I Just Need a Break
Define anaerobic.
Without oxygen.
In what type of organisms and what part of the organism does photosynthesis occur?
(Photo)autotrophs in the leaves
- specifically in the mesophyll
What organisms perform cellular respiration?
All organisms perform cellular respiration.
Why are photosynthesis and cellular respiration considered a cycle? How does this apply to plants? How does it apply to animals?
The products of one are the reactants to the other.
In plants: The chloroplast releases O2 and glucose that the mitochondria uses in cell resp; the mitochondria releases CO2 and Water which the chloroplast uses in photosynthesis.
Plants release O2 to the atmosphere and are a food/glucose source, providing animals with the reactants of cellular respiration. Animals exhale CO2, which is used by the plants in photosynthesis.
A plant is placed in continuous darkness but still has access to water and carbon dioxide. Predict which stages of photosynthesis will stop immediately and which will stop indirectly—and explain why
In continuous darkness, the light-dependent reactions stop immediately because they need light to make ATP and NADPH.
The Calvin cycle stops indirectly because it depends on ATP and NADPH from the light reactions to make glucose, so it can’t continue once those run out.
Where is the ETC of photosynthesis? Cell Resp?
Photosynthesis: Thylakoid membrane
Cellular Respiration: Inner Mitochondrial Membrane
Where do the light independent reactions of photosynthesis occur?
Stroma of the thylakoid
During what step of cellular respiration is the most ATP produced?
Oxidative Phosphorylation (ETC & Chemiosmosis)
Explain how ATP acts as an energy “currency” in both processes, but describe how its role differs in photosynthesis versus cellular respiration.
ATP is the cell’s energy “currency” because energy is stored in its phosphate bonds and released when ATP becomes ADP.
In cellular respiration, ATP is the main product made from breaking down glucose. In photosynthesis, ATP is made using light energy but is used right away to help build glucose. So, respiration produces ATP for cell work, while photosynthesis uses ATP to store energy in sugar.
If carbon dioxide levels rise significantly in the atmosphere, explain how this could initially affect photosynthesis and why the effect might not continue indefinitely.
Higher CO₂ can initially increase photosynthesis because more carbon is available for the Calvin cycle.
However, the effect may not continue indefinitely because other factors—like light, water, or nutrients—can limit the rate of photosynthesis.
What type of transport moves the pyruvate into the mitochondria?
Active transport via carrier proteins.
What term describes the movement of protons across the thylakoid membrane to generate ATP?
Chemiosmosis
What happens after glycolysis if oxygen is present? If it is not present?
With oxygen: pyruvate is transported into the mitochondria for pyruvate oxidation
Without oxygen: pyruvate enters fermentation
Compare the role of oxygen in cellular respiration to the role of carbon dioxide in photosynthesis. Why are both essential but in different ways?
Oxygen in cellular respiration acts as the final electron acceptor in the electron transport chain, allowing ATP production to continue. Without oxygen, the chain stops and much less ATP is made.
CO2 in photosynthesis is the carbon source used to build glucose. Without carbon dioxide, sugars cannot be formed.
Both are essential because oxygen allows energy release from food, while carbon dioxide allows energy storage in sugar—but they function in opposite processes.
During intense exercise, muscle cells may switch partially to fermentation. Explain Why!
During intense exercise, muscles may lack enough oxygen for full aerobic cellular respiration.
Cells switch to fermentation (or add in fermentation) to keep producing ATP quickly, even though it makes much less ATP and produces lactic acid.
Compare and contrast NADPH vs NADH
NADPH is in photosynthesis; NADH is in cellular respiration
Both are electron carriers/coenzymes
List the molecules that are cycled between the light independent and dependent rxns of photosynthesis.
Light dependent produces NADPH and ATP for the light independent to use. The light independent produces NADP+ and ADP++Pi
List the VIP (very/most important product) of each step:
1. Glycolysis
2. Pyruvate Oxidation
3. Krebs Cycle
4. Oxidative Phosphorylation
1. 2 Pyruvates
2. Acetyl-CoA
3. Coenzymes: NADH, FADH2
4. ATP!
Compare/contrast the mitochondria and chloroplast inner membrane.
Both inner membranes are the site of the ETC for a process. The mitochondrial inner membrane is folded to increase surface area so their are more electron transport chains, directly supporting its function to make ATP.
If the thylakoid membrane became leaky to hydrogen ions, explain how this would impact ATP production in photosynthesis.
If the thylakoid membrane became leaky, the proton gradient would collapse, so protons couldn’t flow through ATP synthase.
As a result, ATP production would drop and the Calvin cycle couldn’t run efficiently.
The calvin cycle is part of _____. The krebs cycle is part of ___.
photosynthesis, cellular respiration
What is the three-carbon molecule that is a precursor to glucose?
G3P
During lactic acid fermentation, what happens? Why is this important?
Pyruvate is turned into lactate, cycling NADH & NAD+
If there is a high concentration of pyruvate, glycolysis would stop (because it's goal is to make pyruvate) leading to no energy production. Pyruvate converting to lactate makes it so glycolysis will continue, providing some ATP for the cell.
Compare chemiosmosis in chloroplasts and mitochondria. What is fundamentally the same, and what is reversed?
Chemiosmosis in both chloroplasts and mitochondria uses a proton gradient to drive ATP production through ATP synthase.
In mitochondria, protons are pumped from the matrix into the intermembrane space and flow back to the matrix to make ATP.
In chloroplasts, protons are pumped into the stroma and only some will return to the inside of the thylakoid.
The process is the same, but the direction of proton flow is reversed.
If the mitochondrial membrane became leaky to hydrogen ions, explain how this would impact ATP production.
If the mitochondrial membrane became leaky, the proton gradient would collapse, so protons couldn’t flow through ATP synthase.
This would reduce ATP production, making cellular respiration much less efficient.
Differentiate between a CAM plant and a C4 plant
CAM plants have temporal adaptations, meaning their stomata at different times of day.
C4 plants have spatial adaptations, meaning they separate the steps of photosynthesis into different cells/parts of the leaf.
In photosynthesis, what would happen if ATP were produced but NADPH were not?
If ATP were produced and NADPH was not, the light dependent reactions of photosynthesis could not happen because reduction (the second step of the calvin cycle) requires the hydrogen from NADPH to make G3P. Glucose would not be produces.
Explain how the BTB was used to represent the rate of cellular respiration in the exercise lab.
BTB changes color when it comes in contact with an acid that is produced by CO2+H2O.
When a person exhales and releases CO2, this process occurs.
You can tell the rate because after exercise, each exhale will have an increased concentration of CO2, producing the acid faster, shown by the shorter time taken to turn BTB yellow.
Why is photosynthesis not simply the “reverse” of cellular respiration, even though their overall chemical equations appear opposite?
Respiration releases energy from glucose using enzymes and electron transport, while photosynthesis stores energy from light to build glucose. The steps and energy flow are not simply backward.
If a toxin blocked NADP⁺ reduction in the chloroplast, explain how this would affect photosynthesis.
If NADP⁺ can’t be reduced to NADPH, the light-dependent reactions can’t store energy.
Without NADPH, the Calvin cycle can’t make glucose, so photosynthesis would stop.