Matter and Energy: Aerobic Respiration and Photosynthesis

In this lesson, which I foresee occurring over a few days, the students will learn how to demonstrate the processes of photosynthesis and cellular respiration while acknowledging the inputs and outputs of each and the distinct differences between cycles. To me, the best way to learn this information is drawing out the process so that students can follow a visual when studying the processes. As before, my goal for this lesson is to lecture less and get the students involved more. I hope to do this by having students model the different cycles.

HS-LS1-7: Use a model to illustrate that aerobic cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed resulting in a net transfer of energy.

HS-LS1-5: Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy.

TIMELINE OF ACTIVITIES:

1. The class will start with a premade/ internet found diagram of aerobic respiration. This activity will allow them to activate prior knowledge from living environment. I will ask the students how they infer the process of aerobic respiration plays out based on what they see and what they already know. This will be a short conversation due to how heavy and how much material there is to cover.

2. I will then switch to lecture style. I need to give a brief overview of what the major 3 steps of the process are (glycolysis, citric acid cycle, and oxidative phosphorylation) and the products we can expect from each major step. I foresee this taking 15 or so minutes.

3. Next, we will begin our guided drawing. The students will help me construct a labelled drawing of aerobic respiration. They will be telling me what to draw or I can ask them these questions while they come up to the board and draw for me. These are the guided questions that will be asked for glycolysis (red), citric acid cycle (blue), and oxidative phosphorylation (purple).

What molecule should we start with? glucose    

How much ATP do we spend to start glycolysis? 2 ATP

How much ATP does glycolysis produce? 4 ATP

What is our net amount of ATP from glycolysis? What else do we also get? Net amount= 2 ATP, 2 NADH

Why is phosphofructokinase important? What does it create? Enzyme that breaks down glucose and creates (down the line) the pyruvate. It also will shut down glycolysis if it gets too acidic or too much ATP is made.

What happens in the absence of oxygen in glycolysis? Lactic acid and alcohol fermentation

How many pyruvates did we receive from glycolysis? 2 pyruvates

How many turns of the citric acid cycle do we complete? 2 turns

Pyruvate turns into Acetyl coA and condenses with oxaloacetate to form citric acid.

How much CO2 is created during one turn? What else comes from one turn? 2 CO2, 3 NADH, 1 FADH2, 1 ATP

How much do we get (net) from 2 turns: 4 CO2, 6 NADH, 2 FADH2, 2 ATP

How many ATP do we have now? 4 ATP

Oxidative phosphorylation is made up of electron transport chain and chemiosmosis.

NADH and FADH2 pass their electrons to the start of the electron transport chain and turn into the reduced form, NAD+ and FAD.

The membrane of the mitochondria is now made up of H ions

Now, the H ions pass through ATP synthase to go back into the matrix.

How many ATP is produced? 26-28 ATP

GRAND TOTAL OF 32 ATP from one glucose

This is a possible drawing that could result from this. Students will now have this as study material.

4. The next day will focus on photosynthesis. I will start class the same way. This activity will allow them to activate prior knowledge from living environment. I will ask the students how they infer the process of photosynthesis plays out based on what they see and what they already know. This will be a short conversation due to how heavy and how much material there is to cover.

5. I will then switch to lecture style. I need to give a brief overview of what the major 2 steps of the process are (light dependent and calvin cycle) and the products we can expect from each major step. I foresee this taking 20 or so minutes.

6. Next, we will begin our guided drawing. The students will help me construct a labelled drawing of aerobic respiration. They will be telling me what to draw or I can ask them these questions while they come up to the board and draw for me. These are the guided questions that will be asked for light dependent (red) and calvin cycle (blue). 

Light hits the thylakoid membrane and activates photosystem 2.

Water enters the system. What happens when it enters? Splits water to oxygen

Electrons in photosystem 2 get excited. Where is that excitement pushed to? Primary electron acceptor

How do the electrons travel to the cytochrome complex? The electron transport chain

What product is created here? ATP

Electrons follow through to photosystem 1.

More light comes in and gets the electrons super excited. What accepts these electrons? Primary electron acceptor

The electron transport chain then helps reduce NADP+.

What is the reduced form that we get? NADPH

What are our end products? ATP and NADPH

What is essentially going on? Z scheme

ATP and NADPH are inputted into the calvin cycle, our light independent step.

What are the 3 phases of the cycle? Fixation, reduction, regeneration

Our first main input is carbon dioxide.

Carbon dioxide is fixed to what in our fixation phase? RuBP

Our products from the fixation stage are… 6 (3-C sugars), 3-PG

3-PG breaks down into what during our reduction phase? G3P

Which of our preexisting inputs come in? ATP and NADPH

How many G3Ps are produced? How many are used in the next phase? 6,5

What happens to the G3P that doesn’t get used? Glucose

What is produced in the regeneration phase? RuBP

What is inputted in the regeneration phase? ATP

This is a possible drawing that could result from this. Students will now have this as study material.

7. To wrap up the lesson, I would spend a third day (only half the day) talking about how the two processes are similar and different. This would be the activity I give in class. The students can work in pairs or lab groups.

 

Products and where they occur at each stage of cellular respiration:

1. Glycolysis- 2 ATP, 2 NADH, 2 pyruvate-- cytosol

2. Pyruvate oxidation- CO2, NADH, acetyl coA-- pyruvate transport through the inner mit. mem.

3. Citric acid cycle- 4 CO2, 2 ATP, 2 FADH2, 6 NADH-- matrix

4. Oxidative phosphorylation- 26-28 ATP-- inner mit. mem.

Products and where they occur at each stage of photosynthesis:

1. Light dependent- ATP, NADPH, O2-- thylakoid mem.

2. Calvin cycle- stroma

1. Fixation- 6 (3-C sugars), 3-PG

2. Reduction- 6 G3P (one is released for use and 5 continue to be used in next step)

3. Regeneration- RuBP

2 possible destinations for electrons in photosystem 1-- cyclic e- flow (go back to make more ATP), NADP+ reduced to become NADPH

cellular respiration-- catabolic/anabolic-- endergonic/exergonic

Photosynthesis-- catabolic/anabolic-- endergonic/exergonic

REFLECTION:

When it came to this specific lesson, I struggled trying to come up with an activity/lesson plan that would satisfy my goal of not lecturing as much. It is hard with some topics because they are so content heavy and the teacher only has a few days to cover what needs to be covered. Even though I lectured a little more than I wanted to in this lesson, I still think I was able to satisfy my goal. By guiding the students through the construction of the diagram, I was able to give them a little bit more creative reign than just putting a diagram up on the board and asking them to copy it. The diagram was a group effort because each move I made was dictated by how they interpreted my guided questions. I was able to work on literacy and oracy through this specific activity too, which was an added bonus. Overall, I do think I reached my goal because not every lesson is going to allow for the most hands on approach or most time to deviate from learning the facts in a lecture format.