Respiration

Where is the pentose phosphate pathway? Why can't it run in the chloroplast?

cytosol and plastids (it's an alternative to more dominant glycolysis for oxidizing sugars) It cannot run in the chloroplast because it is inhibited by its products fructose-6-phosphate and glyceraldehyde-3-phosphate, which are formed in the chloroplasts as part of the Calvin Cycle.

Why do plants respire? What is the overall equation of respiration?

it releases energy stored in carbon compounds for cellular use, and generates carbon precursors for photosynthesis. free energy is released and stored in ATP that can readily be used by plant cells. reduced carbon comes mainly from sucrose, triose phosphates, and other sugars, lipids, and organic acids (sometimes proteins). overall equation: C12H22O11+ 12O2 --> 12CO2 + 11H2O essentially the oxidation of sucrose and reduction of O2 to water

How do plants adapt to tolerate flooding? name two possible ways.

1. aerenchyma: ducts in the shoot conducting air to roots (basically a ventilation system so that roots have internal oxygen) 2. pneumatophores: root outgrowths that protrude out of water that contain patches that are porous to air on their surface -this is present in plants that are too large for slow aerenchyma oxygen movement

What are the glycolysis reactions? When does anaerobic respiration occur, and what are its end products?

Glycolysis in plants uses sucrose as the substrate, has unique regulatory features, and makes malate and pyruvate as end products. The first three steps require energy input. 1. Sucrose is split into glucose and fructose, and UDP-glucose. 2. These are converted to glucose-6-phosphate and fructose-6-phosphate. 3. These are split into two 3-carbon triose phosphates, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. The second half of steps release energy, yielding small amount of ATP and NADH. 4. The triose phosphates are oxidized to produce two 3-carbon organic acid molecules, phosphoenolpyruvate (PEP), which can be converted to pyruvate, yielding ATP, or oxaloacetate, and then malate. 5. pyruvate and malate can enter mitochondrion to be used in the CAC. Anaerobic respiration occurs when there is no oxygen available so the CAC and oxidative phosphorylation cannot occur, so glycolysis is the main energy source. With fermentation, pyruvate and malate are broken down into ethanol and CO2 or lactic acid. energy production: 4 ATP per sucrose

How does respiration typically respond to higher temperature? Why? How does this typically influence plant growth? Are there exceptions? If plants grow a long time at higher temperature what happens to their respiration rates? What are the implications for atmospheric CO2 and feedback on global temperature?

It typically increases because overall metabolic activity increases with increased temperatures (they require lots of energy). This typically slows growth because increased night time respiration cannot be mitigated by photosynthesis (there are 2 exceptions to this). At first, their respiration rates will increase, but they will eventually acclimate and return to original rates. increased CO2 means increased temperatures and therefore increased respiration. BUT at the same time, with more CO2, plants can also do more photosynthesis, and they have potentials to acclimate to changing conditions as well. Plant scientists continue to study this because there are many possibilities.

What is oxidative phosphorylation? Where does it occur? What are its inputs and outputs? What is the role of chemiosmotic gradient in oxidative phosphorylation, and where does it exist?

What: the mitochondrial process that uses oxygen and high-energy electrons to produce ATP and water. it consists of electron transport intermembrane-bound proteins. Where: intermembrane space of the mitochondrion Inputs: NADH and FADH2 Outputs: ATP and H2O Role of chemiosmotic gradient: drives the generation of ATP from ADP by the F0F1-ATPY synthase; it's also involved in the movement of organic acids of the CAC, and ATP, out of the mitochondria. Where chemiosmotic gradient exists: attached to the matrix side of the inner membrane

How does the chemiosmotic gradient help to move organic acids

carbon compounds are transported in and out of matrix to intermembrane space in association with transport of OH- and Pi2- to the intermembrane space, exchanged with H+ and Pi-

Please describe the citric acid cycle, indicating what are the inputs and outputs, and additionally using the following terms: mitochondrion, pyruvate dehydrogenase, succinate dehydrogenase.

inputs: pyruvate and acetyl co-A outputs: NADH, CO2, FADH2, ATP The CAC involves reactions carried out by enzymes in the matrix of mitochondria, except for succinate dehydrogenase which is in the inner mitochondrial membrane (this allows for coordination with oxidative phosphorylation later). Sucrose is broken down to pyruvate yielding 25% less than energy in sucrose, with the rest stored in pyruvate. 1. pyruvate is moved through the impermeable inner mitochondrial membrane via a specific transport protein. 2. pyruvate is decarboxylated by pyruvate dehydrogenase, making CO2, NADH, and acetyl-Co-A which enters the cycle. 3. Oxidative decarboxylations occur (with additional CO2 release), and NADH, ATP, and FADH2 are made. The CAC in plants has more flexibility than in animals because its intermediates can be interconverted (malate to pyruvate).

How does plant respiration change with flooding?

it decreases with flooding of the roots (except when plants have special adaptations)

In which step(s) of aerobic respiration does virtually all energy production occur?

most energy is yielded through the CAC (50 ATP/sucrose) vs 10 ATP/sucrose produced in glycolysis

How do tissues differ in respiration rates?

the greater the overall metabolic activity, the greater the respiration rate. developing buds like fine roots and leaves respire the most. respiration declines as tissues and whole plants age

How does the chemiosmotic gradient help move ATP out of the mitochondria?

the high positive charge in the intermembrane space allows ATP to be exchanged for ADP via the ADP/ATP transporter.