TEST 2 MATERIAL Flashcards
Which compound is the first reactant in the krebs cycle? Which reaction takes place as it enters the mitochondrion, and what is the product of this reaction?
Pyruvate is oxidized to form acetyl CoA as it enters the mitochondrion, by releasing CO2 to be replaced by Coenzyme A.
What is FAD/FADH2, and what is it’s role?
FAD is an electron transporter, similar to NAD+, but with lower energy electrons. Also, it must remain in the mitochondrion.
What are the yields of the Krebs cycle?
1 ATP, 2 CO2, 3 NADH, and 1 FADH2. (per pyruvate)
What is the role of NADH and FADH2?
The cell uses the energy found in the high energy electrons that these molecules contain to create a proton motor force, the electrons are passed to the electron transport chain and a protein complex of electron carriers will pump H+ into the inner membrane space.
What is oxidative phosphorylation, chemiosmosis and the electron transport chain?
The electron transport chain is the process in which energy in the electrons from NADH and FADH2 are used to pump H+ into the inner membrane space. Chemiosmosis is the process by which the H+ molecules diffuse back into the mitochondrion matrix using ATP synthase, which produces ATP as H+ makes it spin as it passes through. Oxidatitive phosphorylation is the combination of both these processes.
What happens to the H+ molecules as they enter the mitochodrion matrix during chemiosmosis?
To maintain the H+ concentration gradient between the mitochondrial matrix and the inner membrane space, the cell must get rid of H+ molecules inside the matrix. This is done by binding them to the electrons coming out of the electron transport chain and binding these to O2 to form H2O. This is aerobic respiration, in anaerobic respiration, the binding molecule is not O2.
What are the yields of chemiosmosis?
30 ATP (net)
What is fermentation, and why does it occur?
Fermentation is a process alternative to respiration, it occurs when the cell does not have enough oxygen present, and cannot bind electrons product of the electron transport chain to O2. Instead, it uses an organic molecule product of glycolysis. Only glycolysis occurs. This occurs to allow for the recycling of NAD+ from NADH and for glucose metabolism to continue.
What enzymatic rections are the 2 checkpoints where the metabolism of glucose is regulated? By what mechanism and molecule are these enzymes regualted?
- Phosphofructokinase: allosteric regulation. ADP stimulates, ATP and citrate inhibit.
- Pyruvate dehydrogenase: alosteric regulation. Acetyl CoA, NADH and ATP inhibit, while ADP and Pyruvate stimulate
Why is it important to regulate cellular respiration? How is this process regulated (What is this regulation an example of)?
It is important to regulate cellular respiration not to deplete certain metabolites or have an accumulation of others.
Cellular respiration is regulated by feedback inhibition, where later products in a biochemical pathway inhibits earlier reactions.
What is the difference between aerobic and anaerobic respiration?
Aerobic respiration is when an organism uses oxygen to bind electrons from the electron transport chain and H+ from chemiosmosis to make H2O when binding to O2. Anaerobic respiration is when a different molecule than O2 is used to bind H+ and electrons.
What is the role of pigments in photosynthesis? how do they accomplish this?
To capture light energy in the visible range and to transform this energy into chemical energy.
To capture this visible light, the magnesium ion in the center of chlorophyll is excited by the photon, and through resonance in the polyphorin ring, electrons move from one atom to the next in resonance to pass energy to another molecule.
What are the names of the possible pigments found in plants, and where are they located in the cell? How do they absorb
Chlorophyll A, Chlorophyll B, and carotenoids. These pigments are found in the thylakoid membrane.
What are the components in a photosystem?
Antena complex, made of chlorophyll molecules, and the reaction center, made of 2 chlorophyll A molecules that can trap energy
Explain the mechanism of the passing of electrons in the reaction center.
An electron in the reaction center is excited by the energy harvested in the antenna complex, then leaves to carry out photosynthesis and is replaced by an electron resulting from the breakdown of water.
What are the 4 steps of light dependent reactions, and what are they?
1: primary photoevent, pigments are excited by a photon
2: charge separation, energy is transfered to an electron in the reaction center
3: electron transport chain, the electron is passed through the electron transport chain to create an H+ gradient, and the electrons are used to reduce NADPH
4: chemiosmosis, H+ come back to make ATP
How is NADPH and ATP generated from photosystems II and I, and what is this energy used for in each reaction?
Quinone transports the high energy electron to the electron transport chain, (b6-f complex) by photosystem II, (P680), this creates ATP through chemiosmosis. Then, the electron is stimulated in photosystem I, (P700) and is used to reduce NADP+, to NADPH.
The energy from both these reactions are used to power the calvin cycle, and produce sugar.
Where are the H+ molecules being pumped to in photosynthesis, and where do they come from?
into the lumen, and they come from water that is broken down for it’s electrons.
What are the 3 steps in the calvin cycle, and what are they?
1: carbon fixation: the rubisco enzyme binds CO2
2: reduction: it then reduces CO2 to form G3P
3: regeneration of RuBP: some G3P is used to generate stocks of RuBP, an acceptor of CO2
What are the net products and losses of the calvin cycle?
1 G3P, -9 ATP, -6 NADP
What is photorespiration?
Photorespiration is the process in which O2 binds to rubisco instead of CO2. This is competitive inhibition, as they both bind to the active site of rubisco due to CO2 and O2’s similar structures.
What are the advanteges and disadvantages of photorespiration?
Pro: allows for the cell to get rid of O2, which can be toxic, as it can cause photo-oxidative damage.
Con: Releases CO2 at the cost of ATP.
What factors influence the frequency of photorespiration, and why?
Levels of CO2/O2, as this interaction is one of competitive inhibition, the concentration of both substances around the active site of rubisco will determine which one is most likely to bind.
Temperature and water levels, at certain temperatures, the stomata of the plant will close to prevent excessive loss of water. This means that CO2 cannot be taken in and O2 cannot be taken out of the plant. Thus, this will cause an increase in O2 levels in the plant, and a decrease in the efficiency of the calvin cycle.
What are the 3 mechanisms plants have developed to regulate the frequency of photorespiration? How do these mechanisms work?
C3: no mechanism
C4: fixes CO2 to PEP, which delivers the CO2 directly to the active site of rubsico. There 2 types of cells, mesophyll cells that bind the CO2 and bundle sheath cells that take it. Calvin cycle only occurs in bundle sheath cells.
CAM: C4 reactions at night, when it is cooler. Calvin cycle in the day. all in mesophyll cell.
