glucose be attracted to or repelled by the hydrocarbon tails of the phospholipid bilayer?

Glucose will be repelled by the interior hydrocarbon tails of the phospholipid bilayer.

Molecules like glucose and amino acids require more oversight in their access to the cell. Specific

molecules called carrier proteins are needed to get these substances into the cell.

26. What is the name of this process where particles diffuse across the membrane with the help of a carrier protein?

Facilitated diffusion is the diffusion of a large or charged particle across a membrane using a carrier protein.

27. Is this movement of glucose an example of active transport (that requires additional energy) or passive transport (that does not require additional energy)?

Diffusion (including facilitated diffusion too) does not require any additional energy, and is always a form of passive transport.

Sometimes a cell needs to move substances against their natural concentration gradient. The sodium

potassium pump is an example of a moving substance from areas of low concentration to areas of high

concentration. Moving substance in this way requires additional energy—this means we need the

energy currency of the cell!

28. Which molecule delivers energy to this process of moving ions against their concentration gradient?

ATP is the energy currency of the cell.

29. Is the sodium-potassium pump an example of active transport or passive transport?

Because additional energy is required, this is an example of active transport.

Sometimes the cell needs to move more than just individual molecules, or the molecule may be very

large and polar—the cell has to move a lot of material all at once, in bulk! In this case, the cell will wrap

these molecules up in part of the cell membrane (a phospholipid bilayer) to make a vesicle. In this way,

the cell can actively move large amounts of material into and out of the cell.

30. Draw a simple picture of a vesicle.



Use your textbook to help you describe the process for each of the four types of vesicular transport that

are identified below.

31. Describe phagocytosis (a form of endocytosis).

Literally meaning “cellular-eating", this process takes large materials into the cell by folding the plasma membrane around the material.

32. Describe pinocytosis (a form of endocytosis).

Literally meaning “cellular-drinking", this process takes portions of extracellular fluid into the cell by folding of the plasma membrane around the fluid.

33. Describe receptor-mediated endocytosis.

Specific particles are brought into the cell by the activation of specific receptors on the cell’s membrane. The membrane pinches in to make a vesicle.

34. Describe exocytosis.

Vesicles (phospholipid bilayer) from inside the cell fuse with the plasma membrane and release contents into the extracellular fluid.


Photosynthesis and Making Glucose 8

Section 7.2 Photosynthesis and Making Glucose Directions for the Student:


Objectives: 1. Define biomass, producers, autotrophs, consumers and heterotrophs. 2. Explain how photoautotrophs form biomass using the process of photosynthesis. 3. Explain the experiments that helped us understand photosynthesis.

Materials Required:

Cutout sheets of 6 carbon atoms, 12 hydrogen atoms, 18 oxygen atoms, and 36 stick bonds, and a chloroplast (and a bag to keep the cutouts in)

Scissors for each person

Living organisms have a certain way to make things. Molecules from living organisms generally look

different from nonliving sources. Examine the two molecules below and look for some differences.

Molecule A

Molecule B

1. What are some of the differences between the two molecules?

Molecule A is cyclic and molecule B is not. Molecule B has a carbon backbone, and molecule A does not.

2. Which of the molecules is organic and which is inorganic? (Make sure you look up a definition for organic and inorganic compounds, if you are not sure what those terms mean.)

Molecule A is inorganic (without carbon) and molecule B is organic (carbon-based).

Humans can make all sorts of things in laboratories—but when we do, we call these chemicals synthetic,

not natural. In nature, living organisms make all kinds of chemicals, like carbohydrates, proteins, lipids

and nucleic acids.

Remember, every substance that you can see, touch, taste, smell, or have any kind of interaction with is

a chemical. Calling something a chemical does not mean it is bad—pretty much everything is a chemical.



Carbohydrates, lipids, proteins and nucleic acids are often referred to as the four macromolecules or

biomolecules. These are the large molecules that organisms break apart and rebuild in the ways that

they want to build their bodies—and they are all carbon-based (also called organic).

3. If an organism wants to make some NEW carbon-based (organic) molecules, where would the organism get the carbon from, generally speaking? (Hint: This is called carbon fixation, and it happens in thin air!)

Generally speaking, organisms that can capture (or fix) carbon to make larger molecules get their carbon from carbon dioxide in the air.

4. What kind of organisms can fix (or capture) carbon to make larger molecules with? (Hint: What is the name for organisms that can make their own food?)

Autotrophs (or producers) can fix carbon from carbon dioxide in the air to make larger molecules (and make their own food).

Plants are the most common producers, or autotrophs. Plants make their own food, and they get the

carbon to do this from carbon dioxide in the air. The next time you see a big tree, remember that most

of the stuff in that tree came from the air! It may sound weird, but plants are able to take carbon out of

the air and pack it together to make big molecules. Plants are the main producer of living material, or

biomass.

But, what is so special about carbon? Why aren’t large molecules built with oxygen backbones, or

nitrogen backbones, or some other element?

5. Draw a Lewis dot structure (electron dot diagram) for carbon. Remember to only draw the valence electrons around the “C”.

.

. C . .

6. How many times can a carbon atom bond with other atoms?

Carbon can bond four times, forming four strong bonds.

Carbon is a great element for building large molecules—it can bond four times, forming four strong

bonds. Carbon can act like a connector between all kinds of other elements, making long chains of

organic molecules.

You may think you can make a mean burrito, or maybe fried chicken or some other meal, but did you

really make that food?

7. Write down three of your favorite things to make for a meal.

Answers will vary.



8. For each of the foods you listed in #7, write the main ingredient for each one.

Answers will vary.

9. If any of the ingredients you listed in #8 were animals, list what the animal(s) eat. (For example, chickens generally eat grains and seeds.)

Answers will vary, but students should be able to make the connection that they eat plants or eat animals that eat plants, etc.

Generally speaking, if you trace back how your food was actually formed, you will eventually get to

plants! Plants are producers, or autotrophs, that can make their own food (in the form of the energy-

storing molecules called carbohydrates). Animals eat plants to get food (carbohydrates) and take those

large carbon-based molecules that the plants made.

10. What is the name of the process where plants use the energy from light to make their own food (carbohydrates)?

Photosynthesis is the process that plants use to make their own food while using the energy from light.

11. Look up the meaning of the words “photo-” and “synthesis” and write them down.

Photo means light (although many students may think it means picture—actually, graph means picture, so photograph means “light picture” or picture of light).

Synthesis means to combine things to make something new.

Animals just use carbohydrates (sugars) for energy, but plants use carbohydrates for both energy and to

make their bodies with. Plants are the primary producers on Earth, which is why we say most of the

energy for life on Earth comes from the sun.

There are some autotrophs that don’t get their energy from the sun.

12. Where do chemoautotrophs get their energy from? (Hint: What does “chemo-” sound like?)

Chemoautotrophs get their energy from chemicals, or inorganic compounds.

Chemoautotrophs are able to make organic compounds from carbon dioxide (usually) using the energy

in chemicals (like hydrogen, or methane). But chemoautotrophs are not very common, so most organic

material is made from photoautotrophs, which is where most of the lesson will focus.

13. If there two types of organisms that can make organic material (photoautotrophs and chemoautotrophs), why do we only focus on how photoautotrophs make organic material?

Chemoautotrophs are not very common, but are still important producers in a few ecosystems on Earth. The vast majority of organic material is produced by photoautotrophs using the energy from the sun.



Most of the biomass (organic, carbon-based, living material) on Earth is produced by photoautotrophs,

in the process called photosynthesis. Let’s look at this process a little bit more closely.

The whole point of photosynthesis is to make an energy-storing molecule, a carbohydrate called

glucose. Plants are able to take the energy in sunlight and make the carbohydrate glucose.

14. Where is energy from the sun stored in this energy-storing molecule called glucose?

Glucose stores the energy from the sun in its chemical bonds.

Building up molecules takes energy and building materials. But how did we ever figure out how plants

perform photosynthesis? Just as many other great mysteries of the natural world were solved, we

figured out photosynthesis with the contribution of many people over a long period of time.

15. Using your resources, briefly explain the experiments and/or ideas of the following scientists that helped unlock the secrets of photosynthesis.

Jan Baptist van Helmont

Joseph Priestley

Jan Ingenhousz

Julius von Mayer

Cornelius Bernardus van Neil

Jan Baptist van Helmont carefully measured the amount of soil in a potted plant and the amount of water he gave it for five years. He found that the amount of soil was basically unchanged but the plant had absorbed the water. He showed water was necessary for photosynthesis.

Joseph Priestley put animals and plants under glass jars, showing that animals use oxygen and plants release oxygen.

Jan Ingenhousz placed jars over aquatic plants to show that plants made bubbles of oxygen while they were in light, but stopped making bubbles when the plants were in the dark.

Julius von Mayer proposed that the light gave the plant the energy to make carbohydrates.

Cornelius Bernardus van Neil showed that the oxygen came from the splitting of water, not from the carbon dioxide.

After these experiments, we could make the equation that models photosynthesis, with its reactants

(the things that go into photosynthesis) and its products (the things that come out of photosynthesis).

Instructions for engaging photosynthesis – refer to the cutouts at the end of this section.



1. Cut out each of the 6 carbon atoms, 12 hydrogen atoms, 18 oxygen atoms, and 36 stick bonds. Don’t

cut too close to each figure—leave just a little bit of white paper around each part. Remember that

hydrogen can only bond once, oxygen can bond twice, and carbon can bond four times!

2. Make the reactants for photosynthesis . . . 6 carbon dioxide molecules and 6 water molecules. Make

sure you use all of the materials (there should not be anything left over).

Water

Carbon Dioxide

3. The Light-Dependent reactions take place in the thylakoid membrane. Look at the picture of the

chloroplast (the organelle where photosynthesis takes place). Light energy is going to enter the

chloroplast and go all the way into the membrane around the thylakoid. The chloroplast is an organelle

with a double membrane around it, but the thylakoid (which is inside the chloroplast) also has a

membrane around it. In the membrane of the thylakoid, there is chlorophyll—a pigment that absorbs

light. Here, in the thylakoid membrane, water is split using the energy from light. The oxygen atoms

from water bond together to form O2 (whenever there are free oxygen atoms, they bond together like

that).

Take the water molecules apart, link the oxygen atoms from the water together with a double bond,

and move the new O2 molecules away to symbolize their release (plants release oxygen during

photosynthesis). Leave the hydrogen atoms in your work area because you’ll need them later to make

glucose. Make sure to use a double bond between the oxygen atoms.

4. The Light-Independent reactions occur in the stroma, inside the chloroplast, but outside the

thylakoid. Also known as the Calvin Cycle, the Light-Independent reactions are actually very complex.

But, essentially what happens is that carbon dioxide and the hydrogen atoms from water are bonded

together to form glucose (an energy-storing carbohydrate).

Take apart the carbon dioxide molecules. Link the remaining 12 hydrogen atoms (from the water) and

the 6 carbon atoms together with 6 of the oxygen atoms from the carbon dioxide. There will be 6

leftover oxygen atoms that you can form into 3 more O2 molecules.

Glucose comes in different shapes, but glucose always has the chemical formula C6H12O6. Try to make

both forms of glucose shown.



5. Whichever form of glucose you made, count each atom and stick bonds in glucose and in the oxygen

molecules. Remember, at the start of photosynthesis, there were 6 water molecules and 6 carbon

dioxide molecules, for a total of 6 carbon atoms, 12 hydrogen atoms and 18 oxygen atoms. Now you

have 6 O2 molecules, and 1 large, energy-storing glucose molecule.

Do you still have the same number of carbon, hydrogen and oxygen atoms as when you started?

The fact that all of the atoms that went into this reaction came out in the products is called the

conservation of mass, and it states that whatever you put into a reaction will come out. Or, maybe you

have heard it stated this way: Matter can neither be created or destroyed (except for in nuclear

reactions).

Please note: Photosynthesis is a very complicated process, and this activity was a simplification of the

overall reaction. There are many steps that have been left out or slightly changed, but the activity

remains a great place to start your journey into this amazing process that we couldn’t live without. Take

a look at the picture below and make some notes on the overall reactions in photosynthesis.



[Author: Daniel Mayer]

16. What are the reactants for photosynthesis? The reactants for photosynthesis are 6 water molecules and 6 carbon dioxide molecules.

17. What are the products of photosynthesis? The products of photosynthesis are 1 glucose molecule and 6 O2 molecules.

18. What is the energy source for photosynthesis? Sunlight is the energy source for photosynthesis.

19. What is the name of the organelle in eukaryotic cells where photosynthesis occurs?

In eukaryotic cells, photosynthesis occurs in the chloroplast.

20. What are the two series of reactions in photosynthesis?

Photosynthesis has two main sets of reactions, the Light-Dependent reactions and the Light-Independent reactions (or Calvin cycle).



21. Where do the Light-Dependent reactions occur?

The Light-Dependent reactions occur in the membrane of the thylakoid.

22. What is the name of the pigment that absorbs light energy in the chloroplast?

Inside the chloroplast, in the membrane of the thylakoid, the pigment chlorophyll absorbs light energy.

23. What is the other name for the Light-Independent reactions?

The Light-Independent reactions are also known as the Calvin Cycle.

24. Where do the Light-Independent reactions occur?

The Light-Independent reactions occur inside the chloroplast, in the stroma.

25. What does the Conservation of Mass tell us about photosynthesis?

The Conservation of Mass states that matter can neither be created nor destroyed, so whatever atoms go into the photosynthesis must also come out.

26. What is the primary purpose for photosynthesis?

Photosynthesis is the entry point for energy into the ecosystem. It makes the energy-storing carbohydrate glucose.



Section 7.2 Cutouts – Print single-sided

CHLOROPLAST

ATOMS AND BONDS

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––


Making Glucose, Technically Speaking 17

Section 7.3 Making Glucose, Technically Speaking Directions for the Student:


Objectives:


Cellular Respiration: Glucose Gets Split to Make ATP 18

Section 7.4 Cellular Respiration: Glucose Gets Split to Make ATP Directions for the Student:


Objectives: 1. Identify and describe the steps in cellular respiration (glycolysis, the Citric Acid cycle, and the electron transport chain).

2. Describe the relationship between photosynthesis and cellular respiration. 3. Identify and describe the role of the mitochondrion in cellular respiration. 4. Explain the role of Acetyl-CoA in cellular respiration. 5. Identify the number of ATP molecules produced at each step of cellular respiration.

Materials Required:

Cutout sheet for ALA 7.4 (and a bag to keep the cutouts in)

Scissors for each person

Photosynthesis happens in the chloroplast of some eukaryotic cells (cells with a nucleus). Only plants

and algae have chloroplasts, so they are the only eukaryotes who can perform photosynthesis. These

are the producers, the organisms who can make their own food—and food for everything else too!

While photosynthesis makes a large, stable, energy-storing molecules (glucose), what happens when it is

time to use that energy for something?

Well, when organisms need to use that energy in glucose, they perform cellular respiration.

Photosynthesis builds up glucose, and cellular respiration tears glucose down. But, while only a few

types of eukaryotes can perform photosynthesis, all eukaryotes can perform cellular respiration (even

plants can perform cellular respiration).

In eukaryotes, photosynthesis occurs in the chloroplast. Plants and algae are the only eukaryotes with

chloroplasts—so they can perform photosynthesis. In eukaryotes, cellular respiration occurs in the

mitochondrion. All eukaryotes have a mitochondrion, so all eukaryotes can perform cellular respiration.

But the cell can’t use glucose for jobs that require energy in the cell. Instead, the energy of glucose must

be used to charge up the energy currency of the cell—the molecule that is accepted at all cellular jobs,

big or small—ATP.

1. What is the main reason organisms perform photosynthesis?

Organisms perform photosynthesis to build up the energy-storing molecule glucose.

2. What eukaryotes can perform photosynthesis? Plants and algae are the only eukaryotic organisms that can perform photosynthesis.

3. In eukaryotic organisms, where does photosynthesis occur?

In eukaryotes, photosynthesis occurs in the chloroplast.

4. What is the main reason organisms perform cellular respiration?

Organisms perform cellular respiration to release the energy in glucose and charge up ATP.



5. What eukaryotes can perform cellular respiration?

All eukaryotes have mitochondria, so all eukaryotes can perform cellular respiration.

6. In eukaryotic organisms, where does cellular respiration occur?

In eukaryotes, cellular respiration occurs in the mitochondrion.

Examine the table and the equations for photosynthesis and cellular respiration.

Photosynthesis Aerobic Cellular Respiration

Purpose To form glucose To release the energy from glucose

Where In chloroplast In mitochondrion (primarily)

Reactants Water, carbon dioxide and energy (light) Glucose and oxygen

Products Glucose and oxygen Water, carbon dioxide and energy (ATP)

Equation for Photosynthesis—How to Make a Carb

6CO2 + 6H2O + Sunlight Energy C6H12O6 + 6O2 six carbon dioxide molecules + six water molecules + energy yield a glucose molecule + six oxygen molecules

Equation for Aerobic Cellular Respiration—How to Break Down a Carb

C6H12O6 + 6O2 6CO2 + 6H2O + Energy a glucose molecule + six oxygen molecules yield six carbon dioxide molecules + six water molecules + energy

Notice the word “aerobic” before cellular respiration. This is very important because it reminds us that

this process must have oxygen to occur. Without oxygen, we cannot use this pathway.

The stable, energy-storing molecule glucose needs to be broken down to charge up ATP. But how do

organisms make ATP?

The energy in glucose is going to be used to power attaching one more phosphate group onto ADP to

make it ATP—this is called phosphorylation.

There are two ways that we add another phosphate to adenosine diphosphate (ADP) to make adenosine

triphosphate (ATP): Substrate-Level phosphorylation and Oxidative phosphorylation.

A phosphate group, ADP and ATP All ADP needs to do to make ATP is to add a phosphate group. This is called phosphorylation.



There are two ways to make ATP:

1) Substrate-Level Phosphorylation involves the direct transfer of a phosphoryl group onto ADP. It does not use a gradient or the enzyme ATP synthase. This type of phosphorylation happens during glycolysis and in the Citric Acid cycle.

2) Oxidative Phosphorylation uses sets up a concentration gradient of hydrogen ions to pass through the enzyme ATP synthase (enzymes end with “-ase”). As the hydrogen ions pass through the ATP synthase, an ATP molecule is formed. This type of phosphorylation happens during the electron transport chain. Because it forms a gradient of hydrogen ions where the hydrogen ions diffuse from high to low concentrations, it is also called chemiosmotic phosphorylation.

Different parts of cellular respiration use different forms of phosphorylation. Glycolysis and the Citric

Acid cycle make some ATP using substrate-level phosphorylation, and the electron transport chain uses

oxidative phosphorylation.

There are three steps to Aerobic Cellular Respiration:

1) Glycolysis happens in the cytoplasm, outside of the mitochondrion. 2) The Citric Acid cycle (also called the Krebs cycle) occurs inside the mitochondrion. 3) The Electron Transport chain also occurs inside the mitochondrion.

7. What does adenosine diphosphate need to become adenosine triphosphate?

ADP needs to have one more phosphate group added to it to become ATP.

8. What is it called when a phosphate group (really a phosphoryl group) is added to a molecule?

When a phosphate group (really a phosphoryl group) is added to a molecule, it is called phosphorylation.

9. What are the two types of phosphorylation? The two types of phosphorylation are substrate-level phosphorylation and oxidative phosphorylation.

10. What are the three steps to cellular respiration?

The three steps to cellular respiration are glycolysis, the Citric Acid cycle and the electrons transport chain.

11. Where does glycolysis occur? What kind of phosphorylation does it use to make ATP?

Glycolysis occurs in the cytoplasm. Glycolysis used substrate-level phosphorylation to make ATP.

12. Where does the Citric Acid occur? What kind of phosphorylation does it use to make ATP?

The Citric Acid cycle occurs in the mitochondrion. It uses substrate-level phosphorylation.

13. Where does the electron transport chain occur? What kind of phosphorylation does it use to make ATP?

The electron transport chain occurs in the mitochondrion (in the inner membrane). It uses oxidative phosphorylation to make ATP.

Now let’s engage in Cellular Respiration on our own – refer to the cutouts at the end of this section.



The steps in Aerobic Cellular Respiration:

1. Cut out the 6 carbon atoms, the 12 hydrogen atoms, and the 18 oxygen atoms, the Acetyl Coenzyme

A (into a rectangle) and the NADH molecule (into a rectangle). Also cut out the phosphate group, the

ADP molecule, the ATP synthase (into a rectangle), the hydrogen ion and the double membrane system

of the mitochondrion (into a rectangle).

2. Make the reactants for cellular respiration: glucose and 6 O2 molecules. Do not put them into the

mitochondrion yet. Keep them outside of the mitochondrion, in the cytoplasm of the cell. (Remember

that the mitochondrion is an organelle inside of eukaryotic cells.)

3. The first step in cellular respiration is glycolysis. Glycolysis occurs in the cytoplasm, outside of the

mitochondrion, but still inside the cell. Glyco- means glucose, and lysis means split. Split glucose into

two pyruvate molecules. (Move the extra hydrogen atoms out of your work area—they are used in

other parts of the process.)

Pyruvate:

Glycolysis releases enough energy to make 2 ATP molecules using substrate-level phosphorylation.

Move the phosphate group onto the ADP to make ATP—do NOT use the enzyme ATP synthase in this

process. (Use the “O” on the right of the phosphate group to cover up the “OH” on the left of the ADP

H O

H –C – C – C – O – H

H O



molecule.) Do this twice to symbolize that 2 ATPs are formed in glycolysis—count out loud so your group

knows how many ATP molecules you formed.

4. If oxygen is present, the two pyruvate molecules can enter the mitochondrion to start the Citric Acid

cycle (Krebs cycle). The pyruvate releases a carbon to form CO2, and bonds with coenzyme A to form

acetyl CoA.

Take a CO2 off of the pyruvate, and release it (remove it from your work area). The rest of the pyruvate

will bond with coenzyme A to form Acetyl-CoA. Take Acetyl-CoA and put it into the Citric Acid cycle

(Krebs cycle) in the mitochondrion. As the Acetyl-CoA moves around the cycle, it releases two more CO2

molecules.

Acetyl Coenzyme A

Acetyl-CoA moves around the Krebs cycle it charges up two more ATP molecules. Add the phosphate

group to the ADP molecule to make ATP (put the “-O” on the phosphate over the “-OH” on the ADP). Do

this twice to symbolize the 2 ATP molecules that are made during the Krebs cycle (Citric Acid cycle).

Glycolysis and the Krebs cycle use substrate-level phosphorylation, so do not use the ATP synthase.

5. During the Citric Acid cycle, ATP isn’t the only molecule that is made. A high-energy electron carrier

is also produced. NADH carries high-energy electrons and pumps hydrogen ions out of the inner

membrane. This NADH molecule is critical to the last step of cellular respiration: the Electron Transport

chain.

Move the NADH molecule to protein complex I, and have it push one H+ out of the inner membrane

(but not out of the outer membrane). Then, move the hydrogen ion back into the inner membrane

area through the ATP synthase enzyme. As you move the hydrogen ion through ATP synthase, make

an ATP from the phosphate group and ADP. Do this 32 times to represent the 32 ATP molecules made

during the electron transport chain. Since you are using a gradient and the enzyme ATP synthase, this

is oxidative phosphorylation (also called chemiosmotic phosphorylation because it uses a chemical

gradient). Please note: This result is under ideal conditions, and 32 ATPs are not always produced.

NADH

The 4 ATP molecules made by substrate-level phosphorylation during glycolysis and the Krebs cycle are

important, but cannot compare to the large amount produced by oxidative phosphorylation during the

electron transport chain. Using the chemical gradient of hydrogen ions to turn the enzyme ATP synthase

makes a very large amount of ATP molecules.

But, remember—this process can only happen if oxygen is present. If there is no oxygen, then the only

step that a cell can complete is glycolysis.



Please note: Cellular respiration is actually a very complex process, and this activity was a simplification

of the overall series of reactions. There are many steps that have been left out or slightly changed, but

the activity remains a great place to start your journey into this amazing process that we couldn’t live

without.

The main sugar in blood is glucose (which is why we

call it the blood sugar), so we primarily focus on how

glucose is broken down to release its energy.

However, whichever of the three main foodstuffs you

eat (proteins, carbohydrates and lipids), all of those

macromolecules will be broken down and each will be

converted into Acetyl-CoA. If oxygen is present, the

Acetyl-CoA can then enter the mitochondrion and

complete the Krebs cycle and the electron transport

chain.

14. What is the only step in cellular respiration that occurs outside of the mitochondrion?

Glycolysis is the step in cellular respiration that occurs outside of the mitochondrion.

15. What step in cellular respiration is the largest producer of ATP: glycolysis, the Citric Acid cycle or the electron transport chain?

The electron transport chain makes the most ATP molecules during cellular respiration.



16. If there is no oxygen, can aerobic cellular respiration occur?

Cellular respiration requires oxygen to be present, so it cannot occur without it.

17. Copy the sentence and fill in the blank: Glycolysis breaks glucose down into two ____________ molecules.

Glycolysis breaks glucose down into two pyruvate molecules.

18. What molecule enters the Krebs cycle? Acetyl-CoA enters the Krebs cycle.

19. The Krebs cycle makes two ATP molecules. What other molecule does the Krebs cycle make?

In addition to the two ATP molecules, the Krebs cycle also makes the molecule NADH.

20. What does the NADH molecule do during the electron transport chain?

The NADH molecule sets up a concentration gradient by putting hydrogen ions outside of the inner membrane.

21. Under ideal conditions, how many ATP molecules will be made during the electron transport chain?

Under ideal conditions, 32 ATP molecules will be made in the electron transport chain.

22. Under ideal conditions, how many ATP molecules will be made during cellular respiration (glycolysis, the Citric Acid cycle and the electron transport chain)?

Under ideal conditions, 36 ATP molecules will be made during cellular respiration.

23. When someone eats a carbohydrate, it is converted to glucose which is then converted into pyruvate and Acetyl-CoA. What happens to the other macromolecules (proteins and lipids) when someone eats them?

Proteins and lipids are also broken down and converted into Acetyl-CoA, which then can enter the Krebs cycle and the electron transport chain, if oxygen is present.




MITOCHONDRION

ATOMS AND BONDS

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––

C H H O O O –– –– –– –– –– ––




Acetyl Coenzyme A NADH H+

PHOSPHATE GROUP AND ADP

ATP SYNTHASE AND INNER MITOCHONDRION


Chemical Pathways of Aerobic Respiration 27

Section 7.5 Chemical Pathways of Aerobic Respiration Directions for the Student:


Objectives:


Fermentation 28

Section 7.6 Fermentation Directions for the Student:


Objectives: 1. Explain why fermentation is a necessary form of ATP production. 2. Describe the conditions necessary for fermentation to occur. 3. Differentiate between lactic acid fermentation and alcoholic fermentation.

Imagine that you are an artist and you are painting your masterpiece. It’s the middle of the night, but

you are still “in the zone” and painting away. All of a sudden, you notice that you have run out of green

paint! No stores are open at this time, and online ordering will take a day or two.

Then you remember that there is another way to make green paint; just mix equal amounts of blue and

yellow paint together!

You check your supplies and find 12 tubes of blue paint and 5 tubes of yellow paint.

1. Draw the 12 tubes of blue paint and the 5 tubes of yellow paint. Color each tube of paint OR label each one with a “B” for blue and a “Y” for yellow. Do not worry if your tubes of paint are not beautiful—just draw them out as best as you can, quickly.

Students will draw 12 tubes of blue paint and 5 tubes of yellow paint.

2. How many times will you be able to mix a blue tube of paint together with a yellow tube of paint?

You will be able to mix a tube of blue paint with a tube of yellow paint 5 times.

3. How many tubes worth of GREEN paint will you be able to make, total? Explain your answer. (Remember, 1 tube of blue and 1 tube of yellow will make 2 tubes of green after they are mixed.)

You will be able to make 10 tubes of green paint. Because you half of 1 blue tube AND half of 1 tube of yellow paint, you can only mix them as long as you have BOTH ingredients. With only 5 tubes of yellow, and each tube making up half of a new tube of green paint, you can only mix them 5 times to get 10 green, total.

You mix your blue and yellow paint together to make as much green paint as you can. Then, you look in

one more drawer and find a box of blue paint with 100 tubes in it, but no more yellow paint.

4. Now that you found a bunch of blue paint, how much more green paint can you make now? Explain how you got your answer.

You cannot make any more green paint because there is no more yellow paint. To make green paint, you need equal parts blue AND yellow. Without any yellow, you cannot make any green.


Fermentation 29

In this situation, the yellow paint is a limiting factor. This means that the yellow paint will limit how

many times the reaction can occur—as soon as the yellow paint runs out, you can’t make any more

green paint, even if you have a lot more blue paint. This is very similar to glycolysis and fermentation.

Normally, we have enough oxygen and we can perform cellular respiration. Cellular respiration has

three steps: Glycolysis (in the cytosol), the Krebs Cycle (in the mitochondrion) and the Electron

Transport Chain (in the mitochondrion).

The ETC uses NADH to carry its high-energy electrons, and then it gives NAD+ to glycolysis so that

glycolysis can happen again.

Overall, glycolysis looks like this:

1 Glucose + 2 [NAD]+ + 2 ADP + 2 Phosphate groups 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O

Notice the NAD+ is part of the reactants. The electron transport chain gives this important reactant to

glycolysis.

5. What would happen if the ETC did not give a NAD+ to glycolysis? (Think back to what happened when there was not enough yellow paint.)

If the ETC did not give an NAD+ to glycolysis, then glycolysis could not happen at all. Glycolysis depends on having NAD+.

Without all of the reactants, a reaction cannot occur. It’s a good thing the ETC gives NAD+ to glycolysis,

because, without the NAD+, glycolysis couldn’t happen at all!

NAD+


Fermentation 30

But, sometimes, the ETC can’t occur. Sometimes, we don’t have enough oxygen, and, if there is not

enough oxygen, the only step our cells can perform is glycolysis. Conditions that do not supply oxygen

are called anaerobic conditions.

But, how can we get enough NAD+ to glycolysis? Where will the NAD+ come from if our cells do not have

enough oxygen to do the Krebs Cycle and the ETC?

Our cells need a constant supply of ATP. So, to solve this problem, our cells perform fermentation,

which returns an NAD+ and allows glycolysis to continue. This allows our cells to have a supply of ATP

even without oxygen.

6. What does the ETC give to glycolysis? The electron transport chain gives NAD+ to glycolysis, which allows glycolysis to occur.

7. What parts of cellular respiration cannot occur if there is no oxygen?

If there is no oxygen, the Krebs cycle and the electron transport chain cannot occur.

8. Under anaerobic conditions, what is the only way our cells can produce ATP?

Under anaerobic conditions, our cells can only produce oxygen through glycolysis.

9. Without NAD+ from the electron transport chain, glycolysis cannot occur. How does the cell solve this problem?

When the ETC does not occur due to the anaerobic conditions, the cell performs fermentation, which supplies NAD+ so that glycolysis can continue.

There are two types of fermentation:

1. Lactic Acid Fermentation

2. Alcoholic Fermentation

Humans take the pyruvic acids from glycolysis and can convert them to lactic acid. This returns a NAD+ to glycolysis, but it also produces an acid, which is why you may feel a burning sensation during strenuous exercise. The lactic acid takes some time for our bodies to remove.


Fermentation 31

Glycolysis looks like this:

1 Glucose + 2 [NAD]+ + 2 ADP + 2 Phosphate groups 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O

Lactic Acid Fermentation looks like this:

Pyruvic Acid + NADH Lactic Acid + NAD+

Pyruvates are the conjugate base of pyruvic acids and are easily converted to each other. The

difference is that pyruvic acid has an additional hydrogen than pyruvate. Pyruvic acid is CH3COCOOH

while pyruvate is CH3COCOO-.

Glycolysis is form of ATP production that uses substrate-level phosphorylation, producing just 2 ATP

molecules. While it is not as effective as the ETC with its oxidative phosphorylation, glycolysis and

fermentation are necessary because they produce ATP molecules under anaerobic conditions. However,

we can perform glycolysis and fermentation many times, which can end up producing many ATP

molecules.

Lactic Acid fermentation is how many organisms (most eukaryotes and most prokaryotes) continue to

make ATP under anaerobic conditions, but yeasts (which are unicellular eukaryotes) and a few other

microorganisms can perform different type of fermentation.

Alcoholic Fermentation looks like this:

Pyruvic Acid + NADH Alcohol + CO2 + NAD+

This type of fermentation returns NAD+ to glycolysis so that it can keep going (just like Lactic Acid

fermentation), but this produces an alcohol instead of an acid. The alcohol it produces is ethanol.

10. Explain why fermentation is so important. Fermentation returns a needed reactant to glycolysis (NAD+) so that glycolysis can continue to make ATP during anaerobic conditions when the Krebs cycle and the ETC cannot occur.

11. Research how people use fermentation in their daily lives. List and explain a few of its uses.

Answers will vary, but will likely include how people have used yeasts to make bread rise (alcoholic fermentation) and/or how prokaryotes use lactic acid fermentation to produce cheese, sour cream, and pickled foods.

Documents

Integrated General Biology3. Develop a list of substances that a cell may need to move across the plasma membrane. These substances may be moving either into or out of the cell. Oxygen,