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What is the main function of the glycocalyx in bacteria?
All bacteria reproduce through a process called binary fission.
True
What term is used to describe bacteria that maintain a single shape?
Monomorphic
The primary component of the bacterial cell wall is ________.
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Match the types of bacterial morphology with their descriptions:
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Which of the following describes a slime layer of glycocalyx?
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All bacteria are unicellular organisms.
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What are the two main types of glycocalyx found in bacteria?
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What is the primary function of teichoic acids in Gram-positive bacteria?
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Gram-negative bacteria have a thicker layer of peptidoglycan than Gram-positive bacteria.
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What are the two monosaccharides that make up the disaccharide portion of peptidoglycan?
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Lipid A is a component of the ________ in Gram-negative bacteria and acts as an endotoxin when released.
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Which enzymes are involved in the assembly of peptidoglycan on the outside of the plasma membrane?
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The periplasm of Gram-negative bacteria is a viscous fluid that contains enzymes and transport proteins.
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Match the following components with their descriptions:
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What role does the outer membrane of Gram-negative bacteria play in relation to antibiotics?
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What role does the 0 polysaccharide play in bacteria?
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The cell wall of bacteria helps prevent their rupture when water pressure is greater outside than inside the cell.
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What are protoplasts and how do they differ from spheroplasts in terms of cell wall?
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The plasma membrane is described by the ______ model, which emphasizes its fluid and mosaic arrangement.
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Which of the following is not a function of the bacterial cell wall?
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Match the following bacterial components with their main functions:
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Antibiotics primarily target the outer membrane of gram-negative bacteria.
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What is the role of enzymes associated with the plasma membrane?
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Study Notes
Microorganisms
- Are microscopic organisms that can be single-celled (unicellular), a cluster of cells, or acellular (no cells).
- Viruses require a host cell to survive and reproduce
Cell morphology of bacteria
- Cocci are spherical bacteria.
- They can appear as singular, in pairs (diplococci), chains (streptococci), clusters (staphylococci), groups of four (tetrads), or groups of eight (octads).
- Bacilli are rod-shaped bacteria.
- They can appear short, long, thick, thin, pointed, curved, or have blunt ends.
- They can be found in pairs, chains, long filaments, or branched.
- Some rods are short in length, called cocobacilli.
- Spiral, curved bacteria include vibrio (curved), spirilla (helical), and spirochete (spiral-shaped).
- Spiral bacteria usually appear individually, but some species form pairs.
- Bacteria can be monomorphic (single shape) or pleomorphic (many shapes).
Prokaryotic cell structure
- All bacteria are prokaryotes.
- They are 10 times smaller than eukaryotic cells.
- Prokaryotes reproduce using binary fission.
- The cytoplasm of prokaryotes contains a chromosome, ribosomes, and other cytoplasmic particles.
- The cytoplasm is surrounded by a cell wall and sometimes a capsule or slime layer.
Glycocalyx
- Is a viscous, slimy, gelatinous substance composed of polysaccharide, polypeptide, or both.
- It is produced by the cell membrane and secreted outside of the cell wall.
- There are two types:
- Slime layer: unorganized and loosely attached to the cell wall.
- Enables bacteria to glide on solid surfaces.
- Mostly composed of exopolysaccharides, glycoproteins, and glycolipids.
- Capsule: organized and firmly attached to the cell wall.
- Usually consists of polysaccharide, which may be combined with lipids and proteins.
- Protects bacteria from being phagocytosed by white blood cells.
- Slime layer: unorganized and loosely attached to the cell wall.
Peptidoglycan
- Is a unique macromolecule found in bacterial cell walls.
- Provides strength and rigidity to the cell wall.
- Consists of a disaccharide (NAM and NAG) and a tetrapeptide.
- The assembly of peptidoglycan on the outside of the plasma membrane is mediated by periplasmic enzymes, including transglycosylases, transpeptidases, and carboxypeptidases.
Gram positive cell wall
- Consists of many layers of peptidoglycan, forming a thick, rigid structure.
- Contains teichoic acids, linear polymers of polyglycerol or polyribitol substituted with phosphates and a few amino acids and sugars.
- Teichoic acids and lipoteichoic acids are negatively charged.
- Functions of teichoic acids:
- Facilitates cation movement
- Aids in cell growth
- Serves as wall antigenic specific
Gram negative cell wall
- Consists of one or a very few layers of peptidoglycan and an outer membrane.
- The peptidoglycan is bonded to lipoproteins in the outer membrane.
- The periplasm, a gel-like fluid, is located between the outer membrane and the plasma membrane.
- Contains degradative enzymes and transport proteins.
- The outer membrane consists of lipopolysaccharide (LPS), lipoproteins, and phospholipids.
- Functions of the outer membrane:
- Evade phagocytosis and immune response
- Provide a barrier to certain antibiotics and digestive enzymes
- Porins allow the passage of nucleotides, disaccharides, peptides, amino acids, vitamin B12, and iron.
- LPS is composed of Lipid A (endotoxin), core polysaccharide (stability), and O polysaccharide (antigen).
Lipopolysaccharide (LPS)
- Lipid A is the lipid portion of the LPS and is embedded in the top layer of the outer membrane.
- When gram-negative bacteria die, they release lipid A, which functions as an endotoxin.
- Lipid A is responsible for symptoms associated with gram-negative infections like fever, vasodilation, shock, and blood clotting.
- The core polysaccharide attaches to lipid A and contains unusual sugars.
- Provides structural stability.
- The O-polysaccharide extends outward from the core polysaccharide and is composed of sugar molecules.
- Functions as an antigen and is useful for distinguishing species of gram-negative bacteria.
Cell wall function
- Prevents bacterial cells from rupturing when internal water pressure is higher than external pressure.
- Helps maintain the shape of the bacterium and serves as an anchor for flagella.
- Contributes to the ability of some species to cause disease.
- Is the site of action for some antibiotics.
Cell wall damage
- Lysozyme is an enzyme that hydrolyzes the bonds between sugars in peptidoglycan.
- Primarily active against gram-positive bacteria.
- Protoplasts (gram-positive) have their cell wall completely removed.
- Spheroplasts (gram-negative) have their cell wall partially removed.
Cell membrane (plasma membrane)
- Consists of proteins (peripheral and integral) and phospholipids, arranged in a fluid mosaic model.
- Flexible and thin.
- Functions:
- It is a selective barrier for materials entering and exiting the cell (passive and active movement).
- Many enzymes are attached to the membrane, and metabolic reactions occur there.
- Involved in the breakdown of nutrients and the production of energy.
Cytoplasm
- The semi-liquid cytoplasm of prokaryotes consists of water, enzymes, dissolved oxygen, waste products, essential nutrients, proteins, carbohydrates, and lipids.
- It houses all the materials needed for metabolic functions.
Chromatophores
- In some bacteria, pigments and enzymes involved in photosynthesis are found in infoldings of the plasma membrane that extend into the cytoplasm.
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Description
Explore the fascinating world of microorganisms, focusing on their structure and classification. This quiz covers different shapes of bacteria, including cocci, bacilli, and spiral types, as well as the basic features of prokaryotic cells. Test your knowledge and understanding of these essential life forms.
