These unique flagella, called endoflagella, together form what is called an axial filament. Rotation of the endoflagella causes the axial filament to rotate, and propels the spirochete in a twisting motion.
Treponema pallidum , the bacterium that causes syphilis, moves around this way. Gram-negative Bacterial Fimbriae. Most Gram-negative bacteria have these short, fine appendages surrounding the cell; in contrast to Gram-positive bacteria , which never have fimbriae. These protein projections have no role in motility, but instead help bacteria adhere to surfaces and infect host cells. Fimbriae are a major factor in bacterial virulence the ability of a bacterium to cause disease. Bacteria, such as Neisseria gonorrhoeae and N.
These bacteria would be avirulent unable to cause disease without the use of their fimbriae. Monotrichou s: Only one flagellum extending from one end of the bacterium. Lophotrichous : Many flagella extending from one end of the bacterium. Amphitrichous : One flagellum extending from each end of the bacterium.
Peritrichous : Flagella extending from many different sites on the bacterium. Some bacteria even have extensions called sex pili, that they use to share some of their genes with other bacteria. Below is a breakdown of the main bacterial surface appendages. Bacterial Flagella Placement and Number. Flagella singular flagellum are long, thin extensions, like rotating propellers, that allow the bacteria that have them to move about freely in aqueous environments.
Some eukaryotic cells such as human sperm for example also have flagella, but prokaryotic and eukaryotic flagella are constructed and operate in distinct ways. The placement and number of bacterial flagella are distinguished using specific terminology. The four main placements of prokaryotic flagella are:. Virtual Cell Biology. Instructors Corner. You have access to a large collection of free science teaching materials used in high school and college-level introductory science courses.
A thing of watery salt. Held in cohesion by unresting cells,. Which work they know not why, which never halt,. Myself unwitting where their Master dwells.
I do not bid them, yet they toil, they spin. Flagella - in humans, the single, long, hairlike cellular extension that occurs in sperm cells; beat in waves prokaryotic flagella rotate! Cell Wall. Animal cells - no cell wall!
Plant cells - made of cellulose. Fungi - in most made of cellulose; some made of chitin polysaccharide containing nitrogen - similar to exoskeletons of insects and cellulose. Algae - made of cellulose. Protozoans - no cell wall! Glycocalyx - A glycocalyx may exist outside the plasma membrane; composed of carbohydrate chains from glycoproteins in cell membrane. Cytoskeleton not found in prokaryotes. Structure in eukaryotic cells:.
Function - sites of protein synthesis where amino acids are assembled into polypeptides. We will not discuss these organelles in detail, since the focus of this class will be on prokaryotes. Structure - 4 to 8 flattened, membrane-bound sacs loosely stacked on top of one another surrounded by vesicles; looks like a stack of pancakes. Process: transport vesicles from the r. Structure - membrane-bound sacs that could be pinched off pieces of golgi complex, E. Some specialized vesicles:.
Lysosomes - contain enzymes for breaking down proteins, lipids, etc. Function - break down energy containing organic molecules ex. Functions - give the cell shape support , anchor the organelles, transport substances through the cell, involved in cell division.
Structure - paired cylindrical structures composed of protein filaments. Function - during cell division, organize a microtubule network, called spindle fibers; spindle fibers are responsible for moving the chromosomes around in the cell during division.
Definition - the net movement of particles from a greater concentration to a lower concentration down a concentration gradient to distribute the particles uniformly; it's a passive process - molecules move by their own kinetic energy - requires no energy expenditure by the cell no ATP ; molecules will diffuse freely until an equilibrium is reached equal distribution on both sides.
Simple Diffusion through the Cell Membrane - The lipid interior of the cell membrane is a barrier to simple diffusion; most polar molecules polar molecules get "stuck" in the nonpolar fatty acid tails.
Osmosis - a special case of diffusion; the movement of water across a semipermeable membrane - water moves from a high water concentration to a low water concentration or from a low solute concentration to a high solute concentration ; water moves across cellular membranes through pores in channel proteins or through momentary openings in the membrane.
Note: The above examples describe the environment that the cell is in i. You can also talk about the cell in relation to its environment i. You have to make this distinction!! The cells in our bodies try to maintain the isotonic condition so that they are not in danger of lysing or crenating.
Facilitated Diffusion - Again, only small, nonpolar molecules readily diffuse across the cell membrane. Small, polar molecules, like water, and some ions can diffuse through channel proteins. Special selective carrier proteins are located in the membrane to transport molecules like glucose.
In facilitated diffusion, carrier proteins move molecules from a high concentration to a low concentration like in simple diffusion; it is believed that changes in the shape of the carrier protein allow it to envelop and then release the transported substance. Note : Few prokaryotes transport in this way; but may compounds, including most sugars, enter most eukaryotic cells in this way. These processes use energy ATP!!! Active Transport - Carrier proteins move molecules move from low concentration to high concentration against the concentration gradient.
In prokaryotes - most nutrients are transported in this way because many prokaryotes live in low nutrient environments; group translocation is a form of active transport that occurs in some prokaryotes with certain molecules; in group translocation, a molecule is transported into the cell and at the same time chemically changed in to a slightly different molecule; this occur so that the molecule cannot leave the cell.
Vesicle Mediated Transport by Eukaryotes - We will concentrate on the type of vesicle mediated transport called endocytosis , since this is how white blood cells eat bacteria, etc. When solid material is imported into the cell, this type of endocytosis is specifically called phagocytosis "cell eating" ; ex.
Return to Chp. Cell or plasma membrane separates the cell from the outer environment 2. Genetic material DNA 3. Appendages 1.
Pili - straight hairlike appendages; they are usually short; all gram negative bacteria have pili; function is to attach bacteria to other bacteria, other cells, or other surfaces not for locomotion : a.
Glycocalyx - found in most bacteria; slimy or gummy substance that becomes the outermost layer of the cell envelope; a thick glycocalyx is often called a capsule ; a thin glycocalyx is often called a slime layer ; functions: a. Contains: Membrane Lipids: composed primarily of phospholipid molecules a. Contains the following: 1. Cell Wall 1. Plant cells - made of cellulose 3. Algae - made of cellulose 5. Cytoplasm 1. Cytoskeleton not found in prokaryotes a.
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