Question 1

How does paraquat destroy human tissue?

Accepted Answer

Paraquat generates oxygen radicals by diverting electrons from complex I of the respiratory chain. These oxygen radicals lead to the production of substances that damage and kill tissue.

Question 2

What is the mechanism of action by which the herbicide paraquat kills plants?

Accepted Answer

Paraquat kills plants by generating highly reactive oxygen radicals when electrons attached to it are used to reduce oxygen. This process interferes with Photosystem I (PSI) function, as paraquat competes with ferredoxin for electrons from the PSI reaction center. The reactive oxygen species produced can damage chloroplasts and other cellular components, leading to the plant's death. Therefore, all the mechanisms listed contribute to the herbicidal action of paraquat.

Question 3

______is a small,water-soluble,iron-sulfur protein that transfers electrons to NADP⁺ to form NADPH.

Accepted Answer

The description fits the function of ferredoxin, which is a small, water-soluble iron-sulfur protein that transfers electrons to NADP+ to form NADPH. Ferritin is a protein that stores iron, sulfotriene and sulfate are not related to electron transfer, and sulferritin is not a recognized protein.

Question 4

Why are plants unlikely to produce many carbohydrates at night?

Accepted Answer

Selected enzymes of the Calvin cycle are inactive in the dark because they require reduction with thioredoxin, a compound that becomes oxidized at night, preventing the enzymes from functioning properly. Therefore, plants are unlikely to produce many carbohydrates at night.

Question 5

The reduction of ________ is accomplished with electrons passed through ferredoxin;this substance then reduces certain _______ in selected Calvin cycle enzymes.

Accepted Answer

The reduction of thioredoxin is accomplished with electrons passed through ferredoxin. This reduced thioredoxin then reduces certain disulfide bridges in selected Calvin cycle enzymes, thereby activating them.

Question 6

Algal cultures in sealed containers were exposed to radiolabeled [¹⁴C]O₂ for a brief incubation period.Soluble molecules were extracted from the algae and subjected to 2D-paper chromatography.How many carbons are found in the most predominant spot on the chromatogram?

Accepted Answer

The answer of Algal cultures in sealed containers were exposed...

Question 7

Calvin originally thought that the acceptor molecule for carbon dioxide during carbon fixation contained how many carbons?

Accepted Answer

The answer of Calvin originally thought that the acceptor molecule...

Question 8

A cluster of what kind of ions is responsible for passing electrons one-at-a-time to the nearby P680+ in the reaction center?

Accepted Answer

The cluster of 4 manganese ions and one calcium ion, also known as the oxygen-evolving complex, is responsible for passing electrons one-at-a-time to the nearby P680+ in the reaction center during photosynthesis. This process is crucial for the generation of oxygen and the conversion of light energy into chemical energy.

Question 9

Starch stored as granules in the chloroplasts serves what purpose?

Accepted Answer

Starch stored in the chloroplasts serves as a reserve of glucose for the plant. During the night, when photosynthesis is not occurring, the plant can break down the starch and use the glucose to produce energy.

Question 10

Why is the conversion of CO₂ to a 6-carbon sugar so energetically expensive?

Accepted Answer

CO₂ is a highly oxidized and low energy form of carbon due to its double bonds and lack of attached hydrogen atoms. Converting it to a 6-carbon sugar requires the addition of hydrogen atoms and the formation of new carbon-carbon bonds, which requires a significant input of energy.

Question 11

What is the mechanism by which the herbicides diuron,atrazine and terbutryn are able to kill plants?

Accepted Answer

Diuron, atrazine, and terbutryn are all herbicides that act as inhibitors of photosynthesis in plants. They specifically target the photosystem II (PSII) complex, which is responsible for using light energy to split water molecules and produce oxygen and electrons for use in the photosynthetic electron transport chain. These herbicides block electron transport through PSII by binding to the D1 protein, which is involved in the transfer of electrons from the water-splitting complex to the plastoquinone electron acceptor. This disrupts the normal function of the photosynthetic electron transport chain, leading to an accumulation of reactive oxygen species and ultimately causing damage to the plant's photosynthetic apparatus and death.

Question 12

What waste product of photolysis is released to the environment?

Accepted Answer

The waste product released during photolysis is oxygen, as water molecules are split into oxygen and hydrogen ions by high energy light. Carbon dioxide, ammonia, and precipitated manganese are not byproducts of photolysis.

Question 13

Which molecule carries electrons to the luminal side of the positively charged PSI reaction center where they are transferred to pigment P700⁺,the positively charged reaction-center pigment of PSI?

Accepted Answer

Plastocyanin is a small protein that binds to a copper ion and carries it to the PSI reaction center. The copper ion helps to transfer the electrons from the LHC to the PSI reaction center where they are used for photosynthesis.

Question 14

A mechanism that is known to regulate basic cell processes,like protein folding,transcription,translation and chloroplast metabolism,by controlling the activity of proteins is known as ________.

Accepted Answer

The mechanism mentioned is most likely referring to redox control, which involves regulating cellular processes by controlling the activity of proteins through oxidation and reduction reactions. This is a fundamental process in maintaining cellular homeostasis and is critical for many important cellular functions. Transubstantiation, internal combustion, oxidation inhibition, and reduction counter-regulation are not related terms in this context.

Question 15

The initial product of carbon fixation contains ____ carbons,but it breaks down into two compounds containing _____ carbons.

Accepted Answer

The initial product of carbon fixation is a 6-carbon compound called 3-phosphoglycerate. This compound is then converted into two 3-carbon compounds, glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, through the process of glycolysis. Therefore, the answer is B) 6,3.

Question 16

Which molecule conveys protons from the chloroplast stroma into the thylakoid lumen?

Accepted Answer

The molecule that conveys protons from the chloroplast stroma into the thylakoid lumen is called cytochrome b6f, a protein complex that includes the cytochrome b6 and cytochrome f subunits.

Question 17

The production of ATP in chloroplasts and mitochondria differs in which of the following ways?

Accepted Answer

In mitochondria, the force driving ATP production is expressed primarily as an electrochemical potential (due to the proton gradient across the inner mitochondrial membrane), whereas in chloroplasts, it is largely due to a pH gradient (protons moving into the thylakoid lumen).

Question 18

Why does an electrochemical potential build up in mitochondria,but not in chloroplasts?

Accepted Answer

In chloroplasts, proton movement into the thylakoid lumen is compensated for by the movement of other ions, such as Mg2+ and K+. This prevents the buildup of an electrochemical potential. In contrast, in mitochondria, protons are pumped into the intermembrane space, and there is no compensatory movement of other ions, leading to the buildup of an electrochemical potential.

Question 19

In chloroplasts,a proton gradient is established with a higher concentration of protons found in the ______ and a lower concentration in the ______.

Accepted Answer

The proton gradient in chloroplasts is established between the thylakoid lumen and stroma, with a higher concentration of protons in the thylakoid lumen and a lower concentration in the stroma.

Question 20

Mercaptoethanol is a reagent that breaks disulfide linkages.If you were to treat Calvin cycle enzymes with this reagent,what effect might it conceivably have on them?

Accepted Answer

The answer of Mercaptoethanol is a reagent that breaks disulfide...

Quiz 6: Photosynthesis and the Chloroplast

How does paraquat destroy human tissue?

What is the mechanism of action by which the herbicide paraquat kills plants?

______is a small,water-soluble,iron-sulfur protein that transfers electrons to NADP⁺ to form NADPH.

Why are plants unlikely to produce many carbohydrates at night?

The reduction of __ is accomplished with electrons passed through ferredoxin;this substance then reduces certain _ in selected Calvin cycle enzymes.

Algal cultures in sealed containers were exposed to radiolabeled [¹⁴C]O₂ for a brief incubation period.Soluble molecules were extracted from the algae and subjected to 2D-paper chromatography.How many carbons are found in the most predominant spot on the chromatogram?

Calvin originally thought that the acceptor molecule for carbon dioxide during carbon fixation contained how many carbons?

A cluster of what kind of ions is responsible for passing electrons one-at-a-time to the nearby P680+ in the reaction center?

Starch stored as granules in the chloroplasts serves what purpose?

Why is the conversion of CO₂ to a 6-carbon sugar so energetically expensive?

What is the mechanism by which the herbicides diuron,atrazine and terbutryn are able to kill plants?

What waste product of photolysis is released to the environment?

Which molecule carries electrons to the luminal side of the positively charged PSI reaction center where they are transferred to pigment P700⁺,the positively charged reaction-center pigment of PSI?

A mechanism that is known to regulate basic cell processes,like protein folding,transcription,translation and chloroplast metabolism,by controlling the activity of proteins is known as ________.

The initial product of carbon fixation contains carbons,but it breaks down into two compounds containing _ carbons.

Which molecule conveys protons from the chloroplast stroma into the thylakoid lumen?

The production of ATP in chloroplasts and mitochondria differs in which of the following ways?

Why does an electrochemical potential build up in mitochondria,but not in chloroplasts?

In chloroplasts,a proton gradient is established with a higher concentration of protons found in the and a lower concentration in the .

Mercaptoethanol is a reagent that breaks disulfide linkages.If you were to treat Calvin cycle enzymes with this reagent,what effect might it conceivably have on them?

Quiz 6: Photosynthesis and the Chloroplast

How does paraquat destroy human tissue?

What is the mechanism of action by which the herbicide paraquat kills plants?

______is a small,water-soluble,iron-sulfur protein that transfers electrons to NADP+ to form NADPH.

Why are plants unlikely to produce many carbohydrates at night?

The reduction of ________ is accomplished with electrons passed through ferredoxin;this substance then reduces certain _______ in selected Calvin cycle enzymes.

Algal cultures in sealed containers were exposed to radiolabeled [14C]O2 for a brief incubation period.Soluble molecules were extracted from the algae and subjected to 2D-paper chromatography.How many carbons are found in the most predominant spot on the chromatogram?

Calvin originally thought that the acceptor molecule for carbon dioxide during carbon fixation contained how many carbons?

A cluster of what kind of ions is responsible for passing electrons one-at-a-time to the nearby P680+ in the reaction center?

Starch stored as granules in the chloroplasts serves what purpose?

Why is the conversion of CO2 to a 6-carbon sugar so energetically expensive?

What is the mechanism by which the herbicides diuron,atrazine and terbutryn are able to kill plants?

What waste product of photolysis is released to the environment?

Which molecule carries electrons to the luminal side of the positively charged PSI reaction center where they are transferred to pigment P700+,the positively charged reaction-center pigment of PSI?

A mechanism that is known to regulate basic cell processes,like protein folding,transcription,translation and chloroplast metabolism,by controlling the activity of proteins is known as ________.

The initial product of carbon fixation contains ____ carbons,but it breaks down into two compounds containing _____ carbons.

Which molecule conveys protons from the chloroplast stroma into the thylakoid lumen?

The production of ATP in chloroplasts and mitochondria differs in which of the following ways?

Why does an electrochemical potential build up in mitochondria,but not in chloroplasts?

In chloroplasts,a proton gradient is established with a higher concentration of protons found in the ______ and a lower concentration in the ______.

Mercaptoethanol is a reagent that breaks disulfide linkages.If you were to treat Calvin cycle enzymes with this reagent,what effect might it conceivably have on them?

______is a small,water-soluble,iron-sulfur protein that transfers electrons to NADP⁺ to form NADPH.

The reduction of __ is accomplished with electrons passed through ferredoxin;this substance then reduces certain _ in selected Calvin cycle enzymes.

Algal cultures in sealed containers were exposed to radiolabeled [¹⁴C]O₂ for a brief incubation period.Soluble molecules were extracted from the algae and subjected to 2D-paper chromatography.How many carbons are found in the most predominant spot on the chromatogram?

Why is the conversion of CO₂ to a 6-carbon sugar so energetically expensive?

Which molecule carries electrons to the luminal side of the positively charged PSI reaction center where they are transferred to pigment P700⁺,the positively charged reaction-center pigment of PSI?

The initial product of carbon fixation contains carbons,but it breaks down into two compounds containing _ carbons.

In chloroplasts,a proton gradient is established with a higher concentration of protons found in the and a lower concentration in the .