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Questions and Answers
What percentage of the cell is protein, and what percentage of phenylalanine is present in the protein?
What percentage of the cell is protein, and what percentage of phenylalanine is present in the protein?
- 50% protein, 5% phenylalanine (correct)
- 60% protein, 10% phenylalanine
- 30% protein, 8% phenylalanine
- 40% protein, 3% phenylalanine
Which amino acids are required by most strains of Staphylococcus epidermidis?
Which amino acids are required by most strains of Staphylococcus epidermidis?
- Methionine, lysine, isoleucine, phenylalanine, glycine, and serine
- Alanine, aspartic acid, glutamine, tyrosine, cysteine, and threonine
- Glutamic acid, asparagine, lysine, histidine, arginine, and leucine
- Proline, arginine, valine, tryptophan, histidine, and leucine (correct)
Which organisms have the most observed requirements for added nucleic acid bases?
Which organisms have the most observed requirements for added nucleic acid bases?
- Lactic acid bacteria (correct)
- Fastidious organisms
- Bacteria and Archaea
- Free-living soil microbes
What forms a highly selective barrier between the external environment and the cytoplasm of a bacterial or archaeal cell?
What forms a highly selective barrier between the external environment and the cytoplasm of a bacterial or archaeal cell?
What type of transport mechanism involves carrier-mediated transport using transmembrane proteins called permeases?
What type of transport mechanism involves carrier-mediated transport using transmembrane proteins called permeases?
Which transport mechanism does not require energy but speeds up the diffusion process, maintaining a constant internal concentration?
Which transport mechanism does not require energy but speeds up the diffusion process, maintaining a constant internal concentration?
What type of transport directly utilizes energy to move solutes against a concentration gradient, involving solute-specific transmembrane proteins?
What type of transport directly utilizes energy to move solutes against a concentration gradient, involving solute-specific transmembrane proteins?
What type of transport mechanism involves the utilization of ATP or a proton gradient for energy?
What type of transport mechanism involves the utilization of ATP or a proton gradient for energy?
What type of transporters are involved in the transport of molecules and are present in bacterial, archaeal, and eukaryotic cells?
What type of transporters are involved in the transport of molecules and are present in bacterial, archaeal, and eukaryotic cells?
What provides the energy for ABC transporters to move molecules into the cell?
What provides the energy for ABC transporters to move molecules into the cell?
Which type of compounds does passive diffusion occur with?
Which type of compounds does passive diffusion occur with?
What do microorganisms utilize to concentrate nutrients inside the cell at levels far exceeding those present externally?
What do microorganisms utilize to concentrate nutrients inside the cell at levels far exceeding those present externally?
What type of transport mechanism involves the movement of solutes with the help of transmembrane proteins called permeases?
What type of transport mechanism involves the movement of solutes with the help of transmembrane proteins called permeases?
What type of transport mechanism is essential for microorganisms to concentrate nutrient solutes inside a bacterial cell, supporting balanced growth?
What type of transport mechanism is essential for microorganisms to concentrate nutrient solutes inside a bacterial cell, supporting balanced growth?
What are the lipid bilayers in cytoplasmic membranes highly selective due to?
What are the lipid bilayers in cytoplasmic membranes highly selective due to?
What type of transport mechanism involves the concentration of nutrients inside the cell at levels far exceeding those present externally?
What type of transport mechanism involves the concentration of nutrients inside the cell at levels far exceeding those present externally?
What is the role of porins in gram-negative bacteria?
What is the role of porins in gram-negative bacteria?
What drives the ATP synthesis and the uptake of substances through transport proteins in bacteria?
What drives the ATP synthesis and the uptake of substances through transport proteins in bacteria?
Which type of transport system carries sugars, anions, or amino acids into the cell accompanied by a proton?
Which type of transport system carries sugars, anions, or amino acids into the cell accompanied by a proton?
What do uniporters transport through electrochemical gradient?
What do uniporters transport through electrochemical gradient?
What is the transport process utilized by bacteria where the transported compound is chemically altered?
What is the transport process utilized by bacteria where the transported compound is chemically altered?
Which system is involved in the transport of sugars like glucose, fructose, and α-glucosides into the cell?
Which system is involved in the transport of sugars like glucose, fructose, and α-glucosides into the cell?
Which enzymes are soluble and present in the cytoplasm in the PTS system?
Which enzymes are soluble and present in the cytoplasm in the PTS system?
Which enzyme is an integral part of the cytoplasmic membrane and the final recipient of the high-energy phosphate in the PTS system?
Which enzyme is an integral part of the cytoplasmic membrane and the final recipient of the high-energy phosphate in the PTS system?
What is the ultimate fate of the high-energy phosphate from phosphoenolpyruvate in the PTS system?
What is the ultimate fate of the high-energy phosphate from phosphoenolpyruvate in the PTS system?
What type of protein is HPr in the PTS system?
What type of protein is HPr in the PTS system?
How many enzymes are directly involved in the PTS system to transport one sugar?
How many enzymes are directly involved in the PTS system to transport one sugar?
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Study Notes
Bacterial Active Transport Systems
- Gram-positive microorganisms transport molecules through the cell wall to the membrane surface, while gram-negative bacteria use porins in the outer membrane to come in contact with binding proteins in the periplasmic space.
- Bacteria utilize the proton motive force, established by a proton gradient during electron transport, to drive ATP synthesis and the uptake of substances through transport proteins.
- Three types of transport systems are uniporters (transport cations through electrochemical gradient), symporters (carry sugars, anions, or amino acids into the cell accompanied by a proton), and antiporters (transport two different substances in opposite directions).
- Uniporters, symporters, and antiporters depend on the generation of a proton gradient across the membrane to drive the transport processes.
- Group translocation is a transport process utilized by bacteria where the transported compound is chemically altered, involving the phosphotransferase system (PTS) for the transport of sugars into the cell.
- The PTS system involves a high-energy phosphate from phosphoenolpyruvate and the direct participation of at least four enzymes to transport sugars like glucose, fructose, and α-glucosides into the cell.
- The PTS system utilizes an electrochemical charge generated across the membrane by electron transport, using the energy in the proton gradient to transport substances across the membrane.
- Enzymes I and HPr are soluble and present in the cytoplasm, while enzymes IIa and IIb are peripheral proteins attached to the inner surface of the cell membrane, involved in the transport of a single sugar, such as glucose.
- Enzyme IIc is an integral part of the cytoplasmic membrane and the final recipient of the high-energy phosphate, which it passes on to phosphorylate the sugar in the transport process.
- The PTS transport system is energy conserving, as the high-energy phosphate from phosphoenolpyruvate ultimately becomes a part of the transported sugar.
- HPr is a heat-stable protein, and the other components of the system are enzymes involved in the PTS for various substrates.
- The PTS transport system is quite complex and involves a high-energy phosphate from phosphoenopyruvate and the direct participation of at least four enzymes to transport one sugar.
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