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Questions and Answers
During the Calvin cycle, what is the primary role of ATP and NADPH in the context of fructose-6-phosphate production?
During the Calvin cycle, what is the primary role of ATP and NADPH in the context of fructose-6-phosphate production?
- To transport carbon dioxide into the chloroplast.
- To break down carbon dioxide into usable carbon molecules.
- To regenerate the starting compound and reduce the resulting molecule. (correct)
- To directly synthesize fructose-6-phosphate from inorganic phosphate.
What is the significance of precursor metabolites in prokaryotic biosynthesis?
What is the significance of precursor metabolites in prokaryotic biosynthesis?
- They are required for the breakdown of toxic substances within the cell.
- They are the building blocks for synthesizing complex polysaccharides directly from carbon dioxide.
- They provide the basic subunits needed for synthesizing lipids, amino acids, and nucleotides. (correct)
- They function primarily in energy storage, ensuring the cell has enough energy for motility.
If a bacterium is unable to synthesize a particular amino acid, what must occur for it to survive?
If a bacterium is unable to synthesize a particular amino acid, what must occur for it to survive?
- It must switch to using an alternative metabolic pathway that bypasses the need for that amino acid.
- The amino acid must be scavenged from the environment or supplied as a growth factor. (correct)
- It has to synthesize the required enzymes.
- The bacterium will synthesize the amino acid from alternative precursors.
In lipid synthesis, how are fatty acids constructed, and what serves as the initial building block?
In lipid synthesis, how are fatty acids constructed, and what serves as the initial building block?
What role does glutamate play in bacterial nitrogen metabolism, and how is it synthesized?
What role does glutamate play in bacterial nitrogen metabolism, and how is it synthesized?
What are the initial carbon sources for the synthesis of aromatic amino acids, and from which metabolic pathways do they originate?
What are the initial carbon sources for the synthesis of aromatic amino acids, and from which metabolic pathways do they originate?
In the synthesis of aromatic amino acids, how does feedback inhibition regulate the process once a sufficient amount of amino acids is present?
In the synthesis of aromatic amino acids, how does feedback inhibition regulate the process once a sufficient amount of amino acids is present?
How do cells ensure that they do not overproduce aromatic amino acids?
How do cells ensure that they do not overproduce aromatic amino acids?
What is the initial form in which DNA and RNA are synthesized, and what subsequent modification is necessary for DNA?
What is the initial form in which DNA and RNA are synthesized, and what subsequent modification is necessary for DNA?
In nucleotide synthesis, how do the construction processes differ between purines and pyrimidines?
In nucleotide synthesis, how do the construction processes differ between purines and pyrimidines?
Flashcards
Calvin Cycle Stages
Calvin Cycle Stages
Incorporation of CO2, reduction of the resulting molecule, and regeneration of the starting compound.
Prokaryotic Biosynthesis
Prokaryotic Biosynthesis
Prokaryotes synthesize subunits for lipids, amino acids, and nucleotides using precursor metabolites from central metabolic pathways.
Lipid Synthesis
Lipid Synthesis
Requires fatty acids (2-carbon units from acetyl-CoA) and glycerol (from dihydroxyacetone phosphate).
Role of Glutamate
Role of Glutamate
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Aromatic Amino Acid Synthesis
Aromatic Amino Acid Synthesis
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Amino Acid Feedback Inhibition
Amino Acid Feedback Inhibition
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Purine vs. Pyrimidine Synthesis
Purine vs. Pyrimidine Synthesis
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Study Notes
- The Calvin cycle includes three key steps: carbon dioxide incorporation into organic compounds, reduction of the resulting molecule, and regeneration of the starting compound.
- Six turns of the Calvin cycle are needed to incorporate six carbon dioxide molecules into one fructose-6-phosphate molecule.
- This process requires 18 ATP and 12 NADPH per fructose molecule.
Anabolic Pathways
- Prokaryotes use remarkably similar biosynthesis processes.
- They synthesize subunits for lipids, amino acids, and nucleotides using precursor metabolites from central metabolic pathways.
- If a bacteria lacks certain enzymes, the end product must be supplied for it to survive.
- Fastidious bacteria need many growth factors.
Lipid Synthesis
- Lipid synthesis requires fatty acids and glycerol.
- Fatty acids are formed by adding 2-carbon units to an acetyl group from acetyl-CoA.
- Fatty acids usually contain 14, 16, or 18 carbon atoms.
- Glycerol is synthesized from dihydroxyacetone phosphate that is generated during glycolysis.
Amino Acid Synthesis
- Glutamate provides bacteria with a mechanism for incorporating nitrogen into organic material.
- Glutamate is synthesized in one step by adding ammonia to α-ketoglutarate.
- Transamination can then be used to create other amino acids.
Aromatic Amino Acids
- The synthesis of aromatic amino acids, such as tyrosine and phenylalanine, is a multi-step, branching pathway.
- Phosphoenolpyruvate (3-carbon) and erythrose-4-phosphate (4-carbon) join to form a 7-carbon compound.
- The precursors originate in glycolysis and the pentose phosphate pathway.
- Then the 7-carbon compound is modified through a series of steps until a branch point.
- If synthesis proceeds in one direction, tryptophan is produced.
- In the other direction, another branch point is reached, from there, either tyrosine or phenylalanine can be made.
- Amino acids are feedback inhibitors of enzymes that direct the branch to their own synthesis.
- Amino acids also inhibit the formation of the original 7-carbon compound.
- As a result, the cell does not produce amino acids that are already present.
Nucleotide Synthesis
- DNA and RNA are initially synthesized as ribonucleotides, which can be converted to deoxyribonucleotides.
- For purines, atoms are added to ribose 5-phosphate to form a ring.
- For pyrimidines, the ring is made first, then attached to ribose 5-phosphate.
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