Cytoplasmic Membrane Microbiology Quiz Questions
Chapter 3 Microbiology
Questions and Answers
- 1.
The concept of a prokaryote was first fully outlined in 1962 by
- A.
Watson and Crick
- B.
Stanier and Van Niel
- C.
Hersey and Chase
- D.
Gilbert and Cech
Correct Answer
B. Stanier and Van NielExplanation
Stanier and Van Niel were the scientists who first outlined the concept of a prokaryote in 1962. Prokaryotes are single-celled organisms that lack a nucleus and other membrane-bound organelles. This concept was a significant contribution to our understanding of the diversity of life on Earth, as it distinguished prokaryotes from eukaryotes, which have a nucleus and other membrane-bound organelles. Watson and Crick are known for discovering the structure of DNA, Hersey and Chase conducted the famous Hershey-Chase experiment, and Gilbert and Cech made important contributions to the field of molecular biology.Rate this question:
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- 2.
The genus of bacteria that undergoes cell division in random planes, forming grapelike clusters of round bacteria, are the __________.
Correct Answer
StaphylococciExplanation
Staphylococci is the correct answer because they are a genus of bacteria that divide in random planes, forming grapelike clusters of round bacteria.Rate this question:
- 3.
Bacteria that do not have a fixed shape are said to be __________.
Correct Answer
pleomorphicExplanation
Bacteria that do not have a fixed shape are referred to as pleomorphic. This means that their shape can vary and they do not have a specific, defined shape.Rate this question:
- 4.
A branched network of hyphae formed by the Actinomycetes is called a __________.
Correct Answer
myceliumExplanation
A branched network of hyphae formed by the Actinomycetes is called mycelium. Mycelium is a term used to describe the vegetative part of a fungus, consisting of a network of branching hyphae. Actinomycetes are a group of bacteria that share some characteristics with fungi, including the formation of mycelium. Therefore, when Actinomycetes form a branched network of hyphae, it is referred to as mycelium.Rate this question:
- 5.
Actinomycetes form long filaments called ___________.
Correct Answer
hyphaeExplanation
Actinomycetes are a group of bacteria that form long filaments called hyphae. Hyphae are thread-like structures that are characteristic of fungi, but actinomycetes also produce these structures. The hyphae of actinomycetes allow them to grow and spread through their environment, facilitating the formation of complex networks and colonies. This unique feature plays a crucial role in the ecological and physiological characteristics of actinomycetes.Rate this question:
- 6.
The term used to describe bacteria that are intermediate in shape between spherical and rod shaped is
- A.
Cocci
- B.
Bacilli
- C.
Vibrio
- D.
Coccobacilli
Correct Answer
D. CoccobacilliExplanation
Coccobacilli is the correct answer because it describes bacteria that are intermediate in shape between spherical (cocci) and rod-shaped (bacilli). Coccobacilli are oval or short rod-shaped bacteria that appear slightly elongated and can be mistaken for either cocci or bacilli.Rate this question:
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- 7.
Bacterial cells that are variable in shape are called
- A.
Vibrio
- B.
Pleomophic
- C.
Coccobacilli
- D.
Hyphal
Correct Answer
B. PleomophicExplanation
Pleomorphic bacteria are variable in shape, meaning they can exist in different shapes and sizes. Unlike other bacteria that have a fixed shape, pleomorphic bacteria can change their shape depending on the environmental conditions. This adaptability allows them to survive and thrive in different habitats.Rate this question:
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- 8.
Square planar arrangement of cells that forms when round bacteria remain attached to each other during reproduction are called
- A.
Streptococci
- B.
Staphylococci
- C.
Tetrads
- D.
Sarcinae
Correct Answer
C. TetradsExplanation
Tetrads are a square planar arrangement of cells that form when round bacteria remain attached to each other during reproduction. Streptococci and staphylococci refer to bacteria that form chains and clusters respectively, while sarcinae are bacteria that form cuboidal packets. Therefore, tetrads is the correct answer in this case.Rate this question:
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- 9.
Flexible bacteria with a helical shape are called
- A.
Vibrios
- B.
Spirilla
- C.
Spirochetes
- D.
Coccobacilli
Correct Answer
C. SpirochetesExplanation
Spirochetes are flexible bacteria with a helical shape. They have a unique spiral morphology, allowing them to move in a corkscrew-like motion. This shape enables them to navigate through various environments, including viscous substances and narrow spaces. Vibrios, spirilla, and coccobacilli are all different types of bacteria with distinct shapes and characteristics. Therefore, the correct answer for this question is spirochetes.Rate this question:
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- 10.
Rigid bacteria with a helical cell shape are called
- A.
Vibrios
- B.
Spirilla
- C.
Spirochetes
- D.
Coccobacilli
Correct Answer
B. SpirillaExplanation
Rigid bacteria with a helical cell shape are called spirilla. Vibrios are curved bacteria, spirochetes are flexible bacteria with a helical shape, and coccobacilli are oval-shaped bacteria. Therefore, the correct answer is spirilla.Rate this question:
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- 11.
The term used to describe bacteria that are shaped like curved rods is
- A.
Coccus
- B.
Bacillus
- C.
Vibrio
- D.
Coccobacillus
Correct Answer
C. VibrioExplanation
Vibrio is the correct answer because it is the term used to describe bacteria that are shaped like curved rods. This shape is characteristic of the Vibrio genus, which includes bacteria such as Vibrio cholerae, the causative agent of cholera. The term "vibrio" is derived from the Latin word for "vibrating" or "shaking," which describes the curved shape of these bacteria.Rate this question:
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- 12.
The term used to describe bacteria that are rod shaped is
- A.
Coccus
- B.
Bacillus
- C.
Vibrio
- D.
Coccobacillus
Correct Answer
B. BacillusExplanation
Bacillus is the correct answer because it is the term used to describe bacteria that are rod-shaped. Bacillus bacteria have a cylindrical or rod-like shape, distinguishing them from other bacteria such as cocci (spherical-shaped) or spirilla (spiral-shaped).Rate this question:
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- 13.
The term used to describe bacteria that have a spherical shape is
- A.
Coccus
- B.
Bacillus
- C.
Vibrio
- D.
Coccobacillus
Correct Answer
A. CoccusExplanation
The correct answer is "coccus". The term "coccus" is used to describe bacteria that have a spherical shape. This shape is characteristic of certain types of bacteria, and it helps to distinguish them from other shapes such as rods or spirals. Examples of bacteria that have a coccus shape include Staphylococcus aureus and Streptococcus pneumoniae.Rate this question:
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- 14.
Sterol-like molecules called hopanoids are thought to be important for the structural integrity of many bacteria because of their suspected role in membrane stabilization.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Hopanoids are sterol-like molecules that are found in the membranes of many bacteria. They are believed to play a crucial role in maintaining the structural integrity and stability of the bacterial membrane. By incorporating into the lipid bilayer, hopanoids help to stabilize the membrane, making it less fluid and more resistant to changes in temperature and pressure. Therefore, it is true that hopanoids are thought to be important for the structural integrity of many bacteria due to their role in membrane stabilization.Rate this question:
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- 15.
The cytoplasmic membrane of bacteria
- A.
Retains the cytoplasm and its contents.
- B.
Acts as a selectively permeable barrier, allowing some molecules to pass while preventing the movement of others.
- C.
Is the major site of ATP synthesis in aerobes.
- D.
All of the choices
Correct Answer
D. All of the choicesExplanation
The cytoplasmic membrane of bacteria retains the cytoplasm and its contents, acts as a selectively permeable barrier, allowing some molecules to pass while preventing the movement of others, and is the major site of ATP synthesis in aerobes. Therefore, all of the choices are correct.Rate this question:
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- 16.
The lipopolysaccharide (LPS) that is found in the outer membrane of gram-negative bacteria is also known as
- A.
Exotoxin
- B.
Teichoic acid
- C.
Murein
- D.
Endotoxin
Correct Answer
D. EndotoxinExplanation
Lipopolysaccharide (LPS) is a component found in the outer membrane of gram-negative bacteria. It is commonly referred to as endotoxin because it can cause toxic effects when released into the bloodstream during bacterial infection. This molecule triggers an immune response and can lead to inflammation, fever, and other symptoms of infection. Unlike exotoxins, which are secreted by bacteria, LPS is a structural component of the bacterial cell wall. Teichoic acid and murein are components found in the cell walls of gram-positive bacteria, not gram-negative bacteria.Rate this question:
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- 17.
Which of the following is/are true of capsules?
- A.
They help bacteria escape phagocytosis by host cells.
- B.
They retain water and help prevent desiccation of the bacteria.
- C.
They prevent entry of many bacterial viruses.
- D.
All of the choices
Correct Answer
D. All of the choicesExplanation
Capsules are protective structures produced by some bacteria. They help bacteria escape phagocytosis by host cells by acting as a barrier between the bacteria and the immune system. Capsules also retain water and help prevent desiccation of the bacteria, which is important for their survival in harsh environments. Additionally, capsules prevent the entry of many bacterial viruses, as the viruses are unable to penetrate the capsule. Therefore, all of the choices are true statements about capsules.Rate this question:
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- 18.
Proteins that are loosely associated with the cytoplasmic membrane are called __________ proteins.
- A.
Peripheral
- B.
Integral
- C.
External
- D.
Internal
Correct Answer
A. PeripheralExplanation
Proteins that are loosely associated with the cytoplasmic membrane are called peripheral proteins. These proteins are not embedded within the lipid bilayer of the membrane, but rather they are attached to the surface of the membrane through non-covalent interactions with other membrane proteins or with the lipid molecules. Peripheral proteins can be easily dissociated from the membrane without disrupting the integrity of the membrane itself.Rate this question:
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- 19.
Proteins that are embedded within the cytoplasmic membrane and not easily extracted are called __________ proteins.
- A.
Peripheral
- B.
Integral
- C.
External
- D.
Internal
Correct Answer
B. IntegralExplanation
Integral proteins are embedded within the cytoplasmic membrane and are not easily extracted. They are firmly attached to the membrane and can only be removed by disrupting the membrane structure. This is in contrast to peripheral proteins, which are loosely attached to the membrane and can be easily extracted without disrupting the membrane. Therefore, the correct answer is integral.Rate this question:
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- 20.
Shrinkage of the plasma membrane away from the cell wall when the bacterium is placed in a hypertonic environment is called
- A.
Osmolysis.
- B.
Plasmolysis
- C.
Hydrolysis
- D.
Hypertonolysis
Correct Answer
B. PlasmolysisExplanation
Plasmolysis is the correct answer because it refers to the shrinkage of the plasma membrane away from the cell wall when a bacterium is placed in a hypertonic environment. In a hypertonic environment, there is a higher concentration of solutes outside the cell compared to inside, causing water to move out of the cell. This loss of water causes the plasma membrane to shrink and detach from the cell wall, leading to plasmolysis. Osmolysis, hydrolysis, and hypertonolysis do not accurately describe this phenomenon.Rate this question:
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- 21.
Lipids with polar and nonpolar ends are said to be
- A.
Amphipathic
- B.
Amphibolic
- C.
Bilateral
- D.
None of the choices
Correct Answer
A. AmphipathicExplanation
Lipids with polar and nonpolar ends are said to be amphipathic because they have both hydrophilic (water-loving) and hydrophobic (water-fearing) properties. The polar end of the lipid molecule is attracted to water, while the nonpolar end repels water. This dual nature allows amphipathic lipids to interact with both water and lipid molecules, making them essential for the formation of cell membranes and the transportation of molecules across them.Rate this question:
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- 22.
Although penicillin inhibits peptidoglycan synthesis, bacterial cells will continue to grow normally in the presence of penicillin in a(n) __________ environment.
- A.
Hypotonic
- B.
Isotonic
- C.
Hypertonic
- D.
Nonpolar
Correct Answer
B. IsotonicExplanation
In an isotonic environment, the concentration of solutes outside the bacterial cells is the same as inside the cells. This means that there is no net movement of water across the cell membrane, allowing the cells to maintain their normal growth and function. Penicillin inhibits peptidoglycan synthesis, which is important for cell wall formation in bacteria. However, in an isotonic environment, the cells can still grow normally because the external solute concentration does not disrupt their osmotic balance.Rate this question:
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- 23.
All of the following statements about the periplasmic space are true except:
- A.
It is found only in gram-positive bacteria.
- B.
It is located between the plasma membrane and outer membrane of gram-negative bacteria.
- C.
T contains hydrolytic enzymes and binding proteins involved in nutrient acquisition.
- D.
All of the above
Correct Answer
A. It is found only in gram-positive bacteria.Explanation
The periplasmic space is a compartment located between the plasma membrane and the outer membrane of gram-negative bacteria, not just in gram-positive bacteria. It contains hydrolytic enzymes and binding proteins involved in nutrient acquisition. Therefore, all of the statements provided are true except for the statement that it is found only in gram-positive bacteria.Rate this question:
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- 24.
Which of the following protects bacteria from lysis in dilute solutions and helps to determine their cellular morphology or shape?
- A.
Plasma membrane
- B.
Peptidoglycan
- C.
Capsule
- D.
Gas vacuoles
Correct Answer
B. PeptidoglycanExplanation
Peptidoglycan is a substance found in the cell wall of bacteria that provides structural support and protection. It helps to prevent the bacteria from lysing, or bursting, in dilute solutions. Peptidoglycan also plays a role in determining the cellular morphology or shape of bacteria. The plasma membrane is responsible for regulating the movement of substances in and out of the cell. Capsules are outer layers that provide additional protection and help bacteria adhere to surfaces. Gas vacuoles are structures that allow bacteria to control their buoyancy.Rate this question:
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- 25.
Sortase is a protein enzyme of bacteria that
- A.
Plays a key role in directing proteins to the periplasm.
- B.
Catalyzes covalent attachment of some surface proteins to peptidoglycan.
- C.
Directs secretion of proteins across the outer membrane.
- D.
Functions by transporting flagellum proteins to their extracellular site of assembly.
Correct Answer
B. Catalyzes covalent attachment of some surface proteins to peptidoglycan.Explanation
Sortase is a protein enzyme found in bacteria that catalyzes the covalent attachment of certain surface proteins to peptidoglycan. This process is important for the assembly and anchoring of these proteins to the cell wall, contributing to the overall structure and function of the bacterial cell. By catalyzing this attachment, sortase helps to ensure the proper localization and functionality of these surface proteins.Rate this question:
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- 26.
The cell membrane is a rigid structure that provides bacteria with their characteristic shapes.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false because the cell membrane of bacteria is not rigid, but rather flexible and dynamic. The cell membrane is composed of a phospholipid bilayer that allows for movement and flexibility, enabling bacteria to change shape and adapt to their environment. This flexibility is important for processes such as cell division and movement.Rate this question:
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- 27.
Gram-positive bacteria have a thinner layer of peptidoglycan than gram-negative bacteria.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Gram-positive bacteria actually have a thicker layer of peptidoglycan than gram-negative bacteria. The peptidoglycan layer is a major component of the cell wall in bacteria and it provides structural support. In gram-positive bacteria, this layer is much thicker and forms a single, continuous layer outside the cell membrane. In contrast, gram-negative bacteria have a thinner layer of peptidoglycan that is located between two membranes - the inner cell membrane and the outer membrane. This structural difference is one of the key characteristics used to differentiate between gram-positive and gram-negative bacteria.Rate this question:
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- 28.
Gram-positive bacteria have a structurally and chemically more complex cell wall than gram-negative bacteria.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Gram-positive bacteria have a structurally and chemically simpler cell wall compared to gram-negative bacteria. Gram-positive bacteria have a thick layer of peptidoglycan in their cell wall, which provides rigidity and protection. In contrast, gram-negative bacteria have a thinner layer of peptidoglycan and an outer membrane containing lipopolysaccharides, which makes their cell wall more complex. Therefore, the correct statement is false.Rate this question:
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- 29.
Bacteria growing at lower temperatures have more saturated fatty acids in their membranes.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false because bacteria growing at lower temperatures actually have more unsaturated fatty acids in their membranes. Unsaturated fatty acids have double bonds in their carbon chains, which makes them more flexible and allows the bacteria to maintain fluidity in their membranes at lower temperatures. Saturated fatty acids, on the other hand, have no double bonds and are more rigid, making them less suitable for cold environments.Rate this question:
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- 30.
When the cell wall is removed from a Gram-negative bacterium without removing the outer membrane, the resulting form is called a(n) __________.
Correct Answer
spheroplastExplanation
When the cell wall is removed from a Gram-negative bacterium without removing the outer membrane, the resulting form is called a spheroplast. This is because the cell wall provides structural support to the bacterium, and without it, the cell loses its shape and becomes spherical in form. The outer membrane, which is present in Gram-negative bacteria, remains intact even after the removal of the cell wall. Therefore, the correct term for this resulting form is spheroplast.Rate this question:
- 31.
Enzymes that are secreted out of the cell to aid in the acquisition and digestion of environmental nutrients are called __________.
Correct Answer
exoenzymesExplanation
Exoenzymes are enzymes that are secreted out of the cell to help in acquiring and digesting environmental nutrients. They play a crucial role in breaking down complex molecules outside the cell, allowing the cell to absorb the resulting smaller molecules as nutrients. These enzymes are typically produced by bacteria and fungi to break down organic matter in their surroundings for energy and growth.Rate this question:
- 32.
Molecules or regions of molecules that readily interact with water are said to be __________, whereas molecules or regions of molecules that are insoluble in water or do not readily interact with water are said to be __________. (answer, answer)
Correct Answer
hydrophilic, hydrophobicExplanation
Hydrophilic molecules or regions of molecules readily interact with water, meaning they have an affinity for water. This can be due to the presence of polar functional groups or the ability to form hydrogen bonds with water molecules. On the other hand, hydrophobic molecules or regions of molecules are insoluble in water or do not readily interact with water. This is because they are nonpolar or have nonpolar regions that repel water molecules.Rate this question:
- 33.
A __________ layer consists of diffuse unorganized polysaccharide material that lies outside the cell wall and is easily removed.
Correct Answer
slimeExplanation
The given correct answer is "slime". A slime layer is a loose and unorganized layer of polysaccharide material that is found outside the cell wall. It is easily removed and does not have a defined structure. Slime layers can be found in various microorganisms and can serve as a protective barrier or aid in attachment to surfaces.Rate this question:
- 34.
A __________ is a polysaccharide layer that lies outside the cell wall and is not easily removed.
Correct Answer
capsuleExplanation
A capsule is a polysaccharide layer that lies outside the cell wall and is not easily removed. This layer provides protection to the cell and helps it evade the host's immune response. The capsule also aids in the attachment of the bacteria to surfaces and helps in the formation of biofilms. Due to its composition and location, the capsule is difficult to remove and plays a crucial role in the pathogenicity of certain bacteria.Rate this question:
- 35.
A(n) __________ layer is a layer of protein or glycoprotein that exhibits a pattern resembling floor tiles.
Correct Answer
S - 36.
The most widely accepted current model for membrane structures is called the __________ model.
Correct Answer
fluid mosaicExplanation
The fluid mosaic model is the most widely accepted current model for membrane structures. This model suggests that the cell membrane is composed of a fluid lipid bilayer with embedded proteins that can move freely within the membrane. The lipid bilayer provides a flexible and dynamic structure, allowing for membrane fluidity and the ability of proteins to interact with each other and perform various functions. This model accurately represents the organization and behavior of biological membranes.Rate this question:
- 37.
The layers of peptidoglycan of the bacterial cell wall can be cross-linked by peptide intrabridges or by direct cross-linking.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false because the layers of peptidoglycan in the bacterial cell wall can only be cross-linked by peptide intrabridges, not by direct cross-linking. Direct cross-linking does not occur in the bacterial cell wall.Rate this question:
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- 38.
A feature unique to some archaeal plasma membranes is that they may
- A.
Consist of a lipid bilayer that lacks integral membrane proteins.
- B.
Consist of a lipid bilayer with embedded proteins.
- C.
Contain sterols such as cholesterol.
- D.
Consist of a lipid monolayer.
Correct Answer
D. Consist of a lipid monolayer.Explanation
Some archaeal plasma membranes may consist of a lipid monolayer. This is unique to archaea and different from other organisms whose plasma membranes consist of a lipid bilayer. A lipid monolayer means that there is only a single layer of lipids in the membrane, whereas a lipid bilayer has two layers. This structural difference in the plasma membrane of archaea allows them to adapt and function in extreme environments, such as high temperatures or extreme pH levels.Rate this question:
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- 39.
Cell walls of most Archaea and bacteria contain peptidoglycan.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false because while the cell walls of most bacteria contain peptidoglycan, the cell walls of Archaea do not. Archaea have a different type of cell wall composition, typically made up of proteins or polysaccharides, but not peptidoglycan. Therefore, it is incorrect to say that the cell walls of most Archaea and bacteria contain peptidoglycan.Rate this question:
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- 40.
_______ is a peptidoglycan-like molecule found in the cell walls of some archaea.
Correct Answer
PseudomureinExplanation
Pseudomurein is a peptidoglycan-like molecule found in the cell walls of some archaea. It is similar in structure to peptidoglycan, which is found in the cell walls of bacteria. Pseudomurein provides structural support to the cell wall and helps protect the archaeal cell from osmotic stress. It is composed of alternating N-acetylglucosamine and N-acetyltalosaminuronic acid residues, connected by peptide cross-links. This molecule is unique to archaea and is not found in bacteria or eukaryotes.Rate this question:
- 41.
The hydrocarbons found in the membranes of archaea are identical to those found in bacteria.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false because the hydrocarbons found in the membranes of archaea are different from those found in bacteria. Archaea have unique membrane lipids called isoprenoid ethers, while bacteria have fatty acids in their membranes. This distinction in membrane composition is one of the factors that differentiate archaea from bacteria.Rate this question:
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- 42.
Which of the following is not true of bacterial plasmids?
- A.
They can replicate independently of the chromosome.
- B.
They may carry genes for drug resistance.
- C.
They are required for host growth and/or reproduction.
- D.
They may carry genes that enhance survival of the bacterium under certain conditions.
Correct Answer
C. They are required for host growth and/or reproduction.Explanation
Bacterial plasmids are small, circular DNA molecules that can replicate independently of the bacterial chromosome. They may carry genes for drug resistance, which can be transferred between bacteria. Additionally, plasmids may carry genes that enhance the survival of the bacterium under certain conditions, such as genes for toxin production or stress response. However, they are not required for host growth and/or reproduction as bacteria can survive and reproduce without plasmids.Rate this question:
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- 43.
Some photosynthetic bacteria produce gas vacuoles that regulate their buoyancy but contain no lipid.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Some photosynthetic bacteria produce gas vacuoles that regulate their buoyancy. This means that they can control their position in the water column by adjusting the amount of gas in the vacuoles. However, these gas vacuoles do not contain lipids. Lipids are a type of organic molecule that are commonly found in cell membranes, but in this case, the gas vacuoles are composed of proteins. Therefore, the statement that some photosynthetic bacteria produce gas vacuoles that regulate their buoyancy but contain no lipid is true.Rate this question:
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- 44.
Intracellular granules of organic or inorganic material that are stockpiled by bacteria for future use are called __________.
Correct Answer
inclusionsExplanation
Intracellular granules of organic or inorganic material that are stockpiled by bacteria for future use are called inclusions. These inclusions serve as reserves of nutrients or energy sources, allowing bacteria to survive in unfavorable conditions or when essential nutrients are limited. They can include substances such as glycogen, lipids, sulfur, or polyphosphate. Inclusions are important for the bacteria's ability to adapt and survive in various environments.Rate this question:
- 45.
Bacteria have a region of the cytoplasm known as the __________, which is not bounded by a membrane but contains the chromosome.
Correct Answer
nucleoidExplanation
Bacteria have a region of the cytoplasm known as the nucleoid, which is not bounded by a membrane but contains the chromosome. The nucleoid is where the bacterial chromosome is located and is responsible for organizing and compacting the DNA. Unlike the nucleus in eukaryotic cells, the nucleoid does not have a membrane surrounding it. Instead, it is a concentrated area within the cytoplasm where the genetic material is found.Rate this question:
- 46.
Small circular DNA molecules capable of replicating and containing genes that are useful but not necessary to the bacterium are called __________.
Correct Answer
plasmidsExplanation
Plasmids are small circular DNA molecules that can replicate independently from the bacterial chromosome. They contain genes that are not necessary for the bacterium's survival but can provide additional advantages, such as antibiotic resistance or the ability to produce certain enzymes. Plasmids can be transferred between bacteria through horizontal gene transfer, allowing the spread of these useful genes throughout a bacterial population.Rate this question:
- 47.
Some species of aquatic bacteria use inclusion bodies known as ________ to orient themselves in Earth's magnetic field.
Correct Answer
magnetosomesExplanation
Aquatic bacteria use inclusion bodies known as magnetosomes to orient themselves in Earth's magnetic field. Magnetosomes are specialized organelles that contain magnetic minerals, such as magnetite or greigite. These minerals act like tiny compass needles, allowing the bacteria to align themselves with the Earth's magnetic field. This ability helps the bacteria navigate and move towards favorable environments, such as areas with higher oxygen concentrations or nutrient-rich regions. By using magnetosomes, these bacteria can optimize their survival and growth in aquatic habitats.Rate this question:
- 48.
Bacterial and archaeal ribosomes are known as _____ ribosomes, based on their sedimentation coefficient.
- A.
50S
- B.
30S
- C.
80S
- D.
70S
Correct Answer
D. 70SExplanation
Bacterial and archaeal ribosomes are known as 70S ribosomes based on their sedimentation coefficient. The sedimentation coefficient is a measure of the rate at which particles sediment in a centrifugal field. In the case of ribosomes, it refers to their size and density. The 70S ribosomes consist of a larger 50S subunit and a smaller 30S subunit, which combine to form the complete ribosome. This classification is specific to bacteria and archaea, as eukaryotic ribosomes have a different sedimentation coefficient of 80S, with a larger 60S subunit and a smaller 40S subunit.Rate this question:
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- 49.
_______ are the site of protein synthesis in the cell.
Correct Answer
RibosomesExplanation
Ribosomes are small structures found in cells that are responsible for protein synthesis. They are composed of RNA and proteins and are found in both prokaryotic and eukaryotic cells. Ribosomes can be found free in the cytoplasm or attached to the endoplasmic reticulum. They read the genetic information stored in messenger RNA (mRNA) and use it to assemble amino acids into a polypeptide chain, which eventually folds into a functional protein. Therefore, ribosomes are the site of protein synthesis in the cell.Rate this question:
- 50.
Sedimentation coefficients are proportional to the molecular weight of a particle and are not affected by the volume and shape of the particle.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
The statement is false because sedimentation coefficients are not solely determined by the molecular weight of a particle. Other factors, such as the shape and volume of the particle, can also influence the sedimentation coefficient.Rate this question:
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