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Which of the following is a characteristic of the plasma membrane in bacterial cells?
Which of the following is a characteristic of the plasma membrane in bacterial cells?
What is the primary function of the cell wall in bacterial cells?
What is the primary function of the cell wall in bacterial cells?
What is the primary function of flagella in bacterial cells?
What is the primary function of flagella in bacterial cells?
What is the characteristic shape of bacterial cells?
What is the characteristic shape of bacterial cells?
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What is the primary function of fimbriae in bacterial cells?
What is the primary function of fimbriae in bacterial cells?
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Which of the following is a characteristic of bacterial cell walls?
Which of the following is a characteristic of bacterial cell walls?
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Which of the following is a characteristic of bacterial cells?
Which of the following is a characteristic of bacterial cells?
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What is the primary function of the plasma membrane in bacterial cells?
What is the primary function of the plasma membrane in bacterial cells?
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Which of the following is a characteristic of bacterial cells?
Which of the following is a characteristic of bacterial cells?
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What is the primary function of binary fission in bacterial cells?
What is the primary function of binary fission in bacterial cells?
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Study Notes
Bacterial Morphology
- Bacteria range from 0.1 to 10µm in length, with spherical bacteria having diameters of 0.5 to 2µm, and rod-shaped cells being 0.2 to 2µm wide and 1 to 10µm long.
- There are three basic shapes of bacteria: cocci (round or oval), bacilli (rod-shaped), and spiral-shaped bacteria.
Cocci
- Cocci can be arranged in pairs (diplococci), chains (streptococci), or clusters (staphylococci).
Bacilli
- Bacilli can have rounded, tapered, square, or swollen ends.
- Short rods that resemble cocci are called coccobacilli.
- Some rod-shaped bacteria have tapered ends and are termed fusiform.
Spiral-Shaped Bacteria
- Spiral-shaped bacteria are flexible, coiled, and motile, and can be classified as spirilla (rigid) or spirochetes (flexible and undulating).
Cell Wall
- The cell wall is the outermost component of bacteria, protecting them from lysis and allowing them to grow in a wide range of osmotic pressures.
- The main constituent of bacterial cell walls is peptidoglycan.
- Gram-positive bacteria have thick layers of peptidoglycan combined with teichoic acid, while Gram-negative bacteria have a thinner layer of peptidoglycan covered with an outer lipid membrane.
Plasma Membrane
- The plasma membrane is 5-10 nm thick and consists of proteins embedded in a bilayer of phospholipids.
- Functions of the plasma membrane include selective permeability, energy generation, synthesis and assembly of cell wall components, secretion of enzymes and toxins, and protection against osmotic rupture.
Flagella
- Flagella are long, whiplike appendages that move bacteria toward nutrients and other attractants through a process called chemo-taxis.
- Flagella are made of chains of flagellin and are anchored to the cell wall and membrane.
- The system enables bacteria to detect changes in concentration of certain chemicals and to move toward or away from the substance.
Fimbriae or Pili
- Fimbriae or pili are short, rigid rod-like appendages composed of a single protein pilin.
- Functions of fimbriae or pili include facilitating adherence of bacteria to other bacterial cells, red blood cells, or the lining of the intestine.
Prokaryotic Cells
- Prokaryotic cells, such as bacteria, possess a naked DNA molecule without associated basic proteins, divide amitotically by binary fission, and have a semi-rigid cell wall.
- Characteristics of prokaryotic cells include a circular DNA molecule, no nuclear membrane, and 70S ribosomes.
General Features of Bacterial Cells
- Bacteria are the smallest free-living microorganisms that are visible only with the aid of a microscope.
- They are able to carry out their own life processes, such as growth, energy generation, and reproduction, independent of other cells.
- In general, bacteria are typical prokaryotic cells that contain both DNA and RNA, can grow in artificial media, replicate by binary fission, have a rigid cell wall, and are sensitive to antimicrobial agents.
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Description
This quiz covers the structure and morphology of bacteria, including the attachment of bacteriophages, conjugation, and the size and shape of bacterial cells.
