Redox
Where does the name "redox" come from?
It is a combination of the words "reduction" and "oxidation" because a redox reaction is when there is a transfer of electrons.
What are the three parts of substrate-level phosphorylation?
Glycolysis, pyruvate oxidation, and Krebs cycle
Why is cellular respiration also called aerobic respiration?
Aerobic means something requiring oxygen and oxygen is the last electron acceptor in cellular respiration.
What is the source of O2 in photosynthesis?
The splitting of water is the source of O2
What is the source of energy for photosynthesis?
The sun is the source of light energy for photosynthesis
What is the difference between oxidation and reduction?
Oxidation is when a reactant loses electrons and reduction is when a reactant gains electrons.
Why is substrate-level phosphorylation called substrate-level phosphorylation?
Because enzyme-substrate relationships are being used to phosphorylate ADP. Phosphorylating ADP creates ATP which is the main purpose of cellular respiration.
Which is more acidic, the intermembrane space or the matrix, and why?
During the electron transport chain, protons are being pumped from the matrix into the intermembrane space. Since the intermembrane space has more protons, it is more acidic. This means it has a lower pH.
Where is the bulk of ATP produced for plant cells? Chloroplast or mitochondria? Why?
The light reactions of photosynthesis produce ATP but this ATP is used to power the Calvin cycle. That means that plant cells get ATP to use for biochemical processes from cellular respiration.
Is glucose a direct product of the Calvin cycle?
No because glucose is not directly made during the Calvin cycle. Instead, G3P is made and this molecule has 3 carbons, so two G3P molecules can be used to make 1 glucose molecule.
In this reaction, C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O, what is being oxidized?
Glucose is being oxidized to CO2. This is because it is going from glucose (a more complex molecule) to CO2 (a less complex molecule), so glucose is losing electrons/energy.
Describe the priming, cleavage, and energy-harvesting reactions of glycolysis.
The priming reactions are when glucose is primed and 2 ATP are used up. The cleavage reactions are when the 6-carbon molecule is split into two 3-carbon molecules. The energy-harvesting reactions are when ATP and NADH are harvested from each 3-carbon molecule. This produces 4 ATP, 2 NADH, and 2 pyruvate molecules.
Is the process of chemiosmosis passive or active and why?
It is passive because the protons are going down their concentration gradient (from high concentration to low concentration).
What is the main pigment molecule for photosynthesis? What do the accessory pigment molecules do during photosynthesis?
Chlorophyll is the main pigment molecule. Accessory pigments absorb light at different wavelengths and assist chlorophyll with the absorption of light. These accessory pigments pass their absorbed energy to chlorophyll.
What are the two enzymatic activities of Rubisco and when are they both favored?
The two enzymatic activities are carboxylation and photorespiration. Carboxylation is favored under normal conditions and photorespiration is favored in hot, dry conditions.
In this reaction, C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O, what is being reduced?
O2 is being reduced to water. This is because water is a more complex molecule than O2, so O2 is gaining electrons/energy.
Briefly describe the Krebs cycle and the net result of one full cycle.
Acetyl CoA (2-carbon molecule) combines with oxaloacetate (4-carbon molecule) to make citrate (6-carbon molecule). 1 CO2 and NADH is released making a 5-carbon molecule (alpha-ketoglutarate). Another CO2 and NADH is released making a 4-carbon molecule. 1 GTP is made in the next step. 1 FADH2 is made in the step after that. H2O is put into the cycle. Finally, 1 NADH is released and oxaloacetate is created to restart the cycle. The net result is 2 CO2, 3 NADH, 1 GTP, and 1 FADH2.
What is the purpose of the electron carriers (NADH and FADH2) that were made during substrate-level phosphorylation?
They carry electrons which they transfer to the carrier proteins that are embedded in the inner membrane of the mitochondria and are part of the electron transport chain. These electrons are used to pump protons across the inner membrane into the intermembrane space which creates the electrochemical gradient.
During Engelmann's experiment, which wavelengths of light had the most aerobic bacteria and why?
Violet-blue and red light are going to produce the most amount of oxygen because photosynthesis is the most efficient at those wavelengths. That is because chlorophyll absorbs the blue range of light and red range of light the best. Since these wavelengths produce the most oxygen which aerobic bacteria need to survive, they are going to have the most aerobic bacteria.
Describe the three phases of the Calvin cycle.
The three phases are carbon fixation, reduction, and regeneration of RuBP. Carbon fixation is when Rubisco combines CO2 and RuBP (five-carbon molecule) to make six-carbon intermediate. This six-carbon intermediate splits into two molecules of 3-PGA. Reduction is when ATP and NADPH are used to turn 3-PGA molecules into G3P molecules. Some G3P molecules leave the cycle to be turned into glucose. Regeneration is when the rest of the G3P molecules are used to regenerate RuBP to be combined with CO2 again. Additional ATP is used to power this step.
For the electron carrier NAD+/NADH, which is the reduced form and which is the oxidized form?
NAD+ is the oxidized form and NADH is the reduced form. This is because NADH has gained an electron making it neutral instead of having a positive charge.
If cellular respiration has a ΔG of -686 kcal/mol of glucose, what does that tell you about the reaction?
Since ΔG is negative, it means that cellular respiration is a catabolic and exergonic reaction. Since it is exergonic, it is breaking down complex molecules and releasing energy in the process. It is also a spontaneous reaction which means that it can occur without any input from an outside source.
Compare and contrast cellular respiration and photosynthesis.
Photosynthesis converts CO2 and water into O2 and glucose. Cellular respiration converts glucose and O2 into CO2 and water. Both use protein complexes to pump protons and create electrochemical gradient that will be used to make ATP with ATP synthase. Both use electron carriers and ATP. Both use a cycle of some kind (Krebs cycle and Calvin cycle). The Krebs cycle regenerates oxaloacetate, while the Calvin cycle regenerates RuBP. Cellular respiration mainly occurs in the mitochondria, while photosynthesis mainly occurs in the chloroplast. Cellular respiration is a catabolic and exergonic process, while photosynthesis is an anabolic and endergonic process.
Describe how the light-dependent reactions work (think Z-diagram).
Water is split which releases both O2 and electrons. These electrons are taken up by P680 in photosystem II. Light energy hits the pigment molecules and is handed off to P680. The electrons are excited from this energy and they are passed off to a primary electron acceptor. These electrons go down an electron transport chain which pumps protons into the thylakoid space. These protons create an electrochemical gradient that is used to make ATP. The electrons are passed to P700 of photosystem I and light energy excites the electrons. They are passed off to a primary electron acceptor and they go down an electron transport chain. One of the protein complexes in this chain is NADP reductase which reduces NADP to make NADPH.
Describe what happens during photorespiration and how different types of plants overcome this problem.
Photorespiration is when Rubisco fixes oxygen instead of carbon like it usually does for the Calvin cycle. This is not helpful for the plant because it uses up ATP and NADPH to create a waste product that the plant cells can't use. So it is wasting materials with no return.
C4 plants overcome this problem by spatially separating the steps of the Calvin cycle. CO2 is instead fixed in the mesophyll cells and the Calvin cycle runs in the bundle-sheath cells. CO2 is also incorporated into a four-carbon compound using an enzyme that has a higher affinity for CO2 than Rubisco.
CAM plants overcome this problem by temporally separating the steps of the Calvin cycle. The stomata are opened at night and CO2 is incorporated into organic acids. During the day, the stomata are closed and CO2 is released from the organic acids and is used in the Calvin cycle.